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Biomedical subjects

B Lee

Publications and source records attributed to B Lee.

At least 19 recordsLinked to original sources
PubMed2025

HLA-E and NKG2A Mediate Resistance to BCG Immunotherapy in Non-Muscle-Invasive Bladder Cancer.

Bacillus Calmette-Guérin (BCG) is the first-line therapy for high-grade non-muscle-invasive bladder cancer (NMIBC), yet many patients experience recurrence due to immune evasion. We identify HLA-E and NKG2A as mediators of adaptive resistance involving chronic activation of NK and T cells in BCG-unresponsive tumors. Prolonged IFN-γ exposure enhances HLA-E and PD-L1 expression on recurrent tumors, accompanied by the accumulation of NKG2A+ NK and CD8 T cells. HLA-Ehigh tumor cells preferentially cluster near CXCL12-rich stromal regions with dense effector cell presence, underscoring a spatially segregated tumor architecture. Although cytotoxic lymphocytes retain effector potential, their activity is restrained by HLA-E/NKG2A and PD-L1/PD-1 pathways located in their immediate neighborhood within the bladder tumor microenvironment. These data reveal a spatially organized immune escape program that limits anti-tumor immunity. Our findings support dually targeting NKG2A and PD-L1 checkpoint blockade as a rational, bladder-sparing strategy for patients with BCG-unresponsive NMIBC.

BCG-unresponsive↗
PubMed1992

Aggregation of IgE-receptor complexes on rat basophilic leukemia cells does not change the intrinsic affinity but can alter the kinetics of the ligand-IgE interaction.

The aggregation of IgE anchored to high-affinity Fc epsilon receptors on rat basophilic leukemia (RBL) cells by multivalent antigens initiates transmembrane signaling and ultimately cellular degranulation. Previous studies have shown that the rate of dissociation of bivalent and multivalent DNP ligands from RBL cells sensitized with anti-DNP IgE decreases with increasing ligand incubation times. One mechanism proposed for this effect is that when IgE molecules are aggregated, a conformational change occurs that results in an increase in the intrinsic affinity of IgE for antigen. This possibility was tested by measuring the equilibrium constant for the binding of monovalent DNP-lysine to anti-DNP IgE under two conditions, where the cell-bound IgE is dispersed and where it has been aggregated into visible patches on the cell surface using anti-IgE and a secondary antibody. No difference in the equilibrium constant in these two cases was observed. We also measured the rate of dissociation of a monovalent ligand from cell surface IgE under these two conditions. Whereas the affinity for monovalent ligand is not altered by IgE aggregation, we observe that the rate of ligand dissociation from IgE in clusters is slower than the rate of ligand dissociation from unaggregated IgE. These results are discussed in terms of recent theoretical developments concerning effects of receptor density on ligand binding to cell surfaces.

Animals↗
PubMed1992

Characterization of a type II collagen gene (COL2A1) mutation identified in cultured chondrocytes from human hypochondrogenesis.

A subtle mutation in the type II collagen gene COL2A1 was detected in a case of human hypochondrogenesis by using a chondrocyte culture system and PCR-cDNA scanning analysis. Chondrocytes obtained from cartilage biopsies were dedifferentiated and expanded in monolayer culture and then redifferentiated by culture over agarose. Single-strand conformation polymorphism and direct sequencing analysis identified a G----A transition, resulting in a glycine substitution at amino acid 574 of the pro alpha 1(II) collagen triple-helical domain. Morphologic assessment of cartilage-like structures produced in culture and electrophoretic analysis of collagens synthesized by the cultured chondrocytes suggested that the glycine substitution interferes with conversion of type II procollagen to collagen, impairs intracellular transport and secretion of the molecule, and disrupts collagen fibril assembly. This experimental approach has broad implications for the investigation of human chondrodysplasias as well as human chondrocyte biology.

Alleles↗
PubMed1992

Genetic linkage of the Marfan syndrome, ectopia lentis, and congenital contractural arachnodactyly to the fibrillin genes on chromosomes 15 and 5. The International Marfan Syndrome Collaborative Study.

