Upcycling the anthracyclines: New mechanisms of action, toxicology, and pharmacology

The anthracyclines are a family of natural products isolated from soil bacteria with over 2000 chemical representatives. Since their discovery seventy years ago by Waksman and co-workers, anthracyclines have become one of the best-characterized anticancer chemotherapies in clinical use. The anthracyclines exhibit broad-spectrum antineoplastic activity for the treatment of a variety of solid and liquid tumors, however, their clinical use is limited by their dose-limiting cardiotoxicity. In this review article, we discuss the toxicity of the anthracyclines on several organ systems, including new insights into doxorubicin-induced cardiotoxicity. In addition, we discuss new medicinal chemistry developments in the biosynthesis of new anthracycline analogs and the synthesis of new anthracycline analogs with diminished cardiotoxicity. Lastly, we review new studies that describe the repurposing of the anthracyclines, or "upcycling" of the anthracyclines, as anti-infective agents, or drugs for niche indications. Altogether, the anthracyclines remain a mainstay in the clinic with a potential new "lease on life" due to deeper insight into the mechanism underlying their cardiotoxicity and new developments into potential new clinical indications for their use. Keywords: Anthracycline, chemotherapy, toxicology, medicinal chemistry, biosynthesis.

A web-based pedometer programme in women with a recent history of gestational diabetes

AIMS

Women with remote histories of gestational diabetes mellitus can reduce their diabetes risk through lifestyle changes, but the effectiveness of interventions in women with more recent histories of gestational diabetes has not been reported. Therefore, we conducted a pilot study of a low-intensity web-based pedometer programme targeting glucose intolerance among women with recent gestational diabetes.

METHODS

Women with a gestational diabetes delivery within the past 3 years were randomized to a 13-week intervention consisting of a structured web-based pedometer programme which gave personalized steps-per-week goals, pedometers and education regarding lifestyle modification, or to a letter about diabetes risk reduction and screening after delivery for gestational diabetes (control condition). The main outcome measures were change in fasting plasma glucose and 2-h glucose levels on a 75-g oral glucose tolerance test between baseline and 13-week follow-up. Weight was a secondary outcome and behavioural constructs (self-efficacy, social support, risk perception) were also assessed.

RESULTS

Forty-nine women were enrolled. At 13-week follow-up, women randomized to the intervention did not have significant changes in behavioural constructs, physical activity or anthropometrics compared with women in the control group. Changes in fasting plasma glucose (-0.046 mmol/l vs. 0.038 mmol/l, P = 0.65), 2-h glucose values (-0.48 mmol/l vs. -0.42 mmol/l, P = 0.91) and weight (-0.14 kg vs. -1.5 kg, P = 0.13) were similar between the control and intervention groups, respectively.

CONCLUSIONS

Structured web-based education utilizing pedometers is feasible although uptake may be low. Such programmes may need to be supplemented with additional measures in order to be effective for reduction of diabetes risk.

Effects of dietary crude protein and supplemental urea levels on nitrogen and phosphorus utilization by feedlot cattle

