Evaluation of the in vitro genetic toxicity of 4-(2, 4-dichlorophenoxy)butyric acid.

The herbicide 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) is principally used in the USA on peanuts, soybeans and alfalfa. In Europe, it is used on undersown spring barley and grassland (with clover). The genetic toxicity in vitro of the dimethylamine salt of 2,4-DB was examined by employing a range of end points including gene mutation in bacteria (Ames test) and mammalian cell cultures (CHO/HGPRT assay), cytogenetic abnormalities in mammalian cells (CHO/chromosomal aberration assay), and induction of DNA damage and repair in rat hepatocytes. There were no indications of genotoxic potential for 2,4-DB in the first three of these assays. One of the two criteria for a positive response in the UDS assay was exceeded but the increases did not exceed the second criteria for a positive response. The test material was therefore evaluated as weakly active in this assay. The weight of the evidence clearly indicates that 2, 4-DB is not genotoxic to mammals and are consistent with the reported lack of carcinogenic potential for 2,4-DB in both mice and rats.

Randomized, multicenter comparison of oral granisetron and oral ondansetron for emetogenic chemotherapy.

STUDY OBJECTIVES: To compare the antiemetic effectiveness and safety of oral granisetron plus dexamethasone with those of oral ondansetron plus dexamethasone administered before emetogenic chemotherapy. DESIGN: Randomized, prospective, multicenter, open-label study. SETTINGS: University-teaching hospital and veterans health care system. PATIENTS: Sixty-one chemotherapy-naïve patients scheduled to receive emetogenic antineoplastic agents. INTERVENTION: A single-dose oral granisetron 1 mg and dexamethasone 12 mg or single-dose oral ondansetron 16 mg and dexamethasone 12 mg was administered before chemotherapy. MEASUREMENTS AND RESULTS: Twenty-four hours after administration patients were contacted to assess nausea, emesis, and adverse events. There were no statistical differences in frequency of nausea or emesis between groups. Seventy-six percent and 82% of patients receiving ondansetron and granisetron, respectively, experienced no emesis 24 hours after chemotherapy. Complete protection from nausea occurred in 58% and 46% of patients receiving the drugs, respectively. Adverse events were similar between groups. CONCLUSION: Oral granisetron 1 mg and ondansetron 16 mg plus dexamethasone are safe and effective in preventing nausea and vomiting related to emetogenic chemotherapy.

Antispasticity medications.

The article illustrates a practical approach to the challenging management of problematic, generalized spasticity. Use of dose titration to achieve symptomatic relief is described. Currently approved pharmaceuticals used as antispasticity agents and muscle relaxants and other medications with antispasticity effects are reviewed.

Diagnosis and medical management of multiple sclerosis.

There are obviously fundamental differences between MS and SCI in pathology and in the kinds of symptoms; there are also many similarities. If the spinal cord is a prime focus of attack by the autoimmune processes that underlie MS, many of the symptoms produced thereby are the same as those we are accustomed to treating in people with SCI. MS is a more common illness than SCI, and a devastating one. It is one that all of those who manage patients with spinal cord impairments need to become increasingly familiar with.

Lack of genotoxic effects of sucrose acetate isobutyrate (SAIB).

Sucrose acetate isobutyrate (SAIB) was tested for potential genotoxic activity in four different in vitro assay systems. Two independent trials of a Salmonella reverse mutation assay (using strains TA98, TA100, TA1535, TA1537 and TA1538) showed no increases in revertant frequencies at doses up to 10,000 microg/plate which was non-toxic but exceeded the solubility limit. Similarly, no mutagenic response was observed at doses up to 1000 microg/ml at the HGPRT locus in cultured CHO cells; SAIB was toxic and its solubility limit was exceeded at 50 microg/ml. No clastogenic activity was detected in cultured CHO cells at concentrations up to 2000 microg/ml. All three preceding in vitro tests were conducted both in the presence and absence of Aroclor 1254-induced rat liver S-9 metabolic activation systems. An unscheduled DNA synthesis assay also was performed using rat primary hepatocyte cultures with doses up to 1000 microg/ml, and no DNA repair was detectable. Thus, SAIB was stringently tested at doses exceeding the solubility limit in culture medium and causing toxicity to CHO cells without obtaining any evidence for genotoxic activity as a mutagen, clastogen, or DNA-damaging agent.

Conservative management of spontaneous rupture of Kock orthotopic ileal reservoir.

Reports of spontaneous rupture of continent urinary diversions are rare. Management of the reported cases has been solely by exploratory laparotomy with primary repair of the defect. We describe 2 cases of spontaneous rupture of an ileal reservoir successfully managed nonoperatively.

