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Biomedical subjects

G Lee

Publications and source records attributed to G Lee.

At least 307 records · Page 17Linked to original sources
PubMed1989

Improved immunohistochemical detection of prostatic acid phosphatase by a monoclonal antibody.

A monoclonal antibody with high affinity to acid phosphatase isoenzyme 2 (Ab-AcP2) was selected to examine its binding to different normal and tumor tissues using the indirect immunohistochemical method. Both mature prostatic epithelial cells in the prostate and the highly dedifferentiated prostatic cancer cells in the bone marrow showed strong binding to the antibody. Among nonprostatic tissues, only bone marrow, breast, and kidney showed trace staining in some specimens. The specificity of Ab-AcP2 was much better than that of the polyclonal antibody to acid phospatase previously reported. When the antibody to the prostate-specific antigen (Ab-PSA) was used, weak background staining was often encountered, and weak to moderate stains were seen in the prostatic stroma, bone marrow, lung, skin, and melanoma.

Acid Phosphatase↗
PubMed1989

Conformational energy analysis of the leucine repeat regions of C/EBP, GCN4, and the proteins of the myc, jun, and fos oncogenes.

It has been recently proposed that certain DNA binding proteins (including C/EBP, GCN4 and the myc, jun, and fos oncogene proteins) share a common structural motif based on helix-promoting regions containing heptad repeat sequences of leucines. It has been suggested that this structure is critical to the biological activity of these proteins, since it facilitates the formation of functional dimers held together by interdigitating leucine side-chains along the hydrophobic interfaces between long alpha-helical regions of the polypeptide chains in a configuration termed the "leucine zipper." In this paper, conformational energy analysis is used to deterrmine the preferred three-dimensional structures of the leucine repeat regions of these proteins. The results indicate that, in all cases, the global minimum energy conformation for these regions is an amphipathic alpha-helix with the leucine side-chains arrayed on one side in such a way to favor "leucine zipper" dimerization. Furthermore, amino acid substitutions in these regions (such as Pro for Leu), that are known to inhibit dimer formation and prevent DNA binding, are found to produce significant conformational changes that disrupt the amphipathic helical structure. Thus, these results provide support for the proposed "leucine zipper" configuration as a critical structural feature of this class of DNA binding proteins.

Amino Acid Sequence↗
PubMed1989

Conformational effects of amino acid substitutions in the P-glycoprotein of the mdr 1 gene.

The P-glycoprotein of the mdr 1 gene is responsible for the phenomenon of multidrug resistance in human cells. The presumed drug-binding site of the wild-type P-glycoprotein contains a glycine at position 185. A mutant P-glycoprotein which contains valine at this position causes cells to retain resistance to colchicine, but to lose cross-resistance to other drugs such as the chemotherapeutic agents vinblastine and Adriamycin. This has been hypothesized to be due to a conformational change in the protein induced by the amino acid substitution. Using conformational energy analysis, we have determined the allowed three-dimensional structures for the wild-type and mutant proteins in the region of position 185. The results indicate that the wild-type protein adopts a unique left-handed conformation at position 185 which is energically unfavorable for the protein with L-amino acids (including valine) at this position. This conformational change induced by amino acid substitutions for Gly 185 could explain the differences in binding to the P-glycoprotein of various drugs and, hence, the differences in drug resistance exhibited by various cell lines expressing these proteins.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1989

The microtubule binding domain of tau protein.

Tau protein is a microtubule-associated protein implicated in the spatial and temporal specification of microtubules and has been found in the neurofibrillary tangles of Alzheimer's disease. Determination of tau protein structure has revealed three 18 amino acid repeated sequences hypothesized to be tubulin binding sites. Using tau cDNA clones from human fetal brain, we employed E. coli expression systems to synthesize tau protein and fragments of tau protein in order to identify the microtubule binding site. A fragment containing the three repeated sequences binds microtubules, while the amino-terminal half of the protein does not bind. Fragments containing two or one repeat are also capable of binding, indicating that the basic tubulin interacting unit is one repeat.

Amino Acid Sequence↗
PubMed1989

Identification of an intracellular protein that specifically interacts with photoaffinity-labeled oncogenic p21 protein.

