Biomedical subjects

L T Smith

Publications and source records attributed to L T Smith.

At least 73 records · Page 4Linked to original sources

PubMed1993

Prenatal diagnosis of genetic skin disease using fetal skin biopsy samples.

BACKGROUND: Understanding normal skin development and identifying markers of genetic skin disease expressed in postnatal skin have permitted the prenatal diagnosis of many severe genodermatoses: bullous diseases, keratinization diseases, pigment cell disorders, and disorders of the epidermal appendages (ectodermal dysplasias). Samples of 16 to 22 weeks' gestation fetal skin obtained by ultrasound-guided biopsy are evaluated using morphologic, immunohistochemical, and biochemical methods. OBSERVATIONS: The 12-year experience in evaluating samples from fetuses at risk of these disorders has allowed us to establish conditions that must be met before the samples are taken and the criteria for recognizing the disorder, to recommend the site(s) for sampling, and to be mindful of pitfalls that may be encountered in interpreting the tissue structure. CONCLUSIONS: Fetal skin biopsy is an important diagnostic tool that has permitted families in which members carry the abnormal gene for one of these severe skin diseases to undertake a pregnancy knowing that the condition of the fetus can be determined. Nonetheless, the ultimate goal is phase out this procedure when linkage of more of these disorders to specific genes is understood, specific mutations are characterized, and probes are available for molecular diagnoses using tissue obtained at earlier fetal ages. Until this is possible, fetal skin biopsy remains an important tool that can be used with reasonably high levels of safety and confidence.

Amniotic Fluid↗

PubMed1992

Initial observations of human dermatosparaxis: Ehlers-Danlos syndrome type VIIC.

We describe initial observations of an infant with dermatosparaxis (another form of Ehlers-Danlos syndrome, designated as type VIIC), an autosomal recessive disorder characterized by skin fragility and described in several species of domesticated animals. Electron microscopic examination of the skin shows collagen sheets rather than fibrils, and characteristic distortions resembling hieroglyphs. In addition to skin fragility, the disorder is characterized by redundant skin folds and edema, healing with minimal scar formation, large fontanels and wide sagittal and metopic sutures, blue sclerae, micrognathia, and umbilical hernia; after the neonatal period there are joint laxity, growth failure, short limbs, and normal mineralization of the skeleton except for the cranial vault. This disorder may also be a cause of premature rupture of placental membranes and myopia.

Ehlers-Danlos Syndrome↗

PubMed1992

Buschke-Ollendorff syndrome associated with elevated elastin production by affected skin fibroblasts in culture.

Buschke-Ollendorff syndrome (BOS; McKusick 16670) is an autosomal dominant connective-tissue disorder characterized by uneven osseous formation in bone (osteopoikilosis) and fibrous skin papules (dermatofibrosis lenticularis disseminata). We describe two patients in whom BOS occurred in an autosomal dominant inheritance pattern. The connective tissue of the skin lesions showed both collagen and elastin abnormalities by electron microscopy. Cultured fibroblasts from both patients produced 2-8 times more tropoelastin than normal skin fibroblasts in the presence of 10% calf serum. Involved skin fibroblasts of one patient produced up to eight times normal levels, whereas apparently uninvolved skin was also elevated more than threefold. In a second patient, whose involvement was nearly complete, elastin production was high in involved areas and less so in completely involved skin. Transforming growth factor-beta 1 (TGF beta 1), a powerful stimulus for elastin production, brought about similar relative increases in normal and BOS strains. Basic fibroblast growth factor, an antagonist of TGF beta 1-stimulated elastin production, was able to reduce elastin production in basal and TGF beta 1 stimulated BOS strains. Elastin mRNA levels were elevated in all patient strains, suggesting that Buschke-Ollendorff syndrome may result, at least in part, from abnormal regulation of extracellular matrix metabolism that leads to increased steady-state levels of elastin mRNA and elastin accumulation in the dermis.

Blotting, Southern↗

PubMed1992

Basic fibroblast growth factor enhances the coupling of intimal hyperplasia and proliferation of vasa vasorum in injured rat arteries.

