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L Thomas

Publications and source records attributed to L Thomas.

At least 325 records · Page 18Linked to original sources
PubMed1991

Surface topography and molecular stoichiometry of the mitochondrial channel, VDAC, in crystalline arrays.

The mitochondrial outer membrane contains a protein, called VDAC, that forms large aqueous pores. In Neurospora crassa outer membranes, VDAC forms two-dimensional crystalline arrays whose size and frequency can be greatly augmented by lipase treatment of these membranes (C. Mannella, Science 224, 165, 1984). Fourier filtration and surface reconstruction of freeze-dried/shadowed (45 degrees) arrays produced detailed images of two populations of crystals, whose lattices are mirror images of each other. Most likely, this technique has revealed both surfaces of the same two-dimensional crystal with lattice parameters: a = 12.3 +/- 0.1 nm, b = 11.2 +/- 0.1 nm, and theta = 109 +/- 1 degree. Three-dimensional reconstructions of the surface reliefs on both sides of the crystal show them to be very similar. The majority of the protein forming the channel appears to be at or below the level of the membrane. To address the issue of the number of 30-kDa polypeptides that form a VDAC channel, measurements of mass per unit area were carried out by analyzing scanning transmission electron micrographs of unstained, freeze-dried arrays. The crystal form used for mass analysis contained the same motif of six stain-accumulating centers per unit cell, with p2 symmetry as in the oblique configuration, but it had a different orientation relative to the lattice lines. These data yielded a surface density of 1.9 +/- 0.2 kDa/nm2, indicating that there is a one-to-one ratio between VDAC polypeptides and the channels visualized in filtered electron micrographs, and that VDAC membrane crystals contain 68% protein and 32% lipid by mass.

Crystallization↗
PubMed1991

Regulation of cellular water and ionic content in lungs of fetal and adult rats.

Slices of lungs from late-fetal (1 day pre-partum) and adult rats lost K+ and gained Na+, Cl-, water and Ca2+ during pre-incubation at 1 degrees C. These changes were reversed upon restoration to 37 degrees C. The recovery of composition at 37 degrees C was completely dependent on cell respiration in adult slices; by contrast, glycolysis could support partial recovery in the fetal slices. Ouabain completely inhibited K+ reaccumulation at both ages but inhibited net extrusion of water by no more than 50%. Replacement of medium Cl- with NO3- prevented the extrusion of water in the presence of ouabain in adult but not fetal slices. Transmission electron microscopy of type II epithelial cells in slices of both ages showed that ouabain induced the formation of many cytoplasmic vesicles, apparently derived from the Golgi apparatus. Regulation of cell ionic and water content is thus generally similar in late-fetal and adult lung tissue, but there are differences in the source of ATP and in some features of ouabain-resistant volume regulation.

Animals↗
PubMed1991

Pulmonary embolism in patients attending the accident and emergency department with pleuritic chest pain.

A series of 92 patients presenting to an accident and emergency department with pleuritic chest pain is described. Only one of the patients had a diagnosis of pulmonary embolus. All the patients were followed up over a period of 3 months. During this time none of them suffered from mortality or morbidity which could be related to pulmonary embolism. No evidence was obtained during this study that a more aggressive approach to such patients is required in order to achieve the diagnosis.

Adolescent↗
PubMed1991

[Curietherapy-surgery for epidermoid carcinomas of the uterine cervix T1].

Between 1975 and 1985, we have treated 157 patients with carcinoma of the cervix T1. The size of the tumor was always equal or less than 30 mm. Our patient underwent Cesium 137 brachytherapy with Fletchers applicators followed by a modified radical hysterectomy and pelvic lymphadenectomy 4 to 6 weeks later. Intracavitary brachytherapy was performed within three days (low dose rate 0.8-1 Gy/h). The median 60 Gy Isodose was: 65 mm height, 58 mm width and 29 mm thickness. At surgical time we mentioned that vaginal cut out was 2-3 cm and pelvic lymphadenectomy limited to external iliac nodes. The 5 and 10 disease Free Survival was respectively 91.6 and 89.4%. We observed 14 relapses, five were distant metastases only. The tumor size and pelvic node involvement were the main prognostic factors in our data. The sterilization of the cervix wasn't of prognostic value. Complications occurred in 22 patients, 2 (1.3%) were severe urinary injury.

