Structural features of the low-density lipoprotein receptor facilitating ligand binding and release

The LDLR (low-density lipoprotein receptor) is a modular protein built from several distinct structural units: LA (LDLR type-A), epidermal growth factor-like and β-propeller modules. The low pH X-ray structure of the LDLR revealed long-range intramolecular contacts between the propeller domain and the central LA repeats of the ligand-binding domain, suggesting that the receptor changes its overall shape from extended to closed, in response to pH. Here we discuss how the LDLR uses flexibility and rigidity of linkers between modules to facilitate ligand binding and low-pH ligand release.

Effects of Jaoga-Yukmiwon®, a Korean herbal medicine, on chondrocyte proliferation and longitudinal bone growth in adolescent male rats

Externally visible growth of the body is the result of proliferation of chondrocytes and longitudinal bone growth. The effects of the Korean herbal medicine, Jaoga-Yukmiwon((R)), on the growth of adolescent rats were investigated in the present study. The proliferation ratio of chondrocytes was calculated from 5-bromo-2'-deoxyuridine incorporation during DNA synthesis. The 5-bromo-2'-deoxyuridine incorporation ratio of the control group was 21.1 +/- 3.5%, and Jaoga-Yukmiwon((R)) administration markedly increased the ratio to 34.5 +/- 4.6% (p < 0.05). The bone formation rate of longitudinal bone was estimated by labelling with tetracycline, which binds to newly formed bone. The bone formation rate in the tibia of Jaoga-Yukmiwon((R))-administered rats was increased to 405.1 +/- 4.3 micro m (p < 0.05) from 292.2 +/- 11.8 micrometer (control value). The height of the growth plate in the administrated rats was increased to 614.6 +/- 10.0 micro m (p < 0.05) from 552.3 +/- 17.1 micro m. The bone morphogenetic protein-2 immunostaining in the growth plate was also increased. These results suggest that Jaoga-Yukmiwon((R)) may promote longitudinal bone growth during the developmental period.

A simple new formula to assess liver weight

INTRODUCTION

In cadaveric or segmental liver transplantation, accurate assessment of graft volume is desirable but not always easy to achieve based on donor morphometric data. We sought to establish a simple, reliable formula for accurate prediction of liver volume.

METHODS

Data from 1,413 cadaveric adult and pediatric liver donors were analyzed using simple and multiple regression analysis. Liver weight (LW) was plotted against age, height, body weight (BW), body surface area (BSA) or body mass index (BMI); a formula was developed using simple regression: LW (g) = 772 (g/m(2)) x BSA, r = 0.73, P <.01. For donors with BSA </=1.0, a pediatric factor (PF) of 1.0 was included, resulting in the formula: LW (g) = 772 (g/m(2)) x BSA - 38PF, r = 0.73, P <.01. We then applied our formula on 5 published formulae to estimate LW of our donors.

RESULTS

Among donors with BSA >1.0, there was no significant difference between the actual and the estimated mean LW as calculated by the new formula. For pediatric donors, there was no significant difference between estimated and actual mean liver weight with any formula. When the new formula was applied, the difference between the actual and the estimated liver weight was acceptable (<20%) in 1040 (73.6%) cases. In all races, there was no significant difference between actual and estimated mean liver weight as calculated by this formula.

CONCLUSIONS

A simple formula to calculate liver weight in donors with BSA >1.0 is: LW = 772 x BSA, and for donors with BSA </=1.0: Liver Weight = 772 x BSA - 38.

Suppressive effects of PG201, an ethanol extract from herbs, on collagen-induced arthritis in mice

OBJECTIVE

PG201 has been formulated using 12 herbs known to have anti-inflammatory and protective effects on damaged tissue and bone among other functions. The present study was done in order to assess the therapeutic effects of PG201 in collagen-induced arthritis (CIA) in mice.

METHODS

DBA/1 mice were immunized with bovine type II collagen. After a second collagen immunization, mice were treated with PG201 orally at 10 mg/kg once a day for 18 days. Paws were evaluated macroscopically for redness, swelling and deformities. The levels of TNF-alpha and IL-1beta in the ankle were examined. The severity of arthritis within the knee joints was evaluated by histological assessment of cartilage destruction and pannus formation. Molecular indicators related to CIA pathology were analysed by measuring the serum levels of matrix metalloproteinase 2 (MMP-2), tissue inhibitor of matrix metalloproteinase 2 (TIMP-2) and the anti-inflammatory cytokines interleukin (IL)-4 and IL-10.

