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Biomedical subjects

R E Lee

Publications and source records attributed to R E Lee.

At least 73 records · Page 4Linked to original sources
PubMed1996

Gaucher disease: studies of phenotype, molecular diagnosis and treatment.

This report summarizes the results on 39 patients with Gaucher disease who have been genotyped, evaluated, and/or followed at this center. Mutation analysis for 4 common mutations; N370S, L444P, 84gg and IVS2 (+1), was performed for all patients. Mutation analysis identified both mutant alleles in 69% and at least one mutant allele in 90% of all chromosomes. This study group of 39 patients included 32 type 1, four type 2 and three type 3 patients. We include the details of the clinical course of two patients with Gaucher disease treated with enzyme replacement therapy (ERT). One patient with chronic neuronopathic Gaucher disease has been treated with enzyme replacement therapy (ERT) at a dose of 60 U/kg every 2 weeks since 2.5 years of age and has shown no progression of neurologic involvement. A second patient with non-neuronopathic Gaucher disease has demonstrated an unusually delayed response to ERT. No clinical response was noted following 17 months of treatment at 60 U/kg every 2 weeks. Only after the dose was increased to 60 U/kg every week was a clinical response evident. Response to treatment at 15 U/kg every 2 weeks was variable in the four type 1 patients treated at the lower dose. In two of these patients with identical genotypes, one patient demonstrated a positive clinical response to low dose treatment while the other patient did not.

Adolescent↗
PubMed1996

Antimycobacterial action of thiolactomycin: an inhibitor of fatty acid and mycolic acid synthesis.

Thiolactomycin (TLM) possesses in vivo antimycobacterial activity against the saprophytic strain Mycobacterium smegmatis mc2155 and the virulent strain M. tuberculosis Erdman, resulting in complete inhibition of growth on solid media at 75 and 25 micrograms/ml, respectively. Use of an in vitro murine macrophage model also demonstrated the killing of viable intracellular M. tuberculosis in a dose-dependent manner. Through the use of in vivo [1,2-14C]acetate labeling of M. smegmatis, TLM was shown to inhibit the synthesis of both fatty acids and mycolic acids. However, synthesis of the shorter-chain alpha'-mycolates of M. smegmatis was not inhibited by TLM, whereas synthesis of the characteristic longer-chain alpha-mycolates and epoxymycolates was almost completely inhibited at 75 micrograms/ml. The use of M. smegmatis cell extracts demonstrated that TLM specifically inhibited the mycobacterial acyl carrier protein-dependent type II fatty acid synthase (FAS-II) but not the multifunctional type I fatty acid synthase (FAS-I). In addition, selective inhibition of long-chain mycolate synthesis by TLM was demonstrated in a dose-response manner in purified, cell wall-containing extracts of M. smegmatis cells. The in vivo and in vitro data and knowledge of the mechanism of TLM resistance in Escherichia coli suggest that two distinct TLM targets exist in mycobacteria, the beta-ketoacyl-acyl carrier protein synthases involved in FAS-II and the elongation steps leading to the synthesis of the alpha-mycolates and oxygenated mycolates. The efficacy of TLM against M. smegmatis and M. tuberculosis provides the prospects of identifying fatty acid and mycolic acid biosynthetic genes and revealing a novel range of chemotherapeutic agents directed against M. tuberculosis.

Anti-Bacterial Agents↗
PubMed1996

Epidermal abnormalities may distinguish type 2 from type 1 and type 3 of Gaucher disease.

A major clinical challenge in Gaucher disease is the early and presymptomatic discrimination of type 2 (acute neuronopathic) from milder type 1 and type 3 Gaucher patients to enable appropriate management and counseling. Although most patients with Gaucher disease do not have skin abnormalities, a subset of patients with severe type 2 Gaucher disease display ichthyosiform skin. Analogous findings occur in the skin of type 2 (null allele) Gaucher mice. Ultrastructural and functional studies of epidermis from these mice reveal that glucocerebrosidase is required to generate functionally competent membranes for normal epidermal barrier function. We have extended our studies by examining the epidermal lipid content and ultrastructure in all three types of Gaucher patients. Only the type 2 Gaucher patients, some of whom had clinical ichthyosis, demonstrated an increased ratio of epidermal glucosylceramide to ceramide as well as extensive ultrastructural abnormalities, including the persistence of incompletely processed lamellar body-derived contents throughout the stratum corneum interstices. These epidermal alterations may provide a means for early differentiation of type 2 Gaucher disease.

Animals↗
PubMed1996

FIRO-B scores and success in a positive peer-culture residential treatment program.

