Identification of a new group of Chlamydia psittaci strains called TWAR

A new group of Chlamydia psittaci strains has been identified. They are called TWAR after the laboratory designation of the first two isolates. Twelve strains were isolated from pharyngeal swabs of different persons with acute respiratory disease in Seattle, Wash., during 1983 to 1986. One strain was obtained from the eye of a child during the trachoma vaccine study in Taiwan in 1965. Nine strains were characterized in this study. TWAR organisms formed intracytoplasmic inclusions in HeLa cells which were morphologically typical of C. psittaci and iodine stain negative (contained no glycogen). Immunological analysis with various chlamydia-specific monoclonal antibodies revealed that TWAR strains belong to the genus Chlamydia, are distinct from C. trachomatis, and are serologically unique among C. psittaci. All TWAR strains so far isolated appear identical serologically. TWAR organisms grew poorly in egg and cell cultures and demonstrated low virulence to mice by intracerebral, intranasal, and intravenous inoculation. Available data suggest that the TWAR strain is a primary human pathogen.

Nonlinear pulse propagation in the neighborhood of the zero-dispersion wavelength of monomode optical fibers

Nonlinear pulse propagation is investigated in the neighborhood of the zero-dispersion wavelength in monomode fibers. When the amplitude is sufficiently large to generate breathers (N > 1 solitons), it is found that the pulses break apart if lambda - lambda(0) is sufficiently small, owing to the third-order dispersion. Here lambda(0) denotes the zero-dispersion wavelength. By contrast, the solitary-wave (N = 1) solution appears well behaved for arbitrary lambda - lambda(0). Implications for communication systems and pulse compression are discussed.

Beta-adrenergic blockade increases the hepatic extraction of glucose in sepsis

To determine the relationship between hepatic glucose clearance and elevated epinephrine levels in sepsis, dogs with gangrenous cholecystitis were anesthetized and received either propranolol hydrochloride (mean dose, 0.29 mg/kg) or saline solution before intraduodenal glucose injection (2.5 g/kg). The amounts of glucose, insulin, and glucagon in the portal vein, the hepatic artery, and the hepatic vein were determined from the concentrations and the blood flows in these vessels over a two-hour period. Normal dogs served as controls. The amounts of glucose, insulin, and glucagon reaching the livers of both septic groups were the same. However, propranolol treatment increased the percent of glucose extracted by the liver without affecting the extractions of insulin or glucagon. Propranolol reverses the limitation of hepatic glucose extraction in sepsis by a direct effect. Whether the extracted glucose is utilizable as an energy substrate needs to be established.

Amplification and reshaping of solitons in optical fibers with suppression of dispersive waves

Two theoretical schemes for amplifying and reshaping solitons in optical fibers are discussed. In the first of these schemes, solitons are amplified and reshaped without creating dispersive waves. In the second scheme, solitons are amplified while dispersive waves are suppressed. Ways to realize these schemes in practice are discussed.

Induction of branchial (gill) neoplasms in the medaka fish (Oryzias latipes) by N-methyl-N'-nitro-N-nitrosoguanidine

Juvenile medaka were exposed to N-methyl-N'-nitro-N-nitrosoguanidine in water under static renewal conditions for 28 days. Two groups of 134 fish each were pulsed 3 times weekly at nominal concentrations of 1.0 and 0.5 mg/liter with N-methyl-N'-nitro-N-nitrosoguanidine dissolved in dimethylformamide. A third group of 134 fish was exposed to the solvent control, 0.01% dimethylformamide in water. Following the 28-day exposure, and during the recovery period, fish were sampled at intervals of approximately 0, 3, 6, and 9 months and examined grossly. Selected tissues were evaluated microscopically. Many tumor types developed in both N-methyl-N'-nitro-N-nitrosoguanidine exposure groups, but only the gill lesions will be discussed. Approximately 50% of the fish in both treatment groups died from gill damage in the second to third month of the recovery period. More than 90% of the surviving treated fish displayed gill lesions, which progressed from mild epithelial hyperplasia of gill filaments at 0-months recovery to epitheliomatous hyperplasia at 3 months and advanced to a more focal nodular appearance of gill filaments at 6 months. Eight to 9 months after the treatment period, at least four fish displayed branchial blastomas. The control fish had no gill lesions. Chemically induced gill tumors have not been previously observed in fish. Even gill tumors of unknown origin are very rare.

