Renal uptake of bismuth-213 and its contribution to kidney radiation dose following administration of actinium-225-labeled antibody

Clinical therapeutic studies using (225)Ac-labeled antibodies have begun. Of major concern is renal toxicity that may result from the three alpha-emitting progeny generated following the decay of (225)Ac. The purpose of this study was to determine the amount of (225)Ac and non-equilibrium progeny in the mouse kidney after the injection of (225)Ac-huM195 antibody and examine the dosimetric consequences. Groups of mice were sacrificed at 24, 96 and 144 h after injection with (225)Ac-huM195 antibody and kidneys excised. One kidney was used for gamma ray spectroscopic measurements by a high-purity germanium (HPGe) detector. The second kidney was used to generate frozen tissue sections which were examined by digital autoradiography (DAR). Two measurements were performed on each kidney specimen: (1) immediately post-resection and (2) after sufficient time for any non-equilibrium excess (213)Bi to decay completely. Comparison of these measurements enabled estimation of the amount of excess (213)Bi reaching the kidney (γ-ray spectroscopy) and its sub-regional distribution (DAR). The average absorbed dose to whole kidney, determined by spectroscopy, was 0.77 (SD 0.21) Gy kBq(-1), of which 0.46 (SD 0.16) Gy kBq(-1) (i.e. 60%) was due to non-equilibrium excess (213)Bi. The relative contributions to renal cortex and medulla were determined by DAR. The estimated dose to the cortex from non-equilibrium excess (213)Bi (0.31 (SD 0.11) Gy kBq(-1)) represented ∼46% of the total. For the medulla the dose contribution from excess (213)Bi (0.81 (SD 0.28) Gy kBq(-1)) was ∼80% of the total. Based on these estimates, for human patients we project a kidney-absorbed dose of 0.28 Gy MBq(-1) following administration of (225)Ac-huM195 with non-equilibrium excess (213)Bi responsible for approximately 60% of the total. Methods to reduce renal accumulation of radioactive progeny appear to be necessary for the success of (225)Ac radioimmunotherapy.

Winter excess morbidity: is it a summer phenomenon?

BACKGROUND

It was hypothesized that winter excess mortality is a feature of ill health produced by exposure to ambient low temperatures, and will be matched by winter excess morbidity. The aim of the study was to test the prediction that winter excess morbidity would be observable and would show a social class gradient with greater excesses in less affluent groups, who are less able to heat their houses or whose lack of a car exposes them more frequently to outdoor cold exposure.

METHODS

The study was set in the Metropolitan Borough of Stockport and documented, from routine health services hospital admissions data, winter and summer differences in ACORN-specific, age- and sex-standardized hospital admission rates and ratios, for ischaemic heart disease, directly and indirectly standardized using the Stockport population as the standard.

RESULTS

The expected social class gradient in ischaemic heart disease admissions was more clearly observable in the summer than in the winter. Affluent groups showed winter excess morbidity, less affluent groups showed summer excess morbidity.

CONCLUSION

The data serendipitously indicate an alternative hypothesis - that winter excess morbidity is a feature of health benefits derived in the summer and differentially available to the more affluent, such as opportunities for outdoor leisure. This hypothesis deserves testing in a study designed for that purpose, although it is not entirely satisfactory as an explanation of existing data.

Effect of application pressure and gestational age on transfontanel pressure in healthy neonates

We developed and evaluated a transducer holder and calibrated, spring-loaded applicator for the Ladd intracranial pressure monitor. The transducer holder/applicator combination allows reproducibility of application pressure and assures coplanarity of the transducer and the skin of the anterior fontanel. Measured transfontanel pressure (TFP) increased with increasing application pressure. Mean TFP was 9.1 +/- (SD) 2.6 cm H2O with an application pressure of about 10 g/cm2 in a group of healthy preterm and term infants at 6 h postnatal age. Birth weight, gestational age and mode of delivery did not affect TFP, allowing use of a single normative value and set of confidence limits in all infants at 6 h of postnatal age.

Colloid osmotic pressure at birth. Effect of sample site, type, and mode of delivery

Colloid osmotic pressure was measured at birth in 102 newborns. Umbilical vein plasma colloid osmotic pressure correlated with total serum protein, birth weight, and gestational age. Mean colloid osmotic pressure of 11 infants who were small for gestational age was less than, and that of seven infants who were large for gestational age was more than, that of average-sized infants of similar gestation. For infants weighing 1,501 to 3,000 g, mean (+/- SD) colloid osmotic pressure following cesarean section (15.1 +/- 1.6 mm Hg) was lower than that following vaginal delivery (18.4 +/- 2.2 mm Hg). This may reflect the fact that use of maternal fluid therapy preceding cesarean section was greater than before vaginal delivery. The definition of normative values for neonatal plasma colloid osmotic pressure makes it possible to investigate changes in relation to disease, therapy, and subsequent outcome in sick neonates.

Prostaglandin D2 inhibits hypoxic pulmonary vasoconstriction in neonatal lambs

Intrapulmonary injections of prostaglandin D2 (PGD2) reduce pulmonary arterial pressure and resistance in fetal and hypoxic neonatal lambs without affecting systemic arterial pressure. This apparently specific pulmonary effect of PGD2 could be explained by inactivation of the agent during passage through the pulmonary capillary bed. We therefore studied the effects of both pulmonary and systemic infusions of PGD2 on the acute vascular response to a 1-min episode of hypoxia in newborn lambs. Since PGD2 has been reported to be a pulmonary vasoconstrictor in normoxic lambs, we also evaluated its effects during normoxemia. Pulmonary vascular pressures were not affected by either 1- or 10-micrograms . kg-1 . min-1 infusions into the left atrium or inferior vena cava during normoxia. Infusion of 1 microgram . kg-1 . min-1 PGD2 into the inferior vena cava decreased pulmonary vascular resistance and increased systemic arterial pressure. These two parameters were unchanged with the other three infusion regimens. Mean pulmonary vascular resistance rose 83% with hypoxia and no PGD2. PGD2 prevented any change in pulmonary vascular resistance with hypoxia, while systemic arterial pressure increased (1-microgram . kg-1 . min-1 doses) or was unchanged. Thus PGD2 specifically prevents hypoxic pulmonary vasoconstriction while maintaining systemic pressures, regardless of infusion site. PGD2 may be indicated in treatment of persistent pulmonary hypertension of the newborn and other pulmonary hypertensive disorders.