RESULTS

Administration of PG201 significantly suppressed the progression of CIA and inhibited the production of TNF-alpha and IL-1beta in the paws. The erosion of cartilage was dramatically reduced in mouse knees after treatment with PG201. In the serum of PG201-treated mice, the level of TIMP-2 and the ratio of TIMP-2 to MMP-2 were significantly elevated, and the level of IL-4, but not of IL-10, was increased.

CONCLUSION

Administration of PG201 has therapeutic effects on CIA. Protection of cartilage was particularly prominent. PG201 is a potential therapy for rheumatoid arthritis.

Four patients with both thrombotic thrombocytopenic purpura and autoimmune thrombocytopenic purpura: the concept of a mixed immune thrombocytopenia syndrome and indications for plasma exchange

Autoimmune thrombocytopenic purpura (ATP) and thrombotic thrombocytopenic purpura (TTP) are each well recognized clinical syndromes which may appear as single episodes or may have chronic relapsing courses. We present four patients negative for human immunodeficiency virus (HIV) infection who appear to have both diagnoses with either concomitant or intermingled episodes, and we review seven additional patients reported in the literature with similar features. All four of our patients are female, two have underlying connective tissue disorders, and their ATP processes came to our attention because of incomplete response of the platelet count to plasma exchange therapy (PEX) during a TTP phase (Cases 1 and 2) or development of thrombocytopenia in the absence of microangiopathy on the background of prior typical TTP episodes (Cases 3 and 4). Recognition of the ATP diagnosis in each case resulted in discontinuation of PEX (Cases 1 and 2) or not instituting PEX (Cases 3 and 4). In each instance, a satisfactory rise in platelet count followed treatment for ATP. Based upon this experience, we conclude that some individuals may have a mixed immune thrombocytopenia syndrome; careful analysis of the mechanism of thrombocytopenia, especially in recurrent episodes and in patients who respond incompletely to PEX for TTP, is important when deciding whether to initiate or continue PEX, or to consider therapies appropriate for other mechanisms of thrombocytopenia.

Refractive sapphire microlenses fabricated by chlorine-based inductively coupled plasma etching

We have fabricated refractive sapphire microlenses and characterized their properties for what we believe to be the first time. We use thermally reflown photoresist lenslet patterns as a mask for chlorine-based dry etch of sapphire. Pattern transfer to the mechanically hard and chemically inert sapphire substrate is made possible by an inductively coupled plasma etch system that supplies a high-density plasma gas. Processed sapphire microlenses exhibit properties close to the ideal and operate nearly in the diffraction limit.

Implications for familial hypercholesterolemia from the structure of the LDL receptor YWTD-EGF domain pair

The low-density lipoprotein receptor (LDLR) is the primary mechanism for uptake of cholesterol-carrying particles into cells. The region of the LDLR implicated in receptor recycling and lipoprotein release at low pH contains a pair of calcium-binding EGF-like modules, followed by a series of six YWTD repeats and a third EGF-like module. The crystal structure at 1.5 A resolution of a receptor fragment spanning the YWTD repeats and its two flanking EGF modules reveals that the YWTD repeats form a six-bladed beta-propeller that packs tightly against the C-terminal EGF module, whereas the EGF module that precedes the propeller is disordered in the crystal. Numerous point mutations of the LDLR that result in the genetic disease familial hypercholesterolemia (FH) alter side chains that form conserved packing and hydrogen bonding interactions in the interior and between propeller blades. A second subset of FH mutations are located at the interface between the propeller and the C-terminal EGF module, suggesting a structural requirement for maintaining the integrity of the interdomain interface.

