Comparison of Germ Cell Mutagenicity in Male CYP2E1-Null and Wild-Type Mice Treated with Acrylamide: Evidence Supporting a Glycidamide-Mediated Effect

Acrylamide is an animal carcinogen and probable human carcinogen present in appreciable amounts in heated carbohydrate-rich foodstuffs. It is also a germ cell mutagen, inducing dominant lethal mutations and heritable chromosomal translocations in postmeiotic sperm of treated mice. Acrylamide's affinity for male germ cells has sometimes been overlooked in assessing its toxicity and defining human health risks. Previous investigations of acrylamide's germ cell activity in mice showed stronger effects after repeated administration of low doses compared with a single high dose, suggesting the possible involvement of a stable metabolite. A key oxidative metabolite of acrylamide is the epoxide glycidamide, generated by cytochrome P4502E1 (CYP2E1). To explore the role of CYP2E1 metabolism in the germ cell mutagenicity of acrylamide, CYP2E1-null and wild-type male mice were treated by intraperitoneal injection with 0, 12.5, 25, or 50 mg acrylamide (5 ml saline)(-1) kg(-1) day(-1) for 5 consecutive days. At defined times after exposure, males were mated to untreated B6C3F1 females. Females were killed in late gestation and uterine contents were examined. Dose-related increases in resorption moles (chromosomally aberrant embryos) and decreases in the numbers of pregnant females and the proportion of living fetuses were seen in females mated to acrylamide-treated wild-type mice. No changes in any fertility parameters were seen in females mated to acrylamide-treated CYP2E1-null mice. Our results constitute the first unequivocal demonstration that acrylamide-induced germ cell mutations in male mice require CYP2E1-mediated epoxidation of acrylamide. Thus, CYP2E1 polymorphisms in human populations, resulting in variable enzyme metabolic activities, may produce differential susceptibilities to acrylamide toxicities.

Antiretroviral therapy effects on genetic and morphologic end points in lymphocytes and sperm of men with human immunodeficiency virus infection

Many human immunodeficiency virus (HIV)-infected persons receive prolonged treatment with DNA-reactive antiretroviral drugs. A prospective study was conducted of 26 HIV-infected men who provided samples before treatment and at multiple times after beginning treatment, to investigate effects of antiretrovirals on lymphocyte and sperm chromosomes and semen quality. Several antiretroviral regimens, all including a nucleoside component, were used. Lymphocyte metaphase analysis and sperm fluorescence in situ hybridization were used for cytogenetic studies. Semen analyses included conventional parameters (volume, concentration, viability, motility, and morphology). No significant effects on cytogenetic parameters, semen volume, or sperm concentration were detected. However, there were significant improvements in sperm motility for men with study entry CD4 cell counts >200 cells/mm(3), sperm morphology for men with entry CD4 cell counts < or =200 cells/mm(3), and the percentage of viable sperm in both groups. These findings suggest that nucleoside-containing antiretrovirals administered via recommended protocols do not induce chromosomal changes in lymphocytes or sperm but may produce improvements in semen quality.

Etoposide induces heritable chromosomal aberrations and aneuploidy during male meiosis in the mouse

Etoposide, a topoisomerase II inhibitor widely used in cancer therapy, is suspected of inducing secondary tumors and affecting the genetic constitution of germ cells. A better understanding of the potential heritable risk of etoposide is needed to provide sound genetic counseling to cancer patients treated with this drug in their reproductive years. We used a mouse model to investigate the effects of clinical doses of etoposide on the induction of chromosomal abnormalities in spermatocytes and their transmission to zygotes by using a combination of chromosome painting and 4',6-diamidino-2-phenylindole staining. High frequencies of chromosomal aberrations were detected in spermatocytes within 64 h after treatment when over 30% of the metaphases analyzed had structural aberrations (P < 0.01). Significant increases in the percentages of zygotic metaphases with structural aberrations were found only for matings that sampled treated pachytene (28-fold, P < 0.0001) and preleptotene spermatocytes (13-fold, P < 0.001). Etoposide induced mostly acentric fragments and deletions, types of aberrations expected to result in embryonic lethality, because they represent loss of genetic material. Chromosomal exchanges were rare. Etoposide treatment of pachytene cells induced aneuploidy in both spermatocytes (18-fold, P < 0.01) and zygotes (8-fold, P < 0.05). We know of no other report of an agent for which paternal exposure leads to an increased incidence of aneuploidy in the offspring. Thus, we found that therapeutic doses of etoposide affect primarily meiotic germ cells, producing unstable structural aberrations and aneuploidy, effects that are transmitted to the progeny. This finding suggests that individuals who undergo chemotherapy with etoposide may be at a higher risk for abnormal reproductive outcomes especially within the 2 months after chemotherapy.

Range of motion and motion patterns in patients with low back pain before and after rehabilitation

STUDY DESIGN

Data were collected from 27 patients who were participating in a rehabilitation program for chronic low back pain. The patients were tested on day 2 and day 11 of a 2-week rehabilitation program.

OBJECTIVES

To determine specific characteristics of trunk motion associated with long-term dysfunction caused by low back pain of various origin, to determine if a neural network analysis system can be effective in distinguishing between patterns, and to determine if the rehabilitation has an effect on range and pattern of motion.

SUMMARY OF BACKGROUND DATA

There is a lack of objective measures for evaluating the efficacy of rehabilitation programs. Numerous studies have established the difficulty of evaluating low back pain. Existing techniques, such as imaging methods, are in many cases either very rough and inaccurate or expensive and ineffective. A technique for evaluation of motion patterns in low back pain was developed based on analysis of dynamic motion features such as shape, velocity, and symmetry of movements.

METHODS

Dynamic motion data were collected before and after rehabilitation from 27 patients with low back pain by using a triaxial goniometer. Range of motion and features of the movement, such as shape, velocity, and repetitiveness, were extracted for analysis.

RESULTS

Motion features showed significant improvement after the rehabilitation program.

CONCLUSIONS

A neural network based on kinematic data is an excellent model for classification of low back pain dysfunction. Such a system could markedly improve the management of low back pain for an individual patient.

Classification of low back pain from dynamic motion characteristics using an artificial neural network

STUDY DESIGN

Data were collected from 183 subjects who were randomly assigned to the training and test groups. During testing of the classification system, knowledge of the low back pain condition or motion characteristics of the patients in the test group was not made available to the system.

OBJECTIVES

To determine specific characteristics of trunk motion associated with different categories of spinal disorders and to determine whether a neural network analysis system can be effective in distinguishing patterns.

SUMMARY OF BACKGROUND DATA

Numerous studies have established the difficulty of evaluating lower back pain. Imaging techniques are expensive and ineffective in many cases. A technique for evaluation of lower back pain was developed on the basis of analysis of such dynamic motion features as shape, velocity, and symmetry of movements, using a neural network classification system.