Three dietary CP concentrations (11.5, 13.0, and 14.5% of DM) and 3 supplemental urea levels (100, 50, and 0% of supplemental N) were used in a completely randomized block design experiment conducted at 2 locations to determine N and P balance and serum urea N (SUN) concentrations of feedlot cattle. Crossbred steers [British and British x Continental; initial BW = 315.0 +/- 3.2 kg at location 1 (n = 27) and initial BW = 353.2 +/- 8.4 kg at location 2 (n = 27)] were used in 3 nutrient balance sampling periods (SP) at the beginning, middle, and end of the feeding period (154 d in location 1 and 159 d in location 2). Fecal N (g/d; P = 0.03), urinary N (g/d; P < 0.01), urinary urea N (UUN; g/d; P < 0.01), apparent N absorption (g/d; P < 0.01), and SUN concentration (mg/dL; P < 0.01) increased linearly as dietary CP concentration increased. Nitrogen retention (g/d) was not affected (P = 0.61) by dietary CP concentration. Phosphorus intake (g/d; P = 0.02), fecal P (g/d; P = 0.04), and urinary P (g/d; P = 0.01) increased linearly as dietary CP increased, reflecting changes in diet composition with increasing CP concentrations. As dietary urea levels increased, urinary N (g/d; P = 0.04), UUN (g/d; P = 0.01), and apparent N absorption (g/d; P = 0.04) increased linearly, but P intake (g/d; P = 0.10) and urinary P (g/d; P = 0.02) decreased linearly. No interactions were observed between SP and dietary treatments for most variables. Evaluation of SP means, however, showed that as days on feed increased, fecal N (g/d; P = 0.01), urinary N (g/d; P < 0.01), UUN (g/d; P < 0.01), apparent absorption of N (g/d; P < 0.01), SUN (mg/dL; P < 0.01), and urinary P (g/d; P < 0.01) increased linearly, whereas retained N (g/d) decreased linearly (P < 0.01) with increasing days on feed. These data suggest that changes in dietary CP and urea levels, as well as stage of the feeding period, markedly alter N and P utilization by feedlot cattle.

Influence of dietary crude protein concentration and source on potential ammonia emissions from beef cattle manure

Emissions of ammonia, as well as other gases and particulates, to the atmosphere are a growing concern of livestock producers, the general public, and regulators. The concentration and ruminal degradability of CP in beef cattle diets may affect urinary and fecal excretion of N and thus may affect ammonia emissions from beef cattle feed yards. To determine the effects of dietary CP concentration and degradability on potential ammonia emissions, 54 steers were randomly assigned to nine dietary treatments in a 3 x 3 factorial arrangement of treatments. Treatments consisted of three dietary CP concentrations (11.5, 13, and 14.5%) and three supplemental urea:cottonseed meal ratios (100:0, 50:50, and 0:100 of supplemental N). Steers were confined to tie stalls, and feces and urine excreted were collected and frozen after approximately 30, 75, and 120 d on feed. One percent of daily urine and feces excretion were added to polyethylene chambers containing 1,550 g of soil. Chambers were sealed, and ammonia emissions were trapped in an acid solution for 7 d using a vacuum system. As the protein concentration in the diet increased from 11.5 to 13%, in vitro daily ammonia emissions increased (P < 0.01) 60 to 200%, due primarily to increased urinary N excretion. As days on feed increased, in vitro ammonia emissions also increased (P < 0.01). Potential ammonia losses were highly correlated (P < 0.01) to urinary N (r2 = 0.69), urinary urea-N (r2 = 0.58) excretion, serum urea-N concentration (r2 = 0.52), and intake of degradable protein N (r2 = 0.23). Although dietary composition can affect daily ammonia losses, daily ammonia emissions must be balanced with effects on animal performance to determine optimal protein concentrations and forms in the diet.

Challenges in measuring moisture content of feeds

Accurate determination of the moisture (water) content in individual feed ingredients and mixed feeds is critical throughout the feed industry. Most analytical methods used to determine apparent water content of feedstuffs are empirical, estimating water by evaporation and loss of weight on drying (oven drying methods). These methods differ greatly in effectiveness, resulting in bias. Bias associated with measuring the water content of feedstuffs is a concern not only because of the lack of confidence in the moisture value itself, but also because moisture determinations affect accurate quantification and expression of other nutrient values. Methods for determining moisture in feeds have frequently been borrowed from the cereal, forage, or other applications without validating the extension of the method. Methods such as Karl Fischer titration measure water by direct comparison to a calibration standard for water and can be used as reference methods for the evaluation of empirical methods. The objective of this paper is to review methods for determining moisture, review comparisons among moisture methods for various feedstuffs, make recommendations for a reference method, and make general recommendations toward improving the results of moisture testing. The need to evaluate and improve moisture methods and standardize practices in laboratories is evident from this study. It also is evident that the methods appropriate for a specific feed ingredient or feed should not be extended to all feeds without proper validation to the new matrices. Part of the validation for empirical methods should be comparison to Karl Fischer or other the direct methods. It also is recommended that the results obtained using oven methods not be termed "moisture;" rather, they should be termed "loss on drying," and the drying conditions should become part of the term.

