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Biomedical subjects

L T Smith

Publications and source records attributed to L T Smith.

At least 55 records · Page 3Linked to original sources
PubMed1995

Dystrophic epidermolysis bullosa inversa: report of two cases with further correlation between electron microscopic and immunofluorescence studies.

Dystrophic epidermolysis bullosa inversa is a rare form of epidermolysis bullosa characterized by blister formation in flexural skin areas and by marked oral and esophageal involvement. Recognition of this subset of dystrophic epidermolysis bullosa is important, because its prognosis differs from all other forms of dystrophic epidermolysis bullosa. Investigators recently reported normal staining with antibodies directed against type VII collagen in 14 patients, but electron microscopy in eight patients showed diminished or absent anchoring fibrils. We report here the cases of two additional patients with dystrophic epidermolysis bullosa inversa. One patient had finger web space scarring that required surgical correction and mild syndactyly of toes. Both patients had normal staining with LH 7:2, but electron microscopy showed diminished and rudimentary anchoring fibrils. These findings support the possibility that dystrophic epidermolysis bullosa inversa may be caused by a structural abnormality of type VII collagen that prevents proper assembly of collagen into distinct anchoring fibrils.

Adolescent↗
PubMed1995

Expression of amphiregulin is regulated in cultured human keratinocytes and in developing fetal skin.

Previous studies have indicated that amphiregulin is a major autocrine factor for human keratinocytes. To evaluate the possibilities that amphiregulin could function in fetal skin morphogenesis and contribute to the growth regulation of epidermis, immunostaining with a specific anti-amphiregulin monoclonal antibody was observed at different stages of fetal skin development, and the results were compared with neonatal and adult skin specimens and cultured neonatal keratinocytes. Immunoreactive amphiregulin was readily detected in the periderm and basal epidermal layers of embryonic epidermis but became gradually less detectable in the periderm concurrent with an increase in staining of the spinous layer as it developed during the fetal period. Basal and spinous keratinocyte expression of amphiregulin was predominantly cytoplasmic, but with punctate nuclear foci, and this pattern persisted into the neonatal period. At all developmental stages, epithelial and mesenchymal cells of the follicle were reactive, often in a nuclear pattern. Dermal mesenchymal cells were increasingly reactive in late fetal skin, but the staining decreased postnatally. In adult skin only randomly scattered nuclei of spinous keratinocytes and follicular structures such as the inner root sheath were stained. Examination by scanning laser confocal microscopy of cultured neonatal keratinocytes showed a nonrandom distribution of amphiregulin to the peripheral cytoplasm and plasma membranes at the outer perimeter of cell colonies, with much less reactivity of apposed keratinocyte membranes at interior sites. Nuclei were heterogeneously stained. Amphiregulin reactivity declined at higher cell densities. These data indicate that expression of amphiregulin is regulated in vitro and developmentally during cutaneous morphogenesis.

Adult↗
PubMed1995

Role of Glycine Betaine and Related Osmolytes in Osmotic Stress Adaptation in Yersinia enterocolitica ATCC 9610.

Yersinia enterocolitica is a gram-negative, food-borne pathogen that can grow in 5% NaCl and at refrigerator temperatures. In this report, the compatible solutes (osmolytes) which accumulate intracellularly and confer the observed osmotic tolerance to this pathogen were identified. In minimal medium, glutamate was the only detectable osmolyte that accumulated in osmotically stressed cells. However, when the growth medium was supplemented with glycine betaine, dimethylglycine, or carnitine, the respective osmolyte accumulated intracellularly to high levels and the growth rates of the osmotically stressed cultures improved from 2.4- to 3.5-fold. Chill stress also stimulated the intracellular accumulation of glycine betaine, but the growth rate was only slightly improved by this osmolyte. Both osmotic upshock and temperature downshock stimulated the rate of uptake of [(sup14)C]glycine betaine by more than 30-fold, consistent with other data indicating that the osmolytes are accumulated from the growth medium via transport.