Basic fibroblast growth factor (bFGF) is mitogenic for smooth muscle cells (SMC) and angiogenic. We examined the in vivo effects of bFGF in balloon denuded carotid arteries of laboratory rats. bFGF was administered continuously from polymer-based devices at 34 ng/d into the periadventitial space of rat carotid arteries for 2 wk. Intimal hyperplasia was not observed in the absence of injury or with lipopolysaccharide induced endothelial dysfunction. Different degrees of vascular injury produced proportionally more intimal hyperplasia. bFGF increased the intimal hyperplastic response 1.3-fold with severe vascular injury, and 2.4-fold with more mild injury. Increased cell proliferation, not extracellular matrix production, accounted for these effects. Cell density was unchanged for the control and bFGF-treated groups, and the number of proliferating intimal cells at 2 wk rose to an amount equivalent to the increase in mass; 1.9- and 4.0-fold for severe and lesser injury, respectively. The relative ability of heparin to reduce SMC proliferation was not altered by the presence of bFGF.bFGF also induced profound angiogenesis within and surrounding the polymeric releasing device, and in the vasa vasorum immediately around the injured arteries. bFGF's effect on vasa was linearly related to the amount of SMC proliferation within the blood vessel. Thus, the in vivo mitogenic and angiogenic potential of bFGF are coupled, and may be similarly modulated by the products of local injury and/or factors in the vessel wall.

Animals↗

PubMed1992

Separation of noncutaneous epithelia in a fetus diagnosed in utero with junctional epidermolysis bullosa.

This study was undertaken to identify the extent of involvement of cutaneous and noncutaneous epithelia during expression in utero of junctional epidermolysis bullosa. Skin and other organs from a 19-wk estimated gestational age fetus affected with junctional epidermolysis bullosa and from age-matched controls were examined by light and transmission electron microscopy. In the affected fetus, skin samples from different body regions including trunk, leg, arm, and finger all showed some separation at the dermal-epidermal junction in the plane of the lamina lucida. Hemidesmosomes were absent or hypoplastic, whereas anchoring fibrils appeared normal in structure and number. Interfollicular epidermis appeared to have separated easily, whereas some follicles remained anchored in the dermis. Areas of epithelium in the trachea and bronchi had separated, but within the lung parenchyma the epithelium of smaller bronchioles and alveoli remained attached to supporting connective tissue. The transitional epithelium of the urinary bladder showed small areas of separation compared with the gall bladder epithelium, which showed extensive separation. Gall bladder epithelium in several control fetuses also was consistently separated. In the affected fetus as well as in controls, gall bladder had multiple layers of basal lamina, a previously unrecognized structural feature of human fetal gall bladder. Epithelia that remained intact included the linings of the stomach and small and large intestines and endothelium of large and small vessels in all organs. Kidney, spleen, liver, and lymph nodes appeared normal in all aspects. In control samples, neither skin nor most of the noncutaneous epithelia had separated from the underlying connective tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Relative fit of new denture resins polymerized by heat, light and microwave energy.

This study compared in vitro the relative fit of seven denture resins polymerized by different methods to their gypsum casts. Relative fit in the molar-to-molar region of the resin bases on their stone casts was evaluated independently by five evaluators at three times (after processing, after polishing and after storage in water) and ranked using non-parametric statistics. The denture resins polymerized by microwave energy, (Acron MC), low heat, (Perform, 45 degrees C), and visible light, (Triad) fit better after polishing and after storage in water than those resins polymerized at higher temperatures (Lucitone 199, 74 degrees C and Accelar 20, Compak and Permacryl 20, 100 degrees C). The traditional heat-polymerized resin (Lucitone) had an average fit after storage in water.

Acrylic Resins↗

PubMed1992

Human dermatosparaxis: a form of Ehlers-Danlos syndrome that results from failure to remove the amino-terminal propeptide of type I procollagen.

Dermatosparaxis is a recessively inherited connective-tissue disorder that results from lack of the activity of type I procollagen N-proteinase, the enzyme that removes the amino-terminal propeptides from type I procollagen. Initially identified in cattle more than 20 years ago, the disorder was subsequently characterized in sheep, cats, and dogs. Affected animals have fragile skin, lax joints, and often die prematurely because of sepsis following avulsion of portions of skin. We recently identified two children with soft, lax, and fragile skin, which, when examined by transmission electron microscopy, contained the twisted, ribbon-like collagen fibrils characteristic of dermatosparaxis. Skin extracts from one child contained collagen precursors with amino-terminal extensions. Cultured fibroblasts from both children failed to cleave the amino-terminal propeptides from the pro alpha 1(I) and pro alpha 2(I) chains in type I procollagen molecules. Extracts of normal cells cleaved to collagen, the type I procollagen synthesized by cells from both children, demonstrating that the enzyme, not the substrate, was defective. These findings distinguish dermatosparaxis from Ehlers-Danlos syndrome type VII, which results from substrate mutations that prevent proteolytic processing of type I procollagen molecules.