Propranolol for the prevention of first esophageal variceal hemorrhage: a lifetime commitment?

Although beta blockers have had significant impact in the treatment of portal hypertension, the question of how long they should be continued for prevention of variceal hemorrhage remains unknown. Prospective studies on beta blockers to prevent variceal hemorrhage lack long-term follow-up, and indefinite administration of beta blockers for primary prevention of variceal bleeding has become standard practice. The aim of this study was to determine the outcomes of patients in whom beta blocker therapy was discontinued. Patients completing a prospective, randomized, double-blind, placebo-controlled trial of propranolol for the primary prevention of variceal hemorrhage were tapered off of propranolol and placebo and followed prospectively for subsequent events. Of the 49 patients in the follow-up study (25 former propranolol, 24 former placebo), 9 experienced variceal hemorrhage (6 former propranolol, 3 former placebo). Following withdrawal of propranolol, the freedom from variceal bleeding was not significantly different between these 2 groups of patients, suggesting that the protective effect of propranolol against variceal hemorrhage, noted previously, was no longer present. Seventeen patients died (12 former propranolol, 5 former placebo) during the follow-up study. Cumulative survival was longer in the placebo group. These trends for EVH and survival were opposite to those observed in the original study population while patients were taking medication. When propranolol is withdrawn, the risk of variceal hemorrhage returns to what would be expected in an untreated population. Patients who discontinue beta blockers experience increased mortality compared with an untreated population. These observations support the current practice of indefinite prophylactic therapy.

Root reshaping: an integral component of periodontal surgery

It is the aim of this article to present a surgical option to the traditional method of returning lost biologic width where invasion of the junctional and/or connective tissue attachment associated with a tooth has occurred. The alternative to conventional osseous resection involves reshaping the existing tooth surface in combination with conservative removal of the supporting alveolar bone to create the width needed for the restoration to be biologically acceptable. This procedure accomplishes several goals: (1) minimum supporting bone is removed; (2) deleterious root surface anatomy, such as grooves, concavities, and cementoenamel projections, is diminished; (3) a smooth root surface that is more biologically acceptable to soft tissue is created; (4) Class I and II furcation lesions may be decreased or eliminated; and (5) improved gingival contours and space for restorative materials can be created in situations in which close root proximity is present. This article will present a step-by-step approach to using root reshaping as an alternative to traditional crown lengthening.

Voluntary intake, digestibility, and subsequent selection of Matua bromegrass, coastal bermudagrass, and alfalfa hays by yearling horses

Matua bromegrass (Bromus willdenowii Kunth. cv. Grasslands Matua) was introduced in 1973, but little information exists concerning its potential as a hay for horses. Thus, voluntary intake and apparent digestibility of OM, CP, and fiber components of Matua by 18 Quarter Horse yearlings (mean initial BW 354 kg; SE 5.8) were compared with alfalfa (Medicago sativa L.) and coastal bermudagrass (Cynodon dactylon L.) as hays in a randomized block design. A 15-d adjustment period was followed by a 5-d collection period during which the hays were consumed ad libitum. Voluntary intake of DM was greater (P<.01) for alfalfa (10.9 kg/d) than for the mean of the grasses, and intake of Matua (10.0 kg/d) was greater (P<.001) than that of bermudagrass (7.4 kg/d). Apparent digestibility of OM was greater (P<.001) for alfalfa (74%) than for the mean of the grasses but did not differ between Matua (64%) and bermudagrass (60%). At the end of the digestion trial, each yearling was offered each of the three forage hays during an 11-d period to determine subsequent preference and effect of previous hay experience. Yearlings preferred alfalfa over the grass hays and generally selected more Matua than bermudagrass. All yearlings consumed less of the forage species to which they had been previously exposed compared with unadapted yearlings. The Matua hay fed in this trial was palatable and met most of the nutritional needs for yearling horses.

