Biomedical subjects

S B Hoath

Publications and source records attributed to S B Hoath.

At least 55 records · Page 3Linked to original sources

PubMed1989

Structural proteins in perinatal rat epidermis: characterization of a high molecular weight prekeratin.

The major water-insoluble proteins of perinatal rat epidermis have been examined by gel electrophoretic techniques. Particular focus has been placed on that family of epidermal structural proteins called keratins which are characterized by mol wt between 40 and 70 kD. Analysis of these proteins by 2-dimensional PAGE revealed the largest member of this family (Mr = 63 kD) to consist of a series of isoelectric variants with isoelectric points ranging between 7.3 and 5.9. Antibodies raised in rabbits against this protein were specific by immunoblot analysis and exhibited no cross-reactivity with keratins isolated from human foreskin epidermis under the same extraction conditions. Ontogenetic examination by Western blot was performed on extracts of whole fetal rat skin from d 17 to d 19 of gestation. Expression of the protein was seen only after the 18th gestational d. Posttranslational modification of neonatal rat keratins by phosphorylation was examined under in vitro conditions at two different ambient temperatures (23 and 37 degrees C). Overall phosphorylation was markedly increased at the higher temperature. A similar qualitative pattern of keratin phosphorylation was seen after in vivo labeling at nest temperature (35 degrees C). In both the in vitro and in vivo experiments, the major radiolabeled moiety was the 63 kD epidermal protein. In summary, insoluble proteins between 40 and 70 kD have been examined in perinatal rat epidermis. The tissue localization, solubility, phosphorylation status, ontogenetic appearance, and mol wt of the 63 kD protein are consistent with the identification of an epidermal prekeratin. We hypothesize that this protein is an important molecular precursor of stratum corneum formation in the perinatal rat.

Animals↗

PubMed1988

Growth hormone enhances hepatic epidermal growth factor receptor concentration in mice.

The effect of growth hormone (GH) on binding of epidermal growth factor (EGF) to liver membrane preparations was investigated in hypophysectomized mice and partially GH-deficient, genetic mutant "little" (lit/lit) mice. The EGF binding of normal male mice and testosterone-treated females was higher than in normal females. Due to diminished receptor concentration, hepatic EGF binding was decreased in male and female lit/lit mice to a level that was unaffected by gender or androgen treatment. GH replacement therapy by intermittent injections and continuous infusion restored the EGF binding of hypophysectomized mice to normal male and female levels, respectively, suggesting a role for the more pulsatile GH secretion in normal males. In lit/lit mice, however, both continuous and intermittent GH resulted in EGF binding levels comparable to those in normal females. In normal males continuous GH suppressed EGF binding. In conclusion, endogenous GH secretion induces EGF receptors in mice and this effect may be modulated by sex differences in GH secretion.

Animals↗

PubMed1988

Epidermal growth factor-induced growth retardation in the newborn rat: quantitation and relation to changes in skin temperature and viscoelasticity.

Somatic growth retardation was studied in neonatal Sprague-Dawley rats following treatment with exogenous epidermal growth factor (EGF). Dose-response data are presented for the first 2 days of postnatal life relating log EGF dose (range 50 to 1000 ng per gram body weight) to incremental daily weight gain. Regression analysis indicated that the effect of EGF to retard somatic growth was not cumulative, and, in fact, the same dose of EGF had less effect on the second day of life than on the first. Concomitant with its ability to retard growth, EGF elicited a transient cutaneous reaction characterized by a marked alteration in skin viscoelasticity and temperature. Neonatal rats treated with exogenous EGF exhibited: (1) a dose-dependent reduction in skin redundancy measured by decrease in the height of the dorsal skinfold; (2) a diminution in integumental water content determined by wet weight/dry weight ratios and relative tissue specific gravities; and (3) a rapid fall in midscapular skin temperature within 60 minutes of systemic administration of EGF. Both the EGF-elicited cutaneous reaction and the ability of EGF to retard somatic growth disappeared by the end of the second week of life. Administration of human biosynthetic EGF resulted in responses identical to the purified mouse protein. In summary, the pharmacological effects of EGF to retard somatic growth in the newborn rodent are confined to the immediate neonatal period and are preceded by transient alteration in skin temperature and cutaneous biomechanical properties.

