Late effects of therapy of thalamic and hypothalamic tumors in childhood: vascular, neurobehavioral and neoplastic.

The late effects in children with hypothalamic and thalamic tumors relate to the effects of the tumor on the surrounding brain, the effects of surgery, radiotherapy (RT) and, to a lesser extent, chemotherapy. The clinical manifestations of late effects include endocrinologic dysfunction, neurocognitive sequelae, behavioral problems and second neoplasia. The prevention of late effects is an integral part of current treatment strategies. Early diagnosis, a rational use of surgery, and deferral of RT are the mainstays of the modern treatment in these patients. The improvement of RT techniques and the use of radioprotective compounds may further help spare normal brain tissue. A better understanding of chemotherapy use and the development of newer agents may increase efficacy, reduce side effects and allow deferral of RT in a greater percentage of patients. Finally, an aggressive management of endocrinological problems, physical and cognitive rehabilitation as well as psychological and school support help provide these children with maximal function within their potential.

Initial management of children with hypothalamic and thalamic tumors and the modifying role of neurofibromatosis-1.

Diencephalic gliomas may be grouped into 2 clinical categories. Optic pathway/hypothalamus gliomas (OPG) arise primarily from a slower-growing juvenile pilocytic astrocytoma, and thalamic gliomas arise primarily from a fibrillary astrocytoma which can become clinically and histologically more aggressive. Children with OPG have an excellent long-term prognosis with a 10-year survival of over 85%. The major therapeutic challenge for these patients is to maximize their quality of life by preserving visual and endocrine function while minimizing treatment-related morbidity. Treatment is often initiated at diagnosis in infants and toddlers who have a major visual impairment or the diencephalic syndrome. The judicious application of chemotherapy may serve to forestall the need for radiotherapy or surgery. Children with neurofibromatosis-1 (NF-1) usually have a more indolent course. Tumors may grow more slowly or occasionally regress spontaneously. However, over 90% of children with OPG without NF-1 will require some form of therapy. Patients with thalamic gliomas present with a shorter history, often with hydrocephalus. Surgical intervention is often required to relieve intracranial pressure and establish the histologic identity of the tumor. Over 75% of these tumors will become locally aggressive. Current multimodality therapy is relatively ineffective. The bithalamic variant behaves similarly to a pontine glioma.

Expression of plasma membrane calcium ATPases in phenotypically distinct canine vascular smooth muscle cells.

Our laboratory has identified at least two types of vascular smooth muscle cells (VSMCs) that exist in canine arteries and veins: type 1 cells, located in the media express muscle specific proteins but do not proliferate in culture; and type 2 cells, located in both media and adventitia, do not express muscle specific protein but proliferate in culture. Plasma membrane Ca(2+)-ATPases (PMCAs) have been implicated in proliferation control. The present study examines the expression of PMCA isoforms and calmodulin-binding domain splice variants in these two types of canine VSMCs. PMCA protein was found in both type 1 and type 2 cells. Reverse transcriptase-polymerase chain reaction assays were developed for canine PMCA calmodulin-binding domain splice variants. We cloned and sequenced isolates corresponding to PMCA1b, 4a and 4b from canine VSMCs. PMCA 2 and 3 were not detected. Freshly isolated type 1 cells expressed PMCA 1b, 4a and 4b, while freshly isolated type 2 cells expressed PMCA1b and 4b. Upon placement in culture, type 2 cells originating from either carotid artery or saphenous vein demonstrated a time-dependent upregulation of PMCA4a mRNA. Treatment with the phosphoinositide 3-kinase inhibitor wortmannin produced concentration-dependent inhibition of both PMCA4a upregulation and [(3)H]thymidine incorporation. These findings suggest a role for phosphoinositide 3-kinase in regulating PMCA expression, which may be important in the control of Ca(2+)-sensitive VSMC functions.

Hypothalamic-pituitary-adrenal function following cranial irradiation.