Journal Article↗
PubMed1995

The natural history of human dermatosparaxis (Ehlers-Danlos syndrome type VIIC).

Dermatosparaxis (Ehlers-Danlos syndrome type VIIC) has only recently been identified in human subjects. Although well documented in animals, to date only three human cases have been recorded, all aged 2 years or under. We document a 15-year-old girl with this newly recognized condition to emphasize the remarkable similarity of physical signs in all four cases. The striking skin fragility which attends the phenotype is highly distinctive, so that the diagnosis may be suspected on clinical grounds. The confirmatory diagnostic procedures are discussed.

Adolescent↗
PubMed1995

Two-dimensional fourier analysis of electron micrographs of human skin for quantification of the collagen fiber organization in the dermis.

Two-dimensional (2-D) Fourier analysis was used to quantify the structural organization of collagen fibers in the dermis of the human skin. The 2-D Fourier spectra of electron micrographs of collagen fibers contained large amplitude Fourier components (1 fundamental and 3 harmonic peaks), representing the predominant structural parameter of the fibers, the center-to-center spacing of collagen fibrils. The average center-to-center spacing of the collagen fibrils was found from the position of the peaks. For a normal fiber of reticular dermis, this spacing was 116 nm. The fibril diameter appeared to modulate the peak heights.

Collagen↗
PubMed1994

Simple reaction time event-related potentials: effects of alcohol and diazepam.

Acute effects of alcohol and diazepam on reaction time (RT) and event-related potential (ERP) measures were examined in 108 healthy male volunteers. The subjects engaged in a simple RT task at two levels of stimulus intensity during baseline and treatment sessions. Lower stimulus intensity produced increased RT's, increased ERP peak latencies, and suppression of peak amplitudes. Moderate and high doses of alcohol, and high doses of diazepam produced increased RT's. Alcohol suppressed P100 and N100 amplitudes, while diazepam suppressed P100 amplitudes only. P100 amplitudes were correlated to RT's under baseline and treatment conditions. These results were taken as evidence for impaired stimulus detection during alcohol and diazepam intoxication, with both drugs influencing sensory-perceptual processes and alcohol alone influencing the degree of attentiveness.

Adult↗
PubMed1994

Patterns of type VI collagen compared to types I, III and V collagen in human embryonic and fetal skin and in fetal skin-derived cell cultures.

The distribution of type VI collagen was examined in human embryonic and fetal skin and in cultured cells and matrix from this tissue. Frozen sections were immunolabeled with primary antibodies against type VI collagen and types I, III or V collagen, and processed further for fluorescence microscopy and immunoelectron microscopy. At 6 weeks estimated gestational age (EGA), type VI collagen was identified by positive fluorescence and by immunogold staining of filaments and fibers beneath the dermal-epidermal junction (DEJ), weaker fluorescence in the fine matrix of the dermis, and stronger fluorescence in the subcutis. At progressive stages of gestation, immunolabeling for type VI collagen increased in the dermis in parallel with increased deposition of types I and III collagen. By 15 weeks EGA, type VI collagen stained intensely throughout the dermis. At 13 weeks EGA, type VI collagen appeared diminished from the growing tips of invaginating hair buds, but as the hair peg developed, type VI collagen accumulated in adnexal sheaths. Cell cultures were derived from fetal skin at 7.5 to 12 weeks EGA. In primary explant cultures containing both keratinocytes and fibroblasts, mats of type V collagen were present beneath keratinocytes and associated with dense spots that co-labeled for both type VI and type V collagen. In passaged cultures of fibroblasts, individual cells with or without pretreatment with monensin were positive for type VI and/or types I, III or V collagen. Fibrous matrix that was labeled for type VI collagen was also immunopositive for type I or III collagen, while filamentous matrix that was type VI collagen positive tended to exclude types I and III collagen but in some areas to overlap with type V collagen. These findings support the hypothesis that type VI collagen present in both filamentous and fibrous matrix and networks of type VI collagen may serve as a fine scaffolding that facilitates the integration of types I and III collagen into developing fibrous matrix.

