Biomedical subjects

A Rosenberg

Publications and source records attributed to A Rosenberg.

At least 19 recordsLinked to original sources

PubMed1992

Regulation of phosphoinositide hydrolysis in cultured astrocytes by sphingosine and psychosine.

The effects of sphingosine and psychosine on phosphoinositide hydrolysis in primary cultured astrocytes were determined. Exposure to sphingosine produced a dose-dependent stimulation of phosphoinositide hydrolysis requiring the presence of external Ca++ for optimal activity. The addition of 10 microM norepinephrine resulted in a stimulation additional to that with sphingosine. The alpha 1-antagonist prazosin completely inhibited norepinephrine-induced phosphoinositide hydrolysis but had no effect on that produced by sphingosine. Psychosine (108 microM), when co-incubated with sphingosine, produced complete inhibition of sphingosine-induced phosphoinositide hydrolysis at all doses of sphingosine tested (33-668 microM). Likewise, psychosine totally inhibited norepinephrine-induced phosphoinositide hydrolysis. The protein kinase C inhibitor staurosporine (1 microM) had no effect on sphingosine-induced phosphoinositide hydrolysis. These findings suggest that lysosphingolipids such as sphingosine and psychosine may play an important role in the regulation of phosphoinositide turnover in astrocytes by a mechanism dependent on extracellular Ca++ and independent of the alpha 1-adrenergic receptor and protein kinase C.

Alkaloids↗

PubMed1992

Developmental patterns of ganglioside sialosylation coincident with neuritogenesis in cultured embryonic chick brain neurons.

Chick brain precursor neurons were observed to introduce sialic acid biosynthetically into only three specific gangliosides: monosialosyl lactosyl ceramide (GM3), disialosyl lactosyl ceramide (GD3), and disialosyl gangliotrihexosyl ceramide (GD2), when sialic acid was labeled metabolically by its obligate precursor, [3H] ManNAc. Sialosyl donor CMP-[3H]NeuAc supplied in the culture medium gave rise uniquely to surface-labeled GD3. Thus sialosyl transferase/GD3 synthase activity is expressed both intraneuronally and in the neuronal exofacial surface. Upon epidermal growth factor-induced onset of neurite outgrowth, labeled complex sialosyl gangliotetrahexosyl ceramide species of gangliosides began to appear in the embryonic neuronal plasma membrane. However, intraneuronal and exofacial sialosyl transferase/GD3 synthase activities remained constant, with or without neurite outgrowth. Moreover, simpler species of gangliosides maintained a steady quantitative sialosyl level (1.6 +/- 0.2 micrograms of sialic acid/mg of protein), whereas more complex species completely absent before neurite outgrowth accrued and reached 4.8 +/- 0.9 micrograms of sialic acid/mg of protein with full neurite development. This analysis of developmental patterns of ganglioside sialosylation has provided evidence that stable neurite outgrowth depends upon generation by the neuron of special plasma membrane with a massive content of complex higher species of gangliosides.

Animals↗

PubMed1992

Viscosity dependence of acrylamide quenching of ribonuclease T1 fluorescence. The gating mechanism.

The structural regulation of the access of acrylamide molecules, as quenchers, to the buried tryptophans of a protein can be modelled by a simple gate concept. Such a gate, when open, allows transient exposure of the fluorophore to the quencher molecule in solution. We have previously shown that the observed viscosity dependence of acrylamide quenching process in ribonuclease T1 (RNAse T1) is not reconcilable with the gating mechanism. However, on that occasion, we neglected the effect of changes in the activity of the quencher molecule and the possible presence of static quenching. The experimental observation of a considerable contribution by static quenching and the realization that static quenching might produce dramatic effects in steady state measurements led us to reexamine the question. It is shown that in a gating model the static component can also influence the apparent dynamic quenching. In this paper, we present derived equations for the gated quenching mechanism including possible contributions from the static component. We also carefully remeasured the acrylamide quenching of RNAase T1 as a function of increasing glycerol concentration. Computer simulations were carried out to compare the experimental data set to the generalized model. We reach the conclusion that even the new, quite complex equations fail to predict the qualitative and quantitative features of the observed quenching experiments. We arrived at the conclusion that the fluorophore is never the target of the quencher molecules in solution.

