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Biomedical subjects

S B Hoath

Publications and source records attributed to S B Hoath.

At least 19 recordsLinked to original sources
PubMed2004

A novel role for vernix caseosa as a skin cleanser.

OBJECTIVES: Skin cleansing is a complex process involving endogenous and exogenous mechanisms. This study examines the role of vernix caseosa in the process of skin cleansing in the perinatal period. METHODS: Vernix was evaluated as an exogenously applied skin cleanser using digitized image analysis which quantified residual carbon particles following a standardized cleansing assay. In addition, the detachment of vernix from human cadaveric skin and Gore-Tex supports was investigated following timed exposures to a variety of commonly used commercial surfactants. Detachment was quantified spectrophotometrically as increased turbidity at 650 nm. RESULTS: Image analysis showed that exogenous application of vernix exhibited a cleansing capability comparable or superior to standard skin cleansers. Dose-dependent increases in solution turbidity (vernix detachment) were seen following exposure of vernix-covered Gore-Tex vehicles to sodium laureth sulfate, sodium lauryl sulfate, and cocamidopropyl betaine solutions. Similar results were seen with cadaveric skin. CONCLUSIONS: These results demonstrate a role for vernix caseosa as a skin cleanser. Previous views of vernix as a soil or skin contaminant at birth need to be reevaluated.

Cadaver↗
PubMed2001

Effect of semipermeable membranes on skin barrier repair following tape stripping.

Reports in the literature suggest that the permeability of a wound dressing to water transport is an important variable in the healing of superficial wounds. Factors that influence skin hydration during barrier repair, therefore, are important in the optimization of wound treatments. In this study, the effects of semipermeable films on human skin following a standardized wound (tape stripping) were evaluated using measurements of transepidermal water loss (TEWL), skin hydration, rate of moisture accumulation, and erythema. Wounds treated with semipermeable films underwent more rapid barrier recovery than either unoccluded wounds or wounds under complete occlusion. Barrier films that produced intermediate levels of skin hydration during recovery produced the highest barrier repair rates. The results support the hypothesis; that semipermeable wound dressings augment barrier repair and skin quality by providing an optimized water vapor gradient during the wound healing process. The choice of wound dressing is discussed within the larger context of the design of vapor-permeable fabrics (smart materials) and the new fields of corneotherapy and comfort science.

Adult↗
PubMed2001

Surface free energy characterization of vernix caseosa. Potential role in waterproofing the newborn infant.

BACKGROUND/AIMS: Vernix caseosa is a proteolipid biofilm synthesized by the human fetus, which progressively covers the fetal skin surface during the last trimester of pregnancy. The exact physiological functions of vernix are unclear. Hypothetically, it serves a role in "waterproofing" the fetus during the critical period of epidermal barrier development before birth. Vernix may also play a role in adaptation of the fetal skin surface to the dry, cool extrauterine environment after birth. Given the strategic position of vernix on the fetal skin surface and the rapidly changing environment encountered by the skin at birth, we proposed that investigation of vernix surface characteristics would facilitate understanding its putative physiological roles. METHODS: In this paper, we focused on the determination of the surface free energy (SFE) of vernix caseosa. Different approaches were used to calculate the SFE of vernix from contact angle (theta) measurements between vernix and various liquids (benzyl alcohol, diiodomethane, glycerol, and water). The critical surface tension (CST) of vernix was calculated using Zisman plots. The dispersive and the polar components of vernix SFE were calculated using the Owens-Wendt geometric mean method. Vernix was contrasted with petrolatum, a commonly used skin protectant. RESULTS: CST of fresh vernix was 40.5 dyne/cm while that of petrolatum was 35.8 dyne/cm. Fresh vernix polar SFE was 1.5 dyne/cm while petrolatum had almost no polar SFE component (0.03 dyne/cm). For all liquids (except the nonpolar diiodomethane) there was a significant decrease in contact angle with time. CONCLUSIONS: The CST and the total SFE values suggest that vernix has very low surface energy and is highly unwettable. These findings are significant insofar as the main component in vernix is water, which is highly energetic. Although vernix has a very high water content, the major part of its SFE is hydrophobic (dispersive). The limited interaction between vernix and hydrophilic liquids supports the hypothesis that vernix acts as a natural protectant cream to "waterproof" the fetus in utero while submerged in the amniotic fluid.

Female↗
PubMed2000

Characterization of vernix caseosa: water content, morphology, and elemental analysis.