Antibodies, Monoclonal↗
PubMed1994

Localization of type I human skin collagenase in developing embryonic and fetal skin.

Type I human skin collagenase (HSC-1) was localized in developing embryonic and fetal skin ranging from 6 to 20 weeks estimated gestational age using an antigen-specific, affinity-purified, polyclonal antiserum to HSC-1 and an avidin-biotin alkaline phosphatase procedure. Double immunolabeling with monoclonal antibodies for Factor VIII-related antigen, type IV collagen, and the 68-kilodalton neurofilament subunit was performed using a direct peroxidase procedure. By 8 weeks estimated gestational age, HSC-1 localized to the periderm, the basal cell epidermal keratinocytes, dermal fibroblasts, and surrounding extracellular matrix. At 12 weeks estimated gestational age, HSC-1 immunolabeling showed a continued association with the epidermis and dermis. Dermal and subcutaneous blood vessels and the surrounding extracellular matrix were positive for HSC-1 labeling. HSC-1 staining was also found around developing nerves and in association with dermal fibroblasts. In the developing hair follicle, HSC-1 was present in keratinocytes of the pre-germ, germ, hair peg, and bulbous hair peg. HSC-1 immunoreactivity was also found in association with the hair canal, the bulge, and the dermal papillae, but was absent from the fetal sebaceous gland. These data demonstrate the association of HSC-1 with the development of interfollicular epidermis, the dermal collagenous matrix, the process of angiogenesis, the development of nerves, and hair follicle morphogenesis.

Antibodies, Monoclonal↗
PubMed1994

Glycine betaine confers enhanced osmotolerance and cryotolerance on Listeria monocytogenes.

Listeria monocytogenes is a gram-positive food-borne pathogen that is notably resistant to osmotic stress and can grow at refrigerator temperatures. These two characteristics make it an insidious threat to public health. Like several other organisms, L. monocytogenes accumulates glycine betaine, a ubiquitous and effective osmolyte, intracellularly when grown under osmotic stress. However, it also accumulates glycine betaine when grown under chill stress at refrigerator temperatures. Exogenously added glycine betaine enhances the growth rate of stressed but not unstressed cells, i.e., it confers both osmotolerance and cryotolerance. Both salt-stimulated and cold-stimulated accumulation of glycine betaine occur by transport from the medium rather than by biosynthesis. Direct measurement of glycine betaine uptake shows that cells transport betaine 200-fold faster at high salt concentration (4% NaCl) than without added salt and 15-fold faster at 7 than at 30 degrees C. The kinetics of glycine betaine transport suggest that the two transport systems are indistinguishable in terms of affinity for betaine and may be the same. Hyperosmotic shock and cold shock experiments suggest the transport system(s) to be constitutive; activation was not blocked by chloramphenicol. A cold-activated transport system is a novel observation and has intriguing implications concerning the physical state of the cell membrane at low temperature.

Adaptation, Physiological↗
PubMed1994

A prominent role for glucosylglycerol in the adaptation of Pseudomonas mendocina SKB70 to osmotic stress.

The mechanism of osmoadaptation in a salt-tolerant (1.2 M NaCl) bacterial isolate identified as Pseudomonas mendocina (N. J. Palleroni, M. Doudoroff, R. Y. Stanier, R. E. Solanes, and R. Mandel, J. Gen. Microbiol. 60:215-231, 1970) was investigated. In response to osmotic stress, this species accumulated a number of compatible solutes, the intracellular levels of which depended on both the osmolarity and the ionic composition of the growth medium. Glucosylglycerol [alpha-D-glucopyranosyl-alpha-(1-->2)-glycerol], N-acetylglutaminylglutamine amide, and L-alpha-glutamate were the major compatible solutes accumulated via de novo biosynthesis. Trehalose was also accumulated, but only in cells grown in the presence of high concentrations of sulfate or phosphate ions. Glycine betaine was accumulated only when supplied exogenously to cells grown at high osmolarity, and its accumulation caused a significant depletion of the intracellular pools of glucosylglycerol and glutamate. Glucosylglycerol was also found to accumulate in the type strains of P. mendocina and P. pseudoalcaligenes. This is the first report demonstrating the pivotal role of glucosylglycerol in osmoadaptation in a nonphotosynthetic microorganism.