Clinical evaluation of Bio-Oss: a bovine-derived xenograft for the treatment of periodontal osseous defects in humans

The purpose of this study was to compare the bovine derived xenograft (BDX) Bio-Oss to demineralized freeze dried bone allograft (DFDBA) in human intrabony defects. 17 healthy patients with no systemic disease with moderate-severe periodontitis (7 males, 10 females; aged 34-67), were treated. Surgically, defects were included only if the intraosseous defect depth was >3.0 mm. Final selection included 30 defects. The sites were randomly assigned treatment with DFDBA or BDX. Soft tissue and osseous defect measurements were taken the day of surgery and 6 months post-operatively at re-entry. Average baseline PD, CAL, and surgical defect depth for the DFDBA group were not statistically different from the BDX group. No adverse healing response occurred. The results showed a statistically significant improvement in PD and AL for both materials at 6 months in 26 defects (4 defects did not respond to therapy). Soft tissue measurements for the DFDBA group included PD reduction of 2.0+/-1.3 mm, and AL gain of 2.6+/-1.6 mm, while the BDX group showed a PD reduction of 3.0+/-1.7 mm, and AL gain of 3.6+/-1.8 mm. Osseous measurements showed bone fill of 2.4 mm (46.8%) for the DFDBA group and 3.0 mm (55.8%) for the BDX group. Defect resolution was 59.4% for the DFDBA group and 77.6% for the BDX group. Statistical analysis revealed there was no statistical difference between the 2 materials in all measurements.

A multipurpose template for implant placement

A case report is presented describing the laboratory fabrication and clinical use of an innovative template. This template was designed to function as a radiographic implant positioning guide, accurate bone sounding guide, and surgical guide. This appliance is intended to serve additional roles as an aid in flap reflection and as a pick-up impression tray.

Inactivity of ethyl acrylate in the mouse bone marrow micronucleus assay

We report ethyl acrylate to be inactive as a micronucleus-inducing agent in the bone marrow of mice following its i.p. injection in either corn oil or water. These data contrast with a strong positive response in this assay reported earlier. This discrepancy is discussed.

Inactivity of methylene chloride in the mouse bone marrow micronucleus assay

Methylene chloride (MC) has been evaluated for its ability to induce micronucleated polychromatic erythrocytes (MPEs) in the bone marrow of treated mice. Groups of five male and five female C57BL/6J/Alpk mice were exposed, by gavage, to doses of 4000, 2500 and 1250 mg/kg MC in corn oil, the highest dose-level being selected to be the maximum tolerated dose. Bone marrow samples were taken 24, 36, 48 and 72 h after dosing. No significant increases in the incidence of MPEs over controls were observed for any of the test groups, and it is concluded that MC is not clastogenic in this assay.

Feedlot performance and carcass characteristics of steers fed diets containing ammonium salts of the branched-chain fatty acids and valeric acid

Two trials were conducted to study the effects of feeding a mixture of ammonium salts of isovaleric, 2-methylbutyric, isobutyric and valeric acids (AS-VFA) on feedlot performance and carcass characteristics of growing and finishing Angus, Hereford and Angus X Hereford steers. In trial 1,192 steers (8 steers/pen, 6 pen/treatment) averaging 251 kg body weight and in trial 2, 240 steers (8 steer/pen, 7 pens/treatment, 9 pens/control treatment) averaging 216 kg body weight were randomly assigned to four anhydrous ammonium salt-volatile fatty acid (AS-VFA) treatment levels: 0 (control), .14, .28 and .42% of the diet dry matter (DM). In each trial, the growing and finishing diets were isocaloric, isonitrogenous and supplemented with monensin (26 mg/kg diet). In both trials, steers received implants of 200 mg progesterone and 20 mg estradiol benzoate. Combined data from the trials confirmed the absence of average daily gain and feed conversion responses during the growing period. During the finishing period, the combined data for gain and feed conversion for the control steers and the steers fed .14, .28 and .42% AS-VFA were 1.43, 7.09; 1.43, 6.99; 1.48, 6.67 and 1.45, 6.80, respectively. Gains increased 3.5% (P less than .10) and feed conversion improved 5.9% (P less than .07) in steers fed .28% AS-VFA compared with gain and feed conversion of the control steers. At the end of the growing period in the first trial, a urea dilution technique was used to estimate the body composition of 12 steers from each treatment. Estimates of percent body fat and percent body protein were similar (P greater than .20) for all steers, irrespective of treatment. At the end of the trials, carcass yield grades for the combined data were 2.6 and 2.8 (P less than .10) for steers fed .28% AS-VFA and for the control steers, respectively. Carcass weight, dressing percentage and marbling score were lower (P less than .10) in steers fed AS-VFA than for steers fed the control. However, in general, carcass characteristics were not greatly influenced by AS-VFA. A possible use for a supplement containing branched-chain fatty acids and valeric acid in finishing steer diets is suggested by the improvement in feedlot performance and by the slight increase in carcass yield.

