1. Stratum Corneum Acidification in Neonatal Skin: Secretory Phospholipase A2 and the Sodium/Hydrogen Antiporter-1 Acidify Neonatal Rat Stratum Corneum 
Joachim W. Fluhr, Martin J. Behne, Barbara E. Brown, David G. Moskowitz, Clare Selden, Man Mao-Qiang, Theodora M. Mauro, Peter M. Elias, Kenneth R. Feingold 
Journal of Investigative Dermatology 
Volume 122, Issue 2, Pages (February 2004)
DOI: /j X x
Copyright © 2004 The Society for Investigative Dermatology, Inc Terms and Conditions

2. Figure 1
Formation of an acidic surface pH develops during the first postnatal week. (A) Surface pH decreases from an initial value of 6.63±0.02 on days 0 to 1 and 7.14±0.02 of the amniotic fluid (white bar) and on intrauterine fetuses 6.80±0.02 on day 19 of gestation to values of 5.35±0.02 on days 7 to 8 after birth. The pH value of adult, shaved rats was 5.90±0.08. (B) Neonates' pH levels are significantly higher not only at the surface of the SC, but also in deeper SC layers than in older neonates (anova, p<0.0001). Deeper layers at both ages are more acidic than superficial layers, suggesting that acidification starts in the lower SC. The pH gradient of adult rats is not different from those of day 4 newborns. No. of D-Squames, the number of attached and removed cellophane tapes. Each D-Squame removes approximately one cell layer.
Journal of Investigative Dermatology  , DOI: ( /j X x)
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3. Figure 2
Zymographic activity of β-glucocerebrosidase in neonatal rat SC. Zymographic analysis of β-glucocerebrosidase activity and localization showed low levels of activity in the intercellular spaces at birth (days 0–1, A), increasing markedly by days 5 to 6 (B). Enzyme activity can be induced on day 1 by acidifying the tissue (C). (C) Positive control to show that the enzyme is present at birth but inactive owing to the high pH. Lowering the pH results in an increase of β-glucocerebrosidase activity. The dotted line represents the dermal/epidermal junction. Negative controls both without substrate (vehicle alone) as well with an inhibitor (CBE) showed the absence of any activity (black figures not shown). Bar, 20 μm.
Journal of Investigative Dermatology  , DOI: ( /j X x)
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4. Figure 3
Despite an elevated SC pH, basal barrier function of neonatal skin is competent. The TEWL, assessed by a closed-loop system (MEECO), showed similar values under basal conditions throughout the entire postnatal period (n=10, differences not significant between different newborn ages). Nevertheless, in adult rats, 24 h after shaving, lower TEWL are observed (n=3).
Journal of Investigative Dermatology  , DOI: ( /j X x)
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5. Figure 4
Colonization with normal flora does not correlate with postnatal SC acidification. (A) Colony-forming units per square centimeter of Micrococcaceae collected from the surface of the newborn rats at different time points after birth with a modified detergent scrub method. The bacteria were grown on sheep blood agar and counted after 48 h of aerobic incubation at 37°C. No correlation could be detected between the formation of an acidic surface pH and surface colonization with Micrococcaceae. (B) Colony-forming units per square centimeter of Propionibacteriae collected from newborn rats as above. Bacteria were grown on reinforced clostridium medium agar supplemented with 60 mg per L furoxine and 1 mL per L Tween 80 and cultivated for 72 h under microareobic conditions at 37°C. No correlation could be detected between the formation of an acidic surface pH and surface colonization with Propionibacteriae.
Journal of Investigative Dermatology  , DOI: ( /j X x)
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6. Figure 5
Changes in histidase activity do not correlate with postnatal acidification. (A) No significant changes in SC histidase activity occurred between day 0 to 1 and day 4 to 5 neonatal rat SC (values expressed as means±SEM, ns; days 0–1, n=6; days 4–5, n=5). (B) No significant changes could be detected in the surface pH of HIS–/– (n=4) 5.62±0.06, HIS+/– (n=7) 5.63±0.04, and wild-type mice (n=2) 5.58±0.08.
Journal of Investigative Dermatology  , DOI: ( /j X x)
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7. Figure 6
NHE1 antiporter contributes to postnatal acidification. Blockade of the NHE1 antiporter by topical HOE694 to for 3 d leads to a significant delay in neonatal acidification in comparison to vehicle-treated animals (n=8 and 11, inhibitor and vehicle, respectively).
Journal of Investigative Dermatology  , DOI: ( /j X x)
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8. Figure 7
sPLA2 activity increases after birth and contributes to postnatal acidification. (A) sPLA2 activity, assessed as total sPLA2 activity by a fluorometric assay on pooled tape strips, increased by 66.4% between days 0 to 1 and days 4 to 5 after birth (p=0.0018). (B) Moreover, a single daily applications of the global sPLA2 inhibitor, BPB, delayed, but did not completely prevent, emergence of an acidic SC. (C) Coapplications of palmitic acid, the product of phospholipid hydrolysis by sPLA2, along with BPB, normalized the rate of postnatal acidification.
Journal of Investigative Dermatology  , DOI: ( /j X x)
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