Beta-carotene and CNS oxygen toxicity in rats

Beta-carotenes are reported to be potent free radical quenchers, singlet oxygen scavengers, and lipid antioxidants. Oxygen free radicals that are produced in excess during exposure to oxygen at high pressures and overwhelm the body's normal antioxidant defense systems seem to mediate the hyperoxic insult. We decided to test the possible protective effect against central nervous system oxygen toxicity of a natural beta-carotene composed of equal amounts of the all-trans and 9-cis isomers obtained from the unicellular halotolerant alga Dunaliella bardawil. Rats implanted with chronic cortical electrodes for continuous electroencephalogram monitoring were fed on ground commercial food enriched with natural beta-carotene (1 g/kg diet). On completion of 1 wk of the diet, the rats were exposed to 0.5 MPa oxygen and then their livers were removed for beta-carotene and vitamin A analysis. A significant increase was noted in the latent period preceding oxygen seizures in the group of rats in which the diet was supplemented by natural beta-carotene compared with rats given a normal diet (38.5 +/- 3.4 vs. 16.8 +/- 1.8 min; P < 0.05). Further experiments are required to evaluate the potential benefit of supplementing the diet of divers and patients exposed to high pressures of oxygen with the beta-carotene-rich D. bardawil.

Muscimol prevents neuronal injury induced by NMDA

The effect of muscimol on N-methyl-D-aspartate (NMDA)-induced injury of primary cultured cerebral cortical neurons was examined. NMDA induced a dose-dependent leakage of LDH activity, which was significantly inhibited by (+-)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclopentan-5,10-imine (MK-801). Muscimol significantly reduced the NMDA-induced increase of lactic dehydrogenase (LDH) leakage, and bicuculline abolished this protective effect of muscimol. Similarly, muscimol reduced the NMDA-induced increase in trypan blue staining of the cells, and bicuculline suppressed this inhibitory action of muscimol. These results suggest that GABAA-receptor stimulation exerts a protective action against the neuronal injury induced by NMDA-receptor activation.

Neuropsychiatric complications of cardiac surgery

Historically, intracardiac operations have carried a higher risk of neurologic complications than coronary artery bypass grafting (CABG) procedures, although the incidence of such complications has been increasing after CABG in recent years. In both intracardiac and extracardiac surgery, macroemboli from the surgical field cause most neurologic complications. The periods of highest risk for emboli are during aortic cannulation, onset of bypass, and weaning from bypass. Risk factors include atherosclerosis of the ascending aorta, advanced age, presence of concomitant cerebral vascular disease, previous neurologic abnormality, duration of surgery, diabetes, and history of failure of the native circulation. Although hypothermia is beneficial in elective circulatory arrest, its usefulness in reducing postoperative central nervous system deficits during routine cardiac operations may be limited. Studies suggest a role for barbiturate protection in intracardiac but not in extracardiac surgery. Studies have not shown better neurologic or neuropsychological outcome with the use of membrane oxygenation and arterial filtration. Recent studies suggest no correlation of neurologic injury with serum glucose levels during CABG, with either duration or severity of hypotension during hypothermic CABG, or with blood gas management during hypothermic CABG.

Neurologic sequelae secondary to atlantoaxial instability in Down syndrome. Implications in otolaryngologic surgery

OBJECTIVE

A comprehensive overview of atlantoaxial instability in Down syndrome as it relates to head and neck surgery and recommendations as derived from a review of the literature.

DATA SOURCES

English-language literature: otolaryngologic problems in Down syndrome and atlantoaxial biomechanics.

DATA SYNTHESIS

Children affected with Down syndrome frequently require otolaryngologic procedures such as myringotomy with ventilation tubes or adenotonsillar surgery. Atlantoaxial instability occurs in 10% to 20% of patients with Down syndrome who are at risk for atlantoaxial subluxation and subsequent complications during anesthetic induction and during positioning and manipulation associated with surgery. To identify patients who are at risk for atlantoaxial subluxation, guidelines have been adapted from the recommendations of the American Academy of Pediatrics and the Special Olympics Inc, which include preoperative neurologic assessments and cervical roentgenograms in the neutral, flexion, and extension positions. Children with an atlantodental interval of greater than 4.5 mm or with peripheral neurologic findings should have further evaluation.