Evaluation of spontaneous and chemical-induced lacI mutations in germ cells from lambda/lacI transgenic mice.

The spontaneous mutant frequency in germ cells isolated from seminiferous tubules of two lambda/lacI transgenic mouse strains, C57BL/6 and B6C3F1 was evaluated. At least 500 000 phage were screened for mutation at lacI for each animal using standardized assay procedures. The germ cell spontaneous lacI mutant frequency was 17.8 +/- 8.1 x 10(-6) in C57BL/6 mice and 17.0 +/- 10.0 x 10(-6) in B6C3F1 mice. The induction of germ cell mutations by three well characterized alkylating agents were also evaluated in C57BL/6 mice on day 3 after a single dose administration. The lacI mutant frequencies were significantly elevated in transgenic mice dosed with ENU at 150 mg/kg (2-fold increase above control) and iPMS at 200 mg/kg (3-fold increase above control) but not in those receiving MMS at 40 mg/kg. These findings suggest that single dose studies using the lambda/lacI transgenic system may be capable of detecting germ mutations induced by chemicals characterized either by point mutations or small, intragenic deletions but not those characterized by a predominance of multi-locus deletions.

Phase I study of high-dose etoposide phosphate in man.

Etoposide is a widely used cytotoxic agent with a broad spectrum of activity in human malignancies. This agent has been incorporated into many transplant regimens although toxicity occurs because of its poor water solubility and toxic excipients. Etoposide phosphate, a water soluble prodrug of etoposide, has been studied at conventional dosages in man and shown to have advantages over the parent compound. We have extended our previous experience with this new agent to evaluate the levels needed in transplantation protocols. This phase I study of intravenous high-dose etoposide phosphate over 2 h on days 1 and 2 was designed to determine whether or not dose linearity between the amount of etoposide phosphate administered to patients and generation of etoposide in vivo as seen with conventional dosages of this agent would be present at transplant-dose levels. In addition, the toxicities of these dose levels with the short infusion schedule were defined. A conservative dose escalation scheme was chosen based upon prior knowledge of etoposide. Thirty-one patients (19 male, 12 female) with CALGB performance status 0-1 with a variety of solid tumors entered this study. The patients were treated with dose levels of etoposide phosphate given as the etoposide-equivalent doses of 250, 500, 750, 1000, 1200, 1400, and 1600 mg/m2/day in 250-400 ml of normal saline given as an intravenous infusion over 2 h on days 1 and 2 every 28 days. After the maximal tolerated dose level was determined on this schedule, additional patients received etoposide phosphate as a 4 h infusion on both days in an attempt to reduce toxicities. G-CSF (5 micrograms/kg/day) was administered subcutaneously to all patients from day 3 until the WBC > or = 10000/microliters. Nonhematologic toxicity was considered to be dose limiting. Serial plasma samples for pharmacokinetics were obtained from patients on day 1 of cycle 1. For the 2 h infusion, the maximum tolerated dose of etoposide phosphate was 1000 mg/m2/day x 2 with dose limiting mucositis. In the small number of patients studied, the maximum tolerated dose was reached for the 4 h infusion at 1400 mg/m2/day of drug, again due to mucositis. Other toxicities, despite the rapid infusion schedule, were modest with transient mild headache being most common. At the highest doses etoposide phosphate was efficiently and rapidly dephosphorylated to etoposide. Etoposide generated by dephosphorylation of etoposide phosphate had plasma disposition curves characteristic of etoposide administered parenterally. One partial response occurred in a patient with small cell lung cancer. Etoposide phosphate can be rapidly infused in modest fluid volumes at dosages required for transplantation protocols with minimal acute side-effects. On a 2 h schedule, mucositis becomes the dose limiting nonhematologic toxicity. Mucositis seems to correlate with peak dose levels of the drug rather than total drug administered. On a 4 h infusion schedule given sequentially for 2 days, the maximum tolerated dosage could be increased 40% compared to the 2 h schedule. The relative ease of administration and the rapid conversion of this prodrug into etoposide should make it useful in high-dose therapy settings.

Injury zone denervation in traumatic quadriplegia in humans.

In order to obtain an electrophysiological characterization of the injury zone in traumatic quadriplegia, we performed electromyography and nerve conduction studies on the upper limbs of 15 patients with cervical cord trauma. Evidence of significant axonal loss was found in multiple myotomes of all patients. In most cases, the level of the most severe denervation, as determined by the absence or diminution of the compound motor action potential and the density of fibrillation potentials, was 2-5 spinal segments below the clinically and radiologically defined injury levels. In patients with injuries, the rostral extent of which is at C5 or higher, the most obvious clinical and electromyographic denervation was seen in the intrinsic hand muscles (C8/T1), with complete loss of C8/T1 motor axons in a subset of these patients. Our results document that spinal cord trauma can cause loss of motor axons in regions several segments caudal to the rostral level of injury. This finding may have implications for the pathophysiology of secondary injury, for recovery potential, and for the design of rehabilitation strategies.