METHODS

Dynamic motion data were collected from 183 subjects using a triaxial goniometer. Features of the movement were extracted and provided as input to a two-stage neural network classifier governed by a radial basis function architecture. After training, the output of the classifier was compared with Québec Task Force pain classifications obtained for the patients. Linear and nonlinear classification techniques were compared.

RESULTS

The system could determine low back pain classification from motion characteristics. The neural network classifier produced the best results with up to 85% accuracy on novel "validation" data.

CONCLUSIONS

A neural network based on kinematic data is an excellent predictive model for classification of lower back pain. Such a system could markedly improve the management of lower back pain in the individual patient.

Genetic toxicities of human teratogens

Birth defects cause a myriad of societal problems and place tremendous anguish on the affected individual and his or her family. Current estimates categorize about 3% of all newborn infants as having some form of birth defect or congenital anomaly. As more precise means of detecting subtle anomalies become available this estimate, no doubt, will increase. Even though birth defects have been observed in newborns throughout history, our knowledge about the causes and mechanisms through which these defects are manifested is limited. For example, it has been estimated that around 20% of all birth defects are due to gene mutations, 5-10% to chromosomal abnormalities, and another 5-10% to exposure to a known teratogenic agent or maternal factor [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis. Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500; K. Nelson, L.B. Holmes Malformations due to presumed spontaneous mutations in newborn infants, N. Engl. J. Med. 320 (1989) 19-23.]. Together, these percentages account for only 30-40%, leaving the etiology of more than half of all human birth defects unexplained. It has been speculated that environmental factors account for no more than one-tenth of all congenital anomalies [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis, Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500]. Furthermore, since there is no evidence in humans that the exposure of an individual to any mutagen measurably increases the risk of congenital anomalies in his or her offspring' [J.F. Crow, C. Denniston, Mutation in human populations, Adv. Human Genet. 14 (1985) 59-121; J.M. Friedman, J.E. Polifka, Teratogenic Effects of Drugs: A Resource for Clinicians (TERIS). The John Hopkins University Press, Baltimore, 1994], the mutagenic activity of environmental agents and drugs as a factor in teratogenesis has been given very little attention. Epigenetic activity has also been given only limited consideration as a mechanism for teratogenesis. As new molecular methods are developed for assessing processes associated with teratogenesis, especially those with a genetic or an epigenetic basis, additional environmental factors may be identified. These are especially important because they are potentially preventable. This paper examines the relationships between chemicals identified as human teratogens (agents that cause birth defects) and their mutagenic activity as evaluated in one or more of the established short-term bioassays currently used to measure such damage. Those agents lacking mutagenic activity but with published evidence that they may otherwise alter the expressions or regulate interactions of the genetic material, i.e. exhibit epigenetic activity, have likewise been identified. The information used in making these comparisons comes from the published literature as well as from unpublished data of the U.S. National Toxicology Program (NTP).

Alterations in the reproductive patterns of female mice exposed to xenobiotics

Chemicals, by virtue of their varied interactions with biological molecules, are expected to differ in the way they may alter female reproduction. Reproductive toxicity may reflect effects either on the female germ cells or on various maternal processes such as ovulation, implantation, pregnancy, and parturition. In either case, the ultimate manifestation of chemical toxicity on female reproduction is a decrease in the number of normal young born. Very little information is available on the effects of chemicals that are nonhormonal in nature on the long-term ability of treated females to produce offspring. This report presents the results of long-term female total reproductive capacity (TRC) tests on 29 chemicals, including pharmaceuticals, pesticides, and alkylating and industrial agents. For each chemical, the minimum test involved an evaluation of the maximum tolerated dose administered as a single intraperitoneal injection. Females were single-pair mated with an untreated male for most of the female's reproductive life span (a minimum of 347 days posttreatment) and scored for the number of live births produced during this period. Confirmatory dominant lethal experiments or histological examinations for numbers of small follicles were carried out when mutagenic effects or cytotoxicity, respectively, were suspected as the basis for reduced fertility. Of the 29 chemicals studied, 17 had reproductive effects which may be grouped into one of three classes: (1) those that reduced the total number of young and litters per female, (2) those that reduced the total number of young but not of litters, and (3) those that had no significant effect on the total number of young produced but reduced the size of the first and/or second litters. The TRC provides a capacity for detecting a range of toxic insults upon female reproduction. Many of the chemicals were indeed shown to affect the reproductive performance of females through mutagenic and/or cytotoxic effects on follicles. In some cases, however, no causative mechanism could be identified for the observed reduction in reproductive performance. Nevertheless, with this report the number of chemicals tested by this TRC procedure has been quadrupled and the categories of chemicals tested have been substantially broadened.

Evidence for a parent-of-origin effect on sperm aneuploidy in mice carrying Robertsonian translocations as analyzed by fluorescence in situ hybridization

Multi-color fluorescence in situ hybridization (FISH) was employed to investigate variations in the frequency of aneuploid spermatids produced by males derived from three separate lines of Robertsonian translocations in mice: Rb(2.8)2Lub, Rb(8.12)22Lub, and Rb(8.14)16Rma, each with one arm involving chromosome 8. The DNA probes used were specific for repetitive sequences on chromosomes 8 and X. Heterozygous males for these Robertsonian translocations produced approximately 1% of spermatids with hyperhaploid for chromosome 8. which was > 80 times higher than the frequency of sperm hyperhaploid for chromosome X within the same animals; consistent elevations in chromosome-8 sperm disomy were observed among lines. In addition, approximately 25% higher fractions of sperm aneuploidy were observed when the Robertsonian translocation was inherited from the father rather than from the mother (p = 0.009). These findings illustrate the sensitivity of the FISH procedure for detecting small differences in the hyperhaploidy in male germ cells and suggest that imprinted factors may influence sperm aneuploidy.

Mutagenicity of anticancer drugs in mammalian germ cells

The evidence for mammalian germ cell mutagenicity induced by anticancer drugs is summarized. Primary attention is paid to the three major mouse germ cell mutagenicity tests- the dominant lethal, heritable translocation, and morphological specific locus tests- from which most germ cell mutagenicity data historically have been obtained. Of the 21 anticancer drugs reviewed, 16 have been tested in one or more of these three tests; with all 16 tested in the most common germ cell test, the male dominant lethal test, and 9 of the 16 also tested in the female dominant lethal test. The patterns of germ cell stage specificity for most of the anticancer drugs are similar, and generally resemble the patterns seen with other types of chemicals; however, some of the patterns are unique. For example, 2 of the 8 chemicals shown to induce dominant lethal mutations in female oocytes, do not induce dominant lethal mutations in male germ cells (adriamycin and platinol). Ten of the 16 chemicals tested in the dominant lethal test were positive in post-meiotic stages (spermatids through mature sperm), and seven also induced reciprocal translocations and/or specific locus mutations in post-meiotic stages. This propensity to induce mutations in post-meiotic stages has been observed with most mutagens. However, 5 of the anticancer drugs also induced dominant lethal mutations in spermatocytes (meiotic prophase cells) and one of them, 6-mercaptopurine, uniquely induced dominant lethal mutations exclusively in preleptotene spermatocytes. Finally, three of the anticancer drugs (melphalan, mitomycin C, procarbazine) are members of a very select group of chemicals shown to induce specific locus mutations in spermatogonial stem cells of mice. The implications for human risk are discussed.

