Fluoro Jade-B Detection of Dying Cells in the SVZ and RMS of Adult Rats After Bilateral Olfactory Bulbectomy

A novel fluorochrome, Fluoro-Jade B, was used to detect dying precursor cells in the subventricular zone (SVZ) and rostral migratory stream (RMS) of adult rats after bilateral olfactory bulbectomy and in control intact rats. The animals in experimental group were left to survive 3 days and from 3 till 16 months after surgical procedure. 1. In the control animals, Fluoro-Jade B positive cells were visible in the SVZ and within the whole extent of the RMS. The number of Fluoro-Jade B positive cells increased in the elbow in comparison to the rest parts of the RMS. 2. In the experimental animals surviving either 3 days or from 3 till 16 months after bilateral olfactory bulbectomy, Fluoro-Jade B positive cells displayed the similar pattern of distribution as in the control animals. However, some quantitative differences in the labeled cells number along the rostral migratory pathway appeared. 3. The average number of degenerating cells within the control SVZ and RMS was 26.24+/- 0.686. In bulbectomized animals, regardless of survival time, an insignificant increase of Fluoro-Jade B positive cells number occurred. We can conclude that dying of precursor cells is a physiological process running within the SVZ/RMS in both control and experimental animals. Moreover, this physiological process is not influenced by survival period after bilateral olfactory bulbectomy. Our results demonstrate Fluoro-Jade B as a useful marker of dying cells.     

Different olfactory system deficits affect the antigonadal action of light deprivation differently in male rats

Twenty-eight day-old male rats were subjected to: Blinding-olfactory bulbectomy, Blinding-peripheral anosmia, Blinding-accessory olfactory bulbectomy and Blinding-sham olfactory operation. A set of rats remained intact. Six weeks later, their pituitary-gonads-accessory sex organs were studied. Bulbectomy as well as peripheral anosmia exaggerated the antigonadal effects of blindness, while the accessory olfactory system impairment did not. It is suggested that olfactory bulbectomy potentiation of the antigonadal effects of light deprivation is due to a lack of sensory function rather than to bulbectomy itself and that the accessory olfactory system which is involved in the priming pheromonal effects does not play any role in the inhibition of the antigonadal effects of blindness.     

Effect of the bilateral olfactory bulbs removal on the daily fluctuations on the plasmatic corticosterone levels (author's transl)]

The influence of the bilateral destruction of the olfactory bulbs on the circadian rhythm of plasmatic corticosterone in rat was investigated. Twentyfive days after bulbectomy, the values of corticosterone in the morning and in the evening were not significantly different. The possible involvement of the stria medularis, habenula, septum and preoptic area in the determination of this phenomenon is discussed.     

Effect of olfactory bulbectomy on plasma levels of glucose, lipids and corticosterone in the rat

The effect of bilateral olfactory bulbs removal on the peripheral glucose, lipids and corticosterone levels has been studied in Wistar male rats. After 30 days of the olfactory bulbectomy there was found: an increase in the basal values of plasmatic glucose, a significant increase in peripheral levels of the free fatty acids, and a notorius decrease in plasmatic corticosterone at 9 a.m. Other biochemical parameters, such as free glycerol, triglycerides and phospholipids, went unaltered. These after bulbectomy variations, especially the increase in free fatty acids, are discussed in relation to a possible role of the olfactory bulbs on the nutritional, endocrine and nervous factors, which are closely related to the mechanisms involved in the regulation of cellular lypolisis.     

Increased Level of β-Amyloid in the Brain of Bulbectomized Mice

Six weeks after bilateral olfactory bulbectomy, a peptide with molecular weight of 4 kD was revealed in extracts of the neocortex and hippocampus from mice. Using monoclonal antibodies 4G8, this peptide was identified as beta-amyloid. Its level was significantly higher in the bulbectomized animals than in sham-operated mice. The bulbectomized mice displayed sharp impairment in spatial memory when tested in the Morris water maze. The results suggest that bulbectomy initiates in the brain a pathological process similar to human Alzheimer's disease in location, biochemistry, and behavioral manifestations.     