Adaptation, Biological↗
PubMed1993

Prenatal detection of epidermolysis bullosa letalis with pyloric atresia in a fetus by abnormal ultrasound and elevated alpha-fetoprotein.

We report on the prenatal diagnosis of epidermolysis bullosa letalis with pyloric atresia in a pregnancy not known to be at risk for this condition. Elevated maternal serum alpha-fetoprotein levels led to ultrasonography which demonstrated gastric dilatation, consistent with pyloric atresia, and echogenic particles in the amniotic fluid, the "snowflake sign," previously described in two pregnancies of fetuses with disorders of skin sloughing. Amniotic fluid alpha-fetoprotein was markedly elevated and the acetylcholinesterase was positive. The diagnosis of epidermolysis bullosa letalis with pyloric atresia was confirmed after delivery by electron microscopy of fetal skin which showed typical changes of hypoplastic absent hemidesmosomes and separation along the dermal-epidermal junction. None of these abnormal prenatal findings are consistently present in pregnancies with epidermolysis bullosa with pyloric atresia. Thus, although useful when abnormal, when the test results are normal, the need for confirmatory fetoscopy and fetal skin biopsy remains.

Abnormalities, Multiple↗
PubMed1993

Dermatosparaxis in children. A case report and review of the newly recognized phenotype.

BACKGROUND: Dermatosparaxis is an autosomal recessive connective tissue disorder in animals that is caused by abnormal processing of type I procollagen and results in skin laxity and fragility. Only three humans with characteristic biochemical and electronmicroscopic findings have been recognized to date. OBSERVATIONS: We describe the clinical and electronmicroscopic findings in an affected boy who presented at birth with large full-thickness groin fissures, micrognathia, large fontanelles, umbilical hernia, and dental laminal cysts. He subsequently exhibited marked skin fragility, blue sclerae, joint laxity, increased bruisability, and growth retardation. The diagnosis of dermatosparaxis was made by electron-microscopic findings consisting of characteristic small, irregular, and circular collagen fibers in the skin. His phenotype is strikingly similar to two other reported children with the disorder, which is now classified in humans as Ehlers-Danlos VII-C. CONCLUSIONS: The newly recognized phenotype of Ehlers-Danlos VII-C is a distinct connective tissue disorder characterized by marked skin fragility and laxity, blue sclerae, increased bruisability, micrognathia, umbilical hernia, and growth retardation. A suspected clinical diagnosis can be confirmed by electron-microscopic and biochemical studies of connective tissue.

Abnormalities, Multiple↗
PubMed1993

Simple reaction time event-related potentials: effects of alcohol and sleep deprivation.

The effects of two levels of alcohol intoxication and 30 hr of sleep deprivation on visual event-related potential (ERP) waveforms concomitant to simple reaction time (RT) were examined in 54 normal male subjects. In a previous study, we reported that alcohol and sleep deprivation each increased RT. At a 0.05 breath alcohol concentration (BAC), the combined treatments produced an additive increase in RT, whereas at a 0.08 BAC the combined treatments produced no increase beyond that seen with each alone. In this study we present the ERP findings. Sleep deprivation alone increased the latency of a 150 msec negative component (N1) of the ERP. Alcohol increased the latency of a 250 msec negative component (N2), but only in the absence of sleep deprivation. Furthermore, this increased latency of N2 was correlated with RT measures. These results suggested that sleep deprivation slowed initial stimulus detection, whereas alcohol slowed later processing and response activation.