Recent studies have prompted interest in the use of epidermal barrier creams as protective biofilms for very low birthweight preterm infants. The key to understanding the role of epidermal barrier films is an elucidation of their interaction with water and a basic knowledge of their composition. In this study, we investigated the morphologic properties and elemental composition of the naturally occurring biofilm, vernix caseosa. This biofilm is typically lacking in preterm infants and its production coincides in utero with terminal differentiation of the epidermis and formation of the stratum corneum. Significantly, vernix (80.5+/-1.0% H2O) had a much higher water content than other barrier creams (Eucerin: 17.1+/-0.6%, Aquaphor: 0.33+/-0.03%, Ilex: 0.19+/-0.02%, petrolatum: 0.03+/-0.01%; all p<0.05). Phase contrast microscopy of vernix showed multiple cellular elements with nucleic "ghosts" embedded in a putative lipid matrix. Transmission electron microscopy revealed flattened structures approximately 1-2 microm in thickness with distinct cellular envelopes indicative of differentiated corneocytes. Compared with mature corneocytes in adult stratum corneum, vernix corneocytes appeared swollen, the density of the keratin filaments was less, and there was a relative lack of tonofilament orientation. Cryofractured specimens were examined by cryoscanning electron microscopy with subsequent elemental localization by X-ray beam analysis. The findings indicate the high water content of vernix is largely compartmentalized within fetal corneocytes. These results are consistent with the novel view of vernix as a "fluid phase" stratum corneum consisting of a hydrophobic lipid matrix with embedded fetal corneocytes possessing unique biomechanical and water-binding properties.

Elements↗
PubMed2000

Adhesives and emollients in the preterm infant.

This chapter focuses on recent advances in preterm infant skin care related to skin adhesion and skin emolliency. Different types of adhesives and hydrating agents are reviewed. Clinical applications are best guided by understanding the biology of epidermal barrier development. The role of xeric stress in accelerating formation of the stratum corneum is discussed along with the effects of occlusive agents and emollients on wound healing and epidermal barrier repair. The principles of skin moisturization are introduced. The concept is advanced that programmatic changes in skin adhesion and water handling occur during the normal ontogeny of superficial biofilms (sebum, sweat, acid mantle).

Adhesives↗
PubMed2000

Continuous measurement of core body temperature in preterm infants.

We tested a transcutaneous core temperature sensor using a method that relies on the principle of zero heat flow. We tested the hypothesis that transcutaneous and rectal temperatures would track within 0.3 degrees C of each other for >90% of the time. A thermistor was placed between the infant's abdomen or back and the incubator's or radiant warmer's mattress, or within the axilla, attached to the skin with a foam adhesive disk insulator. Thirty preterm infants were either placed on their abdomens or backs in a convective incubator or under a radiant warmer, and continuous transcutaneous and rectal temperatures were measured for 1 hour. There were no significant differences between abdominal and core temperatures or between axillary and core temperatures measured in double-walled convective incubators or in radiant warmers. The rectal-abdominal temperature difference was significantly less than the rectal-axillary difference (p < 0.02) in convective incubators, but not when the infant was placed prone under radiant warmers (p = 0.27). Transcutaneous thermometry is reliable for monitoring core body temperature as indicated by rectal temperature in stable preterm infants in a convective incubator.

Body Temperature↗
PubMed2000

Maturation of thermal capabilities in preterm infants.

Very low-birth-weight infants (VLBW) may initially require environmental temperatures higher than skin temperature. We examined the correlation between gestational age, birth weight, and the time to reach skin-air temperature equilibration (TTE) in VLBW infants. We also examined the effect of antenatal steroids on TTE in infants with birth weight < 1000 g. There is a significant exponential correlation between TTE and birth weight or gestational age (p < 0.05). There was no significant change in TTE in infants who were treated antenatally with steroids, as compared with infants who were not treated. Multiple regression analysis with TTE as the dependent variable and birth weight or gestational age, race, betamethasone treatment, and gender as the independent variables showed a significant correlation between gestational age and TTE (p = 0.04). We conclude that thermal capabilities are exponentially correlated with gestational age or birth weight.

Birth Weight↗
PubMed2000

Interaction between pulmonary surfactant and vernix: a potential mechanism for induction of amniotic fluid turbidity.

