Human kin recognition by olfactory cues

T-shirts worn by individual children were correctly identified by the siblings and mothers of those children through olfactory cues alone. Furthermore, parents correctly distinguished between the odors of otherwise identical shirts worn by two of their own children. Bodily odors may therefore be salient stimuli for kin recognition among humans.     

Mothers' recognition of their newborns by olfactory cues

We report that 90% of women tested in the present study identified their newborns by olfactory cues after only 10 min-1 hr exposure to their infants. All of the women tested recognized their babies' odor after exposure periods greater than 1 hr. The robust results are due in part to the implementation of an initial screening phase in which individuals with obvious olfactory deficits were excluded from the sample. These results suggest that odor cues from newborns are even more salient to their mothers than have been thought heretofore.     

Maternal recognition of neonates through olfactory cues

The role of olfactory cues in maternal recognition of neonates was investigated. Mothers were able to identify the garments worn by their own infants (in comparison to garments worn by unfamiliar infants) through odor alone within the first 6 days postpartum. In a second experiment, mothers who had only limited pre-test exposure to their infants recognized the odor of their infant's garment during tests conducted at 20.5-41.7 hr after delivery. Olfaction may be an especially salient modality for recognition of infants.     

NALP3 is not necessary for early protection against experimental tuberculosis

In vitro, Toll-like receptors (TLR)2, 4 and 9 as well as NOD-like receptor 2 critically determine macrophage responses to Mycobacterium tuberculosis (Mtb) infection. However, in low-dose experimental murine tuberculosis, single or multiple deficiencies in TLRs 2, 4, 9 or NOD2 have little, if any, impact on early mycobacterial growth containment, granuloma formation and survival. Here, we analyzed the relevance of NALP3, one component of the danger-signaling inflammasome, for (i) Mtb-induced cytokine secretion in vitro and in vivo, (ii) restriction of Mtb replication in infected organs and (iii) granuloma formation. In the absence of functional NALP3, there was no IL-1β and IL-18 production in Mtb-infected dendritic cells and macrophages in vitro, whereas secretion of IL-1α, IL-12p40 and TNF remained unaffected. After three weeks of infection, NALP3-deficient as well as IL-18-deficient mice were as capable as wildtype mice of restricting Mtb loads at a plateau level within well-differentiated granulomas. In conclusion, despite its involvement in cytokine processing, NALP3 is not essential for induction of protective immunity to Mtb.     

Maternal experience influences the establishment of visual/auditory, but not olfactory recognition of the newborn lamb by ewes at parturition

Maternal behavior in sheep is characterized by the rapid establishment of individual recognition of the lamb through the use of different sensory modalities. Olfactory recognition mediates acceptance at suckling whereas visual/auditory cues are involved in recognition from a distance. This study investigates (a) the timing of both types of recognition and (b) whether they can be influenced by maternal experience. Olfactory recognition was assessed at lambing, 30 min, 1, 2, or 4 hr postpartum by presenting successively an alien and the familiar lamb. Recognition at a distance was assessed at 6, 8, and 12 hr postpartum by using a two-choice test between the familiar and an alien lamb. A majority (33/51) of ewes showed selectivity at suckling as early as 30 min after parturition, and no differences due to maternal experience were observed. By contrast, in the two-choice recognition test, multiparous ewes showed a preference for their familiar lamb at 6 hr whereas primiparous mothers did so only after 24 hr of mother-young contact: The performance of biparous mothers was intermediate. Thus, both types of recognition can be rapidly established after parturition, and maternal experience has a differential effect on the dynamics of these learning processes.     

T cell recognition of cell-surface antigens. II. Antigen recognition is necessary yet not sufficient for triggering T cell-mediated immunity