BACKGROUND: The large glycoprotein fibrillin is a structural component of elastin-containing microfibrils found in many tissues. The Marfan syndrome has been linked to the fibrillin gene on chromosome 15, but congenital contractural arachnodactyly, which shares some of the physical features of the syndrome, has been linked to the fibrillin gene on chromosome 5. METHODS: Using specific markers for the fibrillin genes, we performed genetic linkage analysis in 28 families with the Marfan syndrome and 8 families with four phenotypically related disorders--congenital contractural arachnodactyly (3 families), ectopia lentis (2), mitral-valve prolapse syndrome (2), and annuloaortic ectasia (1). RESULTS: Genetic linkage was established between the Marfan syndrome and only the fibrillin gene on chromosome 15, with a maximum lod score of 25.6 (odds for linkage, 10(25.6):1). Ectopia lentis was also linked to the fibrillin gene on chromosome 15, whereas congenital contractural arachnodactyly was linked to the fibrillin gene on chromosome 5. There was no linkage of mitral-valve prolapse to the fibrillin gene on chromosome 5; studies of chromosome 15 were not informative. Annuloaortic ectasia was not linked to either fibrillin gene. CONCLUSIONS: The Marfan syndrome appears to be caused by mutations in a single fibrillin gene on chromosome 15. Diagnosis of the Marfan syndrome by genetic linkage and analysis is now feasible in many families.

Base Sequence↗
PubMed1992

Quantitative measurement of small through-hydrogen-bond and 'through-space' 1H-113Cd and 1H-199Hg J couplings in metal-substituted rubredoxin from Pyrococcus furiosus.

A method is described for measurement of small unresolvable heteronuclear J couplings. The method is based on quantitative analysis of a phase-purged heteronuclear spin-echo difference spectrum, and is demonstrated for measuring 1H-113Cd and 1H-199Hg J couplings in metal-substituted rubredoxin (M(r) approximately 5.4 kDa) from Pyrococcus furiosus. Couplings from cadmium to backbone amide protons that are hydrogen bonded to the Cys-S atoms directly bonded to Cd vary from smaller than 0.3 to 1.8 Hz; a 'through-space' coupling between Cd and the protons of an alanine methyl group was measured to be 0.3 Hz. Couplings to 199Hg are significantly larger and fall in the 0.4-4 Hz range.

Amino Acid Sequence↗
PubMed1992

Anti-CD4 monoclonal antibody therapy suppresses autoimmune disease in MRL/Mp-lpr/lpr mice.

MRL/Mp-lpr/lpr (MRL/lpr) mice spontaneously develop systemic autoimmune disease, characterized by vasculitis, lymphadenopathy, glomerulonephritis, and autoantibody formation. The target organ inflammatory lesions are composed largely of CD4+ "helper" T cells, while the massively enlarged lymph nodes are composed primarily of CD3+ CD4- CD8- TCR alpha/beta + "double-negative" T cells. In this study we investigated the effect of treatment of MRL/lpr mice with anti-CD4 monoclonal antibody (mAb); control groups consisted of animals treated with normal saline or rat immunoglobulin (Ig). Anti-CD4 mAb treatment, which was started at 4 weeks and continued through 20 weeks of age, resulted in a dramatic reduction of both the frequency and severity of the autoimmune disease, as demonstrated histologically and serologically. Anti-CD4 mAb therapy markedly reduced the frequency of glomerulonephritis and eliminated vasculitis of the major renal arterial branches. Glomerulonephritis was detected in 9 of 9 saline-treated, 9 of 9 rat Ig-treated, but in only 1 of 9 anti-CD4 mAb-treated mice; vasculitis was detected in 6 of 9 saline-treated, 7 of 9 rat Ig-treated, but in none of 9 anti-CD4 mAb-treated mice. The frequency of antinuclear antibodies, titer of anti-dsDNA antibodies, and total Ig levels were all significantly reduced by anti-CD4 mAb therapy. These data support the hypothesis that CD4+ T cells play a central role in the disease process in this autoimmune strain.

Animals↗
PubMed1992

Characterization of the human HOX 7 cDNA and identification of polymorphic markers.

cDNA clones for a human HOX 7 gene obtained with homologous clones of Drosophila were used in human gene mapping studies. The human cDNA clone was isolated from a library constructed from human embryonic craniofacial material. The sequence of the cDNA demonstrates significant homology with mouse HOX 7. A search for RFLPs identified MboII and BstEII variants. A CA dinucleotide repeat with 5 alleles was also identified and allowed placement of HOX 7 into a defined linkage map. Evidence for linkage disequilibrium was found with markers tested. These results place the human HOX 7 gene in a defined position on 4p.

Amino Acid Sequence↗
PubMed1992

Feasibility of an implantable arrhythmia monitor.

