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Biomedical subjects

R Dorfman

Publications and source records attributed to R Dorfman.

13 recordsLinked to original sources
PubMed2001

Biphasic activation of the BMP pathway patterns the Drosophila embryonic dorsal region.

The BMP pathway patterns the dorsal region of the Drosophila embryo. Using an antibody recognizing phosphorylated Mad (pMad), we followed signaling directly. In wild-type embryos, a biphasic activation pattern is observed. At the cellular blastoderm stage high pMad levels are detected only in the dorsal-most cell rows that give rise to amnioserosa. This accumulation of pMad requires the ligand Screw (Scw), the Short gastrulation (Sog) protein, and cleavage of their complex by Tolloid (Tld). When the inhibitory activity of Sog is removed, Mad phosphorylation is expanded. In spite of the uniform expression of Scw, pMad expansion is restricted to the dorsal domain of the embryo where Dpp is expressed. This demonstrates that Mad phosphorylation requires simultaneous activation by Scw and Dpp. Indeed, the early pMad pattern is abolished when either the Scw receptor Saxophone (Sax), the Dpp receptor Thickveins (Tkv), or Dpp are removed. After germ band extension, a uniform accumulation of pMad is observed in the entire dorsal domain of the embryo, with a sharp border at the junction with the neuroectoderm. From this stage onward, activation by Scw is no longer required, and Dpp suffices to induce high levels of pMad. In these subsequent phases pMad accumulates normally in the presence of ectopic Sog, in contrast to the early phase, indicating that Sog is only capable of blocking activation by Scw and not by Dpp.

Animals↗
PubMed2000

Noncovalent interactions of the Apple 4 domain that mediate coagulation factor XI homodimerization.

The Apple 4 (A4) domain of human plasma factor XI (FXI) was used to investigate the process of FXI noncovalent dimer formation. Recombinant 6-histidine-tagged A4 domain proteins were prepared utilizing a bacterial expression system. Purification was accomplished under denaturing conditions, followed by a refolding protocol to facilitate correct disulfide bond formation. Analysis of the A4 domain (C321S mutant) by size exclusion chromatography indicated the presence of a slowly equilibrating reversible monomer-dimer equilibrium. The elution profiles reveal highly symmetrical peaks for both dimeric and monomeric species with elution times that were highly reproducible for varying amounts of both the dimeric and monomeric species. The monomer-dimer equilibrium was found to be dependent upon changes in both pH and salt concentration. Under conditions approximating physiologic salt concentration and pH (20 mm HEPES, 100 mm NaCl, and 1 mm EDTA, pH 7.4), it was determined that the monomer-dimer equilibrium was characterized by a dissociation constant (K(D)) value of 229 +/- 26 nm with a calculated Delta G value of 9.1 kcal/mol. This report identifies electrostatic contributions and the presence of a hydrophobic component that mediate interactions at the A4 domain interface. The rate of dissociation for the recombinant A4 domain C321S mutant was examined by monitoring the increase in 4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid dipotassium salt fluorescence under dissociating conditions, giving a value for a dissociation rate constant (k(off)) of 4.3 x 10(-3) s(-1).

Anilino Naphthalenesulfonates↗
PubMed1997

Effects of low-intensity AC and/or DC electromagnetic fields on cell attachment and induction of apoptosis.

Rat tendon fibroblast (RTF) and rat bone marrow (RBM) osteoprogenitor cells were cultured and exposed to AC and/or DC magnetic fields in a triaxial Helmholtz coil in an incubator for up to 13 days. The AC fields were at 60 and 1000 Hz and up to 0.25 mT peak to peak, and the DC fields were up to 0.25 mT. At various combinations of field strengths and frequencies, AC and/or DC fields resulted in extensive detachment of preattached cells and prevented the normal attachment of cells not previously attached to substrates. In addition, the fields resulted in altered cell morphologies. When RTF and RBM cells were removed from the fields after several days of exposure, they partially reattached and assumed more normal morphologies. An additional set of experiments described in the Appendix corroborates these findings and also shows that low-frequency EMF also initiates apoptosis, i.e., programmed cell death, at the onset of cell detachment. Taken together, these results suggest that the electromagnetic fields result in significant alterations in cell metabolism and cytoskeleton structure. Further work is required to determine the relative effect of the electric and magnetic fields on these phenomena. The research has implications for understanding the role of fields in affecting bone healing in fracture nonunions, in cell detachment in cancer metastasis, and in the effect of EMF on organisms generally.

Animals↗
PubMed1996

Congenital toxoplasmosis transmitted from an immunologically competent mother infected before conception.

Congenital transmission of Toxoplasma gondii from a mother who was apparently immunologically competent and who had toxoplasmic lymphadenitis 2 months before conception is described. Since no T. gondii-specific serological data were available for this mother from the time her lymph node biopsy specimen was obtained, the specimen was studied by polymerase chain reaction (PCR) to determine whether the T. gondii B1 gene was present. The predictive diagnostic value of histologic findings previously considered to be classic signs of T. gondii lymphadenitis also was studied. This was done by correlation of serological tests diagnostic of acute acquired T. gondii infection and presence of characteristic findings in biopsy specimens from persons without known immunocompromise. Both PCR and review of the characteristic features of her lymph node biopsy specimen confirmed the diagnosis of preconceptual infection in the mother. We also discuss two other cases in which apparently immunologically competent mothers with preconceptually acquired infection transmitted this parasite to their fetuses.

Animals↗
PubMed1993

Active site lysines in orotate phosphoribosyltransferase.