An oncogenic 21-kDa (p21) protein (Harvey RAS protein with Val-12) has been covalently modified with a functional reagent that contains a photoactivatable aromatic azide group. This modified p21 protein has been introduced quantitatively into NIH 3T3 cells using an erythrocyte-mediated fusion technique. The introduced p21 protein was capable of inducing enhanced pinocytosis and DNA synthesis in the recipient cells. To identify the putative intracellular protein(s) that specifically interact with the modified p21 protein, the cells were pulsed with [35S]methionine at selected times after fusion and then UV-irradiated to activate the azide group. The resulting nitrene covalently binds to amino acid residues in adjacent proteins, thus linking the p21 protein to these proteins. The cells were then lysed, and the lysate was immunoprecipitated with the anti-p21 monoclonal antibody Y13-259. The immunoprecipitate was analyzed by SDS/PAGE to identify p21-protein complexes. By using this technique, we found that three protein complexes of 51, 64, and 82 kDa were labeled specifically and reproducibly. The most prominent band is the 64-kDa protein complex that shows a time-dependent rise and fall, peaking within a 5-hr period after introduction of the p21 protein into the cells. These studies provide evidence that in vitro the p21 protein becomes associated with a protein whose mass is about 43 kDa. We suggest that the formation of this complex may play a role in mediating early events involved with cell transformation induced by RAS oncogenes.

Affinity Labels↗
PubMed1989

Comparison of the computed structures for the phosphate-binding loop of the p21 protein containing the oncogenic site Gly 12 with the X-ray crystallographic structures for this region in the p21 protein and EFtu. A model for the structure of the p21 protein in its oncogenic form.

The GTP-binding p21 protein encoded by the ras-oncogene can be activated to cause malignant transformation of cells by substitution of a single amino acid at critical positions along the polypeptide chain. Substitution of any non-cyclic L-amino acid for Gly 12 in the normal protein results in a transforming protein. This substitution occurs in a hydrophobic sequence (residues 6-15) which is known to be involved in binding the phosphate moities of GTP (and GDP). We find, using conformational energy calculations, that the 6-15 segment of the normal protein (with Gly 12) adopts structures that contain a bend at residues 11 and 12 with the Gly in the D* conformation, not allowed energetically for L-amino acids. Substitution of non-cyclic L-amino acids for Gly 12 results in shifting this bend to residues 12 and 13. We show that many computed structures for the Gly 12-containing phosphate binding loop, segment 9-15, are superimposable on the corresponding segment of the recently determined X-ray crystallographic structure for residues 1-171 of the p21 protein. All such structures contain bends at residues 11 and 12 and most of these contain Gly 12 in the C* or D* conformational state. Other computed conformations for the 9-15 segment were superimposable on the structure of the corresponding 18-23 segment of EFtu, the bacterial chain elongation factor having structural similarities to the p21 protein in the phosphate-binding regions. This segment contains a Val residue where a Gly occurs in the p21 protein. As previously predicted, all of these superimposable conformations contain a bend at positions 12 and 13, not 11 and 12. If these structures that are superimposable on EFtu are introduced into the p21 protein structure, bad contacts occur between the sidechain of the residue (here Val) at position 12 and another phosphate binding loop region around position 61. These bad contacts between the two segments can be removed by changing the conformation of the 61 region in the p21 protein to the corresponding position of the homologous region in EFtu. In this new conformation, a large site becomes available for the binding of phosphate residues. In addition, such phenomena as autophosphorylation of the p21 protein by GTP can be explained with this new model structure for the activated protein which cannot be explained by the structure for the non-activated protein.

Cell Transformation, Neoplastic↗
PubMed1989

Anatomy of the nasolabial fold: the keystone of the smiling mechanism.