The development of amniotic fluid turbidity during the third trimester is a known marker of fetal lung maturity. We hypothesized that this turbidity results from detachment of vernix caseosa from the fetal skin secondary to interaction with pulmonary-derived phospholipids in the amniotic fluid. To test this hypothesis, we exposed vernix to bovine-derived pulmonary surfactant over a physiologically relevant concentration range. Ten milligrams of vernix was evenly applied to the interior walls of 1.5-mL polypropylene microfuge tubes. Surfactant phospholipids were added to the tubes followed by slow rotation at 37 degrees C overnight. The liquid was decanted and spectrophotometrically analyzed at 650 nm to detect solution turbidity due to vernix detachment and/or emulsification. Increasing concentrations of surfactant phospholipids produced a dose-dependent increase in solution turbidity. A phospholipid mixture closely approximating natural pulmonary surfactant but devoid of surfactant-associated proteins yielded no increase. In other studies, the flow properties of vernix were studied in a Haake flow rheometer at 23 degrees C and 37 degrees C. There was a marked temperature-dependent effect with lower stress required to elicit flow at 37 degrees C compared with 23 degrees C. This temperature dependence was also demonstrated in the turbidity assay with a 124% increase in turbidity at body temperature compared with room temperature. We conclude that under in vitro conditions, pulmonary surfactant interacts with vernix resulting in detachment from a solid phase support. We speculate that in utero, this phenomenon contributes to the increase in amniotic fluid turbidity that is observed near term.

Amniotic Fluid↗
PubMed1999

Effects of antenatal corticosteroids on blood pressure in very low birth weight infants during the first 24 hours of life.

OBJECTIVE: We tested the hypothesis that prenatal glucocorticoids significantly increase mean arterial blood pressure in very low birth weight preterm infants during the first 24 hours after birth. STUDY DESIGN: Prospectively collected data from 178 inborn infants with birth weights between 500 and 1499 gm were examined. A total of 80 infants were born to mothers treated with corticosteroids (birth weight: 1057 +/- 271 gm, gestational age: 28.0 +/- 2.6 weeks), and 98 infants were untreated controls (birth weight: 1030 +/- 280 gm, gestational age: 28.0 +/- 2.8 weeks). The study setting was a university-based tertiary care center for newborn intensive care. RESULTS: Mean blood pressures on admission and at 3, 6, 12, 18, and 24 hours were significantly higher in steroid-treated infants. Steroid-treated infants received significantly less volume expansion (3.8 +/- 8.5 ml/kg versus 14.4 +/- 20.7 ml/kg; p < 0.001) than controls. Vasopressor support was also reduced in the steroid group (2.5% versus 11.5%; p < 0.05). CONCLUSION: Antenatal steroids are associated with both a higher mean systemic blood pressure and a decreased use of vasopressors and plasma expanders in very low birth weight infants during the first 24 hours after birth. This effect is not limited to infants of < 1000 gm; it is also significant in infants with a birth weight between 1000 and 1499 gm, and is already detectable in the first hours of life. We speculate that this finding may contribute to the mechanism of steroid protection against conditions such as intraventricular hemorrhage.

Adrenal Cortex Hormones↗
PubMed1999

A survey of skin care practices for premature low birth weight infants.

PURPOSE: To provide baseline information about current skin care practices in premature low birth weight infants (< 1,000 gm birth weight) in typical NICUs within the U.S. DESIGN: Descriptive survey. SAMPLE: 104 hospitals with at least 2,500 deliveries per year and at least 20 Level III NICU beds. MAIN OUTCOME VARIABLES: Environmental conditions, bathing practices and products, adhesive products used to secure IVs and endotracheal tubes, skin protectants used with diaper rash, treatment systems for fragile preterm skin, and treatment systems for denuded skin. RESULTS: Most units surveyed based their premature low birth weight skin care protocols on a combination of gestational age and birth weight criteria. One-quarter of the units had no skin care protocols at all. Among the units, there was considerable practice variation with respect to common nursing procedures such as bathing, adhesive application, and wound care.

Clinical Protocols↗
PubMed1998

Neonatal skin: the ideal nursing interface.

Human skin holds much fascination for the average person. It is the first thing that is noticed about a person. From a neonatal perspective it is a dynamic interface with the surrounding environment and provides the surface for our nursing interventions. This article will discuss this dynamic interface and why it provides a good scientific basis for neonatal nursing care.

Humans↗
PubMed1997

Effect of tactile stimulation on serum lactate in the newborn rat.