Animals↗

PubMed1987

Characterization of hepatic epidermal growth factor receptors in the developing rat.

Binding of 125I-labeled epidermal growth factor (EGF) was characterized in basolateral plasma membranes prepared from the livers of 21-day gestation fetuses, 14-day-old sucklings and adult Sprague-Dawley rats using a self-generating Percoll gradient method. The membrane preparations employed have been previously assayed in terms of plasma membrane protein yield, enrichment of various marker enzymes and sodium-dependent bile acid and amino acid transport. 125I-EGF binding was saturable and time and temperature dependent. Equilibrium analyses showed that the suckling period is characterized by a marked decrease in overall hepatic EGF binding capacity (460 +/- 50 fmol/mg protein) compared to either the fetal period (1290 +/- 160 fmol/mg) or to adults of either sex (males = 1540 +/- 230, females 1010 +/- 130 fmol/mg). Treatment of the suckling rat with parenteral EGF resulted in a 78% reduction in the observed binding capacity when assessed 2 h after growth factor administration. Comparison of binding affinities revealed no significant difference between the suckling and adult preparations (Kd = 0.40 +/- 0.03 vs. 0.39 +/- 0.02 nM, respectively); however, both preparations differed significantly from the fetal group which exhibited a decreased affinity of binding with a higher overall dissociation constant (Kd = 0.68 +/- 0.06 nM). Thus, it appears that major ontogenetic changes occur in the rat hepatic ligand/receptor system for epidermal growth factor. These changes are discussed in the context of transitional events in mammalian development such as birth and weaning.

Animals↗

PubMed1987

Effect of thyroid hormone and epidermal growth factor on tactile hair development and craniofacial morphogenesis in the postnatal rat.

The facial region of the developing rat is surrounded by seven highly innervated hair follicle groups, of which the lateral tactile hairs have an invariant position between the palpebral fissures and the developing external ears. In this study, we tested the ability of triiodothyronine (T3) or epidermal growth factor (EGF) to alter the direction of lateral tactile hair growth in neonatal rats. To quantitate this effect, we measured the angular displacement of the lateral hairs from the sagittal plane in photomicrographs of 36 six-day-old littermate Sprague-Dawley rats treated on postnatal days 0-5 with saline, T3 (100 ng/g body weight), or EGF 500 ng/g body weight. Midline angular displacements were as follows: control, 45.8 degrees +/- 1.7; T3, 40.9 degrees +/- 1.7; EGF, 59.8 degrees = 2.1; mean +/- SEM, P less than .05 versus controls for T3 and EGF. In addition, the timing of specific topological events of craniofacial development, ie, incisor eruption, ear canal opening, and eyelid unfusion, was compared for the various treatment groups. Thus, at the dosages tested, 1) both hormones accelerate incisor eruption (T3 greater than EGF), 2) EGF is a much more potent accelerator of palpebral morphogenesis than T3, 3) EGF retards while T3 accelerates external ear development, and 4) both hormones elicit a comparable degree of somatic growth retardation. These data provide quantitative evidence in the neonatal rat of differences as well as similarities between two powerful craniofacial morphogens.

Animals↗

PubMed1986

Treatment of the neonatal rat with epidermal growth factor: differences in time and organ response.