Micronuclei induced in round spermatids of mice after stem-cell treatment with chloral hydrate: evaluations with centromeric DNA probes and kinetochore antibodies

The chromosomal effects of chloral hydrate (CH) on germ cells of male mice were investigated using two methods to detect and characterize spermatid micronuclei (SMN); (a) anti-kinetochore immunofluorescence (SMN-CREST) and (b) multicolor fluorescence in situ hybridization with DNA probes for centromeric DNA and repetitive sequences on chromosome X (SMN-FISH). B6C3F1 mice received single intraperitoneal (i.p.) injections of 82.7, 165.4, or 413.5 mg/kg and round spermatids were sampled at three time intervals representing cells treated in late meiosis, early meiosis, or as spermatogonial stem cells. No increases in the frequencies of SMN were detected for cells treated during meiosis using either SMN-CREST or SMN-FISH methods. After spermatogonial stem-cell treatment, however, elevated frequencies of SMN were detected by both methods. With SMN-FISH, dose trends were observed both in the frequencies of spermatids containing micronuclei and in the frequency of spermatids carrying centromeric label. These findings corroborate the recent report by Allen and colleagues [Allen JW et al.(1994): Mutat. Res. 323:81-88] that CH treatment of spermatogenic stem cells induced SMN. Furthermore, our findings suggest that chromosomal malsegregation or loss may occur in spermatids long after CH treatment of stem cells. Further studies are needed to understand the mechanism of action of the CH effect on stem cells and to determine whether similar effects are induced in human males treated with CH.

Aneuploidy in germ cells: etiologies and risk factors

A 2 1/2-day workshop on germ cell aneuploidy was convened September 11-13, 1995 at the National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina to discuss current understandings of the etiology and origin of human aneuploidy, especially in regard to potential environmental causes, and to identify gaps in our research knowledge. The workshop was designed to facilitate interactions among research experts conducting studies on the fundamental biology of chromosomal movement and segregation, on aneuploidy as a human clinical problem, and on toxicological aspects of aneuploidy induction. Overview presentations provided perspectives on aneuploidy as a human clinical problem, the genetics of aneuploidy, and the issues of concern in toxicological testing and regulatory risk assessment. The four chairs introduced the topics for each of their workgroups, setting the stage for subsequent, in-depth discussions on (1) chromosome mover components, (2) altered recombination, (3) parental age effects, and (4) differential chromosome susceptibility. From these discussions, gaps in our research knowledge related to the role of the environment in the etiology of aneuploidy and associated molecular, cellular, and genetic processes involved were identified, and will be used to establish a research agenda for filling those gaps.

Cyclophosphamide: review of its mutagenicity for an assessment of potential germ cell risks

Cyclophosphamide (CP) is used to treat a wide range of neoplastic diseases as well as some non-malignant ones such as rheumatoid arthritis. It is also used as an immunosuppressive agent prior to organ transplantation. CP is, however, a known carcinogen in humans and produces secondary tumors. There is little absorption either orally or intravenously and 10% of the drug is excreted unchanged. CP is activated by hepatic mixed function oxidases and metabolites are delivered to neoplastic cells via the bloodstream. Phosphoramide mustard is thought to be the major anti-neoplastic metabolite of CP while acrolein, which is highly toxic and is produced in equimolar amounts, is thought to be responsible for most of the toxic side effects. DNA adducts have been formed after CP treatment in a variety of in vitro systems as well as in rats and mice using 3H-labeled CP. 32P-postlabeling techniques have also been used in mice. However, monitoring of adducts in humans has not yet been carried out. CP has also been shown to induce unscheduled DNA synthesis in a human cell line. CP has produced mutations in base-pair substituting strains of Salmonella tryphimurium in the presence of metabolic activation, but it has been shown to be negative in the E. coli chromotest. It has also been shown to be positive in Saccharomyces cerevisiae in D7 strain for many endpoints but negative in D62.M for aneuploidy/malsegregation. It has produced positive responses in Drosophila melanogaster for various endpoints and in Anopheles stephensi. In somatic cells, CP has been shown to produce gene mutations, chromosome aberrations, micronuclei and sister chromatid exchanges in a variety of cultured cells in the presence of metabolic activation as well as sister chromatid exchanges without metabolic activation. It has also produced chromosome damage and micronuclei in rats, mice and Chinese hamsters, and gene mutations in the mouse spot test and in the transgenic lacZ construct of Muta Mouse. Increases in chromosome damage and gene mutations have been found in the peripheral blood lymphocytes of nurses, pharmacists and female workers occupationally exposured to CP during its production or distribution. Chromosome aberrations, sister chromatid exchanges and gene mutations have been observed in somatic cells of patients treated therapeutically with CP. In general, there is a maximum dose and an optimum time for the detection of genetic effects because the toxicity associated with high doses of CP will affect cell division. In germ cells, CP has been shown to induce genetic damage in mice, rats and hamsters although the vast majority of such studies have used male mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Limb and lower-body duplications induced by retinoic acid in mice

The zygote and subsequent preimplantation stages of early mammalian development are susceptible to certain chemical perturbations that cause abnormal development of the conceptus. In certain cases, disruption in patterns of gene expression could be a primary event leading to abnormal development. To investigate this hypothesis, we treated pregnant mice with trans-retinoic acid, a known modulator of gene expression. Treatments were administered at various times during pregastrulation stages and the presumed onset of gastrulation. trans-Retinoic acid induced a distinctive set of malformations, as manifest by supernumerary and ectopic limbs and duplication of portions of the lower body, but only when administered during the period of 4.5-5.5 days after mating. (Other malformations were induced at different stages.) The limb and lower-body duplications suggest that exogenous trans-retinoic acid may influence not only the pattern for the hindlimbs but also that for the entire lower body. Since it appears likely that the embryos were affected in the late blastocyst and proamniotic-embryo stages, the provocative possibility arises that aspects of pattern formation of limbs and lower body actually occur prior to gastrulation.