Interlaboratory comparison: liver spontaneous mutant frequency from lambda/lacI transgenic mice (Big Blue) (II).

Spontaneous mutant frequency in livers of two transgenic mouse strains, each carrying identical lambda shuttle vectors with a lacI target gene, was evaluated by two laboratories. These studies investigated variability in spontaneous mutant frequency between animals and as a function of the number of phage screened. Liver DNA was independently isolated from 7-11 week old C57BL/6 and B6C3F1 Big Blue transgenic mice. At least 500,000 phage were screened for mutation at lacI for each animal using standardized assay procedures. In the two labs, the C57BL/6 liver spontaneous mutant frequency was 45 +/- 9 x 10(-6) and 41 +/- 7 x 10(-6). The B6C3F1 liver spontaneous mutant frequency was 42 +/- 10 x 10(-6) at one lab and 43 +/- 12 x 10(-6) and 41 +/- 8 x 10(-6) in two trials at the second lab. Mean mutant frequency data from both labs, calculated in increments of 100,000 plaque forming units (pfu) scored for each mouse strain, show stabilized mean mutant frequency and standard deviation after approximately 200,000-300,000 pfu screened. The frequency of spontaneous lacI mutants was reproducible both within and between labs and was comparable between the two transgenic mouse strains.

Intralaboratory optimization and standardization of mutant screening conditions used for a lambda/lacI transgenic mouse mutagenesis assay (I).

A lambda/lacI shuttle vector transgenic mouse mutagenesis assay has been optimized and standardized for reproducible mutant detection. The mutagenic endpoints are blue lacI- phage plaques on a bacterial lawn resulting from the de-repression of beta-galactosidase activity acting on the chromogenic substrate X-gal. Non-mutant lacI phage plaques remain colorless. Factors demonstrated to affect mutant detection include X-gal concentration per assay tray, plaque density per assay tray, pH of plating agar, incubation time at 37 degrees C and the use of a red translucent screening filter over a light source to enhance mutant plaque visibility. In vivo mutant frequencies for liver in untreated animals using standard protocols and internal controls were repeatable in separate experiments using lambda/lacI B6C3F1 mice (4.3 +/- 1.2 x 10(-5) and 4.1 +/- 0.8 x 10(-5)). These studies analyze the use of internal controls to monitor the level of mutant phage plaque detection in a given experiment and evaluate the repeatability of observed mutant frequencies obtained when using standardized procedures.

Spasticity: a review.

This symposium is concerned with the treatment of spasticity and, in particular, with results from studies of tizanidine as a treatment for patients with MS and spinal cord injury. In this article, the definitions and pathophysiologies of spasticity are reviewed, and the issue of when and if to treat spasticity is evaluated. The merits of newer pharmacologic and invasive therapies are discussed relative to reduction of patient discomfort and the possibility of restored function.

Tremor: classification, diagnosis and management.

Tremor can range from imperceptible physiologic movements to severely handicapping shaking. It can be a single entity, or it can occur in association with a disease that affects the basal ganglia, brainstem, cerebellum or peripheral nervous system. Tremors can be classified according to their anatomic location, the circumstances under which they occur, their frequency and amplitude, and whether they are physiologic or pathologic. As an isolated disorder, tremor should be treated only when it impairs the patient's ability to perform activities. Successful treatment requires the identification of precipitating factors, as well as associated signs and symptoms.

Long lasting excitability changes in human peripheral nerve.

When pairs of equal but submaximal electrical stimuli are delivered to a peripheral nerve, the second stimulus does not always excite the same number of fibers as the first. The number of fibers responding to the second stimulus depends on the interstimulus interval; the refractory period, a well-defined period of hypoexcitability, is followed by longer lasting and less well-characterized periods of hyper- and hypoexcitability. These cycles last at least 200 ms after the initial stimulus. We have carefully studied these cycles of excitability in human peripheral nerve in 12 normal subjects. The magnitude of excitability changes were found to be much greater in motor fibers than in mixed nerve; under some conditions, the motor response was reduced by more than 80% at interstimulus intervals of 40 ms, while the mixed nerve response never varied by more than 20%. In addition, the amplitude of the excitability changes varied as a function of the stimulus strength, so that stimuli that were near threshold or evoked near maximal responses were associated with smaller excitability changes than stimuli evoking midrange responses. Given that the excitability fluctuations are of large magnitude and occur at interresponse intervals easily achieved during physiological firing, it is suggested that they may be important modifiers of firing rate under experimental or physiological conditions.