We investigated whether recognition per se of cell surface antigens by lymphocytes is both necessary and sufficient to trigger sensitization of T cells. We assayed sensitization of normal rat lymphocytes against monolayers of mouse fibroblasts by measuring the acquisition of cytotoxicity against target monolayers syngeneic to the sensitizing monolayer, following 5 days of culturing on living or glutaraldehyde-fixed fibroblasts. Monolayers of either living or glutaraldehyde-treated fibroblasts were used as cellular immunoadsorbents to assay recognition. Glutaraldehyde treatment of mouse fibroblasts did not seem to alter the cell surface antigens detectable by alloantibodies. Yet, rat lymphocytes cultured on such monolayers did not undergo sensitization. This was not due to the lack of feeder effect by the glutaraldehyde-fixed monolayers, since the addition of living rat fibroblasts, which sustained the survival of the lymphocytes, did not result in sensitization. Not even when living fibroblasts were added to syngeneic fixed monolayers did sensitization of the rat lymphocytes against the monolayer cells occur. Yet, addition of living fibroblasts to fixed allogeneic monolayers resulted in sensitization against the living fibroblasts, but not against the fixed cells. To test whether lymphocytes recognize surface antigens of glutaraldehyde-treated monolayers, the capacity of the latter to specifically adsorb lymphocytes possessing receptors for the fibroblast antigen was measured. The nonadhering rat lymphocytes, seeded on glutaraldehyde-treated C3H fibroblasts, lost their capacity to become sensitized against fresh C3H cells, but retained their capacity to react against BALB/c fibroblasts. Recognition of C3H antigen did take place, yet this was not sufficient to trigger sensitization. Thus, rat lymphocytes seem to recognize the antigens of fixed monolayers, but cannot respond to them.     

Gastric aspiration is not necessary for the diagnosis of pulmonary tuberculosis

Despite recommendations, gastric aspirate collected by invasive nasogastric aspiration is still routinely used for the direct detection of Mycobacterium tuberculosis in our institution. Reviewing 82 patients with culture-proven respiratory tuberculosis over a 28-month period, we observed no patient diagnosed solely by gastric aspirate analysis. Moreover, the diagnosis yield of gastric aspirate (60 %) did not significantly differ from that of stool specimen (64 %). These data confirm that gastric aspirate is no longer useful for the diagnosis of respiratory tuberculosis contrary to stool specimen.     

Individual recognition of female hamsters by males: role of chemical cues and of the olfactory and vomeronasal systems

Sexually satiated male hamsters preferred to investigate and to mount an anesthetized, estrous, novel female over a similarly presented female with which the male had become satiated (the Coolidge effect); likewise, such males preferred a novel female recently mated with another male over the familiar female but showed no preference between fresh and mated novel females. Thus the Coolidge effect is at least partly dependent on discrimination of a new female by chemical cues. Another experiment indicated that transfer of a male's own scent during mating is not involved in discrimination between familiar and novel females. Flank gland secretion of females were sufficient for individual discrimination by males, whereas head region scents and vaginal secretions were not sufficient. The presence of female's flank glands was not, however, necessary for such discrimination. Lesions of or removal of the vomeronasal organ did not disrupt the preferences of sexually satiated males for a novel female, but elimination of main olfactory system function by ZnSO4 treatment of the olfactory mucosa did abolish such preferences. Thus olfactory cues are sufficient for individual discrimination of novel females by sexually satiated male hamsters, and such recognition leads to increased sexual arousal. These processes are mediated by the main olfactory system but not the vomeronasal accessory-olfactory system.     

The hippocampus is not necessary for a place response but may be necessary for pliancy

Rats with kainate-colchicine hippocampal lesions (HL) and controls (C) were initially trained in the Morris water maze with procedures that deterred their prepotent thigmotaxic response. Training began with an escape platform that occupied nearly the entire pool. The area to which the rats could escape was made smaller by substituting smaller platforms as training progressed. In contrast to standard procedures, HL rats and C rats showed comparable performance during acquisition and preferentially searched the goal quadrant on probe trials during which the platform was removed. In a follow-up experiment, the platform was moved to a random position along the wall, which required a switch to a thigmotaxic response for most effective escape. HL rats that were thigmotaxic before place training did not switch to a thigmotaxic response as readily as did controls, behavior consistent with the view that hippocampal damage reduces pliancy.     

The postsubiculum is necessary for spatial alternation but not for homing by path integration

The postsubiculum is a structure of interest because it projects to the hippocampal formation and contains head direction cells, grid cells, and border cells. The aim of the current experiment was to test whether the postsubiculum is necessary for homing by path integration. Rats were trained on a homing task on a large circular platform. After exhibiting stable homing, one group of animals (n = 6) received ibotenic acid lesions of the postsubiculum, and a second (n = 5) underwent a control surgery. After recovery, animals with postsubiculum lesions homed as accurately as the control animals. Subsequent testing on a delayed alternation T maze task showed that the lesioned animals were significantly worse than the control animals at delays of 5-, 30-, and 60-s. These findings suggest that the postsubiculum is necessary for memory and avoidance of previously visited locations but is not necessary for homing.     

