Isotope dilution measurement of breast-milk production in Chilean urban mothers

A heavy-water dilution technique has been used to measure mean daily breast-milk output in a group of nursing mothers from an urban community in Santiago, Chile. Infant milk intake was found to correlate significantly with weight (r = 0.646, P less than 0.005) and with weight-for-age (r = 0.640, P less than 0.005), but a much stronger and highly significant correlation was found with infant birth-weight (r = 0.802, P less than 0.001). Milk output was also found to depend on the mother's nutritional status at the beginning of pregnancy and was significantly higher in overweight mothers. An even more marked difference was obtained if mothers were divided into two subgroups, above and below normal, according to their weight-for-height values at the first antenatal check-up (x+ = 1148.1 ml/d, x- = 814.2 ml/d, P less than 0.02). Relationships between milk output and duration of lactation and parity were also apparent from the study but the latter was probably mediated through maternal nutritional status.

Correlation between pulvinar-lateralis posterior complex unit activity and eye movements in the cat

In 15 encéphale isolé cats, 130 units were recorded in the pulvinar-lateralis posterior complex (P-LP); 19 units responded in relation to horizontal eye movements (15%), 9 of which discharged when ipsiversive movements were recorded and the remaining 10 to contraversive movements. Three units discharged during spontaneous nystagnoid eye movement. All units always responded after initiation of the eye movement, with a latency range between 50 and 250 ms. The eye movement-related units were preferentially located (80%) in the border between the pulvinar and the lateralis posterior complex. Our results show the presence of eye movement-related units in the cat's P-LP, and their probable participation in ocular motility.

Rotational behavior in the cat induced by electrical stimulation of the pulvinar-lateralis posterior nucleus complex: role of the cholinergic system

We studied the involvement of the cholinergic system in the contralateral head-eye-body turning induced in the cat through stimulation of the pulvinar-lateralis posterior nucleus complex (P-LP). In 17 cats through a cannula aimed at the P-LP, agonists and antagonists of the cholinergic system were injected. The electrical activity of the P-LP could be recorded through the same cannula or through electrodes attached to it. In addition, electrodes were implanted ipsilaterally in the dorsal hippocampus, caudate nucleus, amygdala, and superior colliculus to record through them and through one screw placed on the skull the electrical activity of those structures and of the cortical P-LP projection. Seven days after surgery, carbachol, an agonist of the cholinergic system was injected in the P-LP, and the behavior and electrical activity of the unrestrained cat (previously accustomed to a plastic cage) were recorded. A control volume of 0.9% NaCl was always injected previously. The usual drug volume injected was 1 microliter; occasionally, 2 microliter were injected. Weekly or biweekly sessions were conducted to determine (a) the threshold for cholinergic activation, (b) the threshold for turning behavior, (c) the blocking effect of local atropine sulfate injected previously, (d) the effect of haloperidol previously injected (locally or systemically), and (e) the effect of dioxolane, an exclusive muscarinic agonist. In 14 of 17 cats, contralateral turning behavior was evoked by carbachol. In two of the three cats that did not respond to carbachol, dioxolane induced turning. The effect of dioxolane was similar to that of carbachol when tried in five cats. Besides turning behavior, carbachol produced numerous symptoms due to cholinergic activation. Atropine blocked the rotational effect of carbachol in all cats, and haloperidol blocked it in 68% of them. Electrolytic coagulation of the dorsal hippocampus surrounding the P-LP did not disturb the effects induced by carbachol. These experiments show that both systems of the P-LP, cholinergic and catecholaminergic, are involved in the contralateral turning. We conclude that the effect induced by carbachol is due to activation of muscarinic receptors because it is totally blocked by local atropine sulfate and is reproduced by dioxolane, an exclusive muscarinic agonist.

Effects of cortical ablations on the turning response evoked by stimulation of the pulvinar-lateralis posterior nucleus complex in the cat

The role played by the cerebral cortex on turning responses elicited by electrical stimulation of P-LP was studied in 9 chronic cats. In three animals the sensorimotor cortex was bilaterally ablated and the threshold values for inducing a turning response were determined. None of the cats showed abnormal threshold values. In six cats the cerebral cortical area known to have reciprocal anatomical connections with P-LP was unilaterally removed. Seven days after surgery, 50% of the electrodes gave no responses; 25% evoked responses with high thresholds and 25% with normal thresholds. One month after surgery the percentages were: 14, 18 and 68 respectively. Histological findings show important fiber and neuronal degeneration in P-LP. It is postulated that this area of the cerebral cortex plays, a facilitatory role on the P-LP ability to induce turning response and that the recovery of this ability can be explained by the development of P-LP denervation supersensitivity.

Effects of subcortical electrolytic lesions on the head-eye turning response induced by electrical stimulation of the cat's pulvinar-lateralis posterior nucleus complex

The relations between three subcortical structures and P-LP, all of them capable of inducing contralateral head-eye turning responses when electrically stimulated, were studied in three groups of cats. In all the experiments stainless steel electrodes were chronically implanted in P-LP and in each group of five cats. Electrodes were also placed respectively in the caudate nucleus, superior colliculus and nucleus centralis lateralis. Series of current intensity threshold values for evoking head-eye turning responses were determined in each group, before and after electrolytic lesion of these three subcortical structures. The total observation period was approximately 30 days. Only the destruction of the superior colliculus produced the loss of the ability of the ipsilateral P-LP to evoke turning response. According to these results it is postulated that the efferent pathway that carries the information for turning response from P-LP runs through the ipsilateral superior colliculus.