Adult↗
PubMed1993

Roles of N-acetylglutaminylglutamine amide and glycine betaine in adaptation of Pseudomonas aeruginosa to osmotic stress.

The mechanism of osmotic stress adaptation in Pseudomonas aeruginosa PAO1 was investigated. By using natural abundance 13C nuclear magnetic resonance spectroscopy, osmotically stressed cultures were found to accumulate glutamate, trehalose, and N-acetylglutaminylglutamine amide, an unusual dipeptide previously reported only in osmotically stressed Rhizobium meliloti and Pseudomonas fluorescens. The intracellular levels of these osmolytes were dependent on the chemical composition and the osmolality of the growth medium. It was also demonstrated that glycine betaine, a powerful osmotic stress protectant, participates in osmoregulation in this organism. When glycine betaine or its precursors, phosphorylcholine or choline, were added to the growth medium, growth rates of cultures in 0.7 M NaCl were increased more than threefold. Furthermore, enhancement of growth could be observed with as little as 10 microM glycine betaine or precursor added to the medium. Finally, the mechanism of osmotic stress adaptation of two clinical isolates of P. aeruginosa was found to be nearly identical to that of the laboratory strain PAO1 in all aspects studied.

Betaine↗
PubMed1993

Ultrastructural findings in epidermolysis bullosa.

BACKGROUND AND DESIGN: Electron microscopy of skin provides diagnostic criteria for distinguishing the simplex, junctional, and dystrophic forms of inherited epidermolysis bullosa (EB). The plane of cleavage in blister formation indicates the localization of structural weakness within the epidermis and basement membrane zone, and, together with ultrastructural changes in affected skin, these are clues to the underlying genetic bases for these disorders. Skin biopsy specimens from individuals with EB were evaluated by electron microscopy to identify structural changes and determine the subtype of EB. RESULTS: Discrete, circumscribed clumps of keratin filaments present in the basal keratinocytes are pathognomonic for EB simplex Dowling-Meara. These and other observations of keratin filament disruption have led to the identification of mutations in keratin genes in Dowling-Meara and Koebner forms of EB simplex. Changes in the density and structure of anchoring fibrils and the relative amount of type VII collagen detected by immunostaining of the dermoepidermal junction in dystrophic EB have led to sequencing of mutations in the type VII collagen gene. Although mutations in junctional EB have not been reported, findings of structural alterations in hemidesmosomes and immunohistochemical studies of kalinin (BM600 and epiligrin), and in junctional EB with pyloric atresia alterations in the integrin alpha 6 beta 4, indicate molecules involved in basal keratinocyte adhesion to the basement membrane that are candidate genes for junctional EB. CONCLUSIONS: Electron microscopy of skin when correlated with mutations in EB will help us understand the significance of these structural molecules in normal skin and the pathogenesis of EB.

Antigens, Surface↗
PubMed1993

Effects of post-curing on mechanical properties of a composite.

The mechanical properties (diametral tensile strength, compressive strength, modulus of elasticity in compression, Knoop hardness, and Rockwell Superficial indentation and recovery) were measured for one light-cured composite (Herculite XRV) post-cured by five different conditions. The post-curing conditions were: boiling water, CRC-100, D.I.-500, Translux EC Light Box, and Triad 2000 with normal light curing as a control. Post-curing Herculite XRV significantly improved the diametral tensile strength (24-39%), Knoop hardness (8-22%) and Rockwell Superficial recovery (3-6%); decreased Rockwell Superficial indentation (0-19%) but did not affect the compressive strength significantly. Modulus of elasticity was not affected, except by the Translux EC Light Box, which increased the modulus by 33%. Post-curing Herculite XRV with the Triad 2000 and Translux EC Light Box produced the most improved properties. Water at 100 degrees C was the least effective of the post-curing methods.

Analysis of Variance↗