Tabulation and assessment of 113 human surveillance cytogenetic studies conducted between 1965 and 1984

There is an increasing tendency to monitor human exposure to genotoxic chemicals by the assessment of chromosomal aberrations or sister-chromatid exchanges (SCEs) in peripheral blood lymphocytes. In order to assess the sensitivity of these techniques, and to discern minimal criteria for their conduct, a survey of 113 human lymphocyte cytogenetic surveillance studies conducted between 1965 and 1984 has been undertaken. The present survey indicates the urgent need for standardization of study protocols. It is suggested that a common method of reporting chromosomal aberrations should be adopted, and that this should be based on the system described by Scott et al. It is also suggested that a minimum acceptable size of control and exposed populations should be agreed, and that potentially important factors such as the gender, the period and extent of exposure and individual smoking habits be defined in advance of the commission of future surveillance studies. As general awareness of the possible hazard presented by exposure of man to genotoxic chemicals increases, so appropriate preventative industrial hygiene measures will be instituted. This implies that future human cytogenetic surveillance studies may yield either weakly positive or negative data. This emphasizes the current need for agreement on appropriate study protocols. The formation of a central repository for control databases, and its subsequent updating and use by those involved in human cytogenetic surveillance studies, is recommended. Minimal experimental criteria for the design of future studies are also outlined.

Chloracetamide-N-metholol: an example of an in vitro and in vivo clastogen which is non-mutagenic to Salmonella

The industrial biocide chloracetamide-N-metholol (CAM) has been shown to be non-mutagenic to 6 strains of Salmonella using both the plate-incorporation and a pre-incubation test protocol. Its biocidal activity is unlikely to have influenced these results since Kathon 886, a more potent biocide, was concomitantly detected as mutagenic to strain TA100. In contrast, CAM was weakly clastogenic to human lymphocytes cultured in vitro and elicited a positive response in the mouse bone marrow micronucleus test when assayed using the intraperitoneal, but not the oral route of administration. A positive response was concomitantly observed for the rodent carcinogen and formaldehyde-releasing agent hexamethylphosphoramide (HMPA) in these 2 clastogenicity assays. Data are presented showing the slow hydrolysis of CAM to formaldehyde in vitro, and both [carbonyl-14C]CAM and [metholol-14C]CAM have been shown to interact covalently with calf-thymus DNA in vitro. It is concluded that CAM may be a direct-acting carcinogen to rodents, but that both the qualitative and quantitative outcome of its bioassay for carcinogenicity will be influenced critically by the bioassay protocol adopted; in particular, by the route of administration selected. These findings emphasize the need to complement the Salmonella gene-mutation assay with an in vitro assay for the induction of chromosomal aberrations if in vivo genotoxins are to be detected efficiently in vitro.

