Effects of continuous inhalation exposure of rats to radon and its progeny at various levels of dose and dose rate: interim results.

Studies of rats at Harwell and CEA [Monchaux et al., Radiat. Res. 152 (Suppl.), S137-S140, 1999] are currently in progress to determine the factors affecting the risk of induction of lung tumors after exposure to radon and radon progeny. Knowledge of the effect of dose, dose rate and characteristics of the aerosol on lung tumor induction in rats may be used to improve estimates of risk from domestic exposure. At Harwell, three studies are in progress, studying the effect of dose, dose rate, and dose rate at low total exposures. Approximately 2000 adult male rats have been exposed. A small number of rats were taken to determine deposition in the respiratory tract and the early effects of exposure on cell proliferation and nuclear aberrations. The remaining animals have been held for their life span. To date 65% of the animals in the first study have been examined. Current results (for 421 rats) suggest that exposure to radon and radon progeny causes elevated incidences of both benign and malignant lung tumors. These findings are based on incomplete tumor incidences. Competing causes of death may affect the results, and full statistical analysis is required before firm conclusions can be drawn about the effect of dose and dose rate.

Paraxial and lateral plate influences on reinitiation of wing development in chicken embryos.

Stephens et al. ([1993] Dev. Dynam. 197:157-168) hypothesized that the chick embryo wing territory is not an equipotential system. They proposed that following extirpation of the wing territory, limb formation is reinitiated, stimulated by more paraxial tissues. It was the purpose of this study to test this hypothesis. Four sets of procedures were undertaken in stage 11-12 chick embryos: 1) the wing territory lateral plate was removed (negative controls); 2) medial (between the central axis and somites), lateral (between the mesonephros and lateral plate), and intermediate (between the somites and mesonephros) foil barriers were placed adjacent to the wing territory (positive controls); 3) barriers were placed as above, with the removal of the lateral plate (experimental); and 4) barriers were placed lateral to the area of lateral plate extirpation (experimental). Normal limbs developed in 89% of the embryos without foil barriers with the lateral plate removed. In 93% of the embryos that contained medial barriers, normal wings developed whether or not the limb territory was extirpated, and in 100% of the embryos with intermediate or lateral barriers, with or without extirpation, deficient limbs occurred. When foil barriers were placed lateral to the wound, 87% of the chick wings were either reduced or absent. Closure of the wound following extirpation appeared to progress from lateral to medial. The data from this study appear to support the hypothesis that the limb territory is not equipotential but is reformed from cells closing the wound from lateral to medial, and is reinitiated from paraxial tissues (medial to lateral) following wound healing.

Care-giver evaluation of anti-gastroesophageal reflux procedures in neurologically impaired children: what is the real-life outcome?

Although the pediatric surgical literature is replete with reports of the success of operations for gastroesophageal reflux, postoperative complications are being reported with increasing frequency for the neurologically impaired subpopulation. Because a large portion of a care-giver's life is involved in attending to a neurologically impaired child, parental satisfaction with the outcome of these operations should be an important consideration when the use of such procedures is contemplated. The purpose of the present study was to assess the impact of antireflux operations with respect to care-giver opinions regarding the procedure. The authors retrospectively reviewed 25 charts (of 13 girls and 12 boys; age range, 3 months to 18 years) and documented (through survey results) perceived child well-being, objective care requirements, and overall care-giver satisfaction with the procedure. Results indicate there was significant improvement in feeding indexes, care-giver perception of the child's comfort, and quality of life postoperatively. Moreover, there was significant improvement in the care-givers' attitudes regarding their child, including the level of frustration in caring for the child, and the parents' overall quality of life. Care-givers also believed that the operation's result was about or better than what they had expected. In conclusion, the study documents care-giver satisfaction with antireflux procedures. Postoperatively, child care is easier and the quality of time spent with the child is better. The impression of better quality of life postoperatively for a neurologically impaired child may be the greatest success in this sometimes frustrating endeavor.

Aggressive fluid resuscitation following intestinal ischemia-reperfusion in immature rats prevents metabolic derangements and down regulates interleukin-6 release.