Cytogenetic and germ cell effects of phosphine inhalation by rodents: II. Subacute exposures to rats and mice

Phosphine (PH3) is a highly toxic grain fumigant to which there is significant human workplace exposure. To determine the in vivo cytogenetic effects of inhalation of PH3, male F344/N rats and B6C3F1 mice were exposed to target concentrations of 0, 1.25, 2.5, or 5 ppm PH3 for 6 hr/day for 9 days over an 11-day period. Approximately 20 hr after the termination of exposures, blood was removed from the mice and rats by cardiac puncture and the lymphocytes cultured for analyses of sister chromatid exchanges and chromosome aberrations in rats and mice, and micronuclei (MN) in cytochalasin B-induced binucleated lymphocytes from mice. In addition, bone marrow (rats) and peripheral blood (mice) smears were made for the analysis of MN in polychromatic and normochromatic erythrocytes. No significant increase in any of the cytogenetic endpoints was found at any of the concentrations examined. These results indicate that concentrations of PH3 up to 5 ppm are not genotoxic to rodents when administered by inhalation for 9 days during an 11-day period as measured by several cytogenetic assays. To evaluate the effects of PH3 on male germ cells, a dominant lethal test was conducted in male mice exposed to 5 ppm PH3 for 10 days over a 12-day period and mated to groups of untreated females (2 females/male) on each of 6 consecutive 4-day mating intervals. None of the 6 groups of females exhibited a significant increase in percent resorptions. These results indicate that exposure to 5 ppm PH3 by inhalation does not induce dominant lethality in male mouse germ cells at steps in spermatogenesis ranging from late differentiating spermatogonia/early primary spermatocytes through mature sperm.

Toxicokinetics of sulfasalazine (salicylazosulfapyridine) and its metabolites in B6C3F1 mice

The toxicokinetics of salicylazosulfapyridine (SASP) and its metabolites were investigated in male and female B6C3F1 mice either following single intravenous (5 mg/kg) or oral (67.5, 675, 1350, and 2700 mg/kg) doses, or following three consecutive daily oral doses (675, 1350, and 2700 mg/kg). Plasma concentrations of SASP and its metabolites were quantified by HPLC. Upon intravenous administration, SASP rapidly disappeared from blood with a mean residence time of 0.45-0.78 hr. The only metabolite of SASP found in plasma after an intravenous dose was sulfapyridine (SP). In both sexes, the absolute oral bioavailability of SASP ranged between 16.6-18.2% at a dose of 67.5 mg/kg, and between 2.6-8.7% at doses of 675-2700 mg/kg. Following oral administration of SASP, both SP and AcSP were identified in plasma. The area under the plasma concentration-time curves (AUC) of SP at all four oral doses were approximately 21- to 32-fold or 5- to 25-fold greater than those of SASP in male or female mice, respectively. The acetylated form of SP and AcSP, produced AUC values higher than SASP but much less than SP. Multiple oral doses with SASP did not alter the temporal patterns of SASP absorption and elimination in comparison to a single dose. However, SP accumulated in both sexes following multiple oral doses. A gender-dependent difference in toxicokinetic profiles for SASP and SP was also observed. Female mice displayed a higher Cmax of SASP and SP than did male mice. Although the volume of distribution of SASP was similar in both sexes, the systemic clearance of SASP in males was about twice that observed in females.(ABSTRACT TRUNCATED AT 250 WORDS)

Fertility, reproduction, and genetic disease: studies on the mutagenic effects of environmental agents on mammalian germ cells

Because genetically based diseases have a major impact on human health, the National Institute of Environmental Health Sciences (NIEHS) has conducted a research and testing program for more than a decade to address chemical induction of heritable genetic damage in the germ cells of mammals. Although most genetic disease results from preexisting mutations, a portion is due to the occurrence of new mutations. The supposition that exposure to mutagenic chemicals contributes to the occurrence of new mutations in the human population is strongly supported by the results from animal models. Such studies clearly demonstrate the potential of environmental chemicals to induce mutations in both somatic and reproductive cells of mammals. This NIEHS program has become a leader in the identification of genetic hazards in the environment and in the acquisition of animal model data used by regulatory agencies in assessing genetic risks to human health.

Bleomycin: female-specific dominant lethal effects in mice

Limited comparative data in mice indicate that chemical mutagens that induce dominant lethal mutations in males are not necessarily effective in females, but those which are effective in females are generally equally or more effective in males. Recently, however, a few chemicals have been identified that are female-specific with respect to induction of dominant lethal mutations. The antitumor antibiotic adriamycin is among them. Another antitumor antibiotic, bleomycin was examined for its ability to induce dominant lethal mutations in the reproductive cells of male and female mice. No dominant lethal or cytotoxic effects were observed in males treated with bleomycin, even at a maximum tolerated dose. In females, on the other hand, a dose nearly 1/4 of that used in males induced not only a high level of dominant lethal mutations but also killed oocytes in certain stages of follicular development. The effectiveness of bleomycin in inducing dominant lethal mutations in mouse oocytes makes it a valuable tool for investigating whether gonadal transport, inherent differences in the configuration of chromatin in the germ cells of the two sexes or other factors are responsible for the differential susceptibility to bleomycin, which implies potential gender-specific genetic risk in cancer chemotherapy.

The safety and effect of topically applied recombinant basic fibroblast growth factor on the healing of chronic pressure sores

The first randomized, blinded, placebo-controlled human trials of recombinant basic fibroblast growth factor (bFGF) for pressure sore treatment were performed. Three different concentrations of bFGF in five dosing schedules were tested for safety using hematology, serum chemistries, urinalysis, absorption, antibody formation, and signs of toxicity. Efficacy was evaluated by wound volumes, histology, and photography. No toxicity, significant serum absorption, or antibody formation occurred. In six of eight subgroups, there was a trend toward efficacy with bFGF treatment. When all subgroups were combined, comparison of the slopes of the regression curves of volume decrease over initial pressure sore volume demonstrated a greater healing effect for the bFGF-treated patients (p < 0.05). Histologically, bFGF-treated wound sections demonstrated increased fibroblasts and capillaries. More patients treated with bFGF achieved > 70% wound closure (p < 0.05). Blinded observers were able to distinguish differences in visual wound improvement between bFGF and placebo groups. These data suggest that bFGF may be effective in the treatment of chronic wounds.

Induction of kinetochore positive and negative micronuclei in mouse bone marrow cells by salicylazosulfapyridine and sulfapyridine

Salicylazosulfapyridine (SASP) and its major metabolite sulfapyridine (SP) have been shown to induce chromosomal damage in vivo. Both chemicals were tested in the micronucleus (MN)/kinetochore (KC) staining test to gain insight into the question of whether chromosomal breakage, aneuploidy-inducing events, or both were important to the observed production of MN in bone marrow cells of mice. In this test, both SASP and SP were shown to be strong inducers of kinetochore positive (KC+) MN. Although small increases in kinetochore negative (KC-) MN were also observed in SP treated mice, as well as in mice receiving the highest dose of SASP tested, the results suggest that both chemicals induce predominantly aneuploidogenic type damage.