Amino Acids↗

PubMed1991

Alpha-fetoprotein and acetylcholinesterase are not predictive of fetal junctional epidermolysis bullosa, Herlitz variant.

Junctional epidermolysis bullosa, Herlitz variant (junctional EB-Herlitz) is a lethal autosomal recessive skin disorder currently amenable to prenatal diagnosis only by direct analysis of fetal skin. However, elevated levels of alpha-fetoprotein, as well as the presence of acetylcholinesterase in amniotic fluid, have been associated with other severe fetal genodermatoses. Fetal skin samplings were performed in ten pregnancies at risk for fetal junctional EB-Herlitz, with three fetuses affected on the basis of electron microscopic detection of blisters within the lamina lucida and abnormal hemidesmosomes. In neither affected nor unaffected pregnancies were maternal serum or amniotic fluid alpha-fetoprotein levels elevated. Moreover, alpha-fetoprotein levels in both maternal serum and amniotic fluid were not statistically different comparing affected and unaffected fetuses. Acetylcholinesterase was not present in the amniotic fluid samples of the three affected pregnancies. Unlike other severe fetal genodermatoses, neither alpha-fetoprotein nor acetylcholinesterase was predictive of junctional EB-Herlitz.

Acetylcholinesterase↗

PubMed1991

Polymerization shrinkage, impact strength and roughness of montmorillonite-modified denture base resins.

Montmorillonite (MMT) was added to two commercial denture base resins, Lucitone (LU) and Accelar (AC) in amounts varying from 0-8 weight percent (wt%). The linear polymerization shrinkage, impact strength and average roughness or polishability were measured after specimens were processed using standard methods. The linear polymerization shrinkage was 1.37 and 1.02% for the unmodified denture base resins and the impact strength was 37.36 and 20.02 J/m; while the average roughness after polishing was 0.026 and 0.047 microns for LU and AC, respectively. The addition of MMT significantly (P less than 0.05) reduced the linear polymerization shrinkage and impact strength, while increasing the roughness of LU and AC.

Acrylic Resins↗

PubMed1990

Intra-epidermal retention of type VII collagen in a patient with recessive dystrophic epidermolysis bullosa.

An infant born with severe blisters on the limbs, face, trunk, and oral mucosa was diagnosed by light and electron microscopy to have recessive dystrophic epidermolysis bullosa. Transmission electron microscopy showed that the basal lamina remained with the epidermis and that the floor of the blister was exposed collagen of the papillary dermis. No banded anchoring fibrils were observed along either the roof or the floor of the blister; however, small filamentous structures, possibly immature anchoring fibrils, extended down from the lamina densa along the blister roof. Some basal and suprabasal keratinocytes contained large vesicles filled with filamentous matrix of variable electron density. Immunofluorescent staining of skin for type VII collagen showed sparse and irregular staining of type VII collagen along the blister roof, and intense intracellular labeling for type VII collagen in clusters of epidermal cells in basal and suprabasal layers. Type VII collagen appeared to be synthesized by keratinocytes but not secreted.

Antibodies, Monoclonal↗

PubMed1990

Preferential osmolyte accumulation: a mechanism of osmotic stress adaptation in diazotrophic bacteria.

A common cellular mechanism of osmotic-stress adaptation is the intracellular accumulation of organic solutes (osmolytes). We investigated the mechanism of osmotic adaptation in the diazotrophic bacteria Azotobacter chroococcum, Azospirillum brasilense, and Klebsiella pneumoniae, which are adversely affected by high osmotic strength (i.e., soil salinity and/or drought). We used natural-abundance C nuclear magnetic resonance spectroscopy to identify all the osmolytes accumulating in these strains during osmotic stress generated by 0.5 M NaCl. Evidence is presented for the accumulation of trehalose and glutamate in Azotobacter chroococcum ZSM4, proline and glutamate in Azospirillum brasilense SHS6, and trehalose and proline in K. pneumoniae. Glycine betaine was accumulated in all strains grown in culture media containing yeast extract as the sole nitrogen source. Alternative nitrogen sources (e.g., NH(4)Cl or casamino acids) in the culture medium did not result in measurable glycine betaine accumulation. We suggest that the mechanism of osmotic adaptation in these organisms entails the accumulation of osmolytes in hyperosmotically stressed cells resulting from either enhanced uptake from the medium (of glycine betaine, proline, and glutamate) or increased net biosynthesis (of trehalose, proline, and glutamate) or both. The preferred osmolyte in Azotobacter chroococcum ZSM4 shifted from glutamate to trehalose as a consequence of a prolonged osmotic stress. Also, the dominant osmolyte in Azospirillum brasilense SHS6 shifted from glutamate to proline accumulation as the osmotic strength of the medium increased.