The ability of exogenous mouse epidermal growth factor (EGF) (500 ng/g body weight/day) to retard somatic growth and to alter the timing of integumental maturation was investigated in the newborn rat. The immediate postnatal period (days 0-3) was identified as the critical time for elicitation of EGF effects. Somatic growth retardation produced by EGF persisted through weaning (day 20) and was asymmetric with maximal organ growth retardation present in liver and kidney and with relative sparing of heart and brain. Treatment of newborn rats with EGF on postnatal days 0-3 advanced the mean time of eyelid opening by 146 versus 31 h for tooth eruption. In contrast, EGF delayed opening of the external ear canal by approximately 48 h. EGF-treated pups thus exhibited a rearrangement in the normal sequence of craniofacial development. In summary, these data provide new information on the critical time of EGF response in the rat, the existence of an asymmetric pattern of organ growth retardation following perinatal EGF exposure, and the ability of EGF to retard morphogenesis of the external ear.

Animals↗

PubMed1986

Influence of epidermal growth factor on fetal rat lung development in vitro.

Epidermal growth factor (EGF) has been shown to enhance cell multiplication or differentiation in a number of developing tissues. We have examined the effects of this growth factor on the biochemical development of explants of fetal rat lung, cultured in serum-free medium for 48 h. EGF enhanced the rate of choline incorporation into phosphatidylcholine and disaturated phosphatidylcholine in a dose dependent fashion. Half maximal stimulation occurred at a concentration of 1.0 nM, similar to the Kd for EGF binding to rat lung cell membranes. There was also significant stimulation of acetate incorporation into all phospholipids, particularly phosphatidylglycerol (539%), and increased distribution of radioactivity from acetate in this phospholipid fraction. Exposure to EGF stimulated PC synthesis in 18- and 19-day explants (term is 22 days) whereas maximal enhancement of DNA synthesis occurred after this time. This sequence differs from that observed during early embryonic development when EGF initially enhances cell multiplication. An additive interaction with regard to enhancement of PC synthesis was observed with EGF and thyroid hormone, but not EGF and dexamethasone. EGF had no effect on the activity of the enzymes of the choline incorporation pathway of phosphatidylcholine synthesis or on the activity of enzymes involved with acidic phospholipid synthesis. Fetal lung EGF content and EGF binding capacity were not increased by glucocorticoid treatment and similarly glucocorticoid binding capacity was not increased by EGF. These data indicate that EGF enhances fetal rat lung phospholipid synthesis in a dose-dependent manner and suggest that this is a direct effect on the lung tissue mediated by specific receptors.

Animals↗

PubMed1985

Epidermal growth factor measurements in mouse plasma: method, ontogeny, and sex difference.

A highly sensitive mouse plasma (serum) epidermal growth factor (EGF) radioimmunoassay was utilized to determine EGF levels in mouse plasma and submandibular gland (SMG) at different ages. Plasma and serum levels were not different. Inferior vena caval blood was used because even at the age of 12 days EGF levels were markedly higher in neck blood. At 2 wk serum EGF levels were 60% of adult female levels. After a temporary decrease, mean EGF concentrations reached adult values at 31 and 60 days in the female but not yet in the male. In adults male serum EGF levels were twofold higher than female levels. This difference is parallel to but much smaller than the sex difference in SMG-EGF. SMG-EGF showed a very different ontogeny. Moreover, no correlation was present in the adults between the SMG and serum EGF concentrations. Testosterone treatment of adult females doubled their serum EGF levels, but the stimulated values were still below the mean of the male levels. The present observed plasma (serum) EGF levels in the mouse are 20-40% of previously reported values, probably because of the absence of EGF contamination from hair (urine) and milk.

Age Factors↗

PubMed1985

Epidermal growth factor binding to neonatal mouse skin explants and membrane preparations--effect of triiodothyronine.