Induction of chromosomal damage in mammalian cells in vitro and in vivo by sulfapyridine or 5-aminosalicylic acid

Sulfapyridine (SP) and 5-aminosalicylic acid (5-ASA) are the two primary metabolites of the anti-inflammatory drug salicylazosulfapyridine (SASP). These two metabolites were studied for induction of chromosomal damage in mammalian cells, in vitro and in vivo, in an attempt to understand better the genetic effects produced by SASP in humans and laboratory mice. To this end, SP and 5-ASA were tested for induction of sister-chromatid exchanges (SCE) and chromosomal aberrations (Abs) in Chinese hamster ovary (CHO) cells in vitro. In addition, they were tested in vivo for induction of micronuclei (MN) in mouse bone marrow polychromatic erythrocytes (PCE). SP gave positive results in the in vitro SCE test and the in vivo MN test, and negative results in the in vitro Abs test. 5-ASA was negative in all three tests. These results indicate that it is the SP metabolite of SASP that is necessary for the induction of chromosomal damage reported to occur in humans and mice after treatment with SASP.

Assessing overdispersion and dose-response in the male dominant lethal assay

In dominant lethal studies the primary variables of interest are typically expressed as discrete counts or proportions (e.g., live implants, resorptions, percent pregnant). Simple statistical sampling models for discrete data such as binomial or Poisson generally do not fit this type of data because of extra-binomial or extra-Poisson departures from variability predicted under these simple models. Extra-variability in the fetal response may originate from parental contributions. These can lead to over- or under-dispersion seen as, e.g., extra-binomial variability in the proportion response. Utilizing a large control database, we investigated the relative impact of extra-variability from male or female contributions on the endpoints of interest. Male-related effects did not seem to contribute to overdispersion in our database; female-related effects were, however, evidenced. Various statistical methods were considered to test for significant treatment differences under these forms of sampling variability. Computer simulations were used to evaluate these methods and to determine which are most appropriate for practical use in the evaluation of dominant lethal data. Our results suggest that distribution-free statistical methods such as a nonparametric permutation test or rank-based tests for trend can be recommended for use.

A prospective randomized evaluator-blinded trial of two potential wound healing agents for the treatment of venous stasis ulcers

Chronic wounds such as venous stasis ulcers have become a socioeconomic problem. Even with successful initial management, the recurrence rate approaches 70%. With the advent of new wound healing agents, nonoperative attempts to heal these wounds appear indicated. This study reports a prospective randomized evaluator-blinded trial comparing two potential wound healing agents to an inert vehicle placebo. Eighty-six evaluable patients completed the trial. Silver sulfadiazine 1% in a cream proved to statistically reduce the ulcer size compared with a biologically active tripeptide copper complex 0.4% cream formulation or the placebo. There was no difference between the latter two treatments. Silver sulfadiazine has been shown to allow keratinocyte replication and to have antiinflammatory properties. In this trial its antibacterial action was not used since all ulcers had comparable bacterial levels (less than or equal to 10(5)/gm of tissue) before treatment. These results suggest that the silver sulfadiazine cream used in this study may facilitate healing in wounds healing largely by the process of epithelialization.

Developmental response of zygotes exposed to similar mutagens

Exposure of mouse zygotes to ethylene oxide (EtO) or ethyl methanesulfonate (EMS) led to high incidences of fetal death and of certain classes of fetal malformations (Generoso et al., 1987, 1988; Rutledge and Generoso, 1989). These effects were not associated with induced chromosomal aberrations (Katoh et al., 1989) nor are they likely to be caused by gene mutations (Generoso et al., 1990). Nevertheless, the anomalies observed in these studies resemble the large class of stillbirths and sporadic defects in humans that are of unknown etiology, such as cleft palate, omphalocoel, clubfoot, hydrops and stillbirths (Czeizel, 1985; Oakley, 1986). Therefore, we continue to study the possible mechanisms relating to induction of these types of zygote-derived anomalies in mice. Effects of zygote exposure to the compounds methyl methanesulfonate (MMS), dimethyl sulfate (DMS), and diethyl sulfate (DES), which have similar DNA-binding properties as EtO and EMS, were studied. DMS and DES, but not MMS, induced effects that are similar to those induced by EtO and EMS. Thus, no site-specific alkylation product was identifiable as the critical target for these zygote-derived anomalies. We speculate that the developmental anomalies arose as a result of altered programming of gene expression during embryogenesis.

Evaluation of the mutagenicity of the anti-inflammatory drug salicylazosulfapyridine (SASP)

Salicylazosulfapyridine, commonly known as sulfasalazine or SASP, is an anti-inflammatory drug that is widely used in the treatment of diseases such as ulcerative colitis and Crohn's disease. Increases in sister chromatid exchanges (SCE) and micronuclei (MN) frequencies have been reported in lymphocytes of patients maintained on SASP therapy for up to 21 months. We have tested SASP for its ability to induce chromosome aberrations (ABS) and SCE in cultured Chinese hamster ovary (CHO) cells, ABS in mouse bone marrow cells, and MN in erythrocytes from both bone marrow and peripheral blood of mice. In vitro assays for ABS and SCE were negative. In vivo, SASP administered by single gavage at doses up to 1000 mg/kg did not increase ABS in bone marrow cells of male B6C3F1 mice; however, increases in MN were observed in the peripheral blood erythrocytes of male and female B6C3F1 mice administered 675, 1350 or 2700 mg/kg SASP by gavage for 90 days. Weak but significant dose-related increases in MN were also observed in the bone marrow cells of male B6C3F1 mice administered 500, 1000 and 2000 mg/kg SASP for 3 days. These positive findings in mice support the role of SASP in the induction of MN and SCE in humans, and suggest the need for further evaluation of possible adverse human health effects associated with SASP therapy.