CONCLUSIONS

A small percentage of patients with Down syndrome are at risk for atlantoaxial instability and subluxation. All patients with Down syndrome should have a preoperative neurologic assessment screening by the operating surgeon and/or a cervical roentgenogram in the lateral, extension, and flexion positions. Any abnormality should be investigated before surgery.

Reducing neurological complications after cardiac transplantation: technical considerations

As the survival rate for cardiac transplantation improves, attention focuses on morbid events that occur perioperatively. Neurological problems have been recognized after transplantation, and appear to have multiple etiologies including thromboembolism, hypoperfusion syndromes, cerebral hemorrhage, and drug toxicities. Since 1988, 113 consecutive adults with end-stage cardiomyopathy were transplanted using a surgical technique that emphasizes precise everting atrial and great vessel anastomoses, a modified order of anastomoses, continuous endocardial and topical cold irrigation, and careful de-airing of the heart. Although a significant fraction of the patients were at high risk for cerebral events, the incidence of early and late neurological complications were each under 2%. The rate of early graft dysfunction was low and no patient was found to develop intracardiac thrombus on intermediate-term follow-up. These technical modifications may contribute to improved neurological outcomes after transplantation.

Neuropsychological abnormalities following CNS prophylaxis in children with acute lymphatic leukemia

The pattern and prevalence of neuropsychological abnormalities in children receiving combination CNS prophylaxis (2000 rads cranial irradiation and intrathecal methotrexate) during therapy for acute lymphoblastic leukemia (ALL) were studied. Thirty five children (25 boys) in the age group 5-15 years (mean 9.3) with no evidence of CNS leukemia were included and 20 age matched normal siblings served as controls. Neuropsychological parameters of general intelligence (Malin's modification of WISC test); attention and concentration (colour cancellation test); memory (modified PGI memory test) and visuomotor perception (Bender Gestalt test) were evaluated at least 6 months after CNS prophylaxis. Six (17.1%) patients had mean intelligence quotients (IQ) less than 85, while all controls had IQ > 85 (p < 0.05). The mean IQ of the patient population (93.4 +/- 11.9) was significantly lower than the control group (107 +/- 8.4) (p < 0.001). Scores on the colour cancellation test were lower in the patients as compared to controls (148.7 +/- 27.7 versus 184.9 +/- 23.9; p < 0.01). The mean memory quotient in the patient population was also lower than in controls (74.5 +/- 12 versus 93.6 +/- 9.2; p < 0.001). Scores on the Bender-Gestalt test did not show a significant difference. The presence of significant neuropsychological abnormalities in patients of ALL indicates the need for modification of the schedule of CNS prophylaxis. A comprehensive psychometric evaluation at regular intervals is essential for longterm rehabilitation.

Superior cerebral protection with profound hypothermia during circulatory arrest

The optimal temperature for cerebral protection during hypothermic circulatory arrest is not known. This study was undertaken to test the hypothesis that deeper levels of cerebral hypothermia (< 10 degrees C) confer better protection against neurologic injury during prolonged hypothermic circulatory arrest ("colder is better"). Twelve male dogs (20 to 25 kg) were placed on closed-chest cardiopulmonary bypass via femoral artery and femoral/external jugular vein. Using surface and core cooling, tympanic membrane temperature was lowered to 18 degrees to 20 degrees C (deep hypothermia, n = 6) or 5 degrees to 7 degrees C (profound hypothermia, n = 6). After 2 hours of hypothermic circulatory arrest, animals were rewarmed to 35 degrees to 37 degrees C on cardiopulmonary bypass. All were mechanically ventilated and monitored in an intensive care unit setting for 20 hours. Neurologic assessment was performed every 12 hours using a species-specific behavior scale that yielded a neurodeficit score ranging from 0% to 100%, where 0 = normal and 100% = brain dead. After 72 hours, animals were sacrificed and examined histologically for neurologic injury. Histologic injury scores were assigned to each animal (range, 0 [normal] to 100 [severe injury]). At the end of the observation period, profoundly hypothermic animals had better neurologic function (neurodeficit score, 5.7% +/- 4.0%) compared with deeply hypothermic animals (neurodeficit score, 41% +/- 9.3%; p < 0.006). Every animal had histologic evidence of neurologic injury, but profoundly hypothermic animals had significantly less injury (histologic injury score, 19.2 +/- 1.2 versus 48.3 +/- 1.5; p < 0.0001).

Antibody-mediated clearance of viruses from the mammalian central nervous system

The novel role of antibody in clearing virus from the central nervous system without the help of other immune effectors is an important phenomenon that has only recently been documented. Possible routes for antibodies across the blood-brain barrier and how they work in the CNS are discussed here.