The development of standard stimulus animals for mouse (Mus musculus) aggression testing by means of olfactory bulbectomy

The usual round-robin technique employed in aggression testing with mice has several major deficiencies. A set of specifications is given for the ideal standard stimulus mouse, which would overcome these deficiencies. In a series of seven experiments, we found that the technique of bilateral olfactory bulbectomy yielded stimulus animals which very closely approximated our ideal. Bulbectomized mice would elicit attack behaviour from normal males, would almost never initiate an attack themselves, rarely fought back when attacked, and were very homogeneous in their capability to release attack behaviour. These findings were obtained whether the mice were tested within a few days after bulbectomy or 40 days afterwards.     

The Ginkgo biloba extract modulates the balance between proliferation and differentiation in the olfactory epithelium of adult mice following bulbectomy.

Abstract - The adult olfactory receptor neurons (ORNs), located in the olfactory epithelium (OE) are permanently renewed thanks to neuronal progenitors present in the deep part of the OE, the globose basal cells (GBCs). Following the ablation of their synaptic target, the olfactory bulb (OB), ORNs degenerate by apoptosis and a wave of neurogenesis, including proliferation of GBCs and neuronal differentiation of their progeny, restores the olfactory function. The Ginkgo biloba extract (EGb 761) (Beaufour Ipsen, France) was administered to adult mice at the doses of 50 or 100 mg/kg, following bilateral bulbectomy and its effects on the expression of PCNA, reflecting the number of proliferating GBCs and on growth associated protein 43 (GAP-43), expressed by differentiating neurons were measured by Western blotting. PCNA expression peaked 9 days post-bulbectomy in untreated animals, but 7 days post-lesion in EGb 761-treated animals. A simultaneous reduction in GAP-43 expression suggested that EGb 761 may temporarily favor the proliferation of GBCs rather than their entry into the differentiation pathway. Probably as a consequence of the earlier onset of the neurogenetic response to bulbectomy, neuronal differentiation was enhanced in the OE, 3 weeks post-bulbectomy. These data suggest that EGb 761 may have beneficial effects upon neurogenesis in the OE through changing the balance between proliferation and differentiation.     

Effect of compensatory hypertrophy of the kidney on the ability of splenocytes to induce a regional graft versus host reaction

The ability of C57BL/6 mouse splenocytes to induce regional GVHR during uni- and bilateral nephrectomy, ligation of the ureter and sham operations was studied. It was shown that any kidney operation enhances the ability of splenocytes to induce the GVHR in contrast to uni- and bilateral sham operations. This phenomenon was first observed during bilateral nephrectomy (after 5 h), unilateral nephrectomy (after 24 h) and ligation of the ureter (after 72 h). The data indicate that deficiency of the tissue is the main cause of changes in the immunity system status rather than changes in antigen properties and functional insufficiency of the kidneys.     

The Response of Ornithine Decarboxylase During Neuronal Degeneration and Regeneration in Olfactory Epithelium

Mature olfactory neurons are continually replaced from a population of progenitor cells. Olfactory nerve section, bulbectomy, or treatment with certain chemicals induces degeneration of olfactory neurons followed in some cases by regeneration. Ornithine decarboxylase (ODC) activity was measured in mouse olfactory tissues as an indicator of cellular regeneration. ODC activity in olfactory tissue (0.2–0.4 nmol/mg protein/h) is 10-30 times higher than in a variety of other cerebral tissues. Within 3 h after unilateral olfactory nerve section, ODC activity in the epithelium declines to 50% of control followed by a slow return to basal activity by 6 days. In the same animals, ODC activity increases severalfold in bulb (1 day) with a gradual decline to normal (9 days). Except for an early transient increase, the effects of unilateral bulbectomy on epithelial ODC activity are similar to those seen after nerve section. The changes in ODC activity following intranasal irrigation with 10 mm -colchicine also closely mimic those seen after nerve section. The effects of intranasal irrigation on ODC activity with 0.5% Triton X-100 or 0.17 m -ZnSO₄ are more complex. Thus, when the mature neuronal population is degenerating after surgery or chemical treatments, ODC activity decreases in the epithelium. The subsequent increase of ODC activity prior to reconstitution of the mature neuronal population probably reflects the regeneration mechanism of the olfactory epithelium. The increase of ODC activity in the olfactory bulb after nerve section is best interpreted as a cellular injury response. These alterations in ODC activity in olfactory tissues after chemical and surgical treatments constitute the earliest biochemical events observed in these tissues in response to cellular damage.     

