Non-iatrogenic pathology of the preterm infant

A Long-Acting Neutralizing Monoclonal ACTH Antibody Blocks Corticosterone and Adrenal Gene Responses in Neonatal Rats

The control of steroidogenesis in the neonatal adrenal gland is of great clinical interest. We have previously demonstrated that the postnatal day (PD) 2 rat exhibits a large plasma corticosterone response to hypoxia in the absence of an increase in plasma ACTH measured by RIA, whereas the corticosterone response to exogenous ACTH is intact. By PD8, the corticosterone response to hypoxia is clearly ACTH-dependent. We hypothesized that this apparently ACTH-independent response to hypoxia in the newborn rat is due to an increase in a bioactive, nonimmunoassayable form of ACTH. To evaluate this phenomenon, we pretreated neonatal rats with a novel, specific, neutralizing anti-ACTH antibody (ALD1611) (20 mg/kg or 1 mg/kg IP) on the morning of PD1, PD7, and PD14. Twenty-four hours later, we measured hypoxia- or ACTH-stimulated plasma ACTH and corticosterone. For long-term effects, ALD1611 was given on PD1 and pups were studied on PD8 and PD15. Pretreatment with ALD1611 significantly decreased baseline corticosterone and completely blocked the corticosterone response to hypoxia and exogenous ACTH stimulation at all ages. The effect of 1 mg/kg ALD1611 on PD1 had dissipated by PD15. The decrease in corticosterone in ALD1611-treated pups was associated with decreases in baseline and hypoxia- and ACTH-stimulated adrenal Ldlr, Mrap, and Star mRNA expression at all ages. The adrenal response to hypoxia in the newborn rat is ACTH-dependent, suggesting the release of nonimmunoassayable, biologically active forms of ACTH. ALD1611 is useful as a tool to attenuate stress-induced, ACTH-dependent adrenal steroidogenesis in vivo.

Effect of a melanocortin type 2 receptor (MC2R) antagonist on the corticosterone response to hypoxia and ACTH stimulation in the neonatal rat

The adrenal stress response in the neonatal rat shifts from ACTH-independent to ACTH-dependent between postnatal days 2 (PD2) and 8 (PD8). This may be due to an increase in an endogenous, bioactive, nonimmunoreactive ligand to the melanocortin type 2 receptor (MC2R). GPS1574 is a newly described MC2R antagonist that we have shown to be effective in vitro. Further experimentation with GPS1574 would allow better insight into this seemingly ACTH-independent steroidogenic response in neonates. We evaluated the acute corticosterone response to hypoxia or ACTH injection following pretreatment with GPS1574 (32 mg/kg) or vehicle for GPS1574 in PD2, PD8, and PD15 rat pups. Pretreatment with GPS1574 decreased baseline corticosterone in PD2 pups but increased baseline corticosterone in PD8 and PD15 pups. GPS1574 did not attenuate the corticosterone response to hypoxia in PD2 pups and augmented the corticosterone response in PD8 and PD15 pups. GPS1574 augmented the corticosterone response to ACTH in PD2 and PD15 pups but had no significant impact on the response in PD8 pups. Baseline adrenal Mrap and Star mRNA increased from PD2 to PD15, whereas Mrap2 mRNA expression was low and did not change with age. The data suggest that GPS1574 is not a pure MC2R antagonist, but rather acts as a biasing agonist/antagonist. Its ability to attenuate or augment the adrenal response may depend on the ambient plasma ACTH concentration and/or developmental changes in early transduction steroidogenic pathway genes.

Insulin sensitivity, leptin, adiponectin, resistin, and testosterone in adult male and female rats after maternal-neonatal separation and environmental stress