We assessed the effect of cranial irradiation on hypothalamic-pituitary (HP)-adrenal function in 17 patients (12 females, 5 males) treated with cranial/ craniospinal irradiation for acute leukemia (2 patients) or tumors distant from the hypothalamus and pituitary (8 medulloblastoma, 3 astrocytoma, 3 rhabdomyosarcoma, 1 ependymoma). Estimated doses of radiation (RT) to the HP region ranged from 18 to 72 Gy. Thirteen of seventeen patients were also treated with chemotherapy. Patients were a median of 3.75 years of age (1.5-19 years) at diagnosis and were studied at a median of 5 years (0.1-20 years) after RT. Patients received corticotropin-releasing factor (oCRF, 1 microgram/kg i.v.), and sampling for cortisol and ACTH levels was performed at -15, 0, 15, 30, 60, 90 and 120 min. The-5- and 0-min levels were combined for a standardized baseline value (Base). Cortisol levels at 0, Base, 30 and 120 min, as well as the peak cortisol response, were significantly lower in the patients. Twelve of seventeen patients' peak cortisol levels fell below the normal range. The patients' mean integrated values for cortisol (area under the curve) were not, however, different from controls. The ACTH responses to oCRF did not differ between patients and controls. No relationship was observed between ACTH or cortisol responses and the time elapsed from treatment or dose of HP RT. Further, in 10 of 12 patients, 0-min dehydroepiandrosterone sulfate levels were lower than the expected normal mean levels for age, sex and pubertal status, and in 4 of these 10 patients the values were below the normal range. These data suggest that some patients treated with HP RT may be at risk for adrenal insufficiency.

Glucocorticoid and polyamine involvement in zinc uptake by COMMA-1D mammary epithelial cells.

The objective was to determine if a mammary cell line shows glucocorticoid stimulation of Zn uptake, and to determine whether polyamines mediate this stimulation. 65Zn uptake by COMMA-1D mouse mammary epithelial cells over a 24-h period increased significantly in cells administered 10(-7) or 10(-6) M hydrocortisone. Incorporation of 65Zn over a 1-h period was not hydrocortisone-responsive, suggesting that these incubation times represent uptake into different pools. The rate of entry into the cells over a 15-min period was significantly increased by supplementing cells with hydrocortisone with or without prolactin. Initially, cells grown in lactogenic hormone-supplemented media (10(-6) M hydrocortisone + 5 micrograms/mL ovine prolactin) had up to 65% greater 65Zn uptake over 24 h than cells in nonsupplemented growth media. 65Zn uptake from hormone media with the spermidine synthesis inhibitor methylglyoxal-bis-(guanylhydrazone) (MGBG, 10(-5)M) added was less than from growth media. Exogenous spermidine (10(-6)-10(-3)M) added to the MGBG + hormone media increased 65Zn uptake. Difluoromethylornithine (DFMO), an inhibitor of spermidine synthesis that blocks ornithine decarboxylase, caused a slight dose-dependent decrease in 65Zn uptake over the range 10(-6)-5 x 10(-3)M (p < 0.002) and tended to decrease 65Zn-uptake in lactogenic hormone-stimulated cells with 8 h of incubation, but not at other times. These data show that Zn uptake in mammary epithelial cells can be hormonally mediated by glucocorticoids and suggest that polyamines may be intracellular mediators of this effect.

Glucocorticoid effects on zinc transport into colostrum and milk of lactating cows.

Colostrum Zn concentrations were measured in eight randomly selected Holstein dairy cows. Overall mean Zn concentrations were highest within 12 h postpartum (257 +/- 14 microM, mean +/- SEM), fell to 141 +/- 8 microM by 24 h, and then declined at a linear rate of 30 microM/d during the following 48 h. Zn concentrations at 3 d (82 +/- 5 microM) were not different from 150-d milk samples (72 +/- microM). In a second experiment, 32 early-gestation cows were blocked by stage of lactation into four groups in a randomized block design and injected with 0, 15, 30, or 45 mg of dexamethasone. Milk and blood samples were collected at 0, 12, and 24 h after injection and analyzed for Zn, and for fat, protein, and lactose in milk. Cows administered 0 and 15 mg of dexamethasone showed no difference in milk Zn concentrations compared to pretreatment measurements; however, milk Zn concentrations in cows administered 30- and 45-mg doses increased significantly. Plasma cortisol decreased in the dexamethasone-treated cows. Plasma Zn and milk fat, protein, and lactose did not change. These data indicate that glucocorticoids can mediate Zn uptake and transport by the mammary glands of lactating cows and suggest that the high Zn concentration in colostrum could be a result of the preparturient surge of cortisol.

