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Biomedical subjects

L Hoffman

Publications and source records attributed to L Hoffman.

At least 37 records · Page 2Linked to original sources
PubMed1999

Passions in girls and women: toward a bridge between critical relational theory of gender and modern conflict theory.

This paper considers (1) some aspects of the lack of dialogue among psychoanalytic schools; (2) Brenner's (1982) conception of drives and drive derivatives as inextricably linked to relationships, and some of its less-appreciated implications; (3) the debate over the importance of childhood sexuality in mental life; (4) the attempts by relational theorists to address and reintegrate the role of sexuality and gender, particularly in the study of feminine psychology; (5) the problematic role of aggression in psychoanalytic theories of women; (6) the avoidance by both men and women of women's passions and their anatomical loci, especially the clitoris, whose only function is the provision of pleasure; and (7) the suggestion that an integrated theory, including an understanding of the role of the body as well as of the passions and the defenses against them, results in the most effective clinical psychoanalytic approach. It then suggests that a bridge could be built between a relational point of view that takes into consideration the role of bodily experiences, and a classical point of view in which drive is seen as inextricably linked to relationships from birth on.

Adolescent↗
PubMed1999

At least three genes account for familial papillary thyroid carcinoma: TCO and MNG1 excluded as susceptibility loci from a large Tasmanian family.

Recent studies have mapped two susceptibility loci which appear to account for familial multinodular goitre (MNG1) and a variant of familial papillary thyroid cancer (PTC), with associated multinodular goitre (TCO). A Tasmanian family (Tas1) has been identified with an autosomal dominant form of PTC. This study has examined the MNG1 and TCO loci to determine if they are similarly predisposing the Tas1 family to PTC. Linkage analysis using identical microsatellite markers described in the two previous studies was used to determine the significance of these loci in the Tasmanian family. The resultant LOD scores were sufficiently negative using multipoint parametric analysis to exclude these two loci from involvement in the Tasmanian family. In addition, six candidate genes, RET, TRK, MET, TSHR, APC and PTEN were also excluded as susceptibility genes in Tas1 by using microsatellites that are positioned in or in close proximity to these genes. These results suggest that there are at least three susceptibility genes that predispose families to familial PTC.

Carcinoma, Papillary↗
PubMed1998

Specific single or double proline substitutions in the "spring-loaded" coiled-coil region of the influenza hemagglutinin impair or abolish membrane fusion activity.

We tested the role of the "spring-loaded" conformational change in the fusion mechanism of the influenza hemagglutinin (HA) by assessing the effects of 10 point mutants in the region of high coiled-coil propensity, HA2 54-81. The mutants included proline substitutions at HA2 55, 71, and 80, as well as a double proline substitution at residues 55 and 71. Mutants were expressed in COS or 293T cells and assayed for cell surface expression and structural features as well as for their ability to change conformation and induce fusion at low pH. We found the following: Specific mutations affected the precise carbohydrate structure and folding of the HA trimer. All of the mutants, however, formed trimers that could be expressed at the cell surface in a form that could be proteolytically cleaved from the precursor, HA0, to the fusion-permissive form, HA1-S-S-HA2. All mutants reacted with an antibody against the major antigenic site and bound red blood cells. Seven out of ten mutants displayed a wild-type (wt) or moderately elevated pH dependence for the conformational change. V55P displayed a substantial reduction (approximately 60- 80%) in the initial rate of lipid mixing. The other single mutants displayed efficient fusion with the same pH dependence as wt-HA. The double proline mutant V55P/ S71P displayed no fusion activity despite being well expressed at the cell surface as a proteolytically cleaved trimer that could bind red blood cells and change conformation at low pH. The impairment in fusion for both V55P and V55P/S71P was at the level of outer leaflet lipid mixing. We interpret our results in support of the hypothesis that the spring-loaded conformational change is required for fusion. An alternate model is discussed.

Animals↗
PubMed1998

A physiologic function for p-glycoprotein (MDR-1) during the migration of dendritic cells from skin via afferent lymphatic vessels.

P-glycoprotein (MDR-1) is a well-known transporter that mediates efflux of chemotherapeutic agents from the intracellular milieu and thereby contributes to drug resistance. MDR-1 also is expressed by nonmalignant cells, including leukocytes, but physiologic functions for MDR-1 are poorly defined. Using an initial screening assay that included >100 mAbs, we observed that neutralizing mAbs MRK16, UIC2, and 4E3 against MDR-1 specifically and potently blocked basal-to-apical transendothelial migration of mononuclear phagocytes, a process that may mimic their migration into lymphatic vessels. Antagonists of MDR-1 then were used in a model of authentic lymphatic clearance. In this model, antigen-presenting dendritic cells (DC) migrate out of explants of cultured human skin and into the culture medium via dermal lymphatic vessels. DC and T cells derived from skin expressed MDR-1 on their surfaces. Addition of anti-MDR-1 mAbs MRK16, UIC2, or the MDR-1 antagonist verapamil to skin explants at the onset of culture inhibited the appearance of DC, and accompanying T cells, in the culture medium by approximately 70%. Isotype-matched control mAbs against other DC molecules including CD18, CD31, and major histocompatibility complex I did not block. In the presence of MDR-1 antagonists, epidermal DC were retained in the epidermis, in contrast to control conditions. In summary, this work identifies a physiologic function for MDR-1 during the mobilization of DC and begins to elucidate how these critical antigen-presenting cells migrate from the periphery to lymph nodes to initiate T lymphocyte-mediated immunity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Inhibition of the 26 S proteasome by polyubiquitin chains synthesized to have defined lengths.