Brachytherapy↗
PubMed1991

Monoclonal antibody GB3 defines a widespread defect of several basement membranes and a keratinocyte dysfunction in patients with lethal junctional epidermolysis bullosa.

An antigen expressed at the dermal-epidermal junction as well as in some other human basement membranes (BM) has been detected by the use of a monoclonal antibody termed GB3. This antigen, synthesized by cultured normal human keratinocytes, has been identified as a 600-kilodalton glycoprotein different from other known components of BM. Using indirect immunofluorescence, GB3 was found to be not reactive with the epidermal BM in patients with lethal junctional epidermolysis bullosa. The present study demonstrates (by indirect immunofluorescence) that GB3 defines a widespread defect of several BM in these patients. Furthermore, it gives evidences for an intrinsic biologic defect of lethal junctional epidermolysis bullosa epidermal keratinocytes using in vitro culture of these cells. Whether the lack of GB3 reactivity is the consequence of a true absence of the antigen or an alteration of its molecular structure is not yet known. Nevertheless, GB3 is a useful probe for both rapid and prenatal diagnosis of lethal junctional epidermolysis bullosa, which will give new insights into the molecular comprehension of this disorder.

Antibodies, Monoclonal↗
PubMed1990

Yeast KEX1 protease cleaves a prohormone processing intermediate in mammalian cells.

A vaccinia virus vector was used to express the yeast KEX1 gene, which encodes a prohormone carboxypeptidase specific for the removal of basic amino acids from prohormone processing intermediates, in mammalian cells. When produced in BSC-40 cells, Kex1p was localized to the perinuclear region and conferred a large increase in enzymatic activity characteristic of this carboxypeptidase. Expression of the KEX1 gene together with the yeast KEX2 gene, which encodes a prohormone endopeptidase specific for cleavage at pairs of basic amino acids, and the mouse proopiomelanocortin (mPOMC) cDNA in BSC-40 cells resulted in the full conversion of mPOMC to mature peptides including gamma-lipotropin. This in vivo processing of mPOMC to mature peptides by the KEX2/KEX1 gene products demonstrates a significant functional homology of the basic prohormone processing machinery in yeast and neuroendocrine cells.

Animals↗
PubMed1990

Scifraud.

Explore the source record for details and available documents.

Attitude↗
PubMed1990

Neuraxin corresponds to a C-terminal fragment of microtubule-associated protein 5 (MAP5).

From cloned DNA, neuraxin has been identified as a tubulin binding protein of predicted molecular weight of 94 kDa. The deduced sequence of the rat protein exhibits high homology to the C-terminal region of mouse microtubule-associated protein 5 (MAP5). Here, we show that different neuraxin antibodies recognize MAP5, but fail to detect a protein of 94 kDa, in subcellular and microtubular fractions of the rat central nervous system. Furthermore, tubulin binding by neuraxin was found to be dependent on taxol. These data are consistent with neuraxin corresponding to a C-terminal fragment of MAP5 that contains a low-affinity tubulin binding site.

Alkaloids↗
PubMed1990

Odor types determined by the major histocompatibility complex in germfree mice.

The major histocompatibility complex (MHC) is the prime but not exclusive determinant of genetically specific constitutive body odors, termed odor types, represented strongly in urine of the mouse. Perception of MHC-determined odor types influences reproductive behavior in the contexts of mate choice and maintenance of early pregnancy, tending to favor the propagation of one MHC type over another. How MHC genotype determines MHC odor type is unknown. One possible explanation is that differential odorants are generated by populations of commensal microorganisms whose composition is somehow geared to MHC diversity. This hypothesis was tested in the Y-maze system in which mice are trained to distinguish the urinary odors of MHC-congenic mice. First, it was shown that mice could readily be trained to distinguish the urines of germfree MHC-congenic mice. Second, it was shown that mice trained to distinguish the urines of conventionally maintained MHC-congenic mice could as readily distinguish the urines of germfree MHC-congenic mice. These results imply that MHC-determined odor types do not depend on odorants generated by microorganisms.

Animals↗
PubMed1990

Effects of dysphoria on maternal exchange dispositions.