Olfactory bulbectomy blocks mating-induced ovulation in musk shrews (Suncus murinus)

In many species, reproductive function can be modified by olfactory inputs. We employed bilateral olfactory bulbectomy (BULBX) to examine the effects of disruption of olfactory inputs on mating behavior and ovulation in female musk shrews. On several measures, sexual behavior was delayed in BULBX females compared to controls. When females were mated on five consecutive days, the majority of unoperated and sham-operated (SHAM) shrews ovulated; only one female subjected to BULBX ovulated. Administration of GnRH induced ovulation in the majority of females. We performed immunocytochemistry to assess the effects of bulbectomy on mating-induced responses of the neural GnRH system. In BULBX and SHAM females, the numbers of cells containing proGnRH immunoreactivity in the medial septum (MS)/diagonal band (DB) were significantly elevated 1 h after mating. Bulbectomy increased the numbers of GnRH-immunoreactive peptide-containing cells in the preoptic area, but it reduced neuron numbers in the MS/DB, as compared with those in SHAM controls. In addition, the GnRH-immunoreactive fiber area in the median eminence was greater in BULBX than in SHAM females. In sum, female musk shrews can display receptivity and engage in copulation without olfactory inputs. However, the olfactory system is essential for mating-induced ovulation.     

The sorting behaviour of olfactory and vomeronasal axons during regeneration

Summary In order to begin to understand how primary olfactory and vomeronasal organ (VNO) axons target specific regions of the olfactory bulb, we examined the sorting behaviour of these axons following neonatal unilateral olfactory bulbectomy. Bulbectomy induced widespread ipsilateral death of the primary olfactory and VNO neurons. After 4 weeks, many new sensory axons had re-grown into the cranial cavity and established a prominent plexus with evidence of dense tufts that were similar in gross appearance to glomeruli. Axons expressing the cell adhesion molecule OCAM, which normally innervate the ventrolateral and rostral halves of the main and accessory olfactory bulbs, respectively, sorted out and segregated from those axons not expressing this molecule within the plexus. In addition, VNO axons formed large discrete bundles that segregated from main olfactory axons within the plexus. Thus, VNO and primary olfactory axons as well as discrete subpopulations of both are able to sort out and remain segregated in the absence of the olfactory bulb. Sorting and convergence of axons therefore occur independently of the olfactory bulb and are probably attributable either to inherent properties of the axons themselves or to interactions between the axons and accompanying glial ensheathing cells.     

Olfactory Bulbectomy Leads to the Development of Epilepsy in Mice

There is a clear link between epilepsy and depression. Clinical data demonstrate a 30–35% lifetime prevalence of depression in patients with epilepsy, and patients diagnosed with depression have a three to sevenfold higher risk of developing epilepsy. Traditional epilepsy models partially replicate the clinical observations, with the demonstration of depressive traits in epileptic animals. Studies assessing pro-epileptogenic changes in models of depression, however, are more limited. Here, we examined whether a traditional rodent depression model—bilateral olfactory bulbectomy—predisposes the animals towards the development of epilepsy. Past studies have demonstrated increased neuronal excitability after bulbectomy, but continuous seizure monitoring had not been conducted. For the present study, we monitored control and bulbectomized animals by video-EEG 24/7 for approximately two weeks following the surgery to determine whether they develop spontaneous seizures. All seven bulbectomized mice exhibited seizures during the monitoring period. Seizures began about one week after surgery, and occurred in clusters with severity increasing over the monitoring period. These results suggest that olfactory bulbectomy could be a useful model of TBI-induced epilepsy, with advantages of relatively rapid seizure onset and a high number of individuals developing the disease. The model may also be useful for investigating the mechanisms underlying the bidirectional relationship between epilepsy and depression.     