Ubiquitin is a covalent signal that targets cellular proteins to the 26 S proteasome. Multiple ubiquitins can be ligated together through the formation of isopeptide bonds between Lys48 and Gly76 of successive ubiquitins. Such a polyubiquitin chain constitutes a highly effective proteolytic targeting signal, but its mode of interaction with the proteasome is not well understood. Experiments to address this issue have been limited by difficulties in preparing useful quantities of polyubiquitin chains of uniform length. We report a simple method for large scale synthesis of Lys48-linked polyubiquitin chains of defined length. In the first round of synthesis, two ubiquitin derivatives (K48C-ubiquitin and Asp77-ubiquitin) were used as substrates for the well characterized ubiquitin-conjugating enzyme E2-25K. Diubiquitin blocked at the nascent proximal and distal chain termini was obtained in quantitative yield. Appropriately deblocked chains were then combined to synthesize higher order chains (tetramer and octamer in the present study). Deblocking was achieved either enzymatically (proximal terminus) or by chemical alkylation (distal terminus). Chains synthesized by this method were used to obtain the first quantitative information concerning the influence of polyubiquitin chain length on binding to the 26 S proteasome; this was done through comparison of different length (unanchored) polyubiquitin chains as inhibitors of ubiquitin-conjugate degradation. K0.5 was found to decrease approximately 90-fold, from 430 to 4.8 microM, as the chain was lengthened from two to eight ubiquitins. The implications of these results for the molecular basis of chain recognition are discussed.

Alkylation↗
PubMed1997

Molecular cloning and expression of subunit 9 of the 26S proteasome.

Seven peptides from subunit 9 (S9) of the human 26S proteasome were sequenced and this information was used to clone a HeLa cDNA that encodes the 46 kDa subunit. Rabbit polyclonal antisera were made against a ubiquitin fusion protein containing 12 amino acids from S9 and against a full-length S9 expressed in E. coli. Western blot analysis showed that the S9-specific antibodies bound the 26S proteasome and its regulatory complex separated on non-denaturing gels. In SDS-PAGE samples of the two complexes, the S9-specific antibodies bound a single 46 kDa subunit. Thus, a cDNA encoding a novel 26S protease subunit has been isolated, sequenced, and expressed.

Amino Acid Sequence↗
PubMed1997

The discovery, characterization and crystallographically determined binding mode of an FMOC-containing inhibitor of HIV-1 protease.

A pharmacophore derived from the structure of the dithiolane derivative of haloperidol bound in the active site of the HIV-1 protease (HIV-1 PR) has been used to search a three-dimensional database for new inhibitory frameworks. This search identified an FMOC-protected N-tosyl arginine as a lead candidate. A derivative in which the arginine carboxyl has been converted to an amide has been crystallized with HIV-1 PR and the structure has been determined to a resolution of 2.5 A with a final R-factor of 18.5%. The inhibitor binds in an extended conformation that results in occupancy of the S2, S1', and S3' subsites of the active site. Initial structure-activity studies indicate that: (1) the FMOC fluorenyl moiety interacts closely with active site residues and is important for binding; (2) the N(G)-tosyl group is necessary to suppress protonation of the arginine guanidinyl terminus; and (3) the arginine carboxamide function is involved in interactions with the water coordinated to the catalytic aspartyl groups. FMOC-protected arginine derivatives, which appear to be relatively specific and nontoxic, offer promise for the development of useful HIV-1 protease inhibitors.

Amino Acids↗
PubMed1997

Effects of nucleotides on assembly of the 26S proteasome and degradation of ubiquitin conjugates.

We have investigated three aspects of nucleotide usage by the 26S proteasome and its regulatory complex (RC). Both particles hydrolyze the four major ribonucleotides, but ATP and CTP have substantially lower Kms for hydrolysis than do GTP and UTP. The Km for ATP hydrolysis is 15 microm for the 26S proteasome and 30 microm for the regulatory complex. Formation of the 26S proteasome from the RC and the 20S proteasome requires about 5 microm ATP. Although measurable degradation of Ubiquitin(Ub)-lysozyme conjugates occurs in the presence of CTP, GTP, and UTP, the best nucleotide for Ub-conjugate degradation by the 26S proteasome is ATP, with an estimated Km of 12 microm. In summary, our studies show that micromolar concentrations of ATP are sufficient for several 26S proteasome activities.