Defining dysphoria as subclinical depression, we explored the extent to which maternal dysphoria influences the quality of relationships within the family and evaluated whether the effect of dysphoria on family relationships is selective or general and whether dysphoric effects on maternal behavior are similar or different when ratings of maternal behaviors are made by mothers versus observers. We expected that dysphoria would have general rather than selective effects on family relations rated by mothers and observers. In a sample of 40 American families at risk of child abuse or neglect, we found that maternal dysphoria did have significantly negative effects on mother-to-child and mother-to-parenting-partner relations, suggesting that maternal dysphoria has general rather than selective effects.

Child Abuse↗
PubMed1990

Synaptophysin binds to physophilin, a putative synaptic plasma membrane protein.

We have developed procedures for detecting synaptic vesicle-binding proteins by using glutaraldehyde-fixed or native vesicle fractions as absorbent matrices. Both adsorbents identify a prominent synaptic vesicle-binding protein of 36 kD in rat brain synaptosomes and mouse brain primary cultures. The binding of this protein to synaptic vesicles is competed by synaptophysin, a major integral membrane protein of synaptic vesicles, with half-maximal inhibition seen between 10(-8) and 10(-7) M synaptophysin. Because of its affinity for synaptophysin, we named the 36-kD synaptic vesicle-binding protein physophilin (psi nu sigma alpha, greek = bubble, vesicle; psi iota lambda os, greek = friend). Physophilin exhibits an isoelectric point of approximately 7.8, a Stokes radius of 6.6 nm, and an apparent sedimentation coefficient of 5.6 S, pointing to an oligomeric structure of this protein. It is present in synaptic plasma membranes prepared from synaptosomes but not in synaptic vesicles. In solubilization experiments, physophilin behaves as an integral membrane protein. Thus, a putative synaptic plasma membrane protein exhibits a specific interaction with one of the major membrane proteins of synaptic vesicles. This interaction may play a role in docking and/or fusion of synaptic vesicles to the presynaptic plasma membrane.

Animals↗
PubMed1990

Human fur gene encodes a yeast KEX2-like endoprotease that cleaves pro-beta-NGF in vivo.

Extracts from BSC-40 cells infected with vaccinia recombinants expressing either the yeast KEX2 prohormone endoprotease or a human structural homologue (fur gene product) contained an elevated level of a membrane-associated endoproteolytic activity that could cleave at pairs of basic amino acids (-LysArg- and -ArgArg-). The fur-directed activity (furin) shared many properties with Kex2p including activity at pH 7.3 and a requirement for calcium. By using antifurin antibodies, immunoblot analysis detected two furin translation products (90 and 96 kD), while immunofluorescence indicated localization to the Golgi apparatus. Coexpression of either Kex2p or furin with the mouse beta-nerve growth factor precursor (pro-beta-NGF) resulted in greatly enhanced conversion of the precursor to mature nerve growth factor. Thus, the sequence homology shared by furin and the yeast KEX2 prohormone processing enzyme is reflected by significant functional homology both in vitro and in vivo.

Amino Acid Sequence↗
PubMed1990

Cultured epithelia from junctional epidermolysis bullosa letalis keratinocytes express the main phenotypic characteristics of the disease.

Keratinocytes from a 1-week-old male infant with junctional epidermolysis bullosa letalis (JEBL) were grown in vitro and then grafted as multi-layered epithelia onto nude mice, to investigate whether the defect in the dermo-epidermal cohesiveness in the disease is of epidermal and not mesodermal origin. In culture, there was a birefringent ring of cells at the edges of the keratinocyte colonies and in places some cells looked as though they had been ejected from the periphery of the colony. At confluence, the multi-layered epithelia were easily detached from the culture flasks using only mechanical agitation. On microscopy the fully-differentiated epithelium on days 21, 30 and 40 after grafting sometimes showed blistering at the dermal-epidermal junction. No labelling was noted using a GB3 monoclonal antibody, that reacts with normal human keratinocytes in culture and with the dermo-epidermal basement membrane zone in normal skin. This indicates that the defect of JEBL may be reproduced in culture and also after grafting the cultured epithelial onto a wound without an epidermis. This suggests a possible role for the junctional structure recognized by GB3 in dermo-epidermal cohesiveness.

Animals↗