FIRO-B Wanted Inclusion, Wanted Affection, and Total scores discriminated between 28 adolescent boys who would be successful graduates of a positive peer-culture residential program and 29 who would not. Successful graduates had higher mean scores on these scales. Successful and unsuccessful residents did not differ in scores on Exner Rorschach Experience Balance, Experienced Stimulation, or Adjusted D. Likewise they did not differ in Verbal IQ or age. Openness to social relationships may be an important variable in assessing for whom group-based treatment will work. Where the capacity for relatedness is not present, staff in a group-based program may have to recognize and treat this if the program is to succeed.

Adolescent↗
PubMed1996

Ethacrynic acid disrupts steady state microtubules in vitro.

PURPOSE: Ethacrynic acid (ECA) has been shown to increase facility of aqueous outflow in whole eyes and perfused anterior segments, to open up spaces between cells in the trabecular meshwork and inner wall of Schlemm's canal, and to cause separation and retraction of trabecular meshwork and endothelial cells in culture. One mechanism by which ECA has been proposed to act in cells is via disruption of microtubules, leading to cell retraction. Although it is known that ECA can inhibit de novo assembly of microtubules from tubulin subunits in vitro, we wanted to determine, as a better correlate to the proposed effect of ECA in cells, whether ECA could disrupt microtubule polymers that had reached steady state. We also wanted to determine whether calcium ion could enhance this process. METHODS: We therefore assembled purified and crude porcine brain tubulin to steady state at 37 degrees C and then added ECA and/or calcium. Reaction kinetics were followed spectrophotometrically. RESULTS: We found that ECA effectively disrupted assembled microtubules in vitro. Although 0.8-1.0 mM ECA was required to produce a half-maximal effect in pure tubulin microtubules and 0.2-0.3 mM ECA was necessary with crude microtubule protein, significant disassembly also occurred in the 0.01-0.2 mM range. Calcium had a greater maximal effect than ECA, and was more potent on a molar basis, showing half maximal effect between 2 and 12 microM free calcium ion. Combination experiments showed that ECA did not act synergistically with calcium to increase microtubule disassembly. CONCLUSIONS: Our results are consistent with the proposed disruptive action of ECA on the assembled microtubules of outflow pathway cells, but do not support a rise in intracellular calcium as being an added factor.

Animals↗
PubMed1995

Identification of a gene involved in the biosynthesis of cyclopropanated mycolic acids in Mycobacterium tuberculosis.

Mycolic acids represent a major constituent of the mycobacterial cell wall complex, which provides the first line of defense against potentially lethal environmental conditions. Slow-growing pathogenic mycobacteria such as Mycobacterium tuberculosis modify their mycolic acids by cyclopropanation, whereas fast-growing saprophytic species such as Mycobacterium smegmatis do not, suggesting that this modification may be associated with an increase in oxidative stress experienced by the slow-growing species. We have demonstrated the transformation of the distal cis double bond in the major mycolic acid of M. smegmatis to a cis-cyclopropane ring upon introduction of cosmid DNA from M. tuberculosis. This activity was localized to a single gene (cma1) encoding a protein that was 34% identical to the cyclopropane fatty acid synthase from Escherichia coli. Adjacent regions of the DNA sequence encode open reading frames that display homology to other fatty acid biosynthetic enzymes, indicating that some of the genes required for mycolic acid biosynthesis may be clustered in this region. M. smegmatis overexpressing the cma1 gene product significantly resist killing by hydrogen peroxide, suggesting that this modification may be an important adaptation of slow-growing mycobacteria to oxidative stress.

Amino Acid Sequence↗
PubMed1995

Isolation of ice-nucleating active bacteria from the freeze-tolerant frog, Rana sylvatica.

Ice-nucleating active (INA) bacteria were isolated from the gut of field-collected freeze-tolerant wood frogs (Rana sylvatica) collected in winter. Thirteen strains of Pseudomonas fluorescens, four strains of Pseudomonas putida, and two strains of Enterobacter agglomerans had ice-nucleating activity. Each of the INA pseudomonad strains was psychrophilic. P. putida strains were differentiated from P. fluorescens strains by gelatinase, lecithinase, and lipase production. The maximum nucleation temperatures (Tmax) of aqueous suspensions (10(9) bacteria/ml) of the four INA P. putida strains ranged from -1.6 to -3.0 degrees C, which places this INA species among the most potent known biological nucleators. Ingestion of INA P. putida isolated from R. sylvatica by another freeze-tolerant frog. Pseudacris crucifer, decreased the capacity of this frog to supercool and remain unfrozen at -2 degrees C. This is the first report of INA bacteria isolated from a vertebrate, and suggests that, as part of the gut flora in some posthibernation freeze-tolerant wood frogs, these bacteria may play a role in enhancing winter survival by promoting ice nucleation at high subzero temperatures (ca. -2 degrees C).