Two cases of lymphosarcoma in channel catfish exposed to N-methyl-N'-nitro-N-nitrosoguanidine

Of 158 channel catfish (Ictalurus punctatus) exposed to N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS:70-25-7] in water for 28 days, 2 developed disseminated lymphosarcoma. One fish was necropsied at 12 months and another at 18 months following exposure. Both fish had a massive neoplastic infiltration of the bilateral pairs of head and trunk kidneys from which the neoplastic cells appeared to originate. The neoplastic infiltration was also observed in the following: thymus, gills, oral mucosa, liver, skin, skeletal muscle of head-neck region, and to a lesser extent spleen and bone marrow. This is probably the first report of lymphosarcoma in channel catfish. Although the occurrence of lymphosarcoma in these 2 catfish appeared to be related to exposure to MNNG, the exact role MNNG played in the tumor formation was not determined.

The flexibility of alternating dA-dT sequences

The flexibility of alternating poly (dA-dT) has been investigated by the technique of transient electric dichroism. Rotational relaxation times, which are very sensitive to changes in the end-to-end length of flexible polymers, are determined from the field free dichroism decay curves of four, well defined fragments of poly (dA-dT) ranging in size from 136 to 270 base pairs. Persistence lengths, calculated from the results of Hagerman and Zimm (Biopolymers (1981) 29, 1481-1502), are in the range 200-250 A. This makes alternating dA-dT sequences about twice as flexible as naturally occurring, "random" sequence DNA. Considering a bend around a nucleosome, for example, this difference in persistence length translates to an energy difference between poly (dA-dT) and random sequence DNA of 0.17 kT/base pair or 1 kcal per 10 base pair stretch. This energy difference is sufficiently large to suggest that dA-dT sequences could serve as markers in DNA packaging, for example, at sites where DNA must tightly bend to accommodate structures.

Twenty-two year experience with the diagnosis and treatment of intrahepatic calculi

Intrahepatic cholelithiasis is commonly associated with suppurative cholangitis and occurs equally in males and females. Patients usually present with a history of recurrent symptoms and a differential diagnosis which includes viral hepatitis, pancreatitis, myocardial infarction and perforated ulcer. Cholangiography including stereocholangiography is essential for localizing intrahepatic stones and ductal strictures. The guiding operative principle is to drain all infected bile distal to ducts obstructed with stones or stricture. This may also necessitate a bilioenterostomy with or without partial hepatic resection. Although these procedures are formidable in an acutely ill patient, a more simple but inappropriate choledocholithotomy and t-tube drainage done proximal to an obstructed intrahepatic duct will be ineffective and may result in continued sepsis and death.

Rapid alterations in substrate profiles after partial hepatectomy in the rat

We compared alterations in circulating levels of insulin and glucagon and metabolic fuels in response to partial (70%) hepatectomy (HP) and sham hepatectomy (SHP) in fasting rats and in unanesthetized, fasting control rats. Within 15 minutes, animals in the HP group were hypoglycemic compared with the SHP and control groups. After 30 minutes, the insulin concentration and the insulin-glucagon molar ratio (IGR) rose in the HP group. After four hours, animals in the HP group were hyperglycemic compared with the SHP and control animals. Comparison of the lipid and amino acid profiles suggested use of these substrates by eight hours. The levels of branched-chain amino acids, although depressed early after HP, were markedly elevated later, when the IGR in the HP group had normalized. The acute loss of hepatic mass by limiting gluconeogenesis may be the cause of hypoglycemia and also could alter the plasma IGR because of the different hepatic clearance rates of these hormones. A switch to lipid and protein as metabolic fuels appears to follow these early changes.