The nasolabial fold is absent in the face of the newborn, disappears in the paralyzed face, but is retained in the face upon death. There is very little information in the literature on what makes up the fold. Four fresh cadavers were studied by taking a strip of facial tissue from each at right angles to the fold; all soft tissue layers through the face were included. Microscopic studies of the strips showed the fold to be made up of (1) dense fibrous tissue, (2) muscle fibers branching from the levator muscles of the upper lip, and (3) striated muscle bundles originating in the fold fascia. The studies also revealed the lip elevator muscles and the "fold muscles" coursing down the lip to traverse the orbicularis oris and insert into the dermis of the upper lip, the cutaneous vermilion junction, and vermilion. The smile is formed in stages, the first stage raising the lip to the fold by the levator muscles and the muscle bundles originating in the fold. The lip meets resistance at the fold because of cheek fat. The second stage involves the raising of the lip and fold upward by the levator muscles of the upper lip. Clinically, this study relates to reanimating the paralyzed face.

Adipose Tissue↗
PubMed1989

The enigma of interstitial cystitis--an autoimmune disease?

Interstitial cystitis (IC) is characterised by recurrent inflammation and destruction of bladder tissue without obvious cause. To determine whether this self-perpetuating disease is the result of an autoimmune disorder, we studied 26 patients with IC of mean duration 5 years and compared the results with those of a control group of similar age and sex with other urological complaints. We performed a standard autoimmune profile and looked for specific antibodies to normal human bladder in the serum, using an indirect immunofluorescence technique. Deep bladder biopsies were examined by conventional histology and cryostat sections were studied with peroxidase-conjugated anti-human antibodies in a search for immunoglobulin deposition within the bladder. Seventeen of 26 patients with IC (65%) and 5 of 14 controls (36%) demonstrated non-organ-specific antibodies; 40% of those with IC had anti-nuclear antibodies; 18 IC patients (75%) and 4 of 10 controls (40%) had anti-bladder antibodies present in the serum, but 5 healthy volunteers showed no such antibody activity. There was no statistically significant difference between the two groups for either type of antibody (Fisher's exact test). Only 5 of 17 patients with IC (29%) showed immunoglobulin deposition in the bladder epithelium, a similar proportion to controls (38%); 4 of these 5 had circulating anti-bladder antibodies present in the serum. Although IC patients demonstrated a non-specific increase in antibody formation, this was not significantly different from a similar group of other urological patients. The lack of specificity makes this immunological response more likely to be a secondary phenomenon associated with inflammatory damage to the bladder rather than the primary cause of the disease.

Adult↗
PubMed1989

Occult fractures of the carpals and metacarpals: demonstration by CT.

Occult fractures of the carpals and metacarpals occur frequently and are associated with major disability. The cross-sectional display and superior resolution of CT are well suited to the demonstration of these fractures. Sixteen patients with pain and negative conventional radiographs were chosen for further evaluation by CT. Imaging was performed in two planes and showed 21 fractures. The transaxial plane was the most revealing imaging plane. Coronal imaging was equal or superior to the transaxial plane in most fractures of the scaphoid, lunate, capitate, and pisiform bones and of the bases of the metacarpal bones. The direct sagittal plane was the best imaging plane in one patient with fractures of the scaphoid and lunate bones. After discovery of the fracture on CT, surgical removal of the avulsed fracture fragment was recommended in seven patients and fusion was recommended in three. Eight patients had a marked decrease in pain after the surgical procedure. The accuracy of CT for the demonstration of occult fractures may result in earlier recognition of these fractures and a reduction in the associated disability.

Carpal Bones↗
PubMed1989

Out on your own: the medical artist in private practice.

It takes a special kind of determination and drive to succeed in self-employment. Natural artistic talent does not necessarily mean you are qualified to run a business. Today help is at hand. Books, teaching programmes and courses abound. For those who have been out of work for at least 8 weeks, assistance is available from the Enterprise Allowance Scheme, well worth looking into as there are free counselling sessions and an excellent back-up of support and advice to steer you towards setting up on your own. We have been hearing and reading much lately about cost recovery in departments within the NHS and universities. This is basically what the freelance medical illustrator has been coping with for years. In running a business the freelancer becomes manager, secretary, book keeper and consultant, as well as a professional illustrator. Once the decision has been taken to leave the safe surroundings of a salaried position, one changes from being a singular artist who is part of a team into a cost-effective, self-sufficient unit.

