Regulation of apoptosis in the endocardial cushions of the developing chick heart

During the early stages of heartdevelopment, there are two main foci of cell death: outflow tract (OT)and atrioventricular (AV) endocardial cushions. These tissuescontribute to the septa and valves of the mature heart and receive cellpopulations from neural crest (NC) cell migration and epicardial cellinvasion. We examined embryonic chick hearts for expression, in thecushions, of bcl-2 family members, caspase-9, and the caspase substrate poly(ADP-ribose) polymerase. Antiapoptotic bcl-2 is expressed heavily in the OT and AV regions throughout embryonic days (ED) 4-7, with a decrease in levels at ED 4 and 5 in OT and AVcushions, respectively. Proapoptotic bax predominantly associatedwith the prongs of the NC-derived aorticopulmonary (AP) septum but was expressed throughout the AV cushions. Proapoptotic bak alsoassociated with the prongs of the AP septum in the OT, while proteinlevels were upregulated at ED 4-5 and 4-6 in OT and AVcushions, respectively. Bid expression showed a similar time course. Wefound the 10-kDa cleavage fragment of active caspase-9 at ED 4-8and 5-8 in OT and AV cushions, respectively, and the 24-kDacleavage fragment of poly(ADP-ribose) polymerase throughout ED 3-8and 7-8 in OT and AV cushions, respectively. Caspase-3 cleavageoccurred throughout the time period examined. Using cushion cellcultures, we found that inhibitors of caspases-3 and -9 and a universalcaspase inhibitor significantly reduced apoptosis, as didretroviral overexpression of bcl-2 using an RCAS expression vector.Premigratory NC cells were fluorescently labeled in vivo with1,1-didodecyl-3,3,3',3'-tetramethylindocarbocyanine. Subsequent nuclearstaining of cushion cells with 4,6-diamidino-2-phenylindole revealedthe presence of apoptotic nuclei in the NC cells in the OT cushionsand in the prongs of the AP septum. These results demonstrate adevelopmentally regulated role for the bcl-2 and the caspase familiesof molecules in the endocardial cushions of the developing heart andlend support to the possibility that some of the dying cells in thecushions are derived from the NC.

     

Noninvasive detection of epicardial and endocardial activity of the heart

Determining electrical activation of the heart in a noninvasive way is one of the challenges in cardiac electrophysiology. The ECG provides some, but limited information about the electrical status of the heart. This article describes a method to determine both endocardial and epicardial activation of the heart of an individual patient from 64 electrograms recorded from the body surface. Information obtained in this way might be helpful for the treatment of arrhythmias, to assess the effect of drugs on conduction in the heart and to assess electrical stability of the heart.     

Effects of vitamin A on endocardial cushion development in the mouse heart

Retinoic acid (RA) (78mg/kg) administered to ICR mice on days 9.0,9.5 and 10.0 of pregnancy (plug day = day 1), resulted in cardiac malformations in 37.6% of the surviving fetuses, including transposition of the great arteries, ventricular septal defects, and double outlet right ventricle. Histological examination of the hearts of embryos observed 24 hours after in vivo or in vitro exposure to RA on day 9 revealed abnormalities in endocardial cushion tissue. The volume of the atrioventricular endocardial was reduced in treated embryos as was the ratio of the size of the cushions to the size of the heart. The endothelial layer of the atrioventricular endocardial cushions appeared to be unaffected by the retinoic acid, however, the mesenchymal cushion cells were significantly reduced in number when compared with controls. Labeling with [3H]-thymidine indicated that the mitotic activity of the mesenchymal cell population was significantly decreased while that of the endothelial cells was comparable to control levels. The extracellular matrix or cardiac jelly of the endocardial cushions also appeared to be affected by RA exposure, as shown by studies utilizing colloidal iron to stain GAGs, which revealed a decrease in the amount of stainable material in treated cushions. Two possible cause for the reduced thymidine index of the cushion mesenchyme are discussed, namely, a direct effect of RA on the mesenchymal cells or an indirect effect via the altered extracellular matrix of the cushion tissue.     

Female reproductive signaling, and male mating behavior, in the olive baboon

Baboon sexual swellings are among the largest and most colorful signals displayed by any mammal, and many baboon studies have shown an association between sexual swellings and both female and male sexual behavior. However, the extent to which female behavior and sexual swellings combine to signal the timing of ovulation and the fertile period to males, and the extent to which males use these and other signals when determining patterns of mating behavior, remain key topics of research. Here we assess the social and sexual behavior of both female and male olive baboons with respect to detailed measures of swelling size made from digital photographs, measures of fecal progestogen and estrogen levels, and estimates of the timing of ovulation and the fertile period based on those levels. Female aggression and grooming behavior were unrelated to fecal progestogen and estrogen levels, but there were some significant relationships between these hormonal measures and presenting behaviors. Measures of female behavior collected during the study did not appear to reveal the timing of ovulation or the fertile period. Male consortship behavior was closely tied to fine-scale changes in sexual swelling size, but copulation behavior was not. Copulation behavior of consorting males was, however, linked to the timing of both ovulation and the fertile period, suggesting that males did have knowledge about these timings. Together these results suggest that males used fine-scale swelling size changes when deciding when to consort, but that consorting males did not use fine-scale swelling size changes in deciding when to copulate. We propose that swelling size may advertise the period during which males should consort with females, with other signals available only from closer inspection then used by consorting males to assess the timing of the fertile period more accurately. An important implication of this interpretation is that different males may have access to different signals of ovulation at any one time. Such a system would allow females to offer different males different information simultaneously, perhaps offering a solution to the ‘female dilemma’ of how females can simultaneously assure and confuse paternity in multi-male societies.     