Critical amount of oligovalent ion binding required for the B-Z transition of poly (dG-m5dC)

By working at very low Na+ concentrations (1mM and less), the number of bound Mg(2+), cobalt hexamine (3+), and spermine (4+) necessary to induce the B-Z transition of poly (dG-m5dC) has been directly measured. The results show that if as little as 1 cobalt hexamine(3+) or spermine(4+) is bound per 40-50 nucleotides the transition will occur. A greater fraction of bound Mg(2+) is required, 1 bound Mg(2+)/10 nucleotides. The dependence of the transition midpoint concentrations of oligovalent ions on Na+ concentrations suggests that specific ion binding energies, not included in counterion condensation theory, are responsible for the transition.

Quantitative analysis of aminophospholipids by high-performance liquid chromatography using succinimidyl 2-naphthoxyacetate as a fluorescent label

A simple and rapid high-performance liquid chromatographic procedure for the quantitative analysis of ethanolamine- and serine-containing phospholipids in tissue is described. The technique involves reaction of lipid extracts with succinimidyl 2-naphthoxyacetate to give fluorescent derivatives of aminophospholipids. Reaction products are separated by a silica gel column with gradient elution. The eluate is monitored by fluorescence detection at 228 nm (excitation) and 342 nm (emission). Ethanolamine and serine plasmalogens can be measured indirectly by converting their derivatives into lysophosphatidylethanolamine and lysophosphatidylserine derivatives with exposure to hydrogen chloride fumes. The method is highly sensitive and selective.

Involvement of abscisic Acid in potato cold acclimation

Upon exposure to 2 degrees C day/night (D/N), leaves of Solanum commersonii (Sc) began acclimating on the 4th day from a -5 degrees C (killing temperature) hardy level to -12 degrees C by the 15th day. Leaves of S. tuberosum L. (St) cv ;Red Pontiac' typically failed to acclimate and were always killed at -3 degrees C. Leaves of control (20/15 degrees C, D/N) and treated plants (2 degrees C, D/N) of St showed similar levels of free abscisic acid (ABA) during a 15-day sampling period. In treated Sc plants, however, free ABA contents increased 3-fold on the 4th day and then declined to their initial level thereafter. The increase was not observed in leaves of Sc control plants.Treated St plants showed a slightly higher content of leaf soluble protein than controls. In Sc, leaves of controls maintained relatively constant soluble proteins, but leaves of treated plants showed a distinct increase. This significant increase was initiated on the 4th day, peaked on the 5th day, and remained at a high level throughout the 15-day sampling period.Exogenously applied ABA induced frost hardiness in leaves of Sc plants whether plants were grown under a 20 degrees C or 2 degrees C temperature regime. When cycloheximide was added to the medium of stem-cultured plants at the beginning of 2 degrees C acclimation, or at the beginning of the ABA treatment in the 20 degrees C regime, it completely inhibited the development of frost hardiness. However, when cycloheximide was added to plants on the 5th day during 2 degrees C acclimation, the induction of frost hardiness was not inhibited. The role of ABA in triggering protein synthesis needed to induce frost hardiness is discussed.

Length changes in solution accompanying the B-Z transition of poly (dG-m5dC) induced by Co(NH3)63+

Transient electric dichroism measurements have been used to observe the rotational relaxation times of 145 base pair fragments of poly (dGm5dC) and random sequence DNA to solution. From these the lengths of the fragments are calculated and the interbase pair separation or rise per base pair (RPB) calculated. The observations show that even in low salt, the addition of very low concentrations of trivalent Co(NH3)63+ results in a transition of the dGm5dC polymer from B-form to Z-form with a change in the RPB from 3.4 +/- .06A to 3.7 +/- .06A, the latter form defined by the criterion of an inverted circular dichroism spectra similar to that observed at high salt in the absence of Co(NH3)63+. The 145 base pair DNA and poly (dGm5dC) are found to be essentially fully extended rods in low salt (0.2 - 2 mM Na+) solutions.

Combined in vitro activity of amphotericin B and 5-fluorocytosine against Cryptococcus neoformans and Candida albicans

The in vitro combined antifungal activity of amphotericin B (AMB) and 5-fluorocytosine (5-FC) against 10 strains of Candida albicans and 8 strains of Cryptococcus neoformans was studied. Serial twofold dilutions of AMB (0.1 to 12.8 micrograms/ml) were tested with serial twofold dilutions of 5-FC (0.39 to 400 micrograms/ml) by using the broth dilution method. A synergistic effect was seen for 17 strains with 50 micrograms of 5-FC per ml added to AMB. Only one strain was killed by 0.8 micrograms per ml or less of AMB alone, whereas all strains were killed with the addition of 50 micrograms of 5-FC per ml.