Journal Article↗

PubMed1990

Osmoregulation in Agrobacterium tumefaciens: accumulation of a novel disaccharide is controlled by osmotic strength and glycine betaine.

We have investigated the mechanism of osmotic stress adaptation (osmoregulation) in Agrobacterium tumefaciens biotype I (salt-tolerant) and biotype II (salt-sensitive) strains. Using natural-abundance 13C nuclear magnetic resonance spectroscopy, we identified all organic solutes that accumulated to significant levels in osmotically stressed cultures. When stressed, biotype I strains (C58, NT1, and A348) accumulated glutamate and a novel disaccharide, beta-fructofuranosyl-alpha-mannopyranoside, commonly known as mannosucrose. In the salt-sensitive biotype II strain K84, glutamate was observed but mannosucrose was not. We speculate that mannosucrose confers the extra osmotic tolerance observed in the biotype I strains. In addition to identifying the osmoregulated solutes that this species synthesizes, we investigated the ability of A. tumefaciens to utilize the powerful osmotic stress protectant glycine betaine when it is supplied in the medium. Results from growth experiments, nuclear magnetic resonance spectroscopy, and a 14C labeling experiment demonstrated that in the absence of osmotic stress, glycine betaine was metabolized, while in stressed cultures, glycine betaine accumulated intracellularly and conferred enhanced osmotic stress tolerance. Furthermore, when glycine betaine was taken up in stressed cells, its accumulation caused the intracellular concentration of mannosucrose to drop significantly. The possible role of osmoregulation of A. tumefaciens in the transformation of plants is discussed.

Betaine↗

PubMed1989

Characterization of three choline transport activities in Rhizobium meliloti: modulation by choline and osmotic stress.

Choline has both a nutritional and osmoregulatory role in Rhizobium meliloti (T. Bernard, J. A. Pocard, B. Perroud, and D. Le Rudulier, Arch. Microbiol. 143:359-364, 1986). In view of this fact, choline transport was studied in R. meliloti 102F34 to determine how the rate of choline uptake is modulated. The effects of the cultural conditions on the kinetics of transport are presented. A high-affinity activity and a low-affinity activity were found in cells grown in minimal medium. The addition of 0.3 M NaCl or other osmolytes to the medium resulted in a marked decrease in the high-affinity activity, whereas the low-affinity activity remained fairly constant. Furthermore, results from osmotic upshock and downshock experiments indicate that the response of the cell to high osmolarity is rapid; hence, the mechanism of regulation by salt likely does not involve gene induction. A second high-affinity transport activity was induced by choline itself. Like the constitutive low-affinity transport activity, this activity was not greatly altered when the cells were grown in media of elevated osmotic strength. We conclude that although all three kinetically distinct transport systems are efficient at low osmolarity, only the induced high- and low-affinity activities are important for osmoregulation. The characteristics of the three transport activities from R. meliloti are compared with those from other bacterial species that use choline for growth and/or osmoregulation.

Biological Transport↗

PubMed1989

An osmoregulated dipeptide in stressed Rhizobium meliloti.

One common mechanism of cellular adaptation to osmotic stress is the accumulation of organic solutes in the cytosol. We have used natural-abundance 13C nuclear magnetic resonance to identify all organic solutes that accumulate to significant levels in Rhizobium meliloti. Our studies led to the discovery of a new dipeptide, N-acetylglutaminylglutamine amide (NAGGN), which is accumulated during osmotic stress. Only rarely have peptides been shown to function in bacteria, and furthermore, this is the first example of a peptide playing a role in osmoregulation. Evidence for the biological role of NAGGN in osmotic-stress protection is presented.

Chromatography, High Pressure Liquid↗

PubMed1989

The relationship between neuropsychological and late component evoked potential measures in chronic alcoholics.