Animals↗
PubMed1997

Intraotic administration of gentamicin: a new method to study ototoxicity in the crista ampullaris of the bullfrog.

A new method of local gentamicin administration was tested in the bullfrog inner ear to achieve ototoxic-induced hair cell destruction. Gelfoam pledgets soaked with known amounts of gentamicin were inserted into the perilymphatic cisterna of the bullfrog through a ventral surgical approach. A dose of 1.20 mg gentamicin, consistent with a perilymphatic concentration of 65 microg/ml, resulted in the desired ototoxic-induced hair cell damage, that is, complete hair cell destruction with minimal disruption of other components of the sensory epithelium. This study demonstrates that this is a useful and simple method to investigate the process of vestibular ototoxicity and hair cell regeneration, including aspects of hair cell destruction and repair.

Administration, Topical↗
PubMed1997

The use of fibrin sealant in the prevention of seromas.

Seroma formation is a difficult problem to treat and prevent. Its sequelae include wound infection, dehiscence, and skin-flap necrosis. The purpose of this study was to determine the effects of fibrin sealant on seroma formation and wound healing. Seromas were created in a rat model by harvesting the latissimus dorsi muscle. In group I (n = 20), only the latissimus dorsi muscle was harvested. In group II (n = 20), the latissimus dorsi muscle was harvested and fibrin sealant applied. Seromas were routinely aspirated. In group III (n = 20), the latissimus dorsi muscle was harvested, and once a seroma was evident clinically, it was aspirated and injected with fibrin sealant. Fibrin sealant was created by combining virally deactivated fibrinogen and thrombin (American Red Cross, Rockville, Md.). In group I, 90 percent of the animals formed seromas compared with only 20 percent in group II. The average total fluid aspirated in group I was 21 cc versus 6 cc in group II. Sixty percent of the animals in group I and 5 percent in group II required serial drainage for chronic seromas. Skin-flap necrosis occurred in 80 percent of the animals in group I, in 10 percent of group II, and in 40 percent of group III. Histologic evaluation confirmed that group II underwent better wound healing. At necropsy, group I animals with seromas had gross capsular formation; this was not readily apparent in the fibrin sealant groups. We conclude that (1) the harvesting of the rat latissimus dorsi muscle is a reliable model for creating seromas, (2) fibrin sealant effectively prevents seroma formation when applied intraoperatively, (3) wound healing in the seroma rat model is improved with intraoperative fibrin sealant application, (4) closed injection of fibrin sealant for existing seromas cannot be recommended at this time, (5) virally deactivated fibrin sealant retains its hemostatic and adhesive properties, and (6) current clinical trials of virally deactivated fibrin sealant may facilitate its use in the United States.

Administration, Topical↗
PubMed1997

The role of the cranial base in facial growth: experimental craniofacial synostosis in the rabbit.

Craniofacial synostosis designates premature fusion in sutures of the cranial vault (calvarium). When craniofacial synostosis is associated with a syndrome (e.g., Apert, Crouzon), premature fusion of the cranial base has been postulated to occur as well. This study was designed to determine whether the primary growth disturbance in craniofacial synostosis is located at the cranial base (i.e., spheno-occipital synchondrosis) or the calvarial vault (i.e., coronal and sagittal sutures) or both. Sixty newborn New Zealand White rabbits were randomly assigned to six groups: (I) calvarial control, (II) cranial base control, (III) cranial base immobilization, (IV) coronal suture immobilization, (V) coronal and sagittal suture immobilization, and (VI) cranial base and coronal and sagittal suture immobilization. An anterior cervical microsurgical approach to the cranial base was used, while cranial vault sutures were exposed through a bicoronal scalp incision. All sutures were fused by periosteal abrasion and application of methyl cyanoacrylate. Cephalograms were taken at 30, 60, and 90 days postoperatively to assess craniofacial growth. Linear and angular measurements of facial, calvarial, and basicranial growth were subjected to multivariate analysis. Analysis indicated that (1) craniofacial length was shortened most significantly by cranial base fusion, (2) cranial base fusion and cranial vault fusion had an additive effect on craniofacial length restriction, (3) the anterior cranial base was significantly shortened by cranial base and cranial vault fusion (p < 0.05), (4) the posterior cranial base was shortened by cranial base fusion only (p < 0.05), and (5) cranial base fusion alone significantly flattened the cranial base angle (p < 0.05), whereas cranial vault fusion alone did not. These results suggest that cranial base fusion alone may account for many dysmorphic features seen in craniofacial synostosis. This model is consistent with the findings of other investigators and confirms both a primary directive and translational role of the cranial base in craniofacial growth.

Animals↗