Sister-chromatid exchanges and cell-cycle delay in Chinese hamster V79 cells treated with 9 organophosphorus compounds (8 pesticides and 1 defoliant)

Significant increase of sister-chromatid exchanges (SCE) in V79 cells treated with 2 organophosphorus pesticides (OPP), fenthion and oxydemeton-methyl, was observed. The other 7 compounds (6 OPP and 1 defoliant) namely, amaze, azinphos-methyl, bolstar, DEF-defoliant, fensulfothion, monitor and nemacur caused no increase of SCE frequencies at the doses tested. All the compounds except fensulfothion and oxydemeton-methyl induced cell-cycle delay in varying degrees. Cell-cycle delay caused by an OPP was found to be dose-dependent. Based on these data as well as others reported, it would appear that OPP which induce no SCE increase and no or slight cell-cycle delay could be considered as good candidates to substitute the pesticides that have been found to be harmful to the environment.

Further studies on the generation of reactive oxygen species from activated anthracyclines and the relationship to cytotoxic action and cardiotoxic effects

The relative ease of generation of reactive oxygen species from a series of reductively activated aglycone and sugar modified anthracyclines was compared by the extents of single strand scission in supercoiled PM2-covalently closed circular (CCC)-DNA. The electrochemical properties of these agents were used as a quantitative measure of the ease of reduction and subsequent reoxidation of the reduced species. The relationship of these processes to various biological properties of the anthracyclines, in particular to the measured cardiotoxicity of the drugs, was examined. An attempt was made to identify those structural changes which ameliorate the cardiotoxic effects measured in other test systems while permitting the expression of antitumor properties.

Retinol (vitamin A) inhibits sister chromatid exchanges and cell cycle delay induced by cyclophosphamide and aflatoxin B1 in Chinese hamster V79 cells

Retinol (vitamin A alcohol) at the doses tested neither induced an increase of frequency of sister chromatid exchanges (SCE) nor cell cycle delay in Chinese hamster V79 cells with or without the metabolic activation of S-9 mix. However, it inhibited SCE frequencies and cell cycle delay in V79 cells induced by the indirect mutagen cyclophosphamide or aflatoxin B1. The inhibition was found to be dose and time dependent. These results suggest that retinol itself may have no direct effect on the genetic materials but rather exert its effects possibly by inhibiting the metabolic activation of an indirect mutagen or carcinogen. Thus, the antitumor activities of retinoids may not be limited to the widely accepted role of preventing the promotion step but also the initiation step of carcinogenesis.

Effects of retinoids on plating efficiency, sister-chromatid exchange (SCE) and mitomycin-C-induced SCE in cultured Chinese hamster cells

The effects of 5 retinoids, namely, all-trans-retinol (ROL), all-trans-retinoic acid (RA), all-trans-retinal (RAL), all-trans-retinyl acetate (RAc), and Ro. 10-9359-TMMP ethyl retinoate on plating efficiency, sister-chromatid exchange (SCE) and on mitomycin-C (MMC)-induced SCE were studied in Chinese hamster V79 cells. All the retinoids caused reduction of plating efficiency in a dose-dependent manner but the degree of plating efficiency reduction varied considerably among the retinoids studies. RAL was the most potent reducer of plating efficiency and this was followed in decreasing order by ROL, RAc, RA and Ro. 10-9359. For the effect of various doses of retinoids on SCE, it was clearly demonstrated that addition of each of the 5 retinoids to exponentially growing V79 cells had no significant effect on SCE frequency as compared to the controls. Besides this, these compounds did not alter DCS frequency induced by MMC.