Effects of ensiling on the digestibility and utilization of whole oilseeds by wethers.

Two digestion and N metabolism trials were conducted with 35-kg wethers to assess the feeding value of whole cottonseed or soybeans ensiled with corn silage in 3.6-m3 concrete silos (1.8 x 1.4 m). Dietary treatments for the cottonseed trial were ensiled whole cottonseed, untreated whole cottonseed, and 21 or 13% cottonseed meal in a basal diet of corn silage. There were no differences among treatments for DM and ADF intakes. Including ensiled or whole cottonseed in rations decreased digestibility of DM and ADF. Digestibility of CP was similar for the 21% cottonseed meal and whole cottonseed treatments. Nitrogen retention was similar for all treatments. Treatments for the soybean trial were ensiled whole soybeans, untreated whole soybeans, and 4 or 14% soybean meal. Lambs fed 14% soybean meal consumed more DM and ADF than those fed whole soybeans. Dry matter and ADF digestibilities were similar for all diets. Lower CP intakes resulted in less retained N for lambs fed whole soybean diets compared with those fed 14% soybean meal. Ensiling soybeans did not affect digestibilities of DM, CP, or ADF, or N retention. Ensiled whole soybeans or whole cottonseed may be fed to wethers as an alternative to separate feeding of oilseed meals with little effect on intake, CP digestibility, or N retention.

High-dose leucovorin reverses acute high-dose methotrexate neurotoxicity in the rat.

Intravenous high-dose methotrexate (HD-MTX) reduces cerebral glucose metabolism and produces behavioral abnormalities and electroencephalographic slowing in an animal model of acute HD-MTX neurotoxicity and in cancer patients undergoing HD-MTX chemotherapy. We used our model of HD-MTX neurotoxicity in the rat to determine if leucovorin (5-formyltetrahydrofolate) reduces this neurotoxicity, and extended our characterization of this model to identify regional as well as global HD-MTX treatment effects and to investigate HD-MTX-induced alterations in regional brain pH. Intravenous high-dose leucovorin reversed the HD-MTX-induced decrease in cerebral glucose metabolism and associated behavioral and electroencephalographic abnormalities in the rat, but low-dose leucovorin was ineffective. The major effect of HD-MTX on cerebral glucose metabolism was a global reduction; however, smaller region-specific treatment effects were identified in auditory, thalamic, and white matter structures. HD-MTX did not alter regional brain pH. These findings suggest a potential clinical role for high-dose leucovorin in severe or prolonged acute HD-MTX neurotoxicity and provide an important justification for the role of positron emission tomography in the early detection of clinical HD-MTX neurotoxicity.

Preradiation high-dose intravenous methotrexate with leucovorin rescue for untreated primary childhood brain tumors.

Although high-dose intravenous (IV) methotrexate (MTX) with leucovorin rescue (HDMTX) is effective for certain recurrent primary brain tumors, concern for inducing leukoencephalopathy has restrained its use as adjuvant therapy following therapeutic brain irradiation (RT). We have conducted a phase I to II clinical trial using four biweekly courses of HDMTX (8 g/m2) in a neoadjuvant setting in ten patients with newly diagnosed high-risk pediatric primary brain tumors. Four patients experienced an objective response after two to four courses of HDMTX alone (medulloblastoma, one; pineoblastoma, one; malignant cerebral astrocytoma, two). All ten patients subsequently received a course of therapeutic RT, and in seven cases, adjuvant chemotherapy with other agents. One patient acquired an acute transient encephalopathy before RT that completely resolved, and another developed a seizure disorder following RT associated with white matter abnormalities on a magnetic resonance imaging (MRI) scan. Five patients have survived a minimum of 33+ months, and four remain in continuous remission. The acute and delayed neurotoxicity of neoadjuvant HDMTX is acceptable, and we favor further use of this neoadjuvant approach in the context of a phase III trial.

Acute high-dose methotrexate neurotoxicity in the rat.