Fees and Charges↗
PubMed1989

Antibacterial activity of norfloxacin against 1700 relatively resistant clinical isolates.

A total of 1724 clinical isolates from patients with different infections were tested in vitro to determine their susceptibility to norfloxacin. Antibacterial activity of norfloxacin was compared with other drugs that were commonly used in the hospital. Of the 919 strains of Enterobacteriaceae tested, all except four isolates of Enterobacter, two of Serratia and one of Proteus were susceptible to norfloxacin. Ninety-five percent of the 199 strains of Pseudomonas aeruginosa were also inhibited by this quinolone. Brucella melitensis (81 strains) was completely susceptible to norfloxacin. All the 250 isolates of Staphylococcus aureus and coagulase-negative staphylococci were also sensitive to norfloxacin. Pseudomonads other than P.aeruginosa, Acinetobacter/Alcaligenes and group D streptococci were less sensitive to norfloxacin, with 56%, 57% and 20% respectively being inhibited by this antimicrobial agent.

Bacteria↗
PubMed1989

The interrelationship between the root surface and alveolar bone of the replanted avulsed tooth after etching.

It has been suggested that removal of the damaged nonvital periodontal ligament (PDL) may result in slower destruction of tooth substance following replantation of teeth. It has also been suggested that citric acid conditioning of surgically exposed dentin may enhance connective tissue attachment on root surfaces. The aim of this study was to examine the interrelationship between the acid etched root surface of the replanted tooth and the alveolar bone. Forty-five available anterior teeth from six monkeys were divided into 3 groups in this experiment. All teeth were extracted and dried for 2 hrs. In the first group the teeth were replanted immediately after endodontic therapy. The teeth in the second group were replanted after immersion in 10% sodium hypochlorite and subsequently irrigation with normal saline. In the third group, the cementum and necrotic PDL were removed by grinding the root surfaces which were then treated with citric acid (PH = 1) for 3 minutes followed by normal saline irrigation. All teeth were replanted without splinting and were subjected to histological examination at 12 week post-replantation. Close apposition of collagen fibrils of the new connective tissue to the exposed root surface was observed in most cases in the second and third group, although bony ankylosis and inflammatory root resorptions were also found in some areas. Teeth in the first group, the control experiment, had much more replacement and inflammatory resorptions. Then the result suggested that demineralization with citric acid on the denuded avulsed tooth prior to replantation may decrease the chance of replacement resorption and result in fibrous adhesion to the alveolar bone.

Adhesiveness↗
PubMed1988

Rapid and transient induction of c-fos, c-myc and c-Ha-ras in rat liver following glycine administration.

Administration of glycine (2.5 mmoles/100 g., i.p.) results in an increased expression of several cell cycle dependent genes such as c-fos, c-myc and c-Ha-ras in the rat liver. The increased expression could be noticed as early as 20-40 minutes and declined by 2 hours following glycine administration. The rapid rise and decline in the mRNA levels of c-fos, c-myc and c-Ha-ras in response to glycine is of significance because in response to a wide variety of growth stimuli, these proto-oncogenes exhibit a temporal sequence in their expression; for example, the expression of c-fos precedes that of c-myc, which in turn precedes the increased expression of c-Ha-ras. The experimental model using a simple amino acid such as glycine will be useful in exploring some of the mechanisms of regulation of expression of these proto-oncogenes.

Animals↗
PubMed1988

The primary structure and heterogeneity of tau protein from mouse brain.

Tau protein is a family of microtubule binding proteins, heterogeneous in molecular weight, that are induced during neurite outgrowth and are found prominently in neurofibrillary tangles in Alzheimer's disease. The predicted amino acid sequences of two forms of tau protein from mouse brain were determined from complementary DNA clones. These forms are identical in their amino-terminal sequences but differ in their carboxyl-terminal domains. Both proteins contain repeated sequences that may be tubulin binding sites. The sequence suggests that tau is an elongated molecule with no extensive alpha-helical or beta-sheet domains. These complementary DNAs should enable the study of various functional domains of tau and the study of tau expression in normal and pathological states.

Amino Acid Sequence↗