Animals↗
PubMed1995

Supercooling, ice inoculation and freeze tolerance in the European common lizard, Lacerta vivipara.

The European common lizard (Lacerta vivipara) is widely distributed throughout Eurasia and is one of the few Palaearctic reptiles occurring above the Arctic Circle. We investigated the cold-hardiness of L. vivipara from France which routinely encounter sub-zero temperatures within their shallow hibernation burrows. In the laboratory, cold-acclimated lizards exposed to subfreezing temperatures as low as -3.5 degrees C could remain unfrozen (supercooled) for at least 3 weeks so long as their microenvironment was dry. In contrast, specimens cooled in contact with ambient ice crystals began to freeze within several hours. However, such susceptibility to inoculative freezing was not necessarily deleterious since L. vivipara readily tolerated the freezing of its tissues, with body surface temperatures as low as -3.0 degrees C during trials lasting up to 3 days. Freezing survival was promoted by relatively low post-nucleation cooling rates (< or = 0.1 degrees C.h-1) and apparently was associated with an accumulation of the putative cryoprotectant, glucose. The cold-hardiness strategy of L. vivipara may depend on both supercooling and freeze tolerance capacities, since this combination would afford the greatest likelihood of surviving winter in its dynamic thermal and hydric microenvironment.

Adaptation, Physiological↗
PubMed1995

Osteogenic sarcoma of the neural arch.

Osteogenic sarcoma arising in the spine, and in particular the neural arch, is rare. We present the case of a 4-year-old girl with an osteogenic sarcoma arising in the left transverse process of the second lumbar vertebra. The child received chemotherapy and delayed surgical excision was performed following a favourable response. The radiological features and differential diagnosis are discussed.

Child, Preschool↗
PubMed1995

Survival mechanisms of vertebrate ectotherms at subfreezing temperatures: applications in cryomedicine.

Various marine fishes, amphibians, and reptiles survive at temperatures several degrees below the freezing point of their body fluids by virtue of adaptive mechanisms that promote freeze avoidance or freeze tolerance. Freezing is avoided by a colligative depression of the blood freezing point, supercooling of the body fluids, or the biosynthesis of unique antifreeze proteins that inhibit the propagation of ice within body fluids. Conversely, freeze tolerance is an adaptation for the survival of tissue freezing under ecologically relevant thermal and temporal conditions that is conferred by the biosynthesis of permeating carbohydrate cryoprotectants and an extensive dehydration of tissues and organs. Such cryoprotective responses, invoked by the onset of freezing, mitigate the osmotic stress associated with freeze-concentration of cytoplasm, attendant metabolic perturbations, and physical damage. Cryomedical research has historically relied on mammalian models for experimentation even though endotherms do not naturally experience subfreezing temperatures. Some vertebrate ectotherms have "solved" not only the problem of freezing individual tissues and organs, but also that of simultaneously freezing all organ systems. An emerging paradigm in cryomedicine is the application of principles governing natural cold hardiness to the development of protocols for the cryopreservation of mammalian tissues and organs.

Adaptation, Physiological↗
PubMed1995

Antifreeze glycoproteins promote intracellular freezing of rat cardiomyocytes at high subzero temperatures.

Despite recent reports that antifreeze glycoproteins (AFGPs) protect mammalian cells during low-temperature preservation, T. Wang, Q. Zhu, X. Yang, J. R. Layne, and A. L. DeVries (Cryobiology 31: 185-192, 1994) reported that AFGPs failed to protect rat hearts during freezing. Rather, the presence of AFGPs exacerbated cardiac damage after freezing. This study examined the effects of freezing (-4 degrees C) in the presence of AFGPs at the cellular level with the use of cryomicroscopy. Large, blunt ice crystals formed in the solutions without AFGPs and excluded most cardiomyocytes from the plane of ice formation. After thawing, cells appeared similar in morphology to unfrozen cells. Ice in 0.5 mg/ml AFGP solution was more dendritic and prismatic than ice formed in the absence of AFGPs. On thawing, many cells exhibited spontaneous contraction, resulting in cell death. Spicular ice formed rapidly in the 10 mg/ml AFGP solution. These needlelike ice crystals appeared to penetrate the cardiomyocytes, resulting in intracellular freezing followed by cell lysis. These AFGP-induced changes in ice crystal structure may account for the injury observed in whole heart and cardiomyocyte experiments.

