Platelet and vascular smooth muscle thromboxane A2/prostaglandin H2 receptors

Thromboxane A2 (TxA2) and prostaglandin H2 (PGH2) aggregate platelets and contract vascular smooth muscle. Inasmuch as both compounds produce the same effects and presumably through the same receptor, their receptors have been referred to as TxA2/PGH2 receptors. Pharmacological studies of stable agonists and antagonists of the TxA2/PGH2 receptors have shown different rank order potencies for these compounds in platelets compared with blood vessels. These studies have provided evidence to support the hypothesis that the platelet TxA2/PGH2 receptor is different from the one found in vascular tissue. The vascular receptor has been named [TxA2/PGH2]tau and the platelet receptor has been named [TxA2/PGH2]alpha. In the past few years several radiolabeled antagonists and agonists have been developed and used in radioligand-binding studies, primarily in platelets. One of these ligands, 125I-labeled PTA-OH, a TxA2/PGH2 receptor antagonist, has been extensively used to characterize the human platelet TxA2/PGH2-binding site. It has been found to have a Kd of approximately 20 nM and a Bmax of 2500 binding sites/platelet. Through the combination of pharmacological and biochemical approaches, it should be possible to characterize platelet and vascular TxA2/PGH2 receptors.     

Parturition in rhesus monkeys (Macaca mulatta)

During five years of birth season fieldwork, we observed two births and three peri-birth instances of behavior of free-ranging rhesus living in Kathmandu, Nepal. These constitute the first two recorded free-ranging rhesus births, and we compare them to the behavior which has been observed in captivity and expected in the wild. The free-ranging parturition behavior was characterized by a general lack of contact with other troop members and by overall inconspicuousness. In the first birth we observed, the troop moved about 70 m up the hill, leaving the laboring female behind on an open hillside. Two males, a female and a juvenile returned and rested about 20 m from the delivering female. During the second delivery, the female stayed with the troop and seemed to participate normally in most troop interactions, although she avoided physical contact with other troop members. We propose that this near-normal behavior may help to assure successful parturition by allowing the female the needed social isolation and inconspicuousness without any loss of troop protection. It may also partly explain why births have not been observed during previous studies. Observations of rhesus parturition behavior reported from studies of captive monkeys and reports from other free-ranging primate studies are compared with our data.     

Specific receptors for thromboxane A2 in cultured vascular smooth muscle cells of rat aorta

The specific binding site for thromboxane A2 (TXA2) was studied in cultured vascular smooth muscle cells (VSMC) of the rat aorta. [3H]SQ29,548, a potent and selective TXA2 receptor antagonist, displayed high-affinity and specificity, as well as saturable and displaceable binding to rat VSMC in culture. Scatchard analysis of equilibrium binding at 24 degrees C revealed a single class of binding sites with a Kd of 1.7 nM and a Bmax of 8.0 fmol/10(6) cells. A series of TXA2 receptor antagonists completely suppressed [3H]SQ29,548 binding to rat VSMC, and the rank order of their inhibitory potencies (Ki) correlated well with the potencies for suppression of the U46619-induced contraction of rat thoracic aorta. These results suggest that specific binding sites for [3H]SQ29,548 represent the TXA2 receptor in rat VSMC.     

Characterization and comparison of testicular LH/hCG receptors of rhesus monkeys (Macaca mulatta) and green monkeys (Cercopithecus aethiops)

Testicular luteinizing hormone (LH/hCG) receptors were characterized in seven green monkeys and compared with those of four rhesus monkeys. Testicular tissue showed high binding affinity for ¹²⁵I-hCG, (0.9–2.5 × 10⁹ M^?1, and 0.7–1.64 × 10⁹ M^?1 respectively, for green and rhesus monkeys) and low binding capacity (0.343–0.682 fmol/mg and 0.198–0.355 fmol/mg testicular homogenate, respectively). There was no difference in binding affinity between the two groups. Testicular LH/hCG receptors in both species bound human LH (hLH) and hCG but did not cross react with ovine LH (oLH). Rat testicular tissue showed similar high binding affinity (6.4 × 10⁹ M^?1) and low binding capacity (1.04 fmol/mg tissue homogenate) for ¹²⁵I-hCG. Rat LH/hCG receptors bound hLH, hCG, and oLH to a similar degree.     

Hydranencephaly in two rhesus monkeys (Macaca mulatta)

Spontaneously occurring hydranencephaly was diagnosed at necropsy and confirmed histologically in two stillborn fetuses that were delivered from young female rhesus macaques (Macaca mulatta).     

Skeptical responding in rhesus monkeys (Macaca mulatta)

Signalers that misinform sufficiently open may become devalued as sources of information; however, “skepticism” and any comparison involved in testing reliability entail a cost that involves delays and energy expenditure. Skepticism may be less costly though, if, as a rule, animals are not equally skeptical of the signals of all conspecifics. Animals with the ability to recognize individual conspecifics and to recall past encounters with them may have the capacity to restrict skepticism to subsets of animals that are most likely to benefit from deception. We played tape-recorded alarm calls of high- and low-ranking rhesus monkeys(Macaca mulatta) to their groups in a feeding context once daily over 8 consecutive days at the Yerkes Primate Center Field Station. Over the sequence of playbacks, response was greater to the calls of high-ranking monkeys, adult response patterns were different from those of juveniles, and for adults especially, decline in responsiveness was punctuated by partial resurgences of response. These differences may be the consequence of the adults’ more extensive histories of interaction with group members that, though generally reliable, vary with respect to the potential benefits of deceptive signaling.     

