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Sexual dimorphism in the human olfactory bulb: females have more neurons and glial cells than males.

Oliveira-Pinto AV, Santos RM, Coutinho RA, Oliveira LM, Santos GB, Alho AT, Leite RE, Farfel JM, Suemoto CK, Grinberg LT, Pasqualucci CA, Jacob-Filho W, Lent R - PLoS ONE (2014)

Bottom Line: Female bulbs weighed 0.132 g in average, while male bulbs weighed 0.137 g, a non-significant difference; however, the total number of cells was 16.2 million in females, and 9.2 million in males, a significant difference of 43.2%.The number of non-neuronal cells also proved higher in women than in men: 9.3 million and 5.7 million, respectively, a significant difference of 38.7%.However, the reported advantage of women as compared to men may stimulate future work on sex dimorphism of synaptic microcircuitry in the olfactory bulb.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

ABSTRACT
Sex differences in the human olfactory function reportedly exist for olfactory sensitivity, odorant identification and memory, and tasks in which odors are rated based on psychological features such as familiarity, intensity, pleasantness, and others. Which might be the neural bases for these behavioral differences? The number of cells in olfactory regions, and especially the number of neurons, may represent a more accurate indicator of the neural machinery than volume or weight, but besides gross volume measures of the human olfactory bulb, no systematic study of sex differences in the absolute number of cells has yet been undertaken. In this work, we investigate a possible sexual dimorphism in the olfactory bulb, by quantifying postmortem material from 7 men and 11 women (ages 55-94 years) with the isotropic fractionator, an unbiased and accurate method to estimate absolute cell numbers in brain regions. Female bulbs weighed 0.132 g in average, while male bulbs weighed 0.137 g, a non-significant difference; however, the total number of cells was 16.2 million in females, and 9.2 million in males, a significant difference of 43.2%. The number of neurons in females reached 6.9 million, being no more than 3.5 million in males, a difference of 49.3%. The number of non-neuronal cells also proved higher in women than in men: 9.3 million and 5.7 million, respectively, a significant difference of 38.7%. The same differences remained when corrected for mass. Results demonstrate a sex-related difference in the absolute number of total, neuronal and non-neuronal cells, favoring women by 40-50%. It is conceivable that these differences in quantitative cellularity may have functional impact, albeit difficult to infer how exactly this would be, without knowing the specific circuits cells make. However, the reported advantage of women as compared to men may stimulate future work on sex dimorphism of synaptic microcircuitry in the olfactory bulb.

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Related in: MedlinePlus

Stages and instruments of the methodological procedures.In A, removal of meninges and blood vessels. B, dissection of the right olfactory bulb (OB) and tract (OT). C, fractionation in a tissue homogenizer. D, DAPI-stained nuclei in the Neubauer chamber. E, NeuN-positive nuclei. The yellow arrows show nuclei that colocalize DAPI and NeuN, therefore considered to be neuronal, and counted as such.
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pone-0111733-g001: Stages and instruments of the methodological procedures.In A, removal of meninges and blood vessels. B, dissection of the right olfactory bulb (OB) and tract (OT). C, fractionation in a tissue homogenizer. D, DAPI-stained nuclei in the Neubauer chamber. E, NeuN-positive nuclei. The yellow arrows show nuclei that colocalize DAPI and NeuN, therefore considered to be neuronal, and counted as such.

Mentions: Eighteen olfactory bulbs (Table 1), seven from male (58–92 years old) and eleven from female (55–94 years old) Brazilian subjects, were obtained 8 to 18 hours after death from the Brain Bank of the Brazilian Aging Brain Study Group [38] of the University of São Paulo Medical School. All subjects resided in the same environment (the city of São Paulo, Brazil) under moderate to high levels of pollution, and had daily activities not particularly dependent on olfactory functions (no professional cooks, coffee-tasters, etc). The corpses were kept in a cold room at 4°C soon after death until the time of autopsy. After that period, the brains were removed from the cranium, meninges were dissected out (Figure 1A), and the olfactory bulbs and tracts were separated (Figure 1B), placed in cassettes and fixed by immersion in 2% paraformaldehyde (PFA) for a period of 36 to 40 hours. They were maintained in PBS at 4°C until the day of chemomechanical dissociation.