Establishment of a preference by the newborn lamb for its mother: the role of opioids

Mother-young relationships in sheep are characterized by individual recognition and a rapidly developing exclusive bond. The authors examined the role of opioids in establishment of the lamb's preference for its mother. Newborn lambs received the opioid receptor antagonist naltrexone (0.0, 1.5, or 3.0 mg/kg i.p.), and lambs were tested at 24 hr and 48 hr of age. At 24 hr, controls spent significantly more time near the mother than near an alien ewe; no significant difference was obtained for the naltrexone-treated groups. The effect of naltrexone persisted at 48 hr. No other significant behavioral difference was observed. Results support the hypothesis that opioids mediate the establishment of mother preference and the view that positive affect associated with social attachment and maternal care may be modulated by opioids.     

Myosin-based contraction is not necessary for cardiac c-looping in the chick embryo

During the initial phase of cardiac looping, known as c-looping, the heart bends and twists into a c-shaped tube with the convex outer curvature normally directed toward the right side of the embryo. Despite intensive study for more than 80 years, the biophysical mechanisms that drive and regulate looping remain poorly understood, although some investigators have speculated that differential cytoskeletal contraction supplies the driving force for c-looping. The purpose of this investigation was to test this hypothesis. To inhibit contraction, embryonic chick hearts at stages 10-12 (10-16 somites, 33-48 h) were exposed to the myosin inhibitors 2,3-butanedione monoxime (BDM), ML-7, Y-27632, and blebbistatin. Experiments were conducted in both whole embryo culture and, to focus on bending alone, isolated heart culture. Measurements of heart stiffness and phosphorylation of the myosin regulatory light chains showed that BDM, Y-27632, and blebbistatin significantly reduced myocardial contractility, while ML-7 had a lesser effect. None of these drugs significantly affected looping during the studied stages. These results suggest that active contraction is not required for normal c-looping of the embryonic chick heart between stages 10 and 12.     

Expression of the dopaminergic phenotype in the olfactory bulb: neither calcitonin gene-related peptide nor olfactory input is necessary.

In the olfactory bulb, expression of tyrosine hydroxylase (TH) in juxtaglomerular neurons is dependent on innervation by the olfactory nerve. The presence of the neuropeptide calcitonin gene-related peptide (CGRP) within the olfactory nerve has led to the hypothesis that CGRP is responsible for regulation of TH expression in the bulbar neurons. On the other hand, other investigators claim that olfactory receptors never produce CGRP and that functional contact with olfactory axons regulates production of TH by bulbar neurons. Two different experimental procedures were used to test whether either CGRP or contact with the olfactory nerve is essential for production of TH by bulbar neurons in vivo. The peptidergic innervation of the olfactory bulb was eliminated either by neonatal capsaicin treatment, or by stereotaxic, electrolytic lesions of the ophthalmic division of the trigeminal nerve. Both of the treatments leave the olfactory innervation of the bulb intact while eliminating the CGRP-immunoreactive fibers in the olfactory nerve and glomeruli. Subsequent immunocytochemistry reveals a normal complement of bulbar TH-immunoreactive juxtaglomerular neurons in the absence of peptidergic innervation. In order to test whether olfactory nerve input is necessary for expression of TH in vivo, the anlage of the olfactory bulb was removed from embryonic (E16) rat pups and transplanted into the anterior chamber. These ectopic olfactory bulbs, although devoid of olfactory nerve input, contain numerous TH-immunoreactive neurons. Thus olfactory nerve input is not necessary for expression of TH in bulbar neurons.     

Olfactory and/or visual cues for spatial navigation through ontogeny: olfactory cues enable the use of visual cues

This study analyzed the spatial memory capacities of rats in darkness with visual and/or olfactory cues through ontogeny. Tests were conducted with the homing board, where rats had to find the correct escape hole. Four age groups (24 days, 48 days, 3-6 months, and 12 months) were trained in 3 conditions: (a) 3 identical light cues; (b) 5 different olfactory cues; and (c) both types of cues, followed by removal of the olfactory cues. Results indicate that immature rats first take into account olfactory information but are unable to orient with only the help of discrete visual cues. Olfaction enables the use of visual information by 48-day-old rats. Visual information predominantly supports spatial cognition in adult and 12-month-old rats. Results point out cooperation between vision and olfaction for place navigation during ontogeny in rats.     