Cell signalling through thromboxane A2 receptors

Thromboxane A2 receptors (TPs) are widely distributed among different organ systems and have been localized on both cell membranes and intracellular structures. Following the initial cloning of this receptor class from human placenta, the deduced amino acid sequence predicted seven-transmembrane spanning regions, four extracellular domains and four intracellular domains, making TP a member of the seven-transmembrane G-protein-coupled receptor (GPCR) super family. A single gene on chromosome 19p13.3 leads to the expression of two separate TP isoforms: TPalpha which is broadly expressed in numerous tissues, and a splice variant termed TPbeta which may have a more limited tissue distribution. Mutagenesis, photoaffinity labelling, and immunological studies have indicated that the ligand binding domains for this receptor may reside in both the transmembrane (TM) and extracellular regions of the receptor protein. In addition, separate studies have provided evidence that this receptor can couple to at least four separate G protein families. As a consequence, TP signalling has been shown to result in a broad range of cellular responses including phosphoinositide metabolism, calcium redistribution, cytoskeletal arrangement, integrin activation, kinase activation, and the subsequent nuclear signalling events involved in DNA synthesis, cell proliferation, cell survival and cell death. While activation of these different signalling cascades can all derive from TP stimulation, the relative signalling preference for a given cascade appears to be both tissue and cell specific. Finally, separate studies have indicated that TP signalling capacity can be both down-regulated by protein kinase activation and up-regulated by GPCR cross-signalling. Thus, the multitude of signalling events which derive from TP activation can themselves be modulated by endogenous cellular messengers.     

A labor readiness index (Bishop score) for rhesus monkeys

A scoring system is presented for quantitative evaluation of labor readiness in macaque monkeys. Cervical position, length, softness and dilation are rated along with fetal head position for a total score of 13. The system is based on experience in evaluating readiness of multiparous rhesus monkeys for labor induction. Guidelines for the examination for use of the score are described.     

Diversity of the killer cell Ig-like receptors of rhesus monkeys

Because the killer cell Ig-like receptors (KIRs) have only been characterized in humans and chimpanzees, we do not have a full understanding of their evolutionary history. Therefore, cDNAs encoding the KIR molecules of five rhesus monkeys were characterized, and were found to differ from the KIR molecules identified in humans and chimpanzees. Whereas only one KIR2DL4 molecule is detected in humans and chimpanzees, two distinct KIR2DL4 homologues were identified in the monkeys. Although the two human KIR3DL molecules are limited in their polymorphism, the KIR3DL homologues in the monkeys were highly polymorphic. Up to five KIR3DL homologues were identified in each monkey that was studied, and eleven distinct KIR3DL molecules were detected in the five rhesus monkeys. Two novel families of KIR molecules were identified in the rhesus monkeys, KIR3DH and KIR1D. The KIR3DH molecules have three Ig domains, transmembrane domains homologous to KIR2DL4 molecules that contain an arginine, and short cytoplasmic domains. With these features, the KIR3DH molecules resemble the activating forms of the human KIR molecules. The KIR1D molecule encodes only one complete Ig domain before a frame-shift in the second Ig domain occurs, leading to early termination of the molecule. Multiple splice variants of KIR1D exist that encode at least one Ig domain, as well as transmembrane and cytoplasmic domains. The extensive diversity of the rhesus monkey KIR3DL homologues and the novel KIR3DH and KIR1D molecules suggests that the KIR family of molecules has evolved rapidly during the evolution of primates.     

Feeding tactics in juvenile rhesus monkeys (Macaca mulatta)

In a group of rhesus monkeys, feeding tactics of juveniles were studied in a competitive situation in which food presentation had been modified, and where food was supplied in a feeding trough six times a day. Juvenile offspring of high-ranking mothers remained longer in the feeding area gathering food. In contrast, juvenile offspring of low-ranking mothers went less often to the feeding area, primarily to collect food. Low-ranking juveniles also gathered the food faster than did dominants and used longer feeding bouts. High-ranking juveniles interrupted their feeding more spontaneously than did subordinate ones. Low-ranking juveniles did so more often as a result of avoiding and being startled. Juvenile males entered the feeding area to satisfy their food requirements more often than females, but were also aggressively expelled more than females. No relation was found between age in months of juveniles and any feeding parameters or causes of interruption. Nor were significant differences found between young and old juveniles. Juvenile rhesus appear to use different tactics in accessing food according to their sex and to their mothers' dominance rank.     

Estrous behavior of free-ranging rhesus monkeys (Macaca mulatta)

The sexual behavior of a group of free-ranging rhesus monkeys (Macaca mulatta) was studied for 13 consecutive months in an attempt to determine whether or not sexual activity occurred year-round, and the importance of sexual attraction to rhesus monkey social organization.Estrous behavior was seen both inter-menstrually and peri-menstrually, producing a shorter mean estrous cycle length than reported by other workers. New data was gathered on the interrelationships among age, dominance rank, and sexual activity; son-mother and brothersister matings; and sexual favoritism among free-ranging rhesus monkeys.A few females who failed to conceive during the fall breeding season showed cyclic estrous behavior throughout the entire annual cycle. Hypotheses are given as to possible physiological bases for birth season sexual cycles.Several forms of inter-animal bonding, including sexual bonding, are enumerated, and their importance to rhesus monkey social organization discussed.