Care of premature infants often requires parental and caregiver separation, particularly during hypoxic and hypothermic episodes. We have established a neonatal rat model of human prematurity involving maternal-neonatal separation and hypoxia with spontaneous hypothermia prevented by external heat. Adults previously exposed to these neonatal stressors show a sex difference in the insulin and glucose response to arginine stimulation suggesting a state of insulin resistance. The current study used this cohort of adult rats to evaluate insulin resistance [homeostatic model assessment of insulin resistance (HOMA-IR)], plasma adipokines (reflecting insulin resistance states), and testosterone. The major findings were that daily maternal-neonatal separation led to an increase in body weight and HOMA-IR in adult male and female rats and increased plasma leptin in adult male rats only; neither prior neonatal hypoxia (without or with body temperature control) nor neonatal hypothermia altered subsequent adult HOMA-IR or plasma adiponectin. Adult male-female differences in plasma leptin were lost with prior exposure to neonatal hypoxia or hypothermia; male-female differences in resistin were lost in the adults that were exposed to hypoxia and spontaneous hypothermia as neonates. Exposure of neonates to daily hypoxia without spontaneous hypothermia led to a decrease in plasma testosterone in adult male rats. We conclude that neonatal stressors result in subsequent adult sex-dependent increases in insulin resistance and adipokines and that our rat model of prematurity with hypoxia without hypothermia alters adult testosterone dynamics.

Association between the markers of FIRS and the morphologic alterations in the liver of neonates autopsied in the perinatal period

Markers of fetal inflammatory response syndrome (FIRS) can influence the morphologic alterations in liver of autopsied neonates. The IL-6, TNF-α, and C-reactive protein (CRP) expression in liver fragments were marked by immunohistochemistry and the intensity of steatosis, percentage of fibrosis, and the number of foci of extramedullary erythropoiesis were evaluated. The degree of steatosis correlated positively with IL-6 (p = 0.06), positively with CRP (p ≤ 0.001), and negatively with TNF-α (p = 0.06). The collagen percentage correlated positively with IL-6 (p = 0.055) and positively with TNF-α (p ≤ 0.001). Erythropoiesis correlated positively with IL-6 (p ≤ 0.001) and negatively with CRP (p = 0.00754). The analyzed markers of FIRS have an important role in triggering hepatic morphologic alterations.

Pulmonary innate immune response and melatonin receptors in the perinatal stress

Objective. To analyze the cytokines of the innate immune pulmonary response and the capacity for local response to melatonin according to the perinatal stress. Methods. 49 cases of pediatric autopsies were evaluated, divided according to cause of death, perinatal stress, gestational age, and birth weight. The percentages of IL-6, C-reactive protein (CRP), IL-1β, TNF-α, and melatonin receptor were evaluated by immunohistochemistry. Results. The IL-6 expression was higher in the children showing chronic stress, anoxia, and infection. The IL-6 expression showed a progressive increase according to the relation between weight and GA. There was no significant difference in the expression of IL-1β and TNF-α. The CRP expression was higher in the cases showing chronic stress and premature cases. The expression of melatonin receptors was significantly higher in the cases showing chronic stress, being more evident in the cases showing infection. Conclusion. The cause of death and the type of stress influence the expression in situ of melatonin and cytokines of the innate immune pulmonary response. The evaluation of IL-6 and CRP may contribute to the understanding of the evolution of neonates with chronic stress. The greater sensitivity of the lung to melatonin in these cases may indicate an attempt at controlling the immunological response, in an attempt to diminish the harmful effects of stress.

Morphologic analysis of fetal stress organsin different causes of perinatal death

Complications act as stress-inducers during pregnancy so the fetus can develop functional compensatory mechanisms or morphologic changes. The cases analyzed are with congenital malformations or acute stress; chronic included cases with ascending infection (AI) and perinatal hypoxia/anoxia (PHA). The hematoxylin-eosin (H&E) was done to analyze the vacuolization, and the immunohistochemistry to the phagocytosis. The discreet standard of vacuolization was observed in 52.6% of the cases, 22.1% moderate, and 25.3% severe. The number of macrophages was higher in PHA. Changes in these organs are closely related to the cause of death and to the period during which the harmful agent.

Sudden Death from Pulmonary Causes

This chapter seeks to survey many of the common pathological entities identified in the lungs at autopsy and the potential role of pulmonary disease in formulating an opinion regarding the cause of death. Appreciation of pulmonary pathology in the medicolegal context is important as it frequently contributes to the immediate or underlying mechanisms of death. The primacy of the lungs in breathing and their coordinated function with the cardiovascular system means that ­pulmonary failure can rapidly compromise tissue oxygenation and body chemistry, leading to an alteration in blood pH, hypoxic damage to downstream tissues and ultimately multiorgan failure and death. Moreover, given that the lungs have direct contact with the environment through inhalation and receive approximately 50% of the cardiac output with each beat of the heart, they may be adversely affected by hazardous agents from the outside world or other pathologic processes not primarily located in the lungs. The range of topics discussed herein is limited by design to deaths due to disease and largely foregoes discussion of more forensically relevant issues relating to toxicology or trauma. Furthermore, the content and format of this chapter is not intended to be encyclopedic, but rather attempts to highlight selected issues regarding pulmonary disease of potential relevance to surgical or forensic pathologists who perform medicolegal postmortem examinations.