Conventional Holter monitoring is of limited benefit in patients with infrequent symptoms suspected to be related to arrhythmia. A small recorder implanted subcutaneously might obviate many limitations of conventional monitoring. To determine the feasibility of obtaining adequate electrocardiographic signals from such a device, a prototype was temporarily implanted in 17 patients undergoing pacemaker implantation. The prototype contained four disc-shaped titanium electrodes, 0.21 inches in diameter embedded in epoxy. The four electrodes were in a square configuration spaced 0.72 inches center to center and were placed face down in a subcutaneous pocket in the left pectoral region. Bipolar recordings were made from a horizontal pair, a vertical pair, and both diagonal paris of electrodes (interelectrode distance 1.02 inches) and recorded on electromagnetic tape after filtering at 0.5-250 Hz. The mean peak-to-peak amplitude in each configuration was determined over a five-beat interval. Clear recordings were obtained from all 17 patients with recognizable P, QRS, and T waves. The amplitude of the signals obtained from the diagonal pairs of electrodes (175 +/- 51 and 170 +/- 54 microV) were greater than obtained from either the vertical pair (142 +/- 62 microV, P = 0.08 compared to diagonal electrodes) or the horizontal pair of electrodes (105 +/- 54 microV, P < 0.01). The maximum amplitude recorded from any configuration was 189 +/- 54 microV. In six patients the device was also tested with the electrodes face up in the subcutaneous pocket.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Clinical and genetic associations in Marfan syndrome and related disorders.

Although Marfan syndrome has been a recognized clinical entity for nearly a century, only in the early 1950s were its manifestations and genetic features firmly and fully established. Similarly, although the identification of the basic defect in Marfan syndrome had been vigorously pursued for several decades, it was only in 1991 that two independent reports implicated fibrillin as the defective gene product. Surprisingly and serendipitously, these studies also revealed genetic heterogeneity of the fibrillin proteins and established linkage between one of these loci and a Marfan-related disorder, congenital contractural arachnodactyly. Like Marfan syndrome, this condition is accompanied by skeletal abnormalities; however, flexion joint contractures replace the loose-jointedness of Marfan syndrome and, more importantly, neither the eye nor the aorta are affected. More recently, a similar association with the fibrillin gene has also been established in the dominantly inherited form of ectopia lentis. These associations of structurally related gene products with Marfan and related syndromes may conceivably imply that other connective tissue disorders are caused by mutations in these or other yet undiscovered fibrillin genes.

Fibrillins↗
PubMed1992

Femoral pseudoaneurysm from drugs of abuse: ligation or reconstruction?

A plan for management of infected arterial pseudoaneurysm has evolved from our experience with 23 such aneurysms treated between 1981 and 1989 and followed for up to 66 months. Eighteen femoral artery aneurysms are the primary focus of this report. Because we were concerned about the high probability of amputation expected from acute interruption of the femoral artery, we were reluctant to limit initial management to ligation and debridement alone. However, significant complications developed in 12 patients who underwent revascularization, requiring 3 amputations and 13 secondary arterial operations in addition to debridements and skin grafts. In contrast, no amputations were required in six patients who underwent primary arterial ligation and debridement. We recommend primary ligation that controls the septic focus, removes the danger of hemorrhage, and is not accompanied by the threat of secondary arterial infection. After ligation, limb viability is assessed during surgery by presence of an audible Doppler signal at the ankle. Revascularization is considered only when absence of a Doppler signal indicates acute limb ischemia.

Adult↗
PubMed1991

Marshall syndrome.

We report on a mother and daughter with Marshall syndrome, with the Robin sequence present in the daughter. Results of our efforts to link this syndrome to a defect in type II collagen are reported. We compare and contrast Marshall syndrome with the Stickler syndrome, and propose that enough phenotypic overlap exists to suggest that they are probably allelic expressions of the same locus.

Abnormalities, Multiple↗
PubMed1991

Linkage of Marfan syndrome and a phenotypically related disorder to two different fibrillin genes.

Marfan syndrome (MFS), one of the most common genetic disorders of connective tissue, is characterized by skeletal, cardiovascular and ocular abnormalities. The incidence of the disease is about 1 in 20,000, with life expectancy severely reduced because of cardiovascular complications. As the underlying defect is unknown, MFS diagnosis is based solely on clinical criteria. Certain phenotypic features of MFS are also shared by other conditions, which may be genetically distinct entities although part of a clinical continuum. Immunohistochemical studies have implicated fibrillin, a major component of elastin-associated microfibrils, in MFS aetiology. Genetic linkage analysis with random probes has independently localized the MFS locus to chromosome 15. Here we report that these two experimental approaches converge with the cloning and mapping of the fibrillin gene to chromosome 15q15-21, and with the establishment of linkage to MFS. We also isolated a second fibrillin gene and mapped it to chromosome 5q23-31. We linked this novel gene to a condition, congenital contractural arachnodactyly, that shares some of the features of MFS. Thus, the cosegregation of two related genes with two related syndromes implies that fibrillin mutations are likely to be responsible for different MFS phenotypes.

Amino Acid Sequence↗
PubMed1991

Isoenthalpic and isoentropic temperatures and the thermodynamics of protein denaturation.