Intravenous high-dose methotrexate chemotherapy may produce acute, subacute, or chronic neurotoxicity in patients with cancer. Acute encephalopathies following high-dose methotrexate treatment are recognized with increasing frequency. This study describes a model of acute high-dose methotrexate neurotoxicity in the rat characterized by a profound dose-dependent depression of cerebral glucose metabolism in association with behavioral and electroencephalographic abnormalities. Alterations in the amino acid profile, similar to those described in cancer patients after high-dose methotrexate treatment, were observed in the absence of biochemical evidence of systemic organ toxicity. This model facilitates the study of the biochemical mechanisms of antifolate neurotoxicity in humans and permits the evaluation of potential therapeutic interventions.

Long-term endocrine sequelae after treatment of medulloblastoma: prospective study of growth and thyroid function.

Endocrine evaluations were performed prospectively in 22 patients with medulloblastoma (ages 2 1/2 to 23 1/2 years at diagnosis), after craniospinal radiation with or without adjuvant chemotherapy. The mean craniospinal hypothalamic-pituitary). and thyroid radiation doses were 3600 and 2400 rads, respectively. Fourteen (73%) of 19 patients who had not yet completed their growth experienced a decrease in growth velocity. However, only three of 10 of these children, who underwent growth hormone stimulation tests, had evidence of deficient growth hormone responses, suggesting that growth hormone secretory or regulatory dysfunction, rather than absolute growth hormone deficiency, is present in the majority of these children. Elevated thyroid-stimulating hormone levels were noted in 15 of 22 patients; one patient had hypothalamic hypothyroidism. Thus, the late effects of therapy for medulloblastoma include frequent endocrine morbidity involving hypothalamic-pituitary and thyroid dysfunction.

Transfer of selenium from blood to milk in goats and noninterference of copper with selenium metabolism.

The mechanism of selenium secretion by the mammary gland and effects of dietary copper and selenium metabolism on selenium in milk were investigated. Radioactive sodium selective selenite was injected into the jugular vein of lactating goats fed concentrates containing 15 or 115 ppm copper. Blood and milk samples were collected hourly for 8 h and daily for 1 wk. Whole blood, plasma, whole milk, and casein, whey, and cream fractions of milk were counted for selenium-75. No significant differences due to dietary copper were seen. The selenium-75 was primarily associated with the casein in milk. The association of selenium with the whey fraction was greater for early periods than later and varied between animals. The specific activity based on protein content was greater in casein than in whey. Peak selenium-75 in whole milk occurred 2 h after the peak in plasma. On day 7 following selenium-75 dosing, kidney had the highest specific activity, and liver was slightly higher than mammary tissue. All subcellular organelle fractions of liver, kidney, and mammary tissue by homogenization and differential centrifugation contained significant selenium-75. Selenium normally is secreted from the mammary secretory cell in combination with protein through the secretory vesicles, metabolism of selenite prior to milk secretion is important, and copper does not interfere with normal metabolism of selenium.

Selenium binding and distribution in goat and cow milk..

Raw milk from goats and cows (bovine) was combined with sodium selenite (.5 muCi/10 ml milk) and incubated at 39 C to allow selenium binding to milk components. After incubation intervals between .5 and 24 h, samples were separated into cream, whey, and casein fractions by centrifugation and acid precipitation. When samples were incubated up to 6 h, the aqueous whey fraction contained the highest amounts of radioactivity, the casein substantially less, and the cream contained little senenium-75. Twenty-four hours of incubation at 39 C caused the samples to curdle, resulting in a major shift of radioactivity from the aqueous phase to the acid precipitable (casein) fraction. This shift occurred in all curdled samples irrespective of time or temperature of incubation. Acidifying milk samples with lactic acid in the presence of a bacterial inhibitor also increased selenium binding by the casein fraction. Samples of whey fractions were applied to a Sephadex gel filtration column for further separation. Most of the selenium-75 was recovered in low molecular weight fractions. Radioaactive selenium appeared to remain largely in the unbound ionic form when added to noncurdled goats' or cows' milk. Most of the selenite added to milk does not combine with proteins at normal pH but increasingly does so as pH falls below 6.0.

Leukoencephalopathy following high-dose iv methotrexate chemotherapy with leucovorin rescue.

