Association of whole blood aggregation response with immunogold-labeled glycoproteins in adult and neonatal platelets.

A growing body of recent data has provided specifics about the hemostatic system in infants, emphasizing differences from adults. Although platelet structure in newborns and adults appears to be quite similar, precise information about platelets in the first week of life indicates functional hyporeactiveness. This study was designed with a twofold purpose: one was to determine if aggregation results corresponded to immunogold-labeled activation markers; the second was to use immunogold labeling to determine if infant platelets circulate in an activated state. The results showed significant differences in ristocetin (P = .03) and collagen (P = .003) impedance, and whole blood aggregation lag times in infants when compared to adults. Treatment of neonatal platelets with collagen yielded decreased ATP release compared with adults. Immunogold labeling of specific activation markers CD62 (P-selectin) and CD63 (GP53) revealed that neonatal platelets were not circulating in an activated state. Significant (P = .04) anti-CD41 (GPIIb) immunogold labeling differences were observed after thrombin stimulation, with adults binding more particles. These data suggest that hyporeactivity of neonatal platelets is not due to a circulating preactivated state, but instead may be a consequence of impaired intracellular signaling that affects both aggregation and membrane activation labeling. Whether this signaling is secondary to an intrinsic neonatal alteration or a maternal (in utero) environmental effect is yet to be determined.

Imparied platelet--dense granule release in neonates.

PURPOSE: The aim of this study is to examine differences in platelet dense granule (PDG) uptake and release between preterm infants, term infants, and adults. METHODS: PDG uptake and release was examined by flow cytometry using mepacrine fluorescent staining in phycoerythrin-anti-GPIIb/IIIa bound platelets taken from cord blood of eight term infants and seven preterm infants and venous blood from eight adults. RESULTS: Analysis of the baseline fluorescence in the untreated versus thrombin-treated samples revealed significant differences in the way infant PDGs responded to thrombin stimulation when compared with adults. Initial uptake of mepacrine in both term and preterm platelets was similar to that in adult platelets. Statistically significant differences between adults and both term and preterm infants, at two concentrations of mepacrine, were observed after stimulation with thrombin. CONCLUSION: Persistent mepacrine staining of infant PDGs, when compared with those of adults, after thrombin stimulation implies defective infant PDG release. This may partially explain why infants have impaired response to agonists requiring ATP release from PDGs.

Flow cytometry of neonatal platelet RNA.

PURPOSE: Serious disorders of hemostasis occur more often in the small, stressed preterm infant, partly due to immaturity of the newborn hemostatic mechanism. Information regarding the maturational development of platelets in infants has been limited by the large amounts of blood historically needed for platelet studies. The objective of this study was to determine differences between platelets in adults and infants by flow cytometric analysis of "reticulated" platelets. PATIENTS AND METHODS: Eighteen normal adults, 42 healthy term infants, and 27 preterm infants were studied. The infants were subdivided by mode of delivery: vaginal or Caesarean section. Platelet-rich plasma from adult whole blood and infant cord blood samples was divided into aliquots containing 5 X 10(6) platelets, fixed with 1% paraformaldehyde, and stained with thiazole orange for RNA content. The percentage of RNA positive "reticulated" platelets in each aliquot was then determined by flow cytometry. RESULTS: Group comparisons using ANOVA statistical analysis showed a significant difference (p<0.05) for platelet RNA content between adults and term infants, the adults having a higher percentage of reticulated platelets. Although the difference was smaller, adults also had a higher percentage of reticulated platelets than preterm infants. There was no significant difference in reticulated platelet values between infants within one gestational age group compared by type of delivery. CONCLUSION: There are demonstratable differences in adult and infant platelet RNA content that may reflect developmental differences in megakaryocytic/platelet kinetics.

Fatal aortic thrombosis in a neonate during infusion of epsilon-aminocaproic acid.