The effect of nicotine on recurrent inhibition in the spinal cord.

Recurrent inhibition via Renshaw cells provides a mechanism by which spinal and supraspinal centers exert control over movement. The conditioned H-reflex technique of Pierrot-Deseilligny and Bussel permits noninvasive assessment of recurrent inhibitory pathways. We employed this technique to investigate changes in Renshaw cell activity due to nicotine (a potent CNS cholinergic agonist that excites Renshaw cells in animals) contained in inhaled tobacco smoke. In 10 normal subjects, cigarette smoking caused a large, rapid drop in the conditioned H-response amplitude, implying increased activation of Renshaw cells. The time course of the change in conditioned H-response amplitude closely approximated the known pharmacokinetics of inhaled nicotine. Nicotine administered via chewing gum had a much slower and less dramatic effect, probably due to the slower rise in blood levels with this mode of administration. Increased activity in Renshaw cells may contribute to spasticity in spinal cord-injured patients, raising the possibility that cigarette smoking could cause further increases in tone in such patients.

Spinal cord injury. An overview.

Advancements in the management of urologic complications such as the neurogenic bladder have been essential to improving the quality of life and longevity of patients with spinal cord injury. These advances are discussed in greater detail in the subsequent articles in this issue. Despite the many improvements that have been made in post-trauma care, spinal cord injury remains a devastating lesion of the nervous system. Current therapies have not proved to be particularly effective in preventing or reversing damage to the spinal cord. Still, every effort should be made to preserve remaining function and to prevent complications. The care of these patients has been significantly improved with the development of specialized multidisciplinary centers. The emphasis in current treatment focuses on rehabilitation and adaptation to the disability and on prevention of secondary disabilities. Research in basic and clinical neuroscience will result in better, more useful care and treatment for those with spinal cord injury. However, even then, a neurorehabilitation team will be essential to care for these patients. Continuing efforts must be made to ensure that people with spinal cord injury lead full and productive lives.

Risk assessment for pressure ulcers: an adaptation of the National Pressure Ulcer Advisory Panel risk factors to spinal cord injured patients.

To estimate risk factors for pressure ulcers, we developed quantitative definitions for each of the nine general areas of risk outlined by the 1989 National Pressure Ulcer Advisory Panel (NPUAP) and evaluated each of these factors in a group of spinal cord injured patients by means of a retrospective chart review at a spinal cord injury referral center serving the New England area. All patients (n = 364) admitted to the spinal cord injury service between January 1, 1989 and December 31, 1990 were studied. We identified a pressure ulcer in 81 of 364 patients (22.3 percent). In the univariate analyses, pressure ulcers were associated with Frankel groups A to B with an odds ratio (OR) of 5.7 (95 percent confidence interval 2.8 to 11.9), low albumin with an OR of 4.9 (95 percent confidence interval 2.8 to 8.6), low hemoglobin with an OR of 2.5 (95 percent confidence interval 1.5 to 4.1), age > or = 60 years with an OR of 1.9 (95 percent confidence interval 1.2 to 3.2) and three independent measures of co-morbidity: Cumulative Illness Rating Scale (CIRS) with an OR of 3.7 (95 percent confidence interval 2.1 to 6.3), Charlson Index with an OR of 2.2 (95 percent confidence interval 1.3 to 3.8), and International Classification of Diseases, Ninth Revision, Clinical Modification count with an OR of 4.2 (95 percent confidence interval 2.4 to 7.2). In the logistic regression model, low albumin, CIRS and Frankel grade A to B and history of pressure ulcers were predictors.(ABSTRACT TRUNCATED AT 250 WORDS)

Discharge properties of single motor units in patients with spinal cord injuries.

To study neurophysiological correlates of spastic paresis, we analyzed the discharge pattern of single motor units (SMUs) during sustained voluntary contraction from muscles weakened by spinal cord injury (SCI) and from muscles of near normal strength just at or above the level of injury. The average firing rate of SMUs was reduced in patients' biceps brachii and tibialis anterior muscles compared with controls, but not in the triceps brachii. Floating serial correlation coefficients obtained from successive interdischarge intervals were significantly more positive in patients than in controls in all three muscles. One statistical measure of regularity of discharge, akin to a coefficient of variation, was best able to differentiate patient and control SMUs. Increased discharge variability in muscles just above the level of injury suggested that subtle effects of traumatic SCIs were more extended than was clinically apparent. Although consistent statistical differences could be measured, these changes were not specific to SCI, nor were all SMUs equally affected.