Orotate phosphoribosyltransferase (OPRTase; EC 2.4.2.10) catalyzes the formation of the nucleotide orotidine-5'-monophosphate from orotate and 5-phosphoribosyl-1-pyrophosphate (PRPP). The bacterial enzyme, unlike its mammalian homolog, is monofunctional and is a dimer of M(r) 23,000 subunits. The availability of large amounts of highly purified crystalline Salmonella typhimurium OPRTase have enabled us to being structure/function studies on the enzyme. Like other phosphoribosyltransferases, OPRTase binds the highly charged MgPRPP complex, as well as anionic orotate, suggesting an active site containing basic residues. The S. typhimurium sequence (Scapin, G., Sacchettini, J. C., Dessen, A., Bhatia, M., and Grubmeyer, C. (1993) J. Mol. Biol. 230, 1304-1308) contains 12 lysine and 13 arginine residues, of which Lys-26, Arg-99, Lys-100, Lys-103, and Arg-156 are conserved as identities among the sequences of OPRTases from other organisms, with Lys-19 and Arg-161 replaced by the alternative basic residue in one or more sequences. The lysine modifier 2,4,6-trinitrobenzene sulfonate inactivated S. typhimurium OPRTase in a pseudo first-order process, and OMP and PRPP provided good protection against inactivation. Spectral quantitation of trinitrophenyl (TNP) group incorporation showed that inactivation was correlated with incorporation of one TNP group per subunit. Surprisingly, tryptic proteolysis followed by high performance liquid chromatography and amino acid sequence analysis revealed that four peptides, containing three distinct lysines, had been modified. Peptides modified at Lys-26, Lys-100 and Lys-103, as well as a doubly modified peptide containing TNP groups at Lys-100 and Lys-103, were identified. Inactivation kinetics showed that the 3 lysine residues were modified at equal rates. Protection studies demonstrated that Lys-26, and to a lesser extent Lys-100 and Lys-103, were protected against modification by OMP, whereas PRPP protected Lys-26, Lys-100 and Lys-103. Pyrophosphate protected Lys-100 and Lys-103. The results suggest active site locations for the sequence-conserved and TNP-modified lysine residues, with Lys-26 interacting with the ribose-5-phosphate moiety of OMP and PRPP, and Lys-100 and Lys-103 interacting with the pyrophosphate moiety of PRPP.

Amino Acid Sequence↗
PubMed1991

Vascular transformation of sinuses in lymph nodes. A study of its morphological spectrum and distinction from Kaposi's sarcoma.

Vascular transformation of lymph node sinuses (VTS) is characterized by conversion of nodal sinuses into capillary-like channels, often accompanied by fibrosis. A detailed study of this entity, based on 76 cases, showed that the morphologic spectrum was much broader than that originally described. The vasoproliferative process caused variable expansion of the subcapsular, intermediate, and medullary sinuses of the lymph nodes and involved single or multiple lymph nodes in a diffuse or segmental fashion. The proliferated vessels formed anastomosing narrow clefts, rounded spaces of different sizes, plexiform channels, or solid spindled to plump cellular foci and often were associated with variable degrees of sclerosis. The vascular spaces were empty, filled with lymph-like fluid, congested with blood, or occasionally thrombosed; extravasation of red cells was common. Several patterns were commonly observed in an individual case. Less common features included perivascular fibrin deposition and the presence of eosinophilic globules. Vascular thrombosis was identified only rarely in extranodal vessels available for histologic assessment. The more cellular forms of this vascular transformation may be mistaken for Kaposi's sarcoma, but can be distinguished from it by the pure sinusoidal distribution, a lack of well-formed spindle cell fascicles, the associated fibrosis, the maturation of the spindle cells into well-formed vascular channels toward the capsular aspect, and the failure of this process to involve the capsule itself, which is frequently affected by Kaposi's sarcoma.

Adolescent↗
PubMed1990

Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease): review of the entity.

This report reviews the clinical and pathologic features of 423 examples of sinus histiocytosis with massive lymphadenopathy (SHML) entered in a case registry, with special emphasis on extranodal manifestations of the disease. The most common sites of extranodal involvement in this population are skin, upper respiratory tract, and bone. However, SHML also can occur in a variety of other sites, including the genitourinary system, lower respiratory tract, oral cavity, and soft tissues. Involvement of kidney, lower respiratory tract, or liver was found to be a poor prognostic sign, and patients with associated immunologic disease often fared poorly. In general, prognosis has been found to correlate both with the number of nodal groups and with the number of extranodal systems involved by SHML. A complete bibliography of publications describing patients with SHML is included, and illustrations of the clinical, histopathologic, and radiographic features of the disease are provided.

Adolescent↗
PubMed1975

1,3-bis(2-chloroethyl)-1-nitrosourea(BCNU), cyclophosphamide, vincristine- and prednisone-(BCOP). A new therapeutic regimen for diffuse histiocytic lymphoma.

Sixty-seven evaluable patients with mixed cellular and histiocytic lymphomas, both nodular and diffuse, were treated with a combined drug regimen of BCNU, cyclophosphamide, vincristine, and prednisone administered for six monthly courses. Of 28 previously untreated patients with diffuse histiocytic lymphoma, 14 (50%) achieved a complete remission, and an additional 7 (25%) had a good partial response for an overall remission rate of 75%. Complete remissions were also obtained among the small number of mixed and nodular histiocytic lymphomas which were treated. The median survival for previously untreated patients with diffuse histiocytic lymphoma who achieved a complete remission is nearly two years and 42% (8/19) of these patients remain in their initial unmaintained remission (range 2-119 weeks). Hematologic toxicity, although acceptable, was the limiting factor. Granulocytes were more often and more severely depressed than platelets.

Carmustine↗