Extended triple intrathecal chemotherapy trial for prevention of CNS relapse in good-risk and poor-risk patients with B-progenitor acute lymphoblastic leukemia: a Pediatric Oncology Group study

PURPOSE

The Pediatric Oncology Group (POG) acute leukemia in childhood (ALinC) 13 study tested two treatment regimens that used different CNS chemoprophylaxis for children older than 12 months with non-T, non-B acute lymphoblastic leukemia (ALL) and with no demonstrable CNS disease at diagnosis.

PATIENTS AND METHODS

With the first regimen, standard (S), six injections of triple intrathecal chemotherapy (TIC), consisting of methotrexate (MTX), hydrocortisone (HC), and cytarabine (ara-C), were administered during intensification treatment and at every-8-week intervals throughout the maintenance phase for 17 additional doses. The second regimen, standard and MTX pulses (SAM), also specified six TICs during intensification, but substituted every-8-week pulses of intermediate-dose parenteral methotrexate (IDM; 1 g/m2) for the 17 maintenance TIC injections, with a low-dose intrathecal (IT) MTX boost administered with the first four maintenance IDM pulses. Otherwise, systemic therapy on regimen SAM was identical to regimen S. There were 1,152 patients randomized to the S and SAM regimens after stratification by risk group (age/leukocyte count) and immunophenotype.

RESULTS

The 5-year probabilities (+/- SE) of an isolated CNS relapse were regimen S: good risk (n = 381), 2.8% +/- 1.3%; poor risk (n = 196), 7.7% +/- 3.2%; good + poor risk (n = 577), 4.7% +/- 1.5%; regimen SAM: good risk (n = 388), 9.6% +/- 2.2%; poor risk (n = 187), 12.7% +/- 4.2%; good + poor risk (n = 575), 10.9% +/- 2.2%. In poor-risk patients, approximately one third of the isolated CNS relapses occurred before preventive CNS therapy was begun at week 9. Hence, regimen S has provided better CNS preventive therapy for both good- and poor-risk patients (P < .001 overall). The difference is statistically significant for good-risk patients (P < .001), but not for poor-risk patients (P = .20). Neither treatment has shown a significant advantage in terms of general outcome.

CONCLUSION

TIC injections extended throughout the intensification and maintenance periods are superior to IDM pulses for prevention of CNS leukemia. Our results with TIC seem comparable with those achieved with other contemporary methods of CNS preventative therapy. Thus, extended TIC affords a reasonable alternative to CNS irradiation plus upfront IT MTX for patients with B-progenitor ALL.

Magnetic resonance imaging of the pituitary area in children treated for acute lymphoblastic leukemia with low-dose (18-Gy) cranial irradiation. Relationships to growth and growth hormone secretion

OBJECTIVE

To determine the effects of 18-Gy cranial irradiation on growth, growth hormone (GH) secretion, and pituitary magnetic resonance imaging in children who underwent previous irradiation for treatment of acute lymphoblastic leukemia.

DESIGN

Clinical survey.

SETTING

Department of Pediatrics of the University of Bologna (Italy).

PATIENTS

Ten boys and 18 girls who were treated for acute lymphoblastic leukemia; median age at diagnosis was 3.1 years and at the end of follow-up was 11.5 years.

MEASUREMENTS AND RESULTS

Height was periodically measured from diagnosis until the end of follow-up, when GH secretion study and magnetic resonance imaging were performed. The mean height SD score was significantly lower than at diagnosis only at the end of treatment. Nocturnal mean GH concentration and GH response to pharmacological tests (arginine and levodopa [L-dopa]) were pathological in 22 cases (81.5%) and 18 cases (64.3%), respectively. Sixteen cases (59.2%) had a blunted GH release to the three tests. Mean pituitary anterior lobe height was reduced and seven subjects (25%) showed an empty sella.

CONCLUSIONS

Cranial irradiation with 18 Gy does not seem to influence the growth pattern of most children who are treated for acute lymphoblastic leukemia, despite severe impairment of GH secretion and morphological abnormalities of the sellar area. However, a follow-up until final height is necessary.