Cardiac output and organ blood flow in young rabbits during intermittent positive-pressure ventilation

Cardiac output and organ blood flow were measured by a microsphere technique in three groups of healthy young rabbits. In one group, animals were subjected to light sedation and intermittent positive-pressure ventilation. Control animals in a second group were sedated but not ventilated. In a third group, animals were conscious and breathing spontaneously. Cardiac output increased significantly (p less than 0.05) in conscious controls and in one measurement in anesthetized controls. It did not change in ventilated rabbits. Blood flow to the brain increased during study in all three groups and to the eye in both control groups. These elevations in cardiac output and cerebral blood flow were attributed to arousal. Blood flow to the kidney decreased in both anesthetized groups. The blood flow to skin, muscle, ileum and colon decreased significantly in the ventilated animals though not in the anesthetized controls. In both groups, similar reductions were found in the fractional distribution of cardiac output to these areas. It was concluded that ventilation at low pressure had no effect on cardiac output. The occurrence of redistribution of the circulation was deduced from the parallel reductions of regional blood flows and fractions of cardiac output received by some organs together with preservation of cerebral blood flow, though it was obscured in the two control groups by simultaneous increases in cardiac output. The circumstances suggested that this redistribution was due to disturbed homeostasis from arousal. Implications for the newborn were discussed.

Ultrastructure of the lung after ventilation

We looked at the ultrastructure of the lung of rabbits ventilated with air moistened with nebulized water ("nebulized group"), and humidified air ("humidified group") compared to a group of controls. Both groups of ventilated rabbits had plasmalemmal vesicles that were larger than in controls. They were fewer in number (P less than 0.001) and less well defined. Early degenerative changes were noted in 6 of 9 rabbits in the nebulized group and 6 of 9 rabbits in the humidified group, while none of the rabbits in the control group were similarly affected. Interstitial oedema of varying severity was seen in 6/9 rabbits from each of the ventilated groups.

Effects of gas temperature and particulate water on rabbit lungs during ventilation

Anesthetized young rabbits were ventilated for 6 hr at 20 cm H2O peak airway pressure using air nebulized with water at 22 degrees C (cold nebulized group, n = 11), at 36 degrees C (warm nebulized group, n = 11) and humidified air at 36 degrees C (warm humidified group, n = 10). Their biochemical status during ventilation and pulmonary morphology at autopsy were compared to those of ten control rabbits. Both nebulized groups had particulate water in the inspired air and water of condensation in the endotracheal tube. The rabbits ventilated with warm humidified air and the control group breathing spontaneously maintained their blood pressure and pHa within physiologic range. Rabbits ventilated with air nebulized with water at 22 and 36 degrees C had a significant decline in mean blood pressure (96 mm Hg leads to 61 mm Hg in cold nebulized and 91 mm Hg leads to 61 mm Hg in warm nebulized) and mean pHa (7.43 leads to 7.23 in cold nebulized and 7.42 leads to 7.31 in warm nebulized). All rabbits in the control and warm humidified groups survived the study whereas 9 of 22 in the nebulized groups died before completion of study (P < 0.005). Morphometric analysis revealed a significant increase in the mean vascular wall thickness in both nebulized groups of rabbits when compared to that in the control and warm humidified groups (P < 0.05). The cold nebulized group also had significantly less air space and correspondingly more interstitial thickness and intraalveolar edema (P < 0.05) compared to control and warm humidified groups. These findings of pulmonary parenchymal damage in rabbits ventilated with air containing particulate water and the greater degree of both physiologic and anatomic change evident in the cold nebulized animals suggest that particulate water and low inspired air temperature may contribute to the genesis of pulmonary damage during intermittent positive pressure ventilation.

Effects of intermittent positive-pressure ventilation on lungs of normal rabbits

We ventilated 10 healthy young rabbits with warm moist air at 20 cm H2O peak airway pressure and compared their pulmonary histology to that of 10 controls. The histological changes were analysed using the Leitz Texture Analysis System. Four hundred high-power fields (240 micrometers X 240 micrometers) were scanned from each section and the mean proportions of air space, interstitium and oedema determined. Calculated bicarbonate decreased significantly in both groups (P < 0.05); this was accompanied by a modest decrease in pHa in the ventilated group. The PaO2 and PaCO2 were maintained within the normal range. The blood pressure decreased in both groups. Seven of 10 ventilated rabbits had interstitial widening while only 1 of 10 controls had a similar lesion (chi 2 = 5.21, P = < 0.05). The area occupied by interstitium ranged from 26 to 46% (mean 37.6%) in controls and 18 to 81% (mean 45.4%) in ventilated rabbits. There was a lack of correlation between clinical and histopathological findings. While 6 of 10 ventilated rabbits had intra-alveolar oedema and a decrease in air space to less than 50% of total area, none developed hypoxaemia. Two of these 6 rabbits also had pHa less than 7.35 by the end of the study, yet all were clinically stable. These data indicate that intermittent partial-pressure ventilation with warm moist air may result in pulmonary parenchymal damage within 6 h in healthy rabbits.