HLA-B*15 diversity in the Korean population

Alleles in the HLA-B*15 group encode molecules belonging to several serologic subgroups, B15 (B62, B63, B75, B76, B77) and B70 (B71, B72), representing many of the most problematic types to assign in routine clinical typing laboratories due to their serologic cross-reactivity resulting from structural similarity. More than 25% of Koreans express HLA-B molecules encoded by the HLA-B*15 alleles. To further characterize HLA-B*15 in this population, B*15-specific polymerase chain reaction (PCR) and sequence-specific oligonucleotide probe (SSOP) hybridization analysis using 39 digoxigenin-labeled probes were applied to DNA samples obtained from 237 B15/B70 serologically positive unrelated individuals. Nine B*15 alleles were identified. B*1501 was the most frequent allele (64.8%) followed by B*1511 (14.1%), B*1507 (8.6%), and B*1518 (5.5%) comprising more than 90% of B*15-positive samples. B62 molecules encoded by 4 of the identified alleles (B*1501, B*1507, B*1525, and B*1527) could not be discriminated by serologic reaction patterns. Among the fifteen B15/B70 apparent homozygotes, eight were heterozygotes carrying two different B*15 alleles. Several B*15 alleles exhibited strong associations with specific Cw, DRB1, and A allelic types (e.g., B*1507-Cw3 (22/22); B*1507-DRB1*04 (21/22), B*1507-A24 (17/22)). The data obtained in this study confirmed B*15 diversity in the study population and will be useful in hematopoietic stem cell donor searches as well as in determining the supplementary DNA typing strategy for B15/B70-positive samples in this population.

Regulation of cytokine production by exogenous nitric oxide in murine splenocyte and peritoneal macrophage

Nitric oxide (NO), products of activated macrophages, have a great impact on the regulation of cytokine production. The role of NO in non-specific host cells is commonly accepted. On the contrary, its role as an immuno-regulatory molecule is still controversial. In this study, we have investigated the effect of NO on the production of cytokines from murine splenocytes and macrophages. S-nitroso-L-glutathione inhibited the release of both interferone-gamma and interleukin-2 produced by Th1 cells and tumor necrosis factor-alpha and interleukin-1beta produced by macrophages, but did not affect the release of interleukin-4 and interleukin-10 produced by Th2 cells. These results suggest that NO exerts a down-regulatory effect on the secretion of cytokines from Th1 cells and macrophages which are implicated in immune response. Thus, NO may have an important role as an immuno-modulatory as well as effector molecule in the immune system.

Localization of the N-terminal domain of the low density lipoprotein receptor

The low density lipoprotein (LDL) receptor is a transmembrane glycoprotein performing "receptor-mediated endocytosis" of cholesterol-rich lipoproteins. At the N terminus, the LDL receptor has modular cysteine-rich repeats in both the ligand binding domain and the epidermal growth factor (EGF) precursor homology domain. Each repeat contains six disulfide-bonded cysteine residues, and this structural motif has also been found in many other proteins. The bovine LDL receptor has been purified and reconstituted into egg yolk phosphatidylcholine vesicle bilayers. Using gel electrophoresis and cryoelectron microscopy (cryoEM), the ability of the reconstituted LDL receptor to bind its ligand LDL has been demonstrated. After reduction of the disulfide-bonds in the N-terminal domain of the receptor, the reduced LDL receptor was visualized using cryoEM; reduced LDL receptors showed images with a diffuse density region at the distal end of the extracellular domain. Gold labeling of the reduced cysteine residues was achieved with monomaleimido-Nanogold, and the bound Nanogold was visualized in cryoEM images of the reduced, gold-labeled receptor. Multiple gold particles were observed in the diffuse density region at the distal end of the receptor. Thus, the location of the ligand binding domain of the LDL receptor has been determined, and a model is suggested for the arrangement of the seven cysteine-rich repeats of the ligand binding domain and two EGF-like cysteine-rich repeats of the EGF precursor homology domain.

Vesicle-reconstituted low density lipoprotein receptor. Visualization by cryoelectron microscopy

The low density lipoprotein (LDL) receptor is a key protein for maintaining cellular cholesterol homeostasis by binding cholesterol-rich lipoproteins through their apoB and apoE apoproteins. The LDL receptor is a transmembrane glycoprotein of M(r) approximately 115 kDa; based on its primary sequence, five distinct structural domains have been identified (Yamamoto, T., Davis, C. G., Brown, M. S., Schneider, W. J., Casey, M. L., Goldstein, J. L., and Russell, D. W. (1984) Cell 39, 27-38). As a first step toward providing a structural description of the intact LDL receptor, the receptor has been purified from bovine adrenal cortices, reconstituted into unilamellar egg yolk phosphatidylcholine vesicles, and imaged using cryoelectron microscopy (cryoEM). CryoEM has the advantage of providing images of the reconstituted LDL receptor in its frozen, fully hydrated state. LDL receptor molecules were visualized as elongated, stick-like projections from the vesicle surface with maximum dimensions approximately 120-A length by approximately 45-A width. In some of the images, a short arm (or arms) was visible at the distal end of the stick-like projections. The LDL receptor was labeled via accessible free cysteine residues, probably including that corresponding to Cys-431 of the known full-length sequence of the human LDL receptor. The accessible cysteine was demonstrated using a maleimide-biotin.streptavidin conjugate and confirmed by labeling with monomaleimido-Nanogold. Images obtained by cryoEM showed that the extracellular stick-like domain of the reconstituted LDL receptor was labeled by Nanogold. This combined cryoEM-Nanogold labeling study has provided the first low resolution structural images of the reconstituted, full-length bovine LDL receptor.