An enhanced olfactory marker protein immunoreactivity in individual olfactory receptor neurons following olfactory bulbectomy may be related to increased neurogenesis

Olfactory marker protein (OMP) is a 19-kD acidic protein found throughout the cytoplasm of mature olfactory receptor neurons (ORNs). Its function remains unknown. Following olfactory bulbectomy, the proportion of ORNs mature enough to express OMP declines greatly. However, in the few remaining mature ORNs, it has been observed that the intensity of OMP immunoreactivity (IR) appears to increase over that of ORNs on the unoperated side. We have now investigated this phenomenon quantitatively in rats subjected to unilateral olfactory bulbectomy. Results show that at all postbulbectomy survival periods examined quantitatively (3 days to 6 months), a significant decrease (19–37%) occurs in the transmission of incident light through OMP(+)-ORNs in bulbectomized versus unoperated olfactory epithelium (OE). Further, we also observed a consistent side-to-side difference in OMP IR in control unoperated animals. Possible explanations for these observations and their relation to the still unknown function of OMP are discussed. To test the possibility that OMP might serve a mitogenic role in the OE, recombinant OMP was added to organotypic explant cultures of fetal olfactory mucosa. Addition of OMP resulted in a dose-dependent increase in the density of bromodeoxyuridine-positive cells in the cultures, with a 50% increase occurring at the plateau OMP concentration of 25 nM. © 1998 John Wiley & Sons, Inc. J Neurobiol 34: 377–390, 1998     

The neurochemical sequelae of olfactory bulbectomy

Olfactory bulbectomy in rodents leads to a variety of neurochemical sequelae involving catecholamine, indolamine, acetylcholine, amino acid and several putative neurotransmitter systems. This review summarizes the research over the last 10 years on the neurochemical consequences of olfactory bulbectomy involving these systems. It also proposes additional experiments designed to expand our knowledge of olfactory bulb-brain neurochemical relationships.     

Decline and recovery of olfactory receptor expression following unilateral bulbectomy

The effects of unilateral olfactory bulb ablation upon the odorant receptor expression were studied during the degeneration/regeneration process in the olfactory epithelium of adult rats. Using the in situ hybridization approach, we compared the time course of decay and recovery of expression for three different receptor subtypes (OR14, OR5, OR124). The number of neurons expressing receptor subtypes dramatically decreased in the olfactory epithelium on the lesioned side and reached a minimum at day 5 postsurgery. A progressive recovery was then observed from day 5 to day 15 postlesion, when a plateau was reached. Noticeable differences in the recovery level of receptor expression were observed according to the zonal patterning: the recovery level for neurons located in the lateral zone reached 70% of the control side value while the recovery levels in the dorsal and medial zones represented 35% and 53% of this value, respectively. Axotomy experiments suggest that zone-specific differences in receptor reexpression reported after bulbectomy might be related to the trophic influence of the olfactory bulb.     

Plasma prolactin in relation to changes in oestrous cyclicity following olfactory bulbectomy in post-pubertal pigs

Prolactin was determined by radioimmunoassay in the peripheral plasma of five post-pubertal Large White gilts before and after olfactory bulbectomy. In the oestrous cycle before bulbectomy and in cycles after bulbectomy, the highest concentrations of prolactin were found during the period from the late luteal phase to oestrus. Throughout the prolonged summer anoestrus which occurred after bulbectomy, the amounts of prolactin were similar to base-line quantities found during the oestrous cycle between Days 3 and 12. These results differ from those found for the seasonally breeding European wild sow where high prolactin levels are associated with a summer anoestrus.     