Maturation of the CNS in neonatal animals is dependent upon both sensory input and the constant availability of metabolic fuel. Previous reports indicate that the preferred metabolic substrate for the developing rat brain is lactate. In this study, we used the neonatal Sprague-Dawley rat to investigate a possible interactive role between touch and the regulation of serum lactate. Two hundred and fifty rats (postnatal d 0-7) were exposed to a standard tactile stimulation (TS) regimen to mimic nonspecific maternal stimulation. This regimen consisted of stroking the dorsum with a soft camel hair brush for 30 s every minute for 10 min. Serum lactate and glucose levels were measured after TS. In newborn (d 0) rats, lactate levels were increased by 207% in stroked pups versus controls. This elevation of serum lactate persisted for 30 min after cessation of TS. On d 7, TS increased lactate only 11%. Glucose levels were unaffected at all ages. In neonatal pups, pretreatment with pentobarbital blocked the effect of TS, whereas epidermal growth factor evoked a synergistic response. Capsaicin pretreatment had no effect. Mixed arteriovenous blood gases revealed a mild increase in pH and a decrease in Pco2 after TS. We conclude that TS in newborn rats is a regulator of circulating lactate. This response is maximal in the immediate postnatal period and wanes over the 1st wk of life. We speculate that the transduction of sensory signals by the skin is a mechanism regulating the availability of cerebral energy substrates in the newborn mammal.

Aging↗
PubMed1996

Surface electrical capacitance as a noninvasive index of epidermal barrier in cultured skin substitutes in athymic mice.

Restoration of an epidermal barrier is a definitive requirement for wound closure. To determine formation of an epidermal barrier as a function of hydration of the stratum corneum, we measured surface electrical capacitance (SEC) of the epidermis in cultured skin substitutes (CSS) in vitro and after grafting to athymic mice. CSS were prepared from human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates. On culture days 3, 7, 14, 17, and 21, SEC was measured in situ. CSS (n = 18; mean +/- SEM) showed a time-dependent decrease of SEC (picoFarads, "pF") from 4721 +/- 28 pF on day 3 to 394 +/- 117 pF on day 14, and subsequent increase to 1677 +/- 325 pF on day 21. After 14-d incubation, parallel CSS samples (n = 5) or murine autografts (n = 5) were grafted orthotopically to athymic mice. After grafting, CSS showed decreases in SEC from 910 +/- 315 pF at 2 wk to 40 +/- 10 pF at 4 wk with no significant decreases thereafter. Control values for murine autograft were 870 +/- 245 pF at 2 wk, and 87 +/- 30 pF at 4 wk. SEC values for native murine skin (n = 10) were 91 +/- 18 pF, and for native human skin (n = 10) were 32 +/- 5 pF. The data demonstrate that SEC decreases with time in culture and that healed or intact skin has approximately 10- to 100-fold lower SEC than CSS in vitro. This noninvasive technique provides a quantitative index of epidermal barrier in CSS in vitro and demonstrates the development of functional epidermal barrier during healing of wounds treated with cultured skin substitutes.

Animals↗
PubMed1995

Effect of different phototherapy lights on incubator characteristics and dynamics under three modes of servocontrol.

Phototherapy is one of the most common therapeutic interventions in modern neonatal medicine. Analysis of physiological responses to phototherapy requires understanding the physical effects of incident light under different modes of environmental control. In this study, we tested the effect of initiation of phototherapy under laboratory conditions in a convective incubator maintained in three clinically used servocontrol modes. Under conditions of air servocontrol, the initiation of phototherapy resulted in an abrupt sustained increase in the surface temperature of an infant simulator (a blackened aluminum disc). In contrast, when the surface (skin) temperature was the controlled variable, there was a profound drop in the incubator air temperature. An algorithm that simultaneously controlled both the skin and the air temperatures showed intermediate effects. Under conditions of skin servocontrol, fluctuations in air and environmental temperatures were observed for a period of 3 hours before steady state was reached. These findings are most clearly demonstrated using phase plane plotting techniques. We conclude that wide, abrupt, and sustained changes in the thermal environment of an incubator occur after phototherapy is initiated. Such changes must be anticipated in physiological studies using phototherapy.

Algorithms↗
PubMed1995

Use of continuous electrical capacitance and transepidermal water loss measurements for assessing barrier function in neonatal rat skin.

A vital function of the skin is to oppose the loss of water to the environment. In this study, two complementary methods, transepidermal water loss (TEWL) and continuous electrical capacitance under occlusion, were used to assess epidermal barrier function in a developmental animal model, the neonatal Sprague-Dawley rat. TEWL monitors barrier function directly while the increase in capacitance under occlusion is related to both the skin's barrier function and to its water holding capacity. Serial tape stripping of the stratum corneum on 1-day-old rat pups led to a significant increase in both TEWL and continuous capacitance measurements. Anatomic site heterogeneity and the effects of surface temperature were also studied. The ventral skin surface exhibited an increase in the continuous capacitance measurements, an effect possibly due to the thinner stratum corneum on the ventral side. Both TEWL and continuous capacitance values were directly correlated with ambient temperatures within the physiological range.

Animals↗