Effect of tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate on induction of sister-chromatid exchanges in Chinese hamster V79 cells treated with mutagens

The effect of a tumor promoter, 12-O-tetradecanoyl-phorbol 13-acetate (TPA) alone and in combination with mitomycin C (MMC) or cyclophosphamide (CPP) on the induction of sister-chromatid exchanges (SCE) in Chinese hamster V79 cells was investigated. TPA alone at various doses and durations caused no increase of SCE frequency. MMC either at the dose of 0.03 or 0.003 microgram/ml alone or in combination with TPA (2 microgram/ml) all caused a significant increase of SCE frequencies. There was no difference in SCE frequencies between the cultures treated with MMC alone at 0.03 microgram/ml and those treated with MMC plus TPA. However, cultures treated with MMC at 0.003 microgram/ml plus TPA had significantly and consistently higher SCE frequencies than those treated with MMC alone at all durations. Treatment of CPP at 1 microgram/ml activated by S9 mix caused significant increase of SCE frequencies. Surprisingly, the cultures treated with CPP, S9 mix plus TPA (2 microgram/ml) caused a drastic reduction of SCE frequencies as compared to those treated with CPP and S9 mix only at all durations. These results indicate that TPA alone had no effect on SCE in V79 cells. TPA enhanced the SCE induction in V79 cells treated with MMC at a low dose, i.e. 0.003 microgram/ml, but it inhibited SCE induction in cultures treated with the indirect mutagen CPP. Thus, TPA has no direct effect on genetic materials but it may indirectly alter the effects of a mutagen.

Measurement of ethanolamine- and serine-containing phospholipids by high-performance liquid chromatography with fluorescence detection of their Dns derivatives

We describe a liquid chromatographic procedure for the analysis of amino group-containing phosphoglycerides in tissue. The total lipid extract is derivatized with Dns-chloride at 50 degrees C for 3 h. Dns derivatives of phosphatidylethanolamine, lysophosphatidylethanolamine, phosphatidylserine and lysophosphatidylserine are separated by a silica gel column with gradient elution. The eluate is monitored by fluorescence detection at 342 nm (excitation) and 500 nm (emission). Ethanolamine and serine plasmalogens can be determined indirectly by converting their derivatives into Dns-lysophosphatidylethanolamine and Dns-lysophosphatidylserine with exposure to HCl fumes. The optimal sample size for derivative formation and analysis by this method is between 1 and 10 nmol of phospholipids (30 and 300 ng of lipid phosphorus), although the lower limit of detection is about 20 pmol. By analyzing the total lipid extract of rat brain we showed that the method was applicable to the quantitative analysis of amino group-containing phosphoglycerides in tissue samples.

Studies on the effects of the antitumor agent camptothecin and derivatives on DNA. Camptothecin potentiated cleavage of DNA by bleomycin in vitro

Addition of sodium camptothecin (2a, Fig. 1) in comparable low concentrations to the glycopeptide antitumor antibiotic bleomycin (BLM) leads to enhanced rates of single-strand scission of PM2-covalently closed circular DNA, whereas sodium camptothecin alone has no effect. A similar enhancement of DNA scission by sodium camptothecin is produced with the 1 : 1 bleomycin-iron complex alone or in conjunction with NADPH as an additional reductant. The interpretation that camptothecin may substitute for the reducing requirement of the antibiotic is supported by its oxidation at 37 degrees C by the 1 : 1 bleomycin iron complex, by iron salts or more efficiently by hydrogen peroxide to the known hemiacetal (3, Fig. 1). Electrochemical studies of 2a, its analogues and selected model compounds established that the alpha-pyridone ring D is most susceptible to a one-electron reduction at a reversible potential of -0.95 +/- 0.01 V. The reduced camptothecin is a transient species readily capable of donating an electron. This process may by compatible with a coupled reduction of the sequestered Fe(III) in the glycopeptide antibiotic necessary for the expression of antibiotic and antitumor properties. The results may provide a mechanistic rationale for the observed potentiation of the antitumor activity of bleomycin by camptothecin in vivo.