Daily treatment of newborn Swiss-Webster mice with triiodothyronine (T3, 500 ng/day) increased epidermal growth factor (EGF) content in whole skin (epidermis + dermis). Separation of the epidermis using 0.01 M dithiothreitol followed by processing for radioimmunoassay measurement reveals levels of EGF 2-to 3-fold higher in epidermis than in whole skin. In vitro flotation of circular skin sections from control and T3 treated neonatal mice in medium containing [I125]EGF showed increased uptake of label following 5 days of in vivo T3 treatment. Mouse skin membrane preparations exhibit saturable, specific binding of [I125]EGF. T3 treatment for 5 days in vivo significantly increased EGF binding capacity in skin membrane preparations but did not alter EGF receptor affinity (Kd 4.5 nM). Protein, RNA, and DNA concentrations were significantly increased in whole neonatal mouse skin following T3 administration. These results suggest one mechanism by which thyroid hormones increase skin EGF concentration is augmentation of skin EGF receptor binding.

Animals↗

PubMed1985

Epidermal growth factor in mouse ocular tissue: effects of thyroxine and exogenous epidermal growth factor.

Using a specific and sensitive epidermal growth factor (EGF) radioimmunoassay, we identified radioimmunoassayable EGF both in developing and adult mouse ocular tissues. In neonatal animals ocular EGF concentrations increase during the first 4-9 days and then decline between 9 and 15 days. Thyroxine (T4) administration (0.4 micrograms/g body weight/day from day 0) increased local EGF concentrations in eye and skin of 7-day-old neonatal mouse pups. However, this treatment did not affect submandibular gland EGF concentrations during the 1st wk of life. Both EGF and T4 are known to accelerate eye opening in the neonatal mouse. Exogenous EGF administration (2 micrograms/g body weight/day) during the first 8 days of life elicited precocious eyelid opening as expected but did not alter the serum T4 concentration, suggesting that EGF does not mediate eye opening by T4 dependent mechanism(s). Tissue EGF measurements revealed that the exogenous EGF was localized in skin and eye; however, other tissues including lung, liver, heart and submandibular gland also contained exogenous EGF. Kidney-EGF concentrations did not rise while brain-EGF levels were significantly decreased after exogenous EGF, suggesting that different EGF uptake and regulatory mechanism(s) exist in different tissues during the neonatal period. T4 administration (0.4 micrograms/g body weight/day) for 10 days to adult mice also increased ocular-EGF concentrations. However, this increase was abolished by sialoadenectomy, suggesting in contrast to the newborn, that submandibular gland is an important source of ocular-EGF in adult mice. These studies indicate that ocular EGF in the mouse is thyroxine responsive only during the neonatal period.

Animals↗

PubMed1984

Structure-activity relation of thyroid hormone analogues and tissue epidermal growth factor concentrations in neonatal and adult mice.

We have shown a positive correlation between the epidermal growth factor concentration in neonatal mouse skin and prior treatment with thyroxine (T4) or triiodothyronine (T3). The results of the present study indicate similar activity of other levorotatory iodothyronine analogues and suggest the following scale of decreasing potency: T3, triiodothyroacetic acid, triiodothyropropionic acid, T4, reverse T3, and diiodothyronine. Metabolically inactive analogues (reverse T3, diiodothyronine) have no effect on skin EGF levels. A similar response pattern was observed in the adult, female mouse submandibular gland, except that T4 seemed relatively more effective.

Animals↗

PubMed1984

Thyroid hormone effects on skin and hepatic epidermal growth factor concentrations in neonatal and adult mice.

Tissue concentrations of mouse epidermal growth factor (skin, submandibular gland and liver) are compared in control and thyroxine-treated neonatal and adult animals. The results identify an early onset thyroid-induced augmentation of EGF levels in neonatal skin with continuation of hormone responsiveness into adult life. Hepatic EGF levels are shown to be low and, unlike skin and submandibular gland, are not augmented by T4. The significance of hormonal modulation of nonsalivary growth factor concentrations is discussed.

Animals↗

PubMed1984

Hormonal modulation of mouse plasma concentration of epidermal growth factor.