Sexual dimorphism in the human olfactory bulb: females have more neurons and glial cells than males.

Oliveira-Pinto AV, Santos RM, Coutinho RA, Oliveira LM, Santos GB, Alho AT, Leite RE, Farfel JM, Suemoto CK, Grinberg LT, Pasqualucci CA, Jacob-Filho W, Lent R - PLoS ONE (2014)

Stages and instruments of the methodological procedures.In A, removal of meninges and blood vessels. B, dissection of the right olfactory bulb (OB) and tract (OT). C, fractionation in a tissue homogenizer. D, DAPI-stained nuclei in the Neubauer chamber. E, NeuN-positive nuclei. The yellow arrows show nuclei that colocalize DAPI and NeuN, therefore considered to be neuronal, and counted as such.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4221136&req=5

pone-0111733-g001: Stages and instruments of the methodological procedures.In A, removal of meninges and blood vessels. B, dissection of the right olfactory bulb (OB) and tract (OT). C, fractionation in a tissue homogenizer. D, DAPI-stained nuclei in the Neubauer chamber. E, NeuN-positive nuclei. The yellow arrows show nuclei that colocalize DAPI and NeuN, therefore considered to be neuronal, and counted as such.
Mentions: Eighteen olfactory bulbs (Table 1), seven from male (58–92 years old) and eleven from female (55–94 years old) Brazilian subjects, were obtained 8 to 18 hours after death from the Brain Bank of the Brazilian Aging Brain Study Group [38] of the University of São Paulo Medical School. All subjects resided in the same environment (the city of São Paulo, Brazil) under moderate to high levels of pollution, and had daily activities not particularly dependent on olfactory functions (no professional cooks, coffee-tasters, etc). The corpses were kept in a cold room at 4°C soon after death until the time of autopsy. After that period, the brains were removed from the cranium, meninges were dissected out (Figure 1A), and the olfactory bulbs and tracts were separated (Figure 1B), placed in cassettes and fixed by immersion in 2% paraformaldehyde (PFA) for a period of 36 to 40 hours. They were maintained in PBS at 4°C until the day of chemomechanical dissociation.

Bottom Line: Female bulbs weighed 0.132 g in average, while male bulbs weighed 0.137 g, a non-significant difference; however, the total number of cells was 16.2 million in females, and 9.2 million in males, a significant difference of 43.2%.The number of non-neuronal cells also proved higher in women than in men: 9.3 million and 5.7 million, respectively, a significant difference of 38.7%.However, the reported advantage of women as compared to men may stimulate future work on sex dimorphism of synaptic microcircuitry in the olfactory bulb.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

ABSTRACT
Sex differences in the human olfactory function reportedly exist for olfactory sensitivity, odorant identification and memory, and tasks in which odors are rated based on psychological features such as familiarity, intensity, pleasantness, and others. Which might be the neural bases for these behavioral differences? The number of cells in olfactory regions, and especially the number of neurons, may represent a more accurate indicator of the neural machinery than volume or weight, but besides gross volume measures of the human olfactory bulb, no systematic study of sex differences in the absolute number of cells has yet been undertaken. In this work, we investigate a possible sexual dimorphism in the olfactory bulb, by quantifying postmortem material from 7 men and 11 women (ages 55-94 years) with the isotropic fractionator, an unbiased and accurate method to estimate absolute cell numbers in brain regions. Female bulbs weighed 0.132 g in average, while male bulbs weighed 0.137 g, a non-significant difference; however, the total number of cells was 16.2 million in females, and 9.2 million in males, a significant difference of 43.2%. The number of neurons in females reached 6.9 million, being no more than 3.5 million in males, a difference of 49.3%. The number of non-neuronal cells also proved higher in women than in men: 9.3 million and 5.7 million, respectively, a significant difference of 38.7%. The same differences remained when corrected for mass. Results demonstrate a sex-related difference in the absolute number of total, neuronal and non-neuronal cells, favoring women by 40-50%. It is conceivable that these differences in quantitative cellularity may have functional impact, albeit difficult to infer how exactly this would be, without knowing the specific circuits cells make. However, the reported advantage of women as compared to men may stimulate future work on sex dimorphism of synaptic microcircuitry in the olfactory bulb.

Show MeSH
Related in: MedlinePlus