We have recently shown improved survival following intestinal ischemia-reperfusion in a model that utilized aggressive crystalloid resuscitation sufficient to eliminate reperfusion-induced cardiovascular instability. The aims of this study were to determine whether the salutary effects associated with this regimen were due to: 1) prevention of systemic metabolic derangements; 2) attenuation of secondary organ injury; or 3) modulation of the systemic immune response. Under anesthesia, 4-week-old (65-85 g) male Sprague-Dawley rats (N = 63) received crystalloids at either 15 or 65 ml.kg-1.h-1 intravenously and were subjected to 90 min of superior mesenteric artery occlusion followed by 90 min of reperfusion (IR15, IR65) or time-matched sham (SH) operation (SH15, SH65). Results indicate that inadequate fluid resuscitation following intestinal IR was associated with significant serum hyperkalemia and hyperphosphatemia, acute renal insufficiency, and enhanced serum interleukin-6 levels. Maintenance of cardiovascular stability with aggressive fluid resuscitation was associated with an attenuation of these alterations. Therefore, the prevention of circulatory shock and the attenuation of distant organ injury and inflammatory response are associated with improved survival when an aggressive crystalloid resuscitation regimen is applied after intestinal ischemiareperfusion in immature rats.

Latissimus-sparing thoracotomy in the pediatric patient: a valuable asset for thoracic reconstruction.

The traditional posterolateral thoracotomy involves division of the latissimus dorsi muscle (LD). While the division results in no functional disability, it does negate the potential for possible future thoracic reconstruction if required in individual cases (eg, bronchopleural fistula, empyema, etc). A latissimus-sparing thoracotomy (LST) mobilizes the muscle dorsad and does not compromise the operation. Thus, the ipsilateral LD can be used when chest wall reconstruction is required. This option has been used frequently for adults; however, its use in children has not been extensively documented. Microvascular anastomoses for a contralateral LD free-flap may be tenuous in the small vessels of the child; thus, reconstruction using the ipsilateral LD could be beneficial and safer. The feasibility of LST has not been established with regard to the chest of the child. The authors present three pediatric thoracic cases that illustrate the value of this procedure, and discuss different situations in which latissimus-sparing thoracotomy is advantageous.

Internal dosimetry using data derived from autoradiographs.

Cancer therapies based on administered radionuclides require accurate information on tumor dose. One of the major factors influencing the distribution of absorbed-dose characteristics is the uniformity of the radiolabel distribution in tissue. To study the effect of nonuniformities, we used image analysis techniques to measure automatically the coordinates of autoradiographic grains (sources) and cell nuclei in cut sections from three different tumors, following treatment with radiolabeled antibodies. The spatial distribution data of sources and cell nuclei from these tumor sections were assessed and the pattern of energy deposition in the cell nuclei calculated, assuming that each autoradiograph grain corresponded to a source of the alpha emitter astatine-211 (211At) or the beta emitter yttrium-90 (90Y). The distribution of deposited energy obtained for the real grain distributions was compared to the distribution assuming a locally uniform source distribution, i.e., simulating grain count averaging as produced by a microdensitometric method within a 100 x 100 microns 2 frame size (frame averaging), and a uniform distribution across the entire section (section averaging). The results show first that when the grain distribution is uniform, the average dose within the section is an adequate estimate of the dose to the cell nuclei. Second, when the grain distribution is nonuniform, the distribution of doses to the cell nuclei is significantly less when calculations use the measured grain coordinates, or frame averaging, than when section averaging is used. Third, when the sources are located on or in the cells, both frame and section averaging produce underestimates of the dose to the cell nuclei.

Prevention of secondary cardiovascular instability after intestinal ischemia and reperfusion improves survival.