Seven patients with bone or soft tissue sarcomas but without metastatic CNS disease developed a chronic leukoencephalopathy after high-dose (8000-15,000 mg/m2) iv methotrexate (MTX) chemotherapy with leucovorin (LV) rescue. Approximately 12 MTX-LV treatments were administered over a 3-7 month period. None of the patients had cranial irradiation. The syndrome usually began several months after the initiation of chemotherapy with subtle personality changes followed by a progressive dementia, focal seizures, pseudobulbar palsy, spastic quadriparesis, and stupor. Computerized tomographic scans revealed diffuse white matter hypodensity in five patients and atropic changes in five patients. Serum MTX concentrations were elevated in four of six patients prior to several MTX-LV treatments, suggesting that MTX persisted in tissues for a long time. Abnormally high levels of MTX were detected in the cerebrospinal fluid of all four patients several days after an MTX-LV treatment, at a time when their encephalopathy was most severe. Pathologic brain material was obtained from three patients and revealed a spectrum of abnormalities. The syndrome observed in our patients clinically resembles the one described in children with acute lymphatic leukemia who received cranial irradiation and large cumulative amounts of low-dose (12-20 mg/m2) systemic MTX without LV.

Transient cerebral dysfunction following chemotherapy for osteogenic sarcoma.

An unusual neurological syndrome occurred in 4 of 158 patients treated for osteogenic sarcoma with combination chemotherapy. There was an abrupt onset of focal cerebral deficits approximately ten days after chemotherapy with vincristine and high-dose methotrexate plus citrovorum factor rescue. The syndrome was short lived and always occurred early in the course of treatment. Prolonged neurological deficits remained in 2 patients. When similar chemotherapy was reinstituted in the 4 patients, no further neurological complications ensued. Possible causes include a leukoencephalopathy related to methotrexate or an embolic cerebral vasculopathy related to necrotic tumor microemboli emanating from the lungs.

Ca++-binding properties of cznine aortic microsomes: lack of effect of c-AMP.

Ca++-binding to a microsomal fraction canine aorta has been studied and compared to Ca++-binding to canine cardiac microsomes. The aortic microsomes bound up to 60 nmoles Ca++/mg protein with a first-order binding rate constant of 0.025 sec-1. The binding rate of 5 sec was about half that of cardiac microsomes, 8 versus 15 nmoles/mg. The Ca++-binding to the aortic microsomes had a pH optimum of 7.4, was inhibited by monovalent cations and showed ATP preference when compared to other nucleotides. The binding was not stimulated by the presence of oxalate. c-AMP stimulated incorporation of 32P into the preparation, but had no effect on Ca++-binding.

Renal sodium-potassium-activated adenosine triphosphatase and sodium reabsorption.

The role of renal Na(+),K(+)-ATPase in sodium reabsorption was further examined in dogs in which digoxin, a specific inhibitor of the enzyme system, was infused into one renal artery in doses ranging from 0.4 to 0.9 mug/kg/min (low dose) and from 1.0 to 4.0 mug/kg/min (high dose). A significant natriuresis occurred with both dose ranges which was accompanied by inhibition of Na(+),K(+)-ATPase of cortex and medulla in the infused kidney. Despite over 90% enzyme inhibition in many experiments, at least 80% of the filtered sodium continued to be reabsorbed. The per cent change in enzyme activity correlated with the rate of digoxin administration and the total dose administered but not with changes in sodium excretion. Changes in medullary Na(+),K(+)-ATPase activity, however, bore a direct relationship to alterations in fractional solute free water reabsorption (T(c) (H2O)). Inhibition of cortical enzyme activity alone was not associated with natriuresis, suggesting that medullary enzyme activity must be depressed for increased sodium excretion to occur during digoxin infusion. In high-dose experiments, significant inhibition of cortical and medullary enzyme in the contralateral control kidney was also observed, but natriuresis did not occur. In these experiments the rate at which digoxin reached the control kidney rose progressively but never equaled the rates in the directly infused kidney with either dose. Nevertheless, it is clear that under certain circumstances enzyme inhibition of either cortex or medulla need not be accompanied by natriuresis. We conclude that the major role of renal Na(+),K(+)-ATPase is in sodium reabsorption in the medulla (ascending limb of Henle's loop) and that it has a relatively small role in proximal sodium reabsorption. The kidney can rely on other sodium reabsorptive mechanisms depending on the rate of enzyme inhibition, so that natriuresis may not occur at all if depression in activity occurs "slowly." The nature of these mechanisms is not clear.