To understand the physiological role of plasma epidermal growth factor (EGF) we studied in adult female mice the effect of endocrine manipulations on serum EGF concentration (S-EGF). Starting 1 month after sham operation (sh) or excision (SX) of the submandibular salivary gland (SMG), groups of 6 mice were given sc injections of T4 (0.4 micrograms/g daily), testosterone propionate (TP, 25 micrograms/g every 48 h), T4 + TP, or SMG extract (20 micrograms EGF daily) for 10 days. They were exsanguinated via the abdominal vena cava on day 11. During treatment the SX mice gained 55% less weight and their S-EGF was 25% lower compared with the sh mice. Hormone effects were clear in the SX mice: T4 caused a 35% decrease in S-EGF and a 5-fold increase in SMG-EGF concentration. TP caused a 1.6-fold increase in S-EGF and a 6-fold increase in SMG-EGF. Twenty-four hours after the last injection of SMG extract S-EGF remained 1.6-fold elevated. We conclude that plasma EGF is largely independent of SMG, and is modified by hormones in ways different from known tissue effects. This is consistent with an endocrine role of EGF.

Animals↗

PubMed1983

Differential hormonal response of epidermal growth factor concentration in the developing mouse: synergism of triiodothyronine and dexamethasone in epidermal maturation.

The hormonal regulation of epidermal growth factor concentration in neonatal mouse skin and submandibular gland is examined by radioimmunoassay. The results show triiodothyronine but not dexamethasone effects an unequivocal elevation in skin EGF content. In contrast, the neonatal submandibular gland is hormonally unresponsive during this period. Combined therapy with T3 and dexamethasone produces precocious incisor eruption compared to the effect of either hormone alone. The mechanism of this synergistic acceleration of an EGF-related developmental event is unknown.

Animals↗

PubMed1983

Effect of thyroid hormones on epidermal growth factor concentration in neonatal mouse skin.

T4 and epidermal growth factor (EGF), given exogenously, both promote similar maturational events in the skin of newborn mice, i.e. precocious incisor eruption and eyelid opening. Moreover, T4 markedly increases the concentration of EGF in developing mouse submandibular glands. To examine the effect(s) of thyroid hormones on local cutaneous levels of EGF, a rapid and sensitive double antibody RIA was developed and standardized for newborn mouse skin. After fixed daily injections of T4, immunoreactive EGF concentrations in whole skin homogenates showed a dose-dependent increase when measured on postnatal days 4, 6, and 17. A similar increase was seen after T3 treatment, but administration of the structurally similar, metabolically inactive analog rT3 produced no significant effect on EGF concentrations. Induction of experimental hypothyroidism with propylthiouracil (PTU) and methimazole produced a relative decrease in skin EGF levels on postnatal day 8. Maternal sialoadenectomy did not result in a significant decrease in neonatal skin EGF, suggesting the presence of an extrasalivary source(s). These studies suggest that the epidermal maturation that follows thyroid hormone administration is mediated by local tissue levels of EGF. Moreover, the results admit of a possible physiological relation between thyroid hormones and EGF during postnatal cutaneous development.

Animals↗

PubMed1981

Effect of thyroxine, testosterone, and corticosterone on nerve growth factor (NGF) and epidermal growth factor (EGF) concentrations in adult female mouse submaxillary gland: dissociation of NGF and EGF responses.