Previous studies of small intestinal ischemia and reperfusion (I/R) in immature rats report secondary systemic organ injury and low survival rates; however, in these studies the cardiovascular stability of the rat was not established. To prevent the secondary hemodynamic deterioration accompanying intestinal I/R, we have developed a model that utilizes aggressive fluid resuscitation. Under anesthesia, 4-wk-old male Sprague-Dawley rats (n = 189) underwent 90 min of I/R (superior mesenteric artery occlusion) or sham (SH) operation while receiving lactated Ringer with 5% dextrose at 15 (IR15, SH15) or 65 (IR65, SH65) ml.kg-1 x h-1 i.v. The results indicate that aggressive fluid resuscitation in the IR65 group significantly attenuated the hypotension, hemoconcentration, metabolic acidosis, and amount of gross bowel injury observed in the IR15 group, while increasing postreperfusion renal and intestinal blood flow, prolonging survival time of nonsurvivors, and improving overall group survival. These findings suggest that maintenance of hemodynamic stability is necessary in models of bowel I/R. Furthermore, this model allows for selective study of the isolated effects of intestinal I/R without the additional complications resulting from secondary cardiovascular instability.

Prevention of postischemic injury in immature intestine by deferoxamine.

Free radical-mediated reperfusion injury has been demonstrated in ischemic neonatal bowel necrosis, but the mechanism of injury remains elusive. To determine whether such an injury can be prevented, 76 weaning rats were studied to test the effects of deferoxamine, an iron chelator, in postischemic injury. Group I (N = 20) had a sham laparotomy without vascular occlusion. Group II (N = 21) was subjected to 90 min of superior mesenteric artery occlusion prior to reperfusion. Group III (N = 35) received deferoxamine 15 mg/kg intravenous prereperfusion, in addition to ischemia and reperfusion as in group II. Survival profiles for each group were determined and a scale of pathologic severity was applied and compared. Group I had 100% long-term survival and group II, 14%. Group III had an overall survival of 28% and demonstrated a prolonged postreperfusion survival profile (P < 0.002) compared to group II. Histology was nearly identical to human necrotizing enterocolitis in degrees of bowel wall destruction and relative paucity of neutrophils. Group III showed a significant reduction in severity of injury compared to group II (P < 0.003). We conclude that neonatal bowel ischemia conditions such as necrotizing enterocolitis may be reperfusion injuries wherein free iron plays an important role in tissue injury. Administration of an iron chelating agent under such conditions has a beneficial effect on survival and histology.

Silastic catheterization of the axillary vein in neonates: an alternative to the internal jugular vein.

The axillary vein is a suitable alternative to the jugular venous system for tunnelled silastic catheterization in neonates, and should be included in the armamentarium of the surgeon who treats neonates. It is technically easy and is comparable to the internal jugular vein in terms of complications. Proper positioning of the catheter tip can sometimes be problematic, but without a resultant increase in morbidity or mortality.

Reperfusion injury following testicular torsion and detorsion in prepubertal rats.

Acute testicular torsion is a surgical emergency which requires immediate intervention. Although damage to the gonad has been well documented, it remains unknown whether the majority of injury occurs during the period of torsion (ischemia) or following detorsion (reperfusion). The aims of this study were to determine: (1) whether damage following testicular torsion-detorsion has a reperfusion component similar to that described in other tissues, and (2) whether iron-catalyzed oxygen radical formation or altered calcium homeostasis plays a role in this injury. To study this, anesthetized prepubertal rats underwent 720 degrees intravaginal testicular torsion and were divided into groups of torsion only (ischemia) and torsion with reperfusion (ischemia/reperfusion). Reperfusion groups were treated prior to detorsion with either deferoxamine (iron chelator), diltiazem (calcium channel blocker), or saline vehicle. The results indicated that detorsion produces a qualitatively distinct reperfusion injury from that of non-reperfused testicles; however, such damage was not ameliorated by deferoxamine or diltiazem. Thus, testicular torsion-detorsion appears to have a significant reperfusion component that appears to not be mediated by iron-catalyzed oxygen radical formation or calcium injury.

Obstructive jaundice associated with polysplenia syndrome in an older child.