The effect of vigabatrin on central nervous system oxygen toxicity in rats

The toxicity of hyperbaric oxygen in the central nervous system is expressed by clinical and electroencephalographic (EEG) manifestations resembling those of generalized tonic-clonic seizures. In the search for drugs effective against these seizures, we tested vigabatrin, an irreversible inhibitor of GABA (gamma-aminobutyric acid) transaminase. Five different doses of vigabatrin (ranging from 50 to 500 mg/kg) or vehicle were injected i.p. in rats implanted with cortical electrodes, 4 h prior to exposure to 5 ATA (0.5 MPa) oxygen. EEG and spectral analysis of the background EEG activity were monitored for the different dosages of the drug. The duration of the latent period before the appearance of electrical discharges in the EEG was used as an index of oxygen toxicity. The protective effect of vigabatrin was dose-related, and complete protection against hyperoxic-induced discharges was at 180 mg/kg. The protective effect lasted 24 h and decreased gradually disappearing completely on the third day. An increase in the low frequency bands of the EEG and a decrease in the faster activity were correlated with the vigabatrin dosage injected. Our results suggest that vigabatrin has the potential of being a useful drug in the treatment and prevention of oxygen-induced seizures during hyperbaric oxygen therapy.

Prevention of H2O2 generation by monoamine oxidase protects against CNS O2 toxicity

Toxicity to the central nervous system (CNS) by hyperbaric oxygen (HBO) presumably relates to increased production of reactive oxygen species. The sites of generation of reactive oxygen species during HBO, however, have not been fully characterized in the brain. We investigated the relationship between regional generation of hydrogen peroxide (H2O2) in the brain in the presence of an irreversible inhibitor of catalase, aminotriazole (ATZ), and protection from CNS O2 toxicity by a monoamine oxidase (MAO) inhibitor, pargyline. At 6 ATA of oxygen, pargyline significantly protected rats from CNS O2 toxicity whereas ATZ enhanced O2 toxicity. In animals pretreated with ATZ, HBO inactivated 21-40% more catalase than air exposure in the six brain regions studied. Because ATZ-mediated inactivation of catalase was H2O2 dependent, the decrease in catalase activity during hyperoxia was proportional to the intracellular production of H2O2. Pargyline, administered 30 min before HBO, inhibited MAO by greater than 90%, prevented ATZ inhibition of catalase activity during HBO, and reversed the augmentation of CNS O2 toxicity by ATZ. These findings indicate that H2O2 generated by MAO during hyperoxia is important to the pathogenesis of CNS O2 toxicity in rats.

The value of assays in tricyclic antidepressant therapy

Studies are reviewed showing that neurotoxicity can be associated with plasma tricyclic antidepressant (TCA) assays above 350 ng/ml. The objective of this study was to develop guidelines in the use of plasma TCA assays from analysis of data of the treatment of patients with endogenous depressions and panic disorders with TCA dosages of 100-300 mgm per day. A total of 38.5% of a small group of patients treated with TCAs and concomitant neuroleptic therapy had plasma assays above 350 ng/ml; 16.7% of a larger group of patients treated with TCAs alone had assays above that level. Guidelines discussed for the use of plasma TCA assays come from analysis of the data and case vignettes.

Low-dose chemotherapy with central nervous system prophylaxis and zidovudine maintenance in AIDS-related lymphoma. A prospective multi-institutional trial

OBJECTIVE

--To ascertain if low-dose multiagent chemotherapy, with central nervous system prophylaxis and antiretroviral therapy, might be associated with increased efficacy and decreased risk of intercurrent infection in patients with malignant lymphoma related to the acquired immunodeficiency syndrome (AIDS).

DESIGN

--A phase II prospective clinical trial, with median follow-up of 33 months.

SETTING

--Eight university hospitals, within the context of the AIDS Clinical Trials Units, sponsored by the National Institute of Allergy and Infectious Diseases.

PATIENTS

--Forty-two patients with AIDS-related malignant lymphoma. All were evaluable for toxicity assessment, and 35 for response.

INTERVENTION

--A low-dose modification of the M-BACOD regimen (day 1): cyclophosphamide, 300 mg/m2 intravenously (IV); doxorubicin, 25 mg/m2 IV; vincristine sulfate, 1.4 mg/m2 IV; bleomycin, 4 mg/m2 IV; dexamethasone, 3 mg/m2 orally on days 1 through 5; methotrexate, 500 mg/m2 IV on day 15, with leucovorin rescue. Intrathecal cytosine arabinoside (50 mg) to all on days 1, 8, 21, and 28, with radiation therapy to a helmet field to those with central nervous system involvement. Zidovudine for 12 months after completion of four to six cycles of chemotherapy.