Induction of sister-chromatid exchanges and cell cycle delay in cultured mammalian cells treated with eight organophosphorus pesticides

Induction of sister-chromatid exchanges (SCE) and cell cycle delay in Chinese hamster cell line V79 after treatment with 8 organophosphorus pesticides (OPP) were studied. In addition, these effects were also studied using 1 of the 8 OPP in 2 human lymphoid cell lines. In V79 cells, 6 of the 8 OPP induced significant increase of frequencies of SCE and all the OPP induced various degrees of cell cycle delay. The 6 OPP in decreasing order of SCE induction are methylparathion, demeton, trichlorfon, dimethoate, malathion and methidathion. The 2 OPP that had no effect on SCE are diazion and disyston. The extents of induced cell cycle delay are generally related to the OPP concentrations but does not necessarily correlate with the extent of induction of SCE among the OPP studied. The results of studies on the effect of methyl-parathion on SCE and cell cycle delay in 2 human cell lines showed that both lines had significant and dose-dependent increase of SCE frequencies similar to those observed in V79 cells. In contrast to V79 cells, however, cell cycle delay was not as prominent in the human lines at comparable doses. These studies indicated that 5-bromodeoxyuridine labeling for analyzing SCE and cell cycle delay is a very sensitive method in assessing mutagenic potential of environmental compounds especially those that are highly toxic to and rapidly degradable in mammalian cells such as OPP.

Plasma Membrane Alterations in Callus Tissues of Tuber-bearing Solanum Species during Cold Acclimation

Plasma membrane alterations in two tuber-bearing potato species during a 20-day cold acclimation period were investigated. Leaf-callus tissues of the frost-resistant Solanum acaule Hawkes ;Oka 3878' and the frost-susceptible, commonly grown Solanum tuberosum ;Red Pontiac,' were used. The former is a species that can be hardened after subjecting to the low temperature, and the latter does not harden. Samples for the electron microscopy were prepared from callus cultures after hardening at 2 C in the dark for 0, 5, 10, 15, and 20 days. After 20 days acclimation, S. acaule increased in frost hardiness from -6 to - 9 C (killing temperature), whereas frost hardiness of S. tuberosum remained unchanged (killed at -3 C). Actually, after 15 days acclimation, a -9 C frost hardiness level in S. acaule callus cultures had been achieved.Membrane protein particle aggregation was monitored using freeze-fracture electron microscopy. Protein particles were aggregated in S. acaule up to 10 days after the initiation of acclimation treatment and then redistributed almost to the level of control after 15 days. No such changes were observed for S. tuberosum under similar experimental conditions. The change in protein particle aggregation pattern in S. acaule is interpreted as indicating the presence of an adaptive fluidity control mechanism in that species.

Biochemical Changes in Tuber-bearing Solanum Species in Relation to Frost Hardiness during Cold Acclimation

Biochemical changes in potato leaves during cold acclimation have been examined and compared between a frost-tolerant S. acaule and a frost-susceptible S. tuberosum species. Changes were also examined in S. tuberosum, S. acaule, and S. commersonii species when they were hardened at different temperatures to varying hardiness levels.During three weeks of stepwise cold acclimation, S. acaule increased frost hardiness from -6.0 C (killing temperature) to -9.0 C, whereas frost hardiness of S. tuberosum remained unchanged at -3.0 C. Decreases in DNA content on a dry weight basis in both species suggest that matured leaf cells accumulated more dry matter during acclimation. The advantage of using DNA as a reference for comparing metabolite changes during cold acclimation is discussed.Under the stepwise acclimating conditions, both species showed the same trends for increasing total sugar and starch with an insignificant decrease in leaf water content. High levels of total RNA, rRNA, and total and soluble protein were observed in treated S. acaule plants as compared with controls, but not in S. tuberosum. Levels of total lipid and phospholipid also were high in treated S. acaule plants as compared with controls but decreased in S. tuberosum during acclimation.When S. tuberosum, S. acaule, and S. commersonii potatoes were cold-treated at constant day/night temperatures of 10, 5, and 2 C with 14-hour daylength, each species responds differently in terms of frost hardiness increase upon subjecting plants to a low temperature. For instance, after 20 days at 2 C, a net frost hardiness of 3 and 7 C was observed in S. acaule and S. commersonii, respectively, whereas the frost hardiness in S. tuberosum remained unchanged. Also, various levels of frost hardiness can be achieved in a species by subjecting plants to different low temperature treatments. Under a warm regime of 20/15 C day/night temperatures (14-hour light), both S. acaule and S. commersonii can survive at -4.5 C or colder, whereas S. tuberosum can survive only at -2.5 C.Biochemical changes in the leaf tissue of these species were investigated at 5-day intervals during low temperature treatments. Increases in total sugar and starch were found in all three species during hardening, although S. tuberosum failed to harden. Soluble protein contents were increased in both S. acaule and S. commersonii but decreased in S. tuberosum. RNA contents change in a pattern similar to the soluble protein. Net increases of the soluble proteins were positively and significantly correlated with net increases of frost hardiness in S. acaule and S. commersonii.