Hemorrhagic complications are common in patients placed on extracorporeal life support (ECLS), especially in those who have additional risk factors. Several centers use epsilon-aminocaproic acid (EACA) in their high-risk ECLS patients in an attempt to decrease the incidence of such complications, despite the fact that no controlled trials have been performed examining the risks and benefits of its use. The authors report the case of a neonate who had fatal aortic thrombosis during EACA administration. Also included is a discussion of the use of EACA in patients who require cardiopulmonary bypass.

Platelet ultrastructure of high-risk premature infants.

Hemorrhagic and thrombotic complications are common in the term and preterm infant. Limited information is currently available about neonatal platelet structure and function, and how these may predispose infants to bleeding problems. This study comparing platelet ultrastructure of 71 different term and preterm infants with that of 15 adult control subjects revealed certain platelet morphological differences. Specifically, the adult platelets had more pseudopods, larger glycogen deposits, more visible microtubular structure, markedly fewer alpha granules, and smaller areas/perimeters than the infant platelets. Also, in infants greater than 31 weeks gestation, the platelets of vaginally-delivered infants were larger than those of both infants delivered by C-section and normal adults. These differences in platelet size and morphology may be related to developmental differences and/or the stress of delivery. These findings provide a framework for further exploration of neonatal platelet structure and function.

Cerebral infarction associated with protein C deficiency following allogeneic bone marrow transplantation.

Hypercoagulable states associated with deficiencies in circulating anticoagulant protein C occur after chemotherapy for a variety of malignant diseases. Protein C deficiency also occurs following bone marrow transplantation (BMT) and may be responsible for a variety of transplantation-associated complications. We report the case of a child who suffered a stroke associated with low protein C antigen and activity occurring 11 months after allogeneic BMT. Protein C levels recovered spontaneously by 18 months after BMT. We speculate that the protein C deficiency and and resultant hypercoagulable state led to the stroke, and the deficiency of this anticoagulant was a sequela of the transplant.

Intraperitoneal bleomycin for ventriculoperitoneal spread of a hypothalamic astrocytoma.

A pediatric patient is presented in whom malignant ascites developed after ventriculoperitoneal shunt placement for a suprasellar astrocytoma. Paracentesis followed by intraperitoneal bleomycin resulted in decreased fluid re-accumulation with minimal side effects. A review of the literature shows that intracavitary chemotherapy, including bleomycin, can result in safe, effective relief of malignant effusion associated with adult tumors. We have demonstrated that such treatment is also applicable to the pediatric population. In this case, the effectiveness of intracavitary bleomycin may be related to its direct action against brain glioma cells. The need for effective treatment of malignant effusions in pediatric patients is growing because of their increased survival time with tumor. We propose that intracavitary bleomycin may provide relief from this potential complication of childhood solid tumors.

Prolonged echoviral meningitis in a cancer patient with normal serum immunoglobulins.

This is a report of prolonged meningitis caused by echovirus type 20 in a patient with rhabdomyosarcoma. It represents one of the few documented cases of delayed clearance of echovirus in the cerebrospinal fluid in a patient with normal serum immunoglobulins. The case illustrates the prolonged clinical course of echoviral meningitis in a patient receiving cytotoxic drug therapy, and it suggests that factor(s) other than humoral antibodies may be involved in the elimination of echovirus from the central nervous system.

Structural studies on the polyhedral inclusion bodies, virions, and DNA of the nuclear polyhedrosis virus of the cotton bollworm Heliothis zea.

The polyhedral inclusion body of the cotton bollworm nuclear polyhedrosis virus contains virions occluded in an orthogonal crystalline matrix. The virions appear as rods or, more frequently, as oval structures that form upon bending of the nucleocapsid within the viral membrane. The nucleocapsid consists at least of DNA surrounded by a capsid composed of subunits, possibly helically arranged. The viral DNA is circular and supercoiled. It is heterogenous in size with contour lengths ranging from 15 to 45 mum.