Acrylamide↗

PubMed1992

Felbamate monotherapy: controlled trial in patients with partial onset seizures.

Felbamate (FBM) monotherapy was evaluated in 44 patients with uncontrolled partial onset seizures in a unique, single-center, randomized, double-blind, parallel-group trial. During the 56-day baseline period, patients were required to have at least 8 seizures and to be receiving only one standard antiepileptic drug (AED) at a therapeutic level; a second AED was allowed if at a subtherapeutic level. Patients were randomized to valproate (VPA), 15 mg/kg, or to FBM, 3,600 mg/day. In the treatment phase, previous AEDs were discontinued by study day 28 (by one-third decrements on study days 1, 14, and 28). Study end points were completion of 112 study days or the fulfilling of escape criteria. Criteria for escape relative to baseline were: two-fold increase in monthly seizure frequency, two-fold increase in highest 2-day seizure frequency, single generalized tonic-clonic seizure (GTC) if none occurred during baseline, or significant prolongation of GTCs. The predetermined primary efficacy variable was the number of patients escaping in each treatment group. Nineteen patients on VPA and 3 on FBM met escape criteria (p less than 0.001, chi-square test). When overall seizure frequency among study completers was compared with baseline, the FBM group had a 50 to 65% reduction in seizure frequency. FBM adverse experiences were all mild or moderate in severity, and the incidence of adverse experiences was lower in monotherapy. FBM monotherapy was effective in the treatment of partial onset seizures with or without generalization and demonstrated a favorable safety profile.

Adolescent↗

PubMed1992

The effect of viscosity on the accessibility of the single tryptophan in human serum albumin.

When reactions take place with one of the reactants tied to protein matrix, movements along the reaction coordinate towards the transition state can become coupled to structural fluctuations of the protein matrix. This investigation aims to test the assumptions underlying the arguments supporting such a coupling. A coupling is allowed only if the activation barrier is high and broad enough as shown to be the case for the proton catalyzed isotope exchange at Trp-63 of lysozyme. In the present investigation the activation barrier for the same reaction has been lowered radically in an effort to show that the coupling, as measured by the dependence of rate on solution viscosity, will diminish and ideally vanish, despite the unchanged effects of cosolvents on the chemical activities of all the reactants. The isotope exchange rate at the indole nitrogen of the single tryptophan residue of human serum albumin was measured with UV. This residue is rigidly held to the protein surface and the solvent access, although restricted, corresponds to a partially exposed residue. As a consequence, the isotope exchange rates and the bimolecular quenching rate of fluorescence by acrylamide, also measured, are high. The experiments were carried out at pH 5.2 where the molecule is in the N-form and the exchange is catalyzed by OH- ions. The activation energy of the hydroxyl catalyzed reaction is 22 kJ lower than for the proton catalyzed process. Under these conditions the exchange rate is viscosity independent both in the case of glycerol and in ethylene glycol.(ABSTRACT TRUNCATED AT 250 WORDS)

Deuterium↗

PubMed1992

Somatic gene transfer in the development of an animal model for primary hyperparathyroidism.

The overproduction of hormones is associated with a variety of endocrinological disorders. We have used somatic cell gene transfer of human PTH (hPTH) to develop an animal model of hypercalcemia and osteoclastic skeletal resorption. Recombinant retroviruses were used to transduce a functional hPTH gene into cultured rat fibroblasts. The recombinant-derived preproparathyroid hormone peptide was appropriately processed in this ectopic cell, and intact hPTH (1-84) was secreted at a high level (2-5 ng/10(6) cells/24 h). Transplantation of the PTH-secreting cells into syngeneic rat recipients was associated with the development of hypercalcemia mediated by increasing serum concentrations of hPTH. Thyroparathyroidectomy in these hypercalcemic rats producing hPTH did not result in hypocalcemia and tetany, which was observed in control animals undergoing thyroparathyroidectomy. Chronic overproduction of hPTH (60 days) was associated with severe hypercalcemia, metastatic calcification, and histological changes of osteoclastic resorption of bone. This animal model will be useful in studying the pathophysiology of severe hyperparathyroidism in humans and should help in the evaluation of new medical therapies for hypercalcemia.