Activity of bromochlorodifluoromethane (BCF) in three mutation tests

The halocarbon BCF was tested in 3 assays to assess its mutagenicity and clastogenicity. It produced a positive response in Salmonella typhimurium strain TA1535 but was negative in TA1537, TA1538, TA98 and TA100. In an L5178Y mouse lymphoma microwell assay (TK locus), BCF was negative. BCF was administered at 5000 and 50 000 ppm in air for 6 h to groups of C57B1/6J mice of both sexes. Animals were killed at 24, 48 and 72 h after cessation of exposure and the incidence of bone marrow micronuclei per 1000 PCEs determined. There was no significant difference in the incidences of micronuclei between untreated animals and those exposed to either concentration of BCF at any of the sampling times. These results suggest that BCF is mutagenic in vitro in only one strain of Salmonella; in mammalian cells the compound induced no gene mutation in vitro nor clastogenic activity in vivo at doses that also produced clear evidence of toxicity.

The human lymphocyte in vitro cytogenetic assay: positive and negative control observations on approximately 30000 cells

Data are presented from the cytogenetic analysis of the peripheral lymphocytes from 94 male and 15 female donors. However, a much smaller number of regular donors were selected for regular use. A total of 28674 cells were analysed and these acted as negative and positive controls in the in vitro human lymphocyte tests accumulated in this laboratory over a 6-year period. The significant observations were:. (1) in untreated and solvent control treated cultures (a) no chromosomal interchanges were observed in 21570 cells; (b) the incidence of dicentrics was less than 1 per 10000 cells; (c) other types of aberrations were seen with an increased frequency, chromosomal gaps being the most variable. (2) The reference clastogens mitomycin C and cyclophosphamide produced high and remarkably consistent yields of all types of aberrations. It is concluded that when screening compounds in vitro for new genotoxins, aberrations such as chromosomal interchanges and dicentrics (due to their rarity in negative control cultures) should be accorded greater significance than the several other types of aberrations routinely seen. These conclusions emphasize the value of maintaining and updating adequate historical control records.

Cytogenetic effects of benzene: dosimetric studies on rats exposed to benzene vapour

Rats were exposed to benzene vapour at nominal concentrations in air of 1, 10, 100 and 1000 ppm acutely for 6 h. Bone marrow cells from each animal were examined for chromosomal abnormalities 24 h after the end of the exposure period. This analysis was carried out on 250 metaphases per animal where possible and showed a significant increase in the percentage of cells with chromosomal abnormalities, excluding gaps, in the groups of animals exposed to 100 and 1000 ppm benzene. In the 10-ppm and 1-ppm exposure groups there were elevated levels of cells with abnormalities which showed evidence of being dose-related, although they were not statistically significant.

Evaluation of some formaldehyde-release compounds and other biocides in the mouse micronucleus test

A number of biocidal chemicals were tested for clastogenic activity in the micronucleus test using C57Bl/6J mice. The materials tested were: 5-chloro-2-methyl-4-isothiazolin-3-one (I), N-methyl-isothiazolone hydrochloride (II), Glokill 77 and Parmetol A23. Two of the biocides (Glokill and Parmetol) depend on the release of formaldehyde for their activity while the other two compounds are the active chemicals in the biocide Kathon. Hexamethylphosphoramide (HMPA) was tested as the positive control for the series and N,N-dinitrosopentamethylenetetramine (DNPT) as the negative control. HMPA produced significant dose-related increases in the incidence of micronuclei whereas DNPT, I, II, Glokill and Parmetol A23 were without effect.

A comparison of the incidence of micronuclei in blood and bone marrow in 3 strains of mouse dosed with cyclophosphamide or hexamethylphosphoramide (HMPA)

The response of 3 strains of mouse (C57Bl/6J, C3H/C57 hybrid and BALBC/CBA) to cyclophosphamide (75 mg/kg) and hexamethylphosphoramide (HMPA) (1.28 ml/kg) were compared in the micronucleus test. Each compound was administered by intraperitoneal injection on two consecutive days and samples of bone marrow and blood taken for examination at 48 and 72 h after the first injection. Both test chemicals produced a statistically significant increase (P 0.001) in the incidence of micronuclei in bone marrow cells in all strains at both sampling times but the response with HMPA in C57Bl/6J mice appears to occur earlier than in the other two strains. Significant increases in micronuclei were seen in circulating erythrocytes only at 48 h in C57Bl/6J mice with both test chemicals and in C3H/C57 mice only with cyclophosphamide.