The relationships between event-related potential (ERP) measures and neuropsychological measures were investigated in a group of 39 male alcoholics and 22 age-matched male controls. Late component ERP measures such as N1, Nd, and P3 components and neuropsychological measures of perceptual-motor function, semantic and figural memory and verbal abstracting functions were included in a correlational analysis. No significant correlations between N1 amplitude or latency and neuropsychological tests were obtained. However, visual Nd amplitude correlated significantly with perceptual-motor tests and figural memory scores in the alcoholics. Significant correlations were found in alcoholics for visual P3 amplitude at PZ and delayed figural memory scores and two of the perceptual-motor tests. No significant correlations were obtained among the controls. These data indicate that significant relationships exist between some neuropsychological and ERP measures but that these relationships are restricted to measures of perceptual-motor functioning and to delayed figural memory.

Adult↗

PubMed1989

Severe perinatal Marfan syndrome.

The cardiovascular manifestations of the Marfan syndrome in older children and adults have been well described. Clinical, radiographic, and echocardiographic data regarding three patients with severe perinatal Marfan syndrome are described. Two of these patients had the syndrome at birth and died in infancy. The syndrome was diagnosed in the third patient at 6 months of age and the child is still alive at 3 years of age. The possible relationship among the Marfan syndrome, Ehlers-Danlos syndrome, and osteogenesis imperfecta is considered. Patients with Marfan syndrome and severe cardiorespiratory problems early in life tend to have a limited life expectancy.

Acute Disease↗

PubMed1988

Dose effects of methaqualone on stimulus encoding in a memory scanning task.

Three task variables, stimulus quality, memory set size and response type, were used in a Sternberg binary classification task to define stimulus encoding, short-term memory scanning, and response selection stages within a serial stage reaction process. Mean reaction times, and the slopes and intercepts of the function relating reaction time to memory set size, were used to test the hypothesis that performance deficits seen at two doses of methaqualone (2.9 mg/kg and 5.9 mg/kg), in the range formerly in common clinical use, were specific to the stimulus encoding stage of the reaction process. Mean reaction times were increased significantly by the methaqualone at both doses, but the effects of the two doses did not differ from one another. The intercept of reaction time as a function of set size showed significant main effects of methaqualone, stimulus quality, and response type, and a significant hyper-additive interaction of methaqualone with stimulus quality. At 2.9 mg/kg, the intercept was increased by methaqualone but only with degraded stimuli. At 5.9 mg/kg, the intercept was increased by methaqualone for both high and low quality stimuli. These results suggested a dose-dependent selective effect of methaqualone on the stimulus encoding stage of the reaction process.

Adult↗

PubMed1988

Ontogeny of structural components at the dermal-epidermal junction in human embryonic and fetal skin: the appearance of anchoring fibrils and type VII collagen.

The ontogeny and composition of the dermal-epidermal junction (DEJ) in developing human embryonic and fetal skin was studied at progressive stages of gestation by immunofluorescence microscopy and immunocytochemistry using transmission electron microscopy (TEM). The DEJ of embryonic skin at 5 weeks estimated gestational age (EGA) was a simple basement membrane zone limited to the basal cell plasma membrane, lamina lucida, and lamina densa. A network of reticular collagen fibrils (reticular lamina) was deposited beneath the lamina densa by 6 weeks. Coincident with the onset of increased complexity in epidermal and dermal structure, at the time of the embryonic to fetal transition, the DEJ displayed additional components that were markers of maturation. At 7-8 weeks EGA, fine filamentous structures extended from the DEJ into the reticular lamina. By 9 weeks EGA hemidesmosomes and banded anchoring fibrils were recognizable, although distributed sparsely at the DEJ. With increasing gestational age, these structures displayed greater electron density and structural completeness. By the end of the first trimester, the DEJ appeared ultrastructurally similar to that of mature skin. Weak immunofluorescent labeling demonstrated the presence of type VII collagen at the DEJ by 8 weeks EGA. From 10-12 weeks EGA immunofluorescent labeling of the DEJ for type VII collagen was distinctly punctate, while immunoperoxidase labeling observed by TEM was linear, continuous, and sublamina densa in position. With ongoing gestation the immunofluorescent labeling became increasingly stronger at the DEJ. Thus, type VII collagen was present at the DEJ in the zone immediately beneath the lamina densa, before the appearance of mature anchoring fibrils but coordinate with the appearance of fine filamentous, unbanded structures, and appeared to increase with the development and accumulation of anchoring fibrils.

Collagen↗