On the quantification of suckling intensity in primates

The inhibitory effect that suckling has on the reproductive function of primate mothers varies as a function of the intensity with which they are suckled. Here we present an easily computed index of one parameter of suckling intensity, namely the temporal patterning of suckling bouts. High intensity suckling is characterized by frequent nursing bouts demarcated by short interbout intervals. Therefore, our suckling index is based on the brevity of observed interbout intervals, more specifically the proportion of such intervals that fail to exceed a criterion length. The index is an appropriate means of making interspecific comparisons of the development of infant suckling and is well suited for application to field data that include interbout intervals that were not observed in their entirety. To demonstrate its utility, we apply the index to field data collected on the suckling behavior of free-ranging rhesus monkey (Macaca mulatta) infants in India. In this context, we demonstrate that, in rhesus, between-infant differences in suckling intensity manifest themselves early in the postpartum period and contribute to between-female differences in the timing of first mating postpartum. Am J Phys Anthropol 105:33–42, 1998. © 1998 Wiley-Liss, Inc.     

On the origins of body size dimorphism in primates

Among many explanations concerning the origins of dimorphism in Primates, none has received as little attention as the differences in energy requirements of the two sexes. It is hypothesised that among Primates, a common strategy for overcoming the extra metabolic load of pregnency and lactation experienced by females during the greater part of their adult lifetimes, is for them to reduce their bodyweights relative to those of males. Such a strategy allows the mother plus infant combination to weight approximately as much as the species target weight or slightly less, preserving the balance between the species and the environment. Once such body weight dimorphysm had evolved, they might secondarily lead to modifications in behaviour in the species. For example, the now relatively larger males might take on the role of troop protection as a result of their larger size. Such secondarily acquired social and behavioural roles would be expected to show a reasonably strong correlation with the existence of sexual size dimorphism in Primates, even though they may not have been the cause of the dimorphism, but only the result of it. It is evident however, that many dimorphic features in Primates, such as pelage differences, and differential canine size, have been the subject of different selection processes from those which led to the acquisition of differential body size.     

On oscillatory responses of the Limulus retina

Published observations of the dynamic properties of lateral and self-inhibition in the Limulus retina lead to a non-linear integral equation for the response of ommatidia located near the center of a uniformly illuminated region. Coleman and Renninger (1976, 1978) showed that when the excitation is constant in time and the sum of the inhibitory coefficients for the illuminated region exceeds a critical value, the integral equation has a stable periodic solution describing a sustained, spatially synchronized, oscillatory response in which bursts of activity alternate with silent periods. Such spatially synchronized bursting has been observed in the Limulus retina in situ by Barlow and Fraioli (1978), using the preparation of Barlow and Kaplan (1971). Employing experimental data on the temporal dependence of lateral and self-inhibition, which were then available only for the excised eye, Coleman and Renninger calculated a value of 0.34 s for the period p of the bursting response, which is significantly above the range, 0.11–0.20 s, of values of p observed for the Limulus eye in situ. Brodie et al. (1978) have recently published measurements of the temporal dependence of lateral and self-inhibition for the in situ preparation. Here we show that when the kernel functions in Coleman and Renninger's integral equation are chosen in accord with these new data, the periodic solutions of the equation have a period of approximately 0.13s, which is in the range (0.11–0.20 s) required for agreement with experiment. Other properties of the periodic solutions, i.e., their general form and the threshold levels of inhibition required for their existence, are also in accord with published observations of the behavior of the retina in situ.     

On the carrying behaviour of basic South American primates

InCallithrix, Saguinus, Aotus, andCallicebus other group members than the mother participate in infant care. Differences among these species are obvious in respect to the time of being off any caregiver, and in respect to the carrying position (Aotus andCallicebus). Alloparental care, a basic behaviour pattern in these species, has evolved from the parking behaviour of the prosimians. The infants are «parked» at other group members.     

Early postresuscitation centralization of the blood circulation

Experiments on cats were made to study the cardiac output and its main fractions supplying blood to the epi- and subdiaphragmal parts of the body during the postresuscitation period. The phenomenon of early postresuscitation centralization of circulation was established, correlating with the gravity of the sustained terminal state in the severity and duration.     

On the stability of DNA in photoreceptor cells of rat retina

Summary DNA turnover in post-mitotic photoreceptor cells of F344 rat retina was investigated. Developing retinas of newborn rats were labelled by multiple injections of (methyl-³H)thymidine. One eye was removed on day 60 and embedded in paraffin. The groups of rats were killed 180, 365, 540 or 730 days later and the second eye was removed. Autoradiographic studies on pairs of eyes showed no detectable DNA turnover in photoreceptor cells up to the end of the experiment (near median life-span, 50% survival age). The DNA of these photoreceptor cells is not replaced through the life span of the animals; the results thus suggest that it is very stable and possibly protected in a specific manner.     

The evolution of nervous system centralization

It is yet unknown when and in what form the central nervous system in Bilateria first came into place and how it further evolved in the different bilaterian phyla. To find out, a series of recent molecular studies have compared neurodevelopment in slow-evolving deuterostome and protostome invertebrates, such as the enteropneust hemichordate Saccoglossus and the polychaete annelid Platynereis. These studies focus on the spatially different activation and, when accessible, function of genes that set up the molecular anatomy of the neuroectoderm and specify neuron types that emerge from distinct molecular coordinates. Complex similarities are detected, which reveal aspects of neurodevelopment that most likely occurred already in a similar manner in the last common ancestor of the bilaterians, Urbilateria. This way, different aspects of the molecular architecture of the urbilaterian nervous system are reconstructed and yield insight into the degree of centralization that was in place in the bilaterian ancestors.     

On the inhibition of camel retina acetylcholinesterase activity by cycloheximide in vitro

The kinetic parameters of inhibition of camel retinal acetylcholinesterase (AChE) activity by cycloheximide (CH) were investigated. For the control system, the Michaelis–Menten constant (K _m)for the hydrolysis of acetylthiocholine iodide was found to be 0.076 mmol/L and the V _max was 0.547 mol/min per mg protein. In contrast, these parameters were decreased in the CH-treated systems. Dixon and Lineweaver–Burk plots, and their secondary replots, indicated that the inhibition was of the linear mixed type, which seems to be a combination of partial competitive and pure noncompetitive inhibition. The values of K_i(slope) and K _I(intercept) were estimated to be 3.50 and 5.68 mmol/L, respectively. K _i was greater than K_i, indicating that CH has a greater binding affinity for the peripheral site than the active site.