Polysplenia syndrome includes malrotation and various forms of heterotaxy. Associated with this and malrotation are extrahepatic biliary anomalies. Actual obstruction, other than in associated biliary atresia, is extremely rare, and rarer still in older children. An 11-year-old girl presented with obstructive jaundice, malrotation, and heterotaxy, which were found in association with common bile duct anomalies and intermittent common bile duct obstruction. This case illustrates that the differential diagnosis of obstructive jaundice, even in older children, should include congenital anomalies, and that biliary anomalies should be considered in cases of malrotation and heterotaxy.

Retention of misonidazole in normal and malignant tissues: interplay of hypoxia and reductases.

Tritiated misonidazole (MISO) was injected intravenously (iv) into mice bearing five different tumors. At 24 hr the tumors were removed for analysis of bound MISO, and at the same time three normal tissues were removed (liver, labial gland, and esophagus). The labial gland and esophagus were selected as representatives of sebaceous and stratified squamous tissues, respectively, tissues that in many parts of the body retain high levels of MISO. The tumors used were early transplant generations of spontaneous mouse tumors of mammary gland, lung, and liver. The levels (mean +/- SEM) of MISO at 24 hr for the five tumors and three normal tissues, expressed as percentage of the injected dose per gram of tissue were: A110 (0.03 +/- 0.007), A114 (0.103 +/- 0.04), A150 (0.09 +/- 0.005), A167 (0.037 +/- 0.012), A168 (0.122 +/- 0.0016), esophagus (0.507 +/- 0.09), labial gland (0.125 +/- 0.013), liver (0.11 +/- 0.004). Histochemical examination of the normal tissues showed reductase activity in all three. In the esophagus and labial gland, inhibition of the reaction by dicumarol indicated the likely presence of the reductase DT-diaphorase which, by 2-electron transfer, can be expected to reduce MISO to a reactive, locally-binding metabolite, even in the presence of oxygen.

Spinal anesthesia reduces the hazard of apnea in high-risk infants.

General anesthesia in premature babies is associated with a significant risk of life-threatening apnea. Spinal anesthesia in the high-risk infant is simple, safe, and effective, but the incidence of apnea with its use has not been previously determined. The total absence of apnea in 84 high-risk infants suggests that surgery below the umbilicus under spinal anesthesia can safely be performed on an outpatient basis in preterm infants or babies with a history of apnea. Ketamine as an adjunctive agent adds no apparent risk. The technique is relatively easy, surgery is not compromised, and parental acceptance is high.

Distribution of pimonidazole and RSU 1069 in tumour and normal tissues.

The tritium-labelled analogues of pimonidazole and RSU 1069 were injected into mice bearing the KHT murine sarcoma which has a hypoxic cell fraction of approximately 10%. The distribution of activity at 24 h was recorded using autoradiography and measurement of tissue activity. Autoradiographs with both drugs showed high activity in particular cells within tumour, eye (melanin-associated cells), eyelid (Meibomian gland), liver (centrilobular area), skin (sebaceous gland and melanin), stomach (squamous area), footpad, oesophagus, labial gland, Zymbal's gland, preputial gland, parotid gland (intralobular ducts) and airway epithelium. These tissues had previously been identified as sites of binding of misonidazole. The measurement of total tissue radioactivity showed significantly higher activity in liver, eyelid (Meibomian gland), oesophageal lining, kidney and labial gland than was found in the tumour.

The effect of the alpha-particle emitter astatine-211 in the mouse at the minimum toxic dose.

The radioactive halogen astatine-211 was injected into mice in an amount producing minimal toxicity. Histopathological examination of tissues at intervals between 3 d and 16 weeks showed the following changes: 1. Radiation-induced necrosis and progressive fibrosis of the thyroid gland. The gland was reduced to 25% of its original mass with only a few relatively normal follicles persisting. 2. A small, temporary, reduction in peripheral blood lymphocytes, platelets and red cells and a significant persistant increase in polymorphs. 3. Severe reduction in reproductive cells in the testis with some signs of recovery at 16 weeks.

NAD(P)H nitroblue tetrazolium reductase levels in apparently normoxic tissues: a histochemical study correlating enzyme activity with binding of radiolabelled misonidazole.