Female-specific dominant lethal effects in mice

For some chemicals, induction of presumed dominant lethal mutations has been observed only in female mice and not in males. In those cases, questions arise as to (1) whether the increased embryonic mortality is due to genetic effects of the chemicals in the oocyte or, (2) is caused indirectly through maternal toxicity, and, if genetic, (3) the basis for the sex difference. These questions were studied using the compounds adriamycin and platinol. Neither compound induces dominant lethals in male germ cells, but both increased early embryonic mortality when females were treated prior to mating (treatment of maturing oocytes). Reciprocal zygote transfer experiments ruled out, either entirely or for the large part, maternal toxicity as the cause, and cytogenetic analysis of first-cleavage metaphases revealed high incidences of chromosomal aberrations. The results of both of these experiments thus provide evidence that the early embryonic mortality resulted from genetic effects induced in oocytes. Most interestingly, each compound produced unexpected types of chromosomal aberrations. Adriamycin produced deletions, rings, and presumed chromosome-type rearrangements. Platinol, on the other hand, produced a few chromatid-type aberrations, but the bulk of aberrations were characterized by disorganization of the chromatin, minute fragments, and thread-like chromatin bridges between fragments and chromosomes or between two or more chromosomes. The latter type of cytogenetic damage was observed primarily in the centromeric region. It is hypothesized that the female-specific dominant lethal effects of the two compounds are associated with the diffused state of the maturing oocyte chromosomes.

Purification of octyl beta-D-glucopyranoside and re-estimation of its micellar size

The commercial non-ionic detergent octyl beta-D-glucopyranoside is often contaminated by significant amounts of UV absorbing and/or ionic compounds that can associate with membrane proteins. Such impurities can be monitored by several techniques (i.e., spectrophotometry, size exclusion chromatography, and pH, conductivity, and surface tension measurements) and can be removed using mixed-bed ion exchange chromatography. High performance size exclusion chromatography, dynamic light scattering, and ultracentrifugation have been used to re-estimate the size of micelles of octyl beta-D-glucopyranoside since previously published data varied over a wide range. Aggregation numbers were 27 to 100 for micellar molecular weights 8000 to 29,000. Direct physical methods that do not perturbate the sample indicated a large size for the micelles (hydrodynamic radius 23 +/- 3 A; Mr 22,000 +/- 3000; aggregation number 75 +/- 10 for a 34 mM aqueous solution). In contrast the chromatographic micellar size appeared to be smaller (hydrodynamic radius 15 +/- 1 A; Mr 8000 +/- 1000; aggregation number 27). This underestimation may be the result of adsorption and/or alteration of the micelles.

Mechanisms of intranephronal proteinaceous cast formation by low molecular weight proteins

Proteinaceous cast formation in the distal nephron of the kidney from low molecular weight proteinuria is a significant, but poorly characterized, cause of renal failure. To study this phenomenon, we: (a) microperfused the loop segment (LS) of rats in vivo with artificial tubule fluid (ATF) containing four different low molecular weight proteins, 0.01-50 mg/ml, to detect alterations in LS function, and (b) examined the interaction between several proteins and Tamm-Horsfall glycoprotein (THP) in vitro with turbidity and dynamic light-scattering measurements. Perfusion of the LS for less than 2 min with cast-forming proteins (Bence Jones protein [BJP3] and myoglobin) decreased chloride absorption and elevated early distal tubule fluid (ED) [Cl-], compared with results obtained with control perfusions that used ATF alone. BJP3 decreased chloride absorption in a concentration-dependent fashion. Perfusion with non-cast-forming proteins (albumin and BJP1) enhanced chloride absorption and decreased ED [Cl-]. In vitro, proteins that had isoelectric points (pI) greater than 5.1 aggregated with THP. Aggregation was enhanced with increasing [NaCl] or [CaCl2]. Albumin (pI 4.8) and beta-lactoglobulin (pI 5.1) did not coprecipitate. The molecular size of THP alone increased when [NaCl] greater than 80 mM. Thus, cast-forming proteins aggregated with THP in vitro and caused in vivo LS dysfunction, which elevated ED [Cl-], facilitating aggregation. In contrast, non-cast-forming proteins either did not interact with THP or lowered ED [Cl-], which did not provide an environment for aggregation. Altered LS function and interaction of some proteins with THP were related to different physicochemical properties of the proteins and independently contributed to the formation of proteinaceous casts in the kidney.

Potentiation of ethyl methanesulfonate-induced germ cell mutagenesis and depression of glutathione in male reproductive tissues by 1,2-dibromoethane

EDB significantly depressed GSH in caput and cauda epididymis, but not in testis, 2 hours following injection. This depression was dose-related. EDB enhanced EMS-induced dominant lethal mutations at mating weeks 2 and 3 (of 6). At mating week 2 the fetal death rate was increased two-fold, while at week 3, the fetal death rate had increased to nearly three-fold greater than the EMS-only controls. Enhancement of fetal death rate was confined to postimplantation loss. As with EMS alone, the EDB potentiation of EMS-induced mutations was limited to postmeiotic stages of spermatogenesis. EDB also enhanced alkylation of rat spermatozoa by labeled EMS. Depression of GSH in reproductive tissues is correlated with a potentiation of dominant lethal mutations, as well as an increase in the binding of EMS to sperm heads.

Chromosome malsegregation and embryonic lethality induced by treatment of normally ovulated mouse oocytes with nocodazole

The mouse egg is ovulated with its nucleus arrested at the metaphase-II stage of meiosis. Sperm entry triggers the completion of the second meiotic division. It has been speculated that damage to the meiotic spindle of normally ovulated eggs at around the time of sperm entry could result in chromosome malsegregation and the death of conceptuses with numerical chromosome anomalies. This hypothesis was tested using nocodazole, a microtubule inhibitor. Nocodazole was administered either to maturing preovulatory oocytes or to normally ovulated eggs at one of the following stages: (1) the time of sperm entry, (2) early pronuclear stage, (3) pronuclear DNA synthesis, (4) prior to first cleavage division, (5) early 2-cell stage, or (6) prior to the second cleavage division. Little or no effect was observed for treatment times other than the time of sperm entry, when the egg is being activated to complete the second meiotic division. Remarkably high frequencies of embryonic lethality, expressed at around the time of implantation, were induced at this stage. Cytogenetic analysis of first cleavage metaphases of zygotes treated at the time of sperm entry revealed a high incidence of varied numerical chromosome anomalies, with changes in ploidy being predominant.

Depression of glutathione in male reproductive tissues and potentiation of EMS-induced germ cell mutagenesis by L-buthionine sulfoximine

Buthionine sulfoximine (BSO) treatment significantly reduced testicular epididymal and vas deferens glutathione (GSH) levels in rats. Testicular levels of GSH were reduced by 20%, while epididymal GSH levels were reduced by more than 50%. BSO treatment correspondingly enhanced ethyl methanesulfonate (EMS)-induced dominant lethal mutations. EMS-induced resorption rates were doubled following BSO treatment. This effect was observed in mating wk 2 and 3 (d 8-19 following treatment), indicating effects on those germ cells which were in late testicular stages or were caput epididymal spermatozoa at the time of EMS treatment. The enhancement of the mutagenic action of EMS by BSO is restricted to the same time period (spermatid-spermatozoa transition, early epididymal maturation) as maximum sensitivity to the clastogenic action of EMS on male germ cells. The temporal pattern of EMS alkylation of rat spermatozoa correlated with the incidence of EMS-induced dominant lethal mutations. BSO depresses GSH in the male reproductive tract in a dose- and time-dependent manner. Perturbation of GSH in the male reproductive tract appears to influence chemical-induced germ cell mutations.