Pig heart calpastatin: identification of repetitive domain structures and anomalous behavior in polyacrylamide gel electrophoresis

Isolation and nucleotide sequencing of the complementary DNA for pig heart calpastatin have been completed. The amino acid sequence of 713 residues predicted from the nucleotide sequence contains five domains, each composed of approximately 140 amino acid residues. A unique N-terminal domain is followed by four mutually homologous domains. The best fit alignment of these four domains gives residue identities between any two domains of 22.5-36.0%. The analysis of the sequence similarities by several methods also suggests the existence of additional shorter repeats at intervals of 60-80 residues. The calculated molecular weight of pig calpastatin of 713 amino acid residues (Mr 77,122) is significantly lower than the value of purified pig heart calpastatin (Mr 107,000) estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). The expression of the calpastatin genes in Escherichia coli and the detection of the translation products of 713, 366, and 140 amino acid residues by the specific anti-calpastatin antibody indicate that the products always migrate considerably slow on SDS-PAGE, giving an average of 1.53 for the ratio of the molecular weight estimated by SDS-PAGE to the value calculated from the amino acid sequences. It is most likely that the discrepancy in the molecular weight is caused by an anomalous behavior of calpastatin in SDS-PAGE.     

Roles of nuclear NPY and NPY receptors in the regulation of the endocardial endothelium and heart function

It is now well accepted that the heart is a multifunctional organ in which endothelial cells, and more particularly endocardial endothelial cells (EECs), seem to play an important role in regulating and maintaining cardiac excitation-contraction coupling. Even if major differences exist between vascular endothelial cells (VECs) and EECs, all endothelial cells including EECs release a variety of auto- and paracrine factors such as nitric oxide, endothelin-1, angiotensin II, and neuropeptide Y. All these factors were reported to affect cardiomyocyte contractile performance and rhythmicity. In this review, findings on the morphology of EECs, differences between EECs and other types of endothelial cells, interactions between EECs and the adjacent cardiomyocytes, and effects of NPY on the heart will be presented. We will also show evidence on the presence and localization of NPY and the Y1 receptor in the endocardial endothelium and discuss their role in the regulation of cytosolic and nuclear free calcium.     

Metastatic adenocarcinoma in the baboon

An adenocarcinoma of undetermined origin, with metastasis to the skeletal system, occurred in a 27 year-old castrated male baboon (Papio species).     

Pathology in the Darajani baboon

The loss of teeth from attrition may limit the life span of free-ranging Darajani baboons. A high frequency of fractures is presumably the result of falls that oocur in chases or flights. The pattern of broken bones emphasizes the digits, the trunk, the face, and the lower limb. Such injuries affect virtually all individuals who survive to a relatively old age. Arthritic-like changes in the skeleton frequently occur in the vertebral column and may reduce the baboon's speed and agility in flight. They have remarkable abilities to survive severe wounds, even amputations, as long as such wounds are clean. Numerous diseases and parasites infect the animals and those who survive must cope with repeated infection. Many of these pathogens affect the individual at the same time and each reduces the likelihood of survival. The brief life expectancy of the individual magnifies the genetic contribution of older animals to the group if the individual is of suitable position in dominance and central hierarchy.     

Expression of baboon endogenous virus in exogenously infected baboon cells.

Strains of low-passage, fetal diploid, baboon (Papio cynocephalus) fibroblasts were susceptible to exogenous infection with three independent isolates of baboon endogenous virus, as measured by an immunofluorescence assay specific for viral p28. Infectivity of the M7 strain of baboon endogenous virus for baboon cells of fetal skin muscle origin was equivalent to that for human and dog cells in that similar, linear, single-hit titration patterns were obtained. The assay for supernatant RNA-dependent DNA polymerase, however, showed that baboon cells produced only low levels of virus after infection compared with the production by heterologous cells. The results showed that baboon endogenous virus was capable of penetrating baboon cells and that viral genes were expressed in infected cells. Replication of complete infectious virus was restricted, however, indicating that in this primate system homologous cells differentially regulated the expression of viral genes.     

Aortic baroreceptor deafferentation in the baboon

Previous animal studies have indicated that removal of the aortic baroreceptors causes a moderate increase in arterial pressure that is not fully buffered by receptors in the carotid sinus. However, the role of these separate baroreceptors in the conscious nonhuman primate has not been examined. To address this question, adult male baboons were chronically maintained on a tether system that permitted them to move freely about their cage. With this system, arterial pressure and heart rate could be monitored continuously over 24-h periods with periodic drug administration to test cardiovascular function. Control values of arterial pressure and heart rate were 85.6 +/- 4.0 mmHg and 77.5 +/- 2.9 beats/min, respectively. Following removal of the aortic baroreceptors, arterial pressure rose to 104.6 +/- 5.5 mmHg and heart rate increased to 117.9 +/- 3.1 beats/min. The variability of these parameters did not change following denervation. There was, however, a suppression of the arterial pressure-heart period relationship and an augmentation in the depressor response to ganglionic blockade with hexamethonium. These data indicate that removal of the aortic baroreceptors causes a reduction in the sensitivity of the heart rate baroreflex and subsequent increase in arterial pressure that is a result of an increased sympathetic nervous system function.