Hack and Helmy's method for the histochemical identification of NAD(P)H nitroblue tetrazolium reductase activity was employed to pinpoint reductase activity in certain cells in the mouse. High activity was observed in the following: lower airway epithelium, liver (centrilobular zone), eyelid (meibomian and sebaceous glands), vulval gland and parotid gland (striated cells of intralobular ducts). All of these cells had previously been identified as sites of binding of the reactive metabolites formed from the enzymic reduction of misonidazole (MISO) (Cobb et al., 1989). It had previously been thought that MISO binding would only take place in significant amounts in hypoxic tissues (tumour and possibly liver) since in normoxic tissues oxygen should reverse the initial one electron enzymic reduction, thus preventing progressive reduction to reactive species. We suggest that the very high levels of reductase in the above listed, probably normoxic, tissues contribute significantly to the accumulation of bound reactive MISO metabolite(s).

Tissue distribution of 14C- and 3H-labelled misonidazole in the tumor-bearing mouse.

The retention of labelled misonidazole (MISO) was measured in a range of normal tissues in the mouse 24 hr after the intravenous injection of [14C]MISO (ring labelled) and [3H]-MISO (side-arm labelled). For [14C]MISO the 24 hr tissue retention, in order of the highest to the lowest levels (excluding pathways of excretion), was esophageal epithelium, liver, foot pad, eyelid, lung, subcutaneous lung tumor (A110), esophageal wall, uterus, eye ball, blood, salivary gland, spleen, voluntary muscle, pancreas, inguinal fat. It was assumed that the 14C represented MISO metabolite(s) bound to macromolecules. An approximately similar pattern was observed for [3H]MISO, but a higher percentage of the injected activity per gram of tissue was retained, probably due to the presence of tritiated water in the tissues. It has generally been assumed that significant levels of MISO binding are restricted to hypoxic tissues, for example tumors, but the present results show that significant levels of binding can also occur in apparently normoxic tissues. The explanation is put forward that this binding may be due to local high levels of nitroreductase capacity.

Nonuniformity of tumor dose in radioimmunotherapy.

The conventional approach to calculating tumor radiation dose from internally administered radioisotopes is by the MIRD schema. The raw input data for such dose calculations is obtained by immunoscintigraphic methods, PLANAR or SPECT imaging. Limitations in the spatial resolution of these techniques can lead to a considerable underestimate of the gross variation in tumor dose. The use of radiolabeled monoclonal antibodies for therapy can result in large nonuniformities in tumor dose. This paper discusses how antibody distribution can influence the energy deposition in the nuclei of target cells. Heterogeneity of antibody binding will lead to an expected decrease in the effectiveness of the radiation delivered. However, enhanced cell killing is possible if the radiolabeled Ab binds to the cell surface membrane and may be further enhanced if the Ab is internalized. Calculations are presented for two cases: (a) a three-dimensional random packing arrangement of cells as a model of the astructural nondifferentiated form seen in some tumors, and (b) differentiated carcinoma of the colon with the cells in tubules. Results for the magnitude of the mean energy deposition to individual cell nuclei from: (a) cell membrane bound 211At, 199Au, 131I, and 90Y-labeled Abs, and (b) a uniform distribution of these sources, as a function of internuclear distance for the two histologies are presented. Energy deposition in tumor cell nuclei from membrane bound radiolabeled antibody may be several times greater than estimated with the assumption of a uniform source distribution.

Autoradiographic study of tritium-labeled misonidazole in the mouse.

The localization of tritiated misonidazole metabolites in a number of normal tissues in the mouse is reported from autoradiography. The labeled misonidazole was injected at 750 or 75 mg/kg body weight (Rel. Sp. Act. 74 and 740 MBq/mg respectively). The grain count ratio, parenchyma:stroma, for selected tissues was: liver (centrilobular zone) 13; meibomian gland (acini) 68, (duct) 116; esophagus (keratinized layer) 61; enamel organ 17. It is concluded that there are a number of tissues which will accumulate MISO metabolites although they may not all be hypoxic.