Significant ABO hemolytic disease of the newborn in a group B infant with a group A2 mother

ABO hemolytic disease of the newborn (HDN) occurs almost exclusively in infants of blood group A or B who are born to group O mothers because IgG anti-A or -B occurs more commonly in group O than in group A or B individuals. We report a case in which clinically significant ABO-HDN occurred in a group B neonate from anti-B of a group A2 mother. The IgG anti-B titer was much higher (256) than that found in a group A1 mother/infant control group (</= 32). The maternal antibody screen was negative and antibodies to low-frequency antigens were not detected. Therefore, when evaluating unexplained HDN in a group B newborn of a group A mother, it may be relevant to determine the subgroup of the mother. As presented here, anti-B from a group A2 mother may, on occasion, be responsible for HDN.

Home telecare system integrated with periodic health reminder and medical record & multimedia health information

The necessity of home telecare system is growing due to increase in desire for health promotion owing to increase in chronic diseases, aged population and medical expenses. Already, we computerized patient's data and offer periodic health reminder to patients for health promotion by using Life-time Health Monitoring Program (LHMP). Our study connected LHMP to the Web on internet by CGI as an electronic medical record; enabling reference to patient's medical records anywhere. The study also made possible video teleconsultation and constructed multimedia database to provide health-related information to the patients. On these bases, a flow chart was developed using the home telecare to practice manage patients with chronic diseases, old patients, and the handicapped. Further standardization in data, establishment of law bases for home telecare system, development of rules for medical fees and active utilization of biomedical telemetry will be needed to extend home telecare system.

Information system for a periodic examination and health promotion center

The periodic examination and health promotion center (PEHPC) in Seoul National University Hospital has developed and adopted an information system supported by computers which use an electronic medical record to improve the quality of patient care, advance the science of medicine, lower health care costs, and enhance the education of health care professionals. This information system adopted the concept of incomplete and evolutionary systems to conduct the pursuit of practicalness and efficacy. It has increased efficiency to save costs and to enhance the quality of the medical service. It has also activated clinical research due to ease of managing data. We are also preparing for telecare. Telecare and WWW-using information system is postponed because the protection of a patients privacy is not established.

Pericytes from microvessel fragment produce type IV collagen and multiple laminin isoforms

In the microvascular system, pericytes are located at the abdominal side of capillary endothelial cells. To discover the role of pericytes in the microvascular system, we have analyzed the extracellular proteins secreted from pericytes isolated from microvessel fragments of rat epididymal fat pads and found that they synthesize substantial amounts of basement membrane components such as type IV collagen and laminins. Secretion of type IV collagen was markedly stimulated by ascorbic acid phosphate. Reducing and nonreducing sodium dodecyl sulfate gel electrophoresis showed that pericytes produce six laminin chains assembled into different trimeric isoforms. Two of them were similar to laminin variants produced by aortic and pulmonal endothelial cells but others were suggested to be novel variants.

Regulated expression of an osteonectin variant in bovine aortic endothelial cells

Using a mouse SPARC (Secreted Protein, Acidic and Rich in Cysteine) cDNA clone as the probe, three clones were isolated from a cDNA library of bovine aortic endothelial cells (BAEC). Inserted sequences in them were identical with that of bovine bone osteonectin except for the deletion of the TGC codon encoding Cys-193. Northern blot analysis and metabolic radio-labeling of BAEC showed that gene expression and synthesis of the osteonectin variant is stimulated by transforming growth factor (TGF) beta, a basic fibroblast growth factor (FGF), or a naturally occurring splicing variant of hepatocyte growth factor (varHGF).

Pulsed room-temperature operation of a blue-green ZnSe quantum-well diode laser

Low-threshold current density operation has been obtained from (Zn, Cd)Se/Zn(S, Se) quantum-well diode lasers in the blue-green spectrum. The devices, with reflective facet coatings, have been operated at room temperature under pulsed conditions with threshold current densities of I(th) approximately 1 kA/cm(2).