Toxicological review of busulfan (Myleran)

Busulfan is a bifunctional alkylating agent that appears to be cytotoxic to slowly proliferating or non-proliferating stem cell compartments, although its specific molecular and cellular mechanisms are unknown. It is the drug of preference in treatment of chronic myelogenous or granulocytic leukemia because its cytotoxic activity results in primary damage or destruction of hematopoietic cells. Additional effects resulting from the cytotoxicity of busulfan in hematological and other tissues, as documented by both human and animal model studies, include lethality, sterility, teratogenicity, and alteration of immune function. Busulfan has been shown to be mutagenic to microorganisms, mammalian cells in culture, Drosophila, and rodents. This agent is also considered potentially carcinogenic to humans. Various tissue hyperplasia and preneoplastic cells have been observed in animal model studies with busulfan, and case reports on human patients implicate busulfan as the causative agent in induction of secondary malignancies. Reports from human and animal studies of busulfan's cytotoxicity, teratogenicity, carcinogenicity, and mutagenicity have been reviewed. This information may be useful in a quantitative assessment of the effects of this agent and the identification of significant deficiencies in the data base. Demonstration that busulfan induces mutations in both somatic and germ cells suggests the need to assess its risk to humans.

Germ-cell mutagenesis and GSH depression in reproductive tissue of the F-344 rat induced by ethyl methanesulfonate

Sensitivity of male F-344 rats to the dominant lethal (DL) mutagenic effect of ethyl methanesulfonate (EMS) was studied in conjunction with an evaluation of EMS-induced depression of glutathione (GSH) in testis, epididymis and vas deferens. At the maximal effect, during week 3 (days 15-19 post-EMS), a dosage of 50 mg/kg caused 13.3% fetal death (FD) vs. 3.3% in controls, while 100 mg/kg caused 56.6% FD in the same interval. EMS maximally depressed GSH to 33%, 54% and 77% of control in vas, epididymis and testis respectively. The slope of the DL dose-response curve for EMS in rats shows a 3-4-fold greater sensitivity than that reported for mice. The steepness of this curve suggests that small perturbations in endogenous protective mechanisms, such as GSH depression, may exert a greater proportional effect on germ-cell mutagenesis in rats which should be more readily observable than in mice. EMS and other electrophilic toxicants may thus influence their own primary reproductive toxicity and/or that of other agents by depression of GSH in male reproductive tissue.

Ethyl methanesulfonate-induced mutations of major genes for quantitative phenotypes: mutant alleles for altered activity of brain or liver enzymes in C57BL/6J mice and their inheritance across several generations

We recently identified and confirmed 8 induced mutations in the N2 and N3 progeny of ethyl methanesulfonate (EMS) treated C57BL/6J mice. Each of these mutations altered specific enzyme activities. These separate mutant sublines have been maintained through several generations as heterozygous mutant carriers. The percent decrease of the specific enzyme activity from normal in each subline was calculated for each generation. Additionally, the percentage of breeders within each mutant subline producing abnormal progeny and the fraction of such breeders' total progeny possessing abnormal activity were determined. The aberrant activity values observed in progeny of a confirmed mutant carrier were all lower than normal. 4 of the mutant sublines had decreases in enzyme activities which were constant across the generations analyzed. 3 of the mutant sublines had decreases in activities which were consistent over early generations but changed significantly in later generations. Another subline with decreased enzyme activity was lost. For 7 of the sublines, the number of progeny having altered activity and the number of breeders producing mutant progeny approximated that expected for single gene inheritance. In the remaining subline, a change in the decrease in enzyme activity probably accounts for the deviation from expected inheritance. Although the phenotypes for these quantitative traits are considered to be quasi-continuous, the data indicate that the mutations are probably of major genes.

Dominant lethal test response with IMS and TEM using different combinations of male and female stocks of mice

We conducted dominant lethal studies with chemical mutagens IMS and TEM to investigate the influence which different treated male stocks might have upon individual female response. In both studies, treated males from a CD-1 random bred stock and each of two F1 hybrid stocks (C57BL/6N X C3H; C57BL/6J X BALB/c) were mated to untreated females from the two F1 hybrid stocks. We found that variation in response due to the treatment effect was modulated by the specific male stock/female stock combination involved. The male-dependent variation observed prevented any meaningful evaluation of relative female stock sensitivity but it was obvious that factors other than differences in repair capacity of female germ cells contributed to the response differences observed.

Pleiotropic and other genetic effects influencing the activities of brain and liver enzymes in congenic lines of C57BL/6J mice with defined electrophoretic variant markers

A single genetic factor may affect the realization of several enzymes. To investigate the extent of pattern pleiotropy in the mouse, the activities of 28 enzymes in livers and brains from an inbred stock of C57BL/6JNctr and five F1 stocks heterozygous for known electrophoretic variants were measured. Five congenic backcross stocks of C57BL/6J, each homozygous for one or more electrophoretic markers, were mated with C57BL/6JNctr to construct the heterozygous variant F1 stocks. One of the five F1 stocks had no enzyme activities significantly different from those of C57BL/6JNctr, while two had one enzyme, one had four enzymes, and another had six enzymes with activities that were significantly different from those of C57BL/6JNctr. The latter two F1 stocks with multiple activity differences were those having the largest proportion of their genome of donor origin. Two of the F1 stocks were different from each other for one enzyme, and two were different for another enzyme. These differences and the relationship of these enzyme activities to the variant genes suggest that several genetic factors may affect an enzyme's realization.

Development of a new biochemical mutation test in mice based upon measurements of enzyme activities. I. Theoretical concepts and basic procedure

A test procedure is described for detecting germ cell mutations which alter activity of enzymes in in vivo mammalian tissues. The objective is to identify those individuals, among a population of F1 animals from treated parents, that are heterozygous for a mutation at an unspecified locus which results in an altered activity of one or more of the enzymes monitored. Animals are evaluated through three analysis screens with emphasis on identification of mutant individuals. In the first screen, activity values of a battery of enzymes are compared to their respective normal ranges to identify those which are aberrant. The mean activities and coefficients of variation useful in defining the normal ranges for 19 enzymes in C57BL/6J Nctr mice are presented along with a set of theoretical normal animal misclassification probabilities for each of these enzymes. The second screen is a Michaelis-Menten kinetic analysis of aberrant enzymes, the goal of which is to correct misclassifications of normal animals made in the first screen. A third screen of aberrant enzyme activities in a subsequent generation is used to demonstrate inheritance and confirm the mutation. The advantages and the limitations, as well as possible variations of the basic procedure are discussed.