Olfactory bulbectomy modifies photic entrainment and circadian rhythms of body temperature and locomotor activity in a nocturnal primate

Studies on rodents have emphasized that removal of the olfactory bulbs modulates circadian rhythmicity. Using telemetric recordings of both body temperature (Tb) and locomotor activity (LA) in a male nocturnal primate, the gray mouse lemur, the authors investigated the effects of olfactory bulbectomy on (1) the circadian periods of Tb and LA in constant dim light condition, and (2) photic re-entrainment rates of circadian rhythms following 6-h phase shifts of entrained light-dark cycle (LD 12:12). Under free-running condition, bulbectomized males had significantly shorter circadian periods of Tb and LA rhythms than those of control males. However, the profiles of Tb rhythms, characterized by a phase of hypothermia at the beginning of the subjective day, and Tb parameters were not modified by olfactory bulbectomy. Under a light-dark cycle, olfactory bulbectomy significantly modified the expression of daily hypothermia, especially by an increase in the latency to reach minimal daily Tb, suggesting a delayed response to induction of daily hypothermia by light onset. Reentrainment rates following both a 6-h phase advance and a 6-h phase delay of entrained LD were also delayed in bulbectomized males. Olfactory bulbectomy led to significant fragmentation of locomotor activity and increased locomotor activity levels during the resting period. The shortening of circadian periods in bulbectomized males could partly explain the delayed responses to photic stimuli since in control males, the longer the circadian period, the better the response to light entrainment. This experiment shows for the 1st time that olfactory bulbs can markedly modify the circadian system in a primate.     

Effect of Lesions of the Olfactory Bulb on the Levels of Amino Acids and Related Enzymes in the Olfactory Cortex of the Guinea Pig

Abstract: Olfactory bulb removal and consequential degeneration of the lateral olfactory tract led to a decreasein the levels of glutaminase and malate dehydrogenase inthe ipsilateral olfactory cortex. These changes in enzyme activity may account for the well established decrease inthe levels of aspartate and glutamate in the olfactory cortex following ipsilateral bulbectomy. The level of glutamine synthetase, a glial marker enzyme, was slightly-increased while the activities of glutamate decarboxylase, glutamate dehydrogenase, and glutamate oxaloacetic transaminase were unchanged.     

Bilateral detection thresholds in dextrals and sinistrals reflect the more sensitive side of the nose, which is not lateralized [published erratum appears in Chem Senses 1998 Dec;23(6):761]

Several fundamental questions remain enigmatic concerning human olfactory sensitivity, including (i) whether detection threshold differences exist between the two sides of the nose (and, if so, whether such differences are influenced by handedness) and (ii) whether bilateral (i.e. binasal) stimulation leads to lower thresholds than unilateral stimulation (and, if so, whether the degree of facilitation is inversely related to general olfactory ability). In this study, and well-validated single staircase procedure was used to establish bilateral and unilateral detection thresholds for the cranial nerve I stimulant phenyl ethyl alcohol in 130 right- and 33 left-handed subjects. No differences in sensitivity between the left and right sides of the nose were observed in either group. Bilateral thresholds were lower, on average, than unilateral thresholds when the latter were categorized in terms of left and right nares. However, the bilateral thresholds did not differ significantly from those of the side of the nose with the lower threshold. Overall smell ability, as measured by the University of Pennsylvania Smell Identification Test, did not interact with any of the test measures. These data imply that (i) the left and right sides of the nose do not systematically differ in detection threshold sensitivity for either dextrals or sinistrals and (ii) if central integration of left:right olfactory threshold sensitivity occurs, its effects do not exceed the function of the better side of the nose.      

Convergence of olfactory inputs from both antennae in the brain of the honeybee.

Electrical activities of the olfactory neurones in the brain of the honeybee were investigated. Odorous stimuli were given to each antenna separately or to both simultaneously. The inputs from the antennae affected both the impulse frequency and the latency of the olfactory interneurones in the protocerebrum. The predominant response was to the stimulation of the ipsilateral antenna. Input from the contralateral antenna produced mainly excitatory effects, although a few inputs gave inhibitory effects. No particular relationships between the loci of the units in the brain and the types of responses produced were found. Most of the units were located in the protocerebral lobe and in the central commissure. The units in the deutocerebrum responded only to the stimulation of the ipsilateral antenna, and the magnitude of response and the latency were not different with respect to unilateral or bilateral stimulation of the antennae. Differences in latency between unilateral and bilateral stimulation were observed in some of the units in the protocerebrum. Neural models which explain these phenomena are postulated.