The standard enthalpy or entropy change upon transfer of a small nonpolar molecule from a nonaqueous phase into water at a given temperature is generally different for different solute species. However, if the heat capacity change is independent of temperature, there exists a temperature at which the enthalpy or the entropy change becomes the same for all solute species within a given class. Similarly, the enthalpy or the entropy change of protein denaturation, when extrapolated to high temperature assuming a temperature-independent heat capacity change, shows a temperature at which its value becomes the same for many different globular proteins on a per weight basis. It is shown that the existence of these temperatures can be explained from a common formalism based on a linear relationship between the thermodynamic quantity and a temperature-independent molecular property that characterizes the solute or the protein. For the small nonpolar molecule transfer processes, this property is the surface area or the number of groups that are brought in contact with water. For protein denaturation, it is suggested that this property measures the polar/nonpolar mix of the internal interaction within the protein interior. Under a certain set of assumptions, this model leads to the conclusion that the nonpolar and the polar groups of the protein contribute roughly equally to the stability of the folded state of the molecule and that the solvent-accessible surface area of the denatured form of a protein is no more than about two-thirds that of the fully extended form.

Mathematics↗
PubMed1991

Mutations in the small subunit of cyanobacterial ribulose-bisphosphate carboxylase/oxygenase that modulate interactions with large subunits.

In the cyanobacterium Anacystis nidulans (Synechococcus PCC6301), ribulose 1,5-bisphosphate carboxylase/oxygenase (Rbu-P2 carboxylase) is composed of eight large subunits and eight small subunits. There are three regions of the small subunit that contain amino acids that are conserved throughout evolution, from bacteria to higher plants. Since the function of the small subunit is not fully understood, site-directed mutagenesis was performed on highly conserved residues in the first and second conserved regions. Ser-16, Pro-19, Leu-21, and Tyr-54 were replaced by Asp-16, His-19, Glu-21, and Ser-54, respectively. Crude extracts containing the recombinant His-19 mutant enzyme indicated that there was little effect on either Rbu-P2 carboxylase activity or interactions between large and small subunits. However, the Asp-16, Glu-21, and Ser-54 mutations showed effects on Rbu-P2 carboxylase activity and the interaction between large and small subunits. The large and small subunits of the Asp-16, Glu-21, and Ser-54 enzymes were found to dissociate during nondenaturing gel electrophoresis or sucrose density gradient centrifugation. However, the dissociated small subunits remained functional and were capable of reconstituting Rbu-P2 carboxylase activity when added to large subunits. These results indicated that Ser-16, Leu-21, and Tyr-54 might play an important role in interactions between large and small subunits of the A. nidulans enzyme.

Amino Acid Sequence↗
PubMed1991

G to T transversion at position +5 of a splice donor site causes skipping of the preceding exon in the type III procollagen transcripts of a patient with Ehlers-Danlos syndrome type IV.

We identified a splicing mutation in a patient with Ehlers-Danlos syndrome type IV, a heritable connective tissue disorder associated with dysfunctions of type III collagen. The mutation was first localized in the patient's type III procollagen mRNA by amplifying the reverse transcribed product in several overlapping fragments using the polymerase chain reaction. Amplified products spanning exon 24-26 sequences displayed two distinct fragments, one of normal size and the other lacking the 99 base pairs of exon 25. Sequencing of amplified genomic products identified a G to T transversion at position +5 of the splice donor site of intron 25 in one of the patient's procollagen III genes. Expression of allelic minigene constructs correlated the T for G substitution with skipping of exon 25 sequences. Like previously characterized splicing mutations in other collagen genes, lowering the temperature at which the patient's fibroblasts were incubated nearly abolished exon skipping. As a part of this study, we also identified a highly polymorphic, intronic DNA sequence whose different allelic forms can be detected easily by the polymerase chain reaction technique.

Alleles↗
PubMed1991

Multiexon deletion in the procollagen III gene is associated with mild Ehlers-Danlos syndrome type IV.

We have characterized a deletion of approximately 9 kilobases which spans from intron 33 to exon 48 of one pro-alpha 1 (III) collagen allele in a patient with Ehlers-Danlos syndrome type IV. The mutation results in the production of an in-frame species of mRNA which lacks the sequences corresponding to residues 595-1,008 of the triple-helical domain. Thus, half of the pro-alpha 1 (III) chains synthesized by the patient's fibroblasts are nearly 30% shorter than normal. The procollagen III molecules composed of either three normal length or three shortened chains are thermally stable and efficiently secreted. In contrast, the procollagen III molecules that contain one or two shortened chains are unstable and are not secreted. Failure to secrete unstable molecules and a residual functional role of the shortened but stable homotrimers may explain the somewhat milder phenotype of this individual compared with that of another Ehlers-Danlos type IV patient bearing a deletion of similar size in the amino-terminal portion of the alpha 1 (III) collagen chain.

Chromosome Deletion↗