Development of a new biochemical mutation test in mice based upon measurement of enzyme activities. II. Test results with ethyl methanesulfonate (EMS)

An experiment with ethyl methanesulfonate (EMS) was conducted to determine the feasibility of detecting chemically induced mutations in mice by quantitative analysis of metabolic characters using the test procedure of Feuers et al. (1982). A test population of 518 F1 mice from matings of untreated C57BL/6J females to C57BL/6J males treated with 0, 100, 175 or 200 mg/kg EMS was evaluated according to a set of multi-level biochemical and genetic screening criteria. The goal of the assay was identification of F1 individuals heterozygous at an unspecified locus for an induced mutant allele which altered the activity of one or more of 19 enzymes in brain and liver tissues of their F2 and F3 progeny, 8 individuals among a population of 345 F1's from the EMS-dosed groups were classified as confirmed mutants having at least 2 of their F2 progeny exhibiting the same enzyme aberrancy and transmitting this aberrancy to the F3 generation. No confirmed mutants were detected in the control population of 173 F1 individuals. These results indicate that this test method can be used to detect chemically induced mutations expressed as quantitative alterations in enzyme activity.

A method for preparing chromosomes from peripheral blood of the mouse

A modified Triman et al. (1975) procedure for preparing metaphase chromosomes from mouse peripheral blood is described. Modifications include: isolation of white blood cells using a ficoll-hypaque gradient; seeding cultures with a known concentration of leucocytes such that the PHA/cell concentration can be controlled for optimum stimulation through 72 h with no media change; and visual monitoring of cell growth to determine when there should be sufficient numbers of dividing cells for harvest and thus eliminate unnecessary harvest of non-productive cultures. We have found this modified procedure to be highly reproducible with the final 0.5 ml fixed cell suspension yielding 50-75 quality metaphase spreads per drop.

The heritable translocation assay: its relationship to assessment of genetic risk for future generations

The Heritable Translocation Assay (HTA) is an in vivo mammalian mutation test which measures specific clastogenic damage. It can be subjected to rigorous statistical scrutiny and detects a type of heritable genetic damage that is known to contribute to the human disease burden. Because of these factors the HTA is one of the major tests of the battery used in regulatory evaluation of potential environmental mutagens. Although tests for detecting inherited translocations have been developed and improved over the past 40 years, further emphasis on several statistical considerations affecting the precision and reliability of HTA animal model data applied to regulatory hazard evaluation and risk assessment seems warranted. In this paper we have presented a brief history and the basic methodology for the HTA. Statistical concepts related to the design and implementation of HTA studies, such as the incorporation of false classification error probabilities in determination of required sample size and use of the single sample binomial versus Fisher's exact test for analysis of data, hory and the basic methodology for the HTA. Statistical concepts related to the design and implementation of HTA studies, such as the incorporation of false classification error probabilities in determination of required sample size and use of the single sample binomial versus Fisher's exact test for analysis of data, hory and the basic methodology for the HTA. Statistical concepts related to the design and implementation of HTA studies, such as the incorporation of false classification error probabilities in determination of required sample size and use of the single sample binomial versus Fisher's exact test for analysis of data, have been examined in detail. We have also suggested a simplified method of extrapolating HTA animal data to man similar to that used with carcinogenesis data and propose other developmental needs and perspectives for application of this assay to regulatory assessment of environmental mutagens.

Persistent tracheostomy stoma

Prolonged presence of a tracheostomy tube or prolonged tracheostomy stoma can result in a failure of spontaneous closure. The stoma may remain open until surgically closed. Muscle flaps as well as skin flaps can be used to close the persistent tracheostomy stoma. These flaps seal the stoma, provide soft tissue between the trachea and the skin, and allow a satisfactory cosmetic result. The sternohyoid muscle is readily accessible for this purpose. This procedure was used in five patients with a satisfactory result in each.

Heritable translocation test in mice

The status of the heritable-translocation test in mice with respect to its usefulness in practical testing was evaluated by using information available in the open literature. A total of 47 reports were evaluated; 29 were judged to contain adequate information to classify whether or not a given chemical induced heritable translocations. Heritable-translocation data were available for 32 compounds; data were not adequate for 15 compounds. Of the remaining 17 compounds, clear-cut determination of positive or negative effects was made for 14 compounds, while data for 3 compounds were only suggestive of either negative or positive effects. 10 chemicals have been shown to induce heritable translocations. These chemicals are either direct or indirect alkylating agents. The heritable-translocation test needs to be improved before it can be used in wide-scale practical testing. The most important question is whether or not historical controls can be used in tests for significance; the cost of concurrent controls is prohibitive. There is a need to standardize methods used in testing laboratories with respect to the size of error involved in classifying translocation heterozygotes and the power of the test. There is also a need to study in the effectiveness of non-alkylating clastogens in inducing heritable translocations in mice.

Infected median sternotomy wound. Successful treatment by muscle flaps

The purpose of this paper is to present the experience at Emory University Hospital with the infected median sternotomy wound and to offer a treatment plan for those patients recalcitrant to the usual therapy of debridement and closed catheter irrigation with antimicrobial agents. When standard treatment fails, we proceed not only with the necessary thorough debridement to convert the wound to a relatively clean one but also concomitant closure by pectoralis major muscle flaps to completely obliterate dead space. Transposition flaps of rectus abdominus muscle or omentum are used when necessary to complete the closure. In the initial phase of this study, there were 3,239 patients who underwent open heart procedures through a median sternotomy approach in the years 1975 through 1978. In the 50 patients who had wound infections (1.54%), there were nine deaths. Three were thought to be unrelated to the sternal wound infection, four patients ruptured the ventricle or aorta, two patients died of generalized sepsis. Of these 50 patients, 22 responded to simple drainage; 28 had involvement of the mediastinum (0.86%). Of the 28 patients, 25 had debridement and closed mediastinal irrigation by catheter. Fourteen of these 25 did not respond. In these failing patients, 12 were treated by further debridement and closure by muscle flaps. Nine of these 12 were rescued. In the past nine months, an additional 1,052 patients had an open heart procedure. Of these, 11 had a median sternotomy infection. There have been no deaths in this latter group of patients, most of whom were treated by the muscle flap procedure. In addition to the improvement in mortality, morbidity has been reduced substantially. This procedure provides for a rational approach that we have found to permit salvage of a high percentage of patients who failed conventional closed irrigation techniques.

The burned female breast

Historically, treatment of the burned female breast has been unsatisfactory. By using the latissimus dorsi myocutaneous flap, many patients can be reconstructed in a single operation. A more aggressive approach in adolescent patients whose breasts are developing may result in more normal breasts. In such patients, nipple reconstruction is delayed until a later time.