Early olfactory learning is influenced by sex in hamsters but not rats

The odor of cedar shavings repels infant and juvenile rats and hamsters reared in pine shavings when animals are tested in a two-choice situation. Housing male and female infants of either species in cedar shavings for 3 days before testing increases preference for both cedar odor and for a mixture of cedar and conspecific odors. Similar exposure of juvenile male and female rats and male hamsters, has little or no significant impact on odor preferences. However, housing female hamsters in cedar at either developmental stage equally influences odor preferences. The data imply that sex differences influence the development of early odor-guided behavior in hamsters but not rats. These species differences may have adaptive significance in that the birth of a litter produces a greater environmental change demanding a larger preference adjustment of solitary female hamsters than colonial female rats.     

Involvement of the medial prefrontal cortex in mediating behavioural responses to odour cues rather than olfactory recognition memory

Sheep form an olfactory recognition memory for their lambs within 2 h of parturition and will subsequently reject the approaches of any strange lamb and protest vocally. In this study we report that following olfactory memory formation, ewes exposed to either their own or a strange lamb show c-fos mRNA expression in the medial frontal cortex, although levels of expression in the pyramidal output cell layer V were significantly higher in ewes that rejected strange lambs. Reversibly inactivating this region by the retrodialysis of the anaesthetic tetracaine before birth reduced aggressive motor responses towards lambs but not protest vocalisations. Similar treatment during the critical period for olfactory memory formation and lamb recognition (0-4 h post-partum) had no effect on ewes maternal behaviour towards their own lambs. It did, however, prevent the normal selective expression of aggressive rejection, and reduced protest vocalisation behaviours directed towards strange lambs. These rejection behaviours did appear 1 h after the termination of tetracaine infusions despite the ewes not being given the opportunity to interact with their own lambs during this time. Therefore, tetracaine blockade of the medial frontal cortex prevents animals from responding with motor aggression, but not vocal aggression, to odour cues from strange lambs, but has no effect on the formation of an olfactory recognition memory for their own lambs. Both pre- and post-partum aggressive rejection of strange lambs was associated with increased concentrations of dopamine, serotonin, glutamate and GABA. When these behaviours were inhibited by the tetracaine infusions, extracellular concentrations of these neurotransmitters were all increased by the anaesthetic but did not change in response to lambs. These findings suggest that a functional medial frontal cortex is not required for the formation of an olfactory recognition memory or for mediating pro-active maternal behaviours. It is however required for the mediation of motor but not vocal aspects of aggressive rejection responses directed towards aversive odour cues from strange lambs.     

Beta1 integrin is not essential for hematopoiesis but is necessary for the T cell-dependent IgM antibody response

Several experimental evidences suggested that beta1 integrin-mediated adhesion of hematopoietic stem cells (HSC) is important for their function in the bone marrow (BM). Using induced deletion of the beta1 integrin gene restricted to the hematopoietic system, we show that beta1 integrin is not essential for HSC retention in the BM, hematopoiesis, and trafficking of lymphocytes. However, immunization with a T cell-dependent antigen resulted in virtually no IgM production and an increased secretion of IgG in mutant mice, while the response to a T cell-independent type 2 antigen showed decreases in both IgM and IgG. These data suggest that beta1 integrins are necessary for the primary IgM antibody response.     

AlphaCaMKII autophosphorylation contributes to rapid learning but is not necessary for memory

Autophosphorylation of alpha calcium-calmodulin-dependent kinase II (alphaCaMKII) has been proposed to be the key event in memory storage. We tested this hypothesis with autophosphorylation-deficient mutant mice in hippocampus- and amygdala-dependent learning and memory tasks and found that the autophosphorylation of alphaCaMKII was required for rapid learning but was not essential for memory. We conclude that alphaCaMKII autophosphorylation contributes to single-trial learning but is dispensable for memory.     

Presynaptic activity in the period immediately after conditioning is not necessary for long-term potentiation

The stratum radiatum of in vitro slices of rat hippocampus was tetanically stimulated to induce long-term potentiation (LTP) in CA1 neurons. One group of slices received test stimuli immediately after tetanisation, whilst another received no test stimuli until 30 min afterwards. No difference (P greater than 0.65) was found between the magnitude of LTP induced in the two groups of slices. This result demonstrates that the induction and maintenance of LTP does not require presynaptic release of transmitter or other neuroactive substances in the period immediately after tetanisation.