Testosterone propionate (TP) and corticosterone acetate (CA) were administered alone and in combination with T4 to assess the effect on submaxillary gland (SMG) nerve growth factor (NGF) and epidermal growth factor (EGF) concentrations in adult female mice. Mice were treated for 5 or 10 days. SMG NGF, and EGF concentrations were measured by specific RIA techniques. Mean SMG NGF (0.68 +/- 0.08 microgram/mg protein) and EGF (0.58 +/- 0.05 microgram/mg protein) concentrations were similar in control mice. T4 (0.4 microgram/g BW, sc, daily) significantly increased mean SMG NGF and EGF concentrations to 469% and 347%, respectively, of control values after 5 days and to 1190% and 568%, respectively, after 10 days of treatment. TP (25 microgram/g BW, sc, every 2 days) significantly increased mean SMG NGF and EGF concentrations to 734% and 767%, respectively, of control values at 5 days and to 1971% and 1953%, respectively, at 10 days. T4 and TP resulted in no further significant increases in either SMG NGF or EGF concentrations above the levels observed after TP alone. CA (25 microgram/g BW, sc, daily) increased mean SMG NGF, but not EGF, concentrations at both 5 and 10 days. Moreover, T4 and CA appeared to exert an additive effect on NGF. In contrast to the observations in adult female mice, T4 increased mean SMG NGF concentrations to 178% of control levels in adult male mice, but had no significant effect of SMG EGF concentrations. These data indicate that T4 and TP modulate SMG NGF and EGF concentrations in adult female mice. T4, however, appears to have a preferential effect on NGF on both male and female mice, unlike the equal effect on TP on both NGF and EGF. CA, like T4, also appears to increase NGF, but not EGF, concentrations in adult female SMG. The present results suggest separate regulatory mechanisms for T4, TP, and CA on SMG NGF and EGF biosyntheses.

Animals↗

PubMedDate not supplied

Incubation of cultured skin substitutes in reduced humidity promotes cornification in vitro and stable engraftment in athymic mice.

Cultured skin substitutes have been used successfully for adjunctive treatment of excised burns and chronic skin wounds. However, limitations inherent to all models of cultured skin include deficient barrier function in vitro, and delayed keratinization after grafting in comparison to native skin autografts. Experimental conditions for incubation of skin substitutes were tested to stimulate barrier development before grafting, and measure responses in function and stability after grafting. Cultured skin substitutes consisted of human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan biopolymer substrates. Parallel cultured skin substitutes were incubated at the air-liquid interface in ambient (48-61%) or saturated (79-91%) relative humidity, and grafted to athymic mice on culture day 14. Additional cultured skin substitutes were incubated in the experimental conditions for a total of 28 days. Cadaveric human skin and acellular biopolymer substrates served as controls. Epidermal barrier was evaluated as the change in surface hydration by surface electrical capacitance with the NOVA Dermal Phase Meter. Cultured skin substitutes and cadaveric skin incubated in ambient humidity had lower baseline surface electrical capacitance and less change in surface electrical capacitance than parallel samples incubated in saturated humidity at all time points in vitro. Data from healing cultured skin substitutes at 2, 4, 8 and 12 weeks after grafting showed an earlier return to hydration levels comparable to native human skin, and more stable engraftment for skin substitutes from ambient humidity. The data indicate that cultured skin substitutes in ambient humidity have lower surface electrical capacitance and greater stability in vitro, and that they reform epidermal barrier more rapidly after grafting than cultured skin substitutes in saturated humidity. These results suggest that restoration of functional epidermis by cultured skin substitutes is stimulated by incubation in reduced humidity in vitro.

Animals↗

PubMedDate not supplied

Development of diaper rash in the newborn.

Diaper rash is a common infant malady. This study documents the earliest stages of rash in a cohort of 31 healthy term newborns over the first 28 days of life. The diaper area was evaluated using a standardized diaper rash grading scale. The anal, buttock, genital, intertriginous, waistband, and leg areas were assessed separately. At birth the average grade was 0.1 and none of the infants had specific features of advanced rash. Nineteen percent had dryness and/or slight redness. By day 7, 71% of infants had some features of skin compromise, giving rise to an overall grade of 0.6. Both the frequency and overall grade increased during postnatal weeks 2 and 3. Overall scores for days 21 and 28 were the same (1.1). The perianal area had the highest overall regional rash grade. Gender differences were present for the genital area only. These findings indicate that epidermal barrier breakdown is an uncommon finding at birth. Clinical signs of irritated skin in the diaper area develop progressively over the first postnatal month. A better understanding of the mechanisms conferring epidermal barrier protection at birth may be important for developing skin care products and practices to extend this protection later into life.

Diaper Rash↗