Sister chromatid exchanges and chromosome aberrations in V79 cells induced by aflatoxin B1, B2, G1 and G2 with or without metabolic activation

Cells from Chinese hamster cell line V79 were pulse treated for one hour with aflatoxin (AF) B1, B2, G1 and G2 at various doses with or without the metabolic activation system-S9 mix. With metabolic activation, all these toxins caused significant increases of frequencies of sister chromatid exchanges (SCE) in a dose-dependent manner. Based on the rate of SCE induction, the relative order of potency was established as AFB1 > G1 > G2 > B2. Without metabolic activation, all four toxins had no or very little effect over the same dose ranges used for SCE induction with activation. Induction of chromosome aberrations in V79 cells after a one hour pulse treatment with AFB1 and G1 plus S9 mix was also studied. A dose and time dependent increase of aberrations was observed for both compounds. AFB1 again is a more potent aberration inducer than AFG1.

Characteristics of Cold Acclimation and Deacclimation in Tuber-bearing Solanum Species

The effect of temperatures on cold acclimation and deacclimation in foliage tissues was studied in Solanum commersonii (Oka 4583), a tuber-bearing potato. The threshold temperature for cold acclimation was about 12 C. In a temperature range of 2 to 12 C, the increase in hardiness was dependent on the acclimating temperature; the lower the acclimating temperature, the more hardiness achieved. A day/night temperature of 2 C, regardless of photoperiod, appeared to the optimum acclimating temperature for the Solanum species studied. A subfreezing temperature hardened plants less effectively. The maximum level of hardiness could be reached after 15 days of cold acclimation. However, it took only 1 day to deacclimate the hardened plants to a preacclimation level when plants were subjected to a warm regime from cold. The degree of deacclimation was dependent on the temperature of the warm regime.Based on cold tolerance and the capacity to acclimate to cold, tuber-bearing Solanum species could be grouped into five categories. Chilling injury was also observed in some of the tuber-bearing Solanum species.

Hydroxyl radical production by free and DNA-bound aminoquinone antibiotics and its role in DNA degradation. Electron spin resonance detection of hydroxyl radicals by spin trapping

The reduced antitumor antibiotic mitomycin C in aqueous solution exposed to air gives a 36-line electron spin resonance spectrum of the semiquinone identified by computer simulation. Incubation of this radical with the spin trap N-tert-butyl-alpha-phenylnitrone (PBN) gives the PBN.OH nitroxide radical identified by independent generation. This nitroxide radical is also formed from similar treatment of a DNA to which mitomycin C is covalently attached. Incubation of the semiquinone from mitomycin C, mitomycin B, or streptonigrin (SN) with catalase or with superoxide dismutase inhibits the generation of OH, implying the intermediacy of H2O2 and O2 in its formation. The formation of the spin-trapped nitroxide radical is similarly inhibited by EDTA, suggesting the intermediacy of trace metal ions in the generation of hydroxyl radicals from SN. The results are consistent with the generation by the aminoquinone antibiotics in vivo of OH. already implicated in the degradation of DNA.

Interactions of low temperature, water stress, and short days in the induction of stem frost hardiness in red osier dogwood

The induction of stem frost hardiness by low temperature, water stress, short days, and their combinations in 2- and 4-month-old growing dogwoods (Cornus stolonifera) were investigated. When plants were subjected to more than one factor, the increased hardiness was the sum of the effects of the individual factors involved. No interactions among these factors on hardiness were observed during a 3-week treatment. Results indicate that low temperature, water stress, and short days initially trigger independent frost-hardening mechanisms. Plant ages significantly influenced the change in low temperature-induced frost hardiness, but not the water stress or short day-induced frost hardiness.