MAIN OUTCOME MEASURES

--Response rate and number of opportunistic infections.

RESULTS

--Response rate was 51% with a complete response of 46%. Of 16 complete responses, relapse occurred in four, none isolated to the central nervous system. Opportunistic infections occurred in 21% of those receiving treatment. Median duration of survival among all 42 patients is 5.6 months, 6.5 months in 35 patients evaluable for response, and 15 months in patients with complete response. Lower concentration of CD4 cells, history of prior AIDS, bone marrow involvement, and stage IV disease were independently associated with decreased survival.

CONCLUSIONS

--Low-dose chemotherapy with central nervous system prophylaxis and zidovudine maintenance may be associated with durable remissions in AIDS-related lymphoma with fewer opportunistic infections than noted in prior reports.

Nimodipine decreases resuscitability in a cardiopulmonary arrest model in the rat

Although calcium has been implicated in ischemia-induced brain death or dysfunction, many animal studies do not show a beneficial effect of calcium-entry blockers given after resuscitation from a cardiopulmonary arrest (CPA). This may be due to the fact that treatment was started too late; we, therefore, evaluated the effect of the calcium-entry blocker nimodipine administered at the earliest feasible postischemic moment, i.e. at the start of the resuscitation attempts. In anesthetized Wistar rats, CPA was induced by an intra-cardiac injection of KCl, and maintained for 7 min by chest restriction. At the start of the resuscitation attempts, 50 rats were blindly and randomly assigned to intravenous treatment with either nimodipine (10 micrograms/kg over 2 min, followed by 1 micrograms/kg per min for 60 min; n = 25) or saline (n = 25). In the nimodipine group, significantly less rats could be resuscitated (11/25 versus 20/25) and the survival rate at the end of the 7 days evaluation period tended to be lower (5/25 versus 11/25). In the rats surviving after 7 days, there was no difference between both groups in incidence of seizures, neurological status and histological lesions in the hippocampus. It is concluded that nimodipine, in the dose tested and given during resuscitation in this rat model, has a detrimental effect on resuscitability and no beneficial effect on the neurological outcome in the surviving animals.

Prevention, early detection, and management of oncologic emergencies

The prevention and early detection of oncologic emergencies is critical in caring for the person with cancer. Although many will not develop an oncologic emergency during the course of their illness, the approach outlined in this paper will contribute significantly to the prevention and relief of suffering in those individuals who may develop them.

Effect of administration of diethylcarbamazine on murine leukemia virus (Cas-Br-M) infected mice

Previous studies indicate that decreased serum viral infectivity and viral antigen levels follow oral administration of diethylcarbamazine (DEC) in feline leukemia virus infected cats, even though DEC has not been shown to exhibit in vitro antiviral activity. In this investigation, DEC was given by oral administration or (single dose) IP injection to murine leukemia virus (Cas-Br-M) inoculated mice to permit evaluation of its effect on viral-induced central nervous system disease. The survival of Cas-Br-M inoculated mice receiving DEC in water was significantly prolonged relative to similarly inoculated mice receiving distilled water. Among the Cas-Br-M inoculated mice euthanatized after the study, higher body weights and trend toward less severe brain and splenic lesions were noted in those receiving DEC in drinking water. Given these results, the possible utility of DEC in treatment of retroviral and other infections warrants further study.

Questionable role of CNS radioprophylaxis in the therapeutic management of childhood rhabdomyosarcoma with meningeal extension

A series of 15 consecutive children with head and neck nonorbital rhabdomyosarcoma (RMSA) with meningeal extension were prospectively treated with chemotherapy consisting of Adriamycin (doxorubicin; Adria Laboratory, Columbus, OH) (ADM), vincristine (VCR), cyclophosphamide (CPM), and dactinomycin (DACT) followed by radiotherapy (60 Gy) to the primary tumor volume, along with intrathecal methotrexate (IT MTX). Thirteen of 15 responded to preradiation chemotherapy. Four of 13 relapsed. Relapse occurred at the level of the primary tumor in three of four. The 3-year progression-free survival (PFS) was 59%, similar to that achieved in a previous series treated with a comparable therapeutic approach that also included whole-brain radiotherapy as a prophylaxis of possible occult meningeal seeding. It is concluded that CNS prophylaxis with radiotherapy is questionable in the management of childhood RMSA with meningeal extension.