Activity of vinyl chloride monomer in the mouse micronucleus assay

C57Bl/6J mice of both sexes were exposed to 50 000 ppm vinyl chloride monomer (VCM) for 6 h. Animals were killed 24 and 48 h after cessation of exposure and examined for the presence of micronuclei in bone marrow cells. At 24 h the control incidences of micronuclei per 1000 polychromatic erythrocytes (PCEs) were 2.6 (male) and 1.2 (female), while in animals exposed to VCM the incidences were 24.6 (male) and 25.0 (female). At 48 h the control incidences were 2.2 (male) and 1.6 (female) and in the VCM exposed animals 7.2 (male) and 4.4 (female).

An assessment of the clastogenic potential of 4-chloromethylbiphenyl in human lymphocytes in vitro

The clastogenic potential of 4CMB was assessed in vitro in human lymphocytes from 4 donors (2 male and 2 female) both with and without auxiliary metabolic activation. Although there were some variation in the response of the cells from different donors to 4CMB using 2 criteria for interpretation of the results; it was concluded that 4CMB was a clastogen, but only at dose levels that caused some cytotoxicity. The response was amplified by the inclusion of chromatid and chromosome gaps in the analysis of chromosome damage.

Issues relevant to the assessment of chemically induced chromosome damage in vivo and their relationship to chemical mutagenesis

Rats have been exposed by different routes of administration (inhalation, orally and intraperitoneally) to known mutagens and their bone-marrow cells sampled at different times to determine the extent of chromosome damage. The mutagens investigated were ethyl methanesulphonate, mitomycin C, trimethylphosphate, benzene and vinyl chloride, at single and/or multiple doses (5 consecutive daily). Various categories of chromosome damage were observed in all cases. However, the extent of damage due to chromosome and chromatid gaps was greater than, and generally increased in parallel with, other categories of damage. It has been suggested tht chromosome and chromatid gaps are indicative of toxic phenomena but this study suggests that such aberrations could be useful and sensitive indicators of chemically induced genetic damage. In addition the study has also confirmed that single exposure is as effective as multiple exposure in producing chromosome damage and that the correct sampling time is necessary to detect this damage. Therefore for screening purposes a time course sampling after a single treatment regime would be suitable for detecting the mutagenic potential of a chemical.

Chromosomal analysis in vinyl chloride exposed workers: comparison of the standard technique with the sister-chromatid exchange technique

A group of 21 workers occupationally exposed to vinyl chloride and 6 controls were examined for the presence of chromosomal aberrations or sister-chromatid exchanges in their peripheral lymphocytes. These people comprised a second sampling from a group of exposed workers and controls first examined 18 months earlier. The vinyl chloride exposed workers showed levels of chromosomal aberrations elevated above those of the controls, but there was only a slight increase in sister-chromatid exchanges (per cell or per chromosome) and this increase was not statistically significant. Sister-chromatid exchanges (SCEs) were also examined from in vitro cultures of lymphocytes exposed in G0/early G1 and late G1/early S phase to vinyl chloride, both with and without metabolic activation. There was no increase in SCEs in vitro without metabolic activation but there was a marked increase with metabolic activation and this increase was shown to be independent of cell-cycle phase. It thus was apparent that the small increases of SCEs in workers were not due to the inability of vinyl chloride to induce SCEs in human lymphocytes but were probably because of low exposures and SCE levels could have returned to normal relatively quickly after exposure. The present study suggested that the analysis of longer-living conventional chromosomal aberrations appeared to be a more sensitive monitor of exposure to vinyl chloride in exposed workers than the estimation of SCEs; however, it should be noted that in a 3rd sampling taken 24 months later the exposed workers had chromosomal aberration levels similar to the controls.