Animals↗
PubMed1995

How reliable are ultrasound measurements of renal length in adults?

Ultrasound assessment of patients with renal impairment commonly includes measurement of bipolar renal length. Reduction in length is considered to indicate chronic renal disease and is a factor in deciding whether to proceed to renal biopsy. To date, no published data are available on interobserver and intraobserver variation in sonographic renal length measurement in adults. Bilateral renal lengths were measured in 20 adult subjects, with no history of renal disease, by three experienced operators, on two separate occasions. Limits of agreement for replicate measurements by each ultrasonographer and for replicate measurements by each pair of ultrasonographers were determined. Values of repeatability (a measure of intraobserver variation) and reproducibility (a measure of interobserver variation) were calculated for all renal length measurements, and for right and left renal lengths separately. Results indicate that replicate renal length measurements differ by less than 1.85 cm in 95% of cases, and the magnitude of variations is similar when measurements are made by either single or different ultrasonographers, and are similar for right and left renal length measurements. This suggests that sonographic bipolar renal length measurements in normal adult kidneys are reasonably reliable. In diseased kidneys, however, in which identification of renal poles is difficult, interobserver and intraobserver variation may be much greater.

Adult↗
PubMed1994

Identification of the apparent carrier in mycolic acid synthesis.

The mycolic acids are large (C70-90) alpha-alkyl, beta-hydroxy fatty acids and are the major determinants of the mycobacterial cell wall's impermeable barrier. The biosynthesis of mycolic acids is barely understood (they are probably the products of specialized elongation and Claisen-type condensation), and yet their synthesis is the site of action of several mainline antituberculosis drugs. We describe the isolation from Mycobacterium smegmatis and the full characterization of a 6-O-mycolyl-beta-D-mannopyranosyl-1-monophosphoryl-3,7,11,15,19,23 ,27- heptamethyl-(2Z,6E,10E)-octacosatrien-1-ol . The identification of a mycolyl-mannosylphosphopolyprenol supported by cell-free labeling experiments and earlier literature suggests unusual biochemical pathways in which mature mycolic acids are formed from beta-oxo precursors while attached to a mannosyl-P-polyprenol, in which form they are transported through the membrane prior to final deposition as arabinan-bound mycolates.

Chromatography, Thin Layer↗
PubMed1994

Post-freeze recovery of peripheral nerve function in the freeze-tolerant wood frog, Rana sylvatica.

We investigated the restoration in peripheral nerve function and simple neurobehavioral reflexes in the freeze-tolerant wood frog (Rana sylvatica). Thirty-two specimens, allowed to freeze for 39 h and ultimately cooled to -2.2 degrees C, were sampled at various time intervals up to 60 h after thawing at 5 degrees C was initiated. The sciatic nerves of treated frogs were initially unresponsive to stimulation, but usually regained excitability within 5 h. Except for a slight reduction in nerve excitability, characteristics of the compound action potentials of treated frogs were indistinguishable from those of control frogs. Recovery times for the hindlimb retraction and righting reflexes were 8 h and 14 h, respectively. Concentrations of the cryoprotectant glucose increased 8.2-fold in the sciatic nerve and 10.5-fold in the underlying semimembranosis muscle of treated frogs, and remained elevated for at least 60 h after thawing was initiated. These organs lost 47.2% and 15.9%, respectively, of their water during freezing, but were rehydrated within 2 h of the onset of thawing. The accumulation of glucose and the withdrawal of tissue water apparently are cryoprotective responses which enable this species to survive freezing.

Action Potentials↗
PubMed1994

Measurement of internal carotid artery stenosis from source MR angiograms.

PURPOSE: To determine whether interpretation of internal carotid artery (ICA) stenosis from source partitions is more accurate than interpretation from maximum-intensity projections (MIPs) from three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography. MATERIALS AND METHODS: The percentage of diameter ICA stenosis was measured on source images and MIPs from sagittal (n = 150) and transverse (n = 140) 3D TOF MR angiography. Measurements were compared with those from conventional angiography. RESULTS: Sensitivity and specificity for distinguishing 70%-99% stenosis were 96% and 78%, respectively, for sagittal MIPs, 88% and 90% for sagittal source images, 92% and 86% for transverse MIPs, and 92% and 95% for transverse source images. Areas under the receiver operating characteristic curves statistically significantly increased (P < .05) with interpretation from source images. Complete loss of intravascular signal was not encountered on source partitions except within a greater than 85% stenosis. CONCLUSION: Interpretation of source partitions rather than MIPs reduces the tendency for overestimation of stenosis with MR angiography and improves the specificity for discriminating 70%-99% stenosis.

Aged↗