Field investigation of perinatal mortality in friesian cattle associated with myocardial degeneration and necrosis

Perinatal mortality and stillbirths were investigated in an extensively managed herd of Friesian cows and heifers calving over a 2-year period: 504 cows were calved and 215 heifers. Cows were bred to Friesian and Jersey bulls using natural service. The perinatal fetal mortality rate was 7.5% for cows and 30% for heifers. An experienced stockman managed these calvings and veterinary assistance was required only on nine occasions. All stillborn fetuses were examined post-mortem by the Veterinary Laboratories Agency, Carmarthen and no infectious agent was identified on any occasion. Thyroid hyperplasia was found in two fetuses. In blood samples taken from 10 late pregnant heifers, mean glutathione peroxidase values were 7.9 +/- 1.7 IU/ml Packed Cell Volume (PCV). Tissues from eight fetuses were submitted to the University of Liverpool for histopathological examination; all presented lesions consistent with myocardial degeneration and necrosis of the left ventricle. Following treatment of 205 late pregnant heifers with sodium selenite and vitamin E, the overall perinatal mortality rate in these cattle fell to below 11%.

Extramedullary haematopoiesis in liver of sudden infant death cases

AIMS

To determine the frequency of extramedullary haematopoiesis (EMH) in sudden infant death and control cases, and to provide descriptive data on extramedullary haematopoietic islands and diffuse cells.

METHODS

The study was carried out in 51 SIDS and 102 non-SIDS cases. Liver-tissue sections were stained with haematoxylin and eosin, and immunohistochemistry was done with streptavidin-biotin-peroxidase complexes by Polyclonal Haemoglobin "A" antibody. The prevalence of data was estimated statistically by Pearson chi-square test, descriptive statistics, and Kruskal-Wallis test.

RESULTS

The Pearson chi-square values (CI: 95%; OR: 0.071-0.49; p: 0.0474) show higher frequency of EMH islands in SIDS than in controls. The number of diffuse extramedullary haematopoetic cells was higher in SIDS cases compared to non-SIDS (p=0.017).

CONCLUSIONS

EMH is a frequent finding in SIDS cases, and this may be a consequence of anaemia associated with intrauterine hypoxia, or infections.

The baboon as a good model for studies of human kidney development

Because of the improved survival of premature neonates in recent years, it is important to investigate the effects of premature delivery on the kidney, in which nephrogenesis is still ongoing during the third trimester. Hence, an appropriate animal model that is similar to humans is essential. The aim of the current study is to determine the time course of nephrogenesis in the baboon, to establish whether it is a suitable model of human nephrogenesis. At the Southwest Foundation for Biomedical Research (San Antonio, TX), fetal baboons were delivered prematurely by cesarean delivery and at term by natural delivery. Fixed kidneys from 125-, 140-, 175-, and 185-d gestation baboons were assessed morphologically for evidence of a nephrogenic zone. Nephron number, kidney volume, and glomerular and corpuscle volume were also estimated using unbiased stereology. Morphologic assessment confirmed the presence of metanephric mesenchyme and immature glomeruli in the nephrogenic zone of the kidneys from the prematurely delivered fetuses at 125 and 140 d gestation. At 175 d gestation and at term, the nephrons seemed to be mature. Both kidney weight (R2= 0.918, p = 0.0002) and kidney volume (R2= 0.837, p = 0.001) were very strongly correlated with nephron number. There was also a direct relationship between gestational age (R2= 0.589, p = 0.03) and birth weight (R2= 0.562, p = 0.03) with nephron number. In conclusion, in this study, nephrogenesis in the baboon is complete before term by 175 d gestation, which is similar to humans. Hence, the baboon is a suitable model for future studies to investigate human kidney development.