The genotoxic potential of bases and nucleosides

This study was conducted to determine if naturally occurring cell constituents could themselves cause mutation. All the bases and their corresponding nucleosides have been shown to produce chromosome damage in P338 mouse lymphoma and Chinese hamster ovary cells in culture. In addition thymidine has produced an increase in V79 cells resistant to 8-azaguanine and ouabain. Such damage probably arises as a result of imbalanced DNA-precursor pools. Thus mutagenic events may arise by mechanisms unrelated to direct alterations to DNA.

Chromosomal analyses in vinyl chloride exposed workers. Results from analysis 18 and 42 months after an initial sampling

In a previous study (Purchase et al., Mutation Res., 57 (1978) 325-334) it was reported that 57 workers occupationally exposed to vinyl chloride had an increase in the incidence of chromosomal abnormalities in their lymphocytes by comparison with 24 control workers. Since that time (July 1974) threshold limit values for vinyl chloride and plant exposure levels have been reduced. In the present study, 2 further samples from the same population of workers have been analysed for chromosomal aberrations 18 and 42 months after the initial sampling. At 18 months, 21 VC workers and 6 on-site controls were investigated as were 23 workers and 8 on-site controls at 42 months. In the second sampling there was a tendency to an increase in chromosomal abnormalities of VC-exposed workers except in those people who had changed occupation. By the third sampling, however, there was a decrease by comparison with previous samplings and the levels of abnormalities had returned to values similar to those of the controls. Thus, reduction in exposure to vinyl chloride is accompanied by a reduction in the chromosomal abnormalities to levels indistinguishabe from those of controls.

Digestibility of chemically treated cotton plant byproduct and effect on mineral balance, urine volume and pH

Effects of chemical treatment of cotton byproduct (CBP) on apparent digestibility, mineral balance, urine volume and pH and in vitro digestibility were studied in three experiments with growing lambs and a rumen-fistulated steer. Apparent dry matter digestibility (DMD) and apparent organic matter digestibility (OMD) of total diets were increased (P < .01) by 35.4 and 35.7% in Exp. 1, and by 16.2 and 13.6% in Exp. 3. The CBP was treated wih 4% (4 kg sodium hydroxide/96 kg CBP dry matter) sodium hydroxide (NaOH) and fed at 70% of the total dietary intake. Treatment of CBP with nitric and sulfuric acid increased (P < .01) both DMD and OMD 25% (Exp. 1). In Exp. 2, NaOH treatment decreased (P < .05) organic matter, cellulose and lignin content of CBP and increased (P < .05) ash content. In vitro digestibilities of dry matter, organic matter and cell walls were increased (P < .05) by NaOH treatment. Volume of urine excreted by lambs in Exp. 1 and 3 was increased (P < .05) 53% but urine pH was affected by NaOH treatment. Acid treatment, however, resulted in a decrease (P < .01) in urine pH (9.4 vs 5.3). Feeding NaOH-treated CBP at increasing percentages of the diet increased Na balance and decreased K, Cl and Mg balance. NaOH-treated CBP had no effect on Ca or P balance. These results indicate the NaOH treatment of cotton byproduct increases apparent digestibility and that consumption of the treated product may increase the animal's requirement of K, Cl and Mg. Furthermore, urine volume is increased but urine pH is not affected by NaOH treatment.

Cancer of the endometrium---a multiparametric study

Haematological and immunological studies were performed on 36 patients with carcinoma of the endometrium prior to treatment. Haematological and coagulation studies, excluding fibrinogen, showed only minimal abnormality. However, tests for acute phase reactant proteins were abnormal in the majority of patients. There was a reduction in T cells in 31% of patients and a reduction in stimulation with PHA and PWM in 84 and 42% of patients, respectively. Autoantibodies to normal tissue antigens were present in half the patients and immune complexes were increased in 45% of patients. Carcinoembryonic antigen and B(2)-microglobulin were increased in 27 and 47% of patients respectively. Although specific tests for endometrial cancer are not yet available, a profile of tests might be of value in the diagnosis and follow-up of patients with the condition.

Chromosomal analyses in vinyl chloride-exposed workers

Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973--1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, gamma-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important.