3T3 Cells↗

PubMed1991

Cementless Gustilo-Kyle and BIAS total hip arthroplasty: 2- to 5-year results.

We conducted extensive radiographic and clinical examination of 58 cementless total hip arthroplasties. Forty BIAS femoral stems had heads made of Co-base F 75 alloy and 18 Gustilo-Kyle femoral stems had Ti6A14V alloy heads. The cross-sectional geometry and location of the porous coating pads of the two stem types was identical, the BIAS component being slightly shorter. At the last follow-up, 27.8% of the Gustilo-Kyle femoral components and 2.5% of the BIAS femoral components were unstable. None of the acetabular components in the BIAS group as against 38.9% of the acetabular components in the Gustilo-Kyle group demonstrated wear of more than 1 mm. All unstable components which did not suffer intraoperative fracture had also acetabular wear of more than 1 mm. The only case with endosteal erosion was seen in a patient with an unstable implant displaying the most extensive wear. Nonparametric statistical analysis showed that the patients with Ti6A14V/polyethylene bearing surfaces had a statistically significantly higher extent of wear and a statistically significant higher incidence of femoral component loosening than patients with CrCoMo/polyethylene bearing surfaces.

Adult↗

PubMed1991

Possible coupling of chemical to structural dynamics in subtilisin BPN' catalyzed hydrolysis.

The viscosity dependence of enzymatic catalysis was examined in subtilisin BPN' catalyzed hydrolysis of N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide and N-succinyl-Ala-Ala-Pro-Phe-thiobenzyl ester. The viscosity of the reaction medium was varied by added glycerol, ethylene glycol, sucrose, glucose, fructose, poly(ethylene glycol) and Ficoll-400. Responses of the Michaelis-Menten parameters associated with hydrolysis were calculated from data obtained by spectrophotometric techniques. The reactions with these two substrates have catalytic rates well below the diffusion-controlled limit and thus enable us to study the viscosity effects on catalytic steps of non-transport nature. It was found that the Km values for both amide and ester reactions remained relatively independent of cosolvents. On the other hand, while the kcat values for amide were insensitive to cosolvents, those for ester were substantially attenuated except in the case of poly(ethylene glycol). The observed rate attenuations cannot be explained by changes in proton activity, water activity, dielectric constant of the reaction medium or shifts of any kinetically important pKa. Instead, the results can be adequately described by microviscosity effects on the unimolecular deacylation step with a coupling constant of 0.65 +/- 0.11. In addition, the different viscosity dependence in the acylation vs deacylation step can be rationalized in terms of fluctuation-dependent chemical dynamics of proton transfers in the context of the Bogris-Hynes model.

Amino Acid Sequence↗

PubMed1991

Felbamate.

Explore the source record for details and available documents.

Administration, Oral↗

PubMed1990

Bone lysis in well-fixed cemented femoral components.

We have reviewed 25 cases of focal femoral osteolysis in radiographically stable, cemented femoral implants. In three hips retrieved at post-mortem from two patients, we have been able to make a detailed biomechanical and histological analysis. The interval between arthroplasty and the appearance of focal osteolysis on clinical radiographs ranged from 40 to 168 months, and in over 70% of the cases this did not appear until after five or more years. Few had significant pain and there was no relation to age, sex or original diagnosis. The most common site for osteolysis were Gruen zones 2 and 3 on the anteroposterior radiograph and zones 5 and 6 on the lateral radiograph. In 15 cases (60%), the area of osteolysis corresponded to either a defect in the cement mantle or an area of very thin cement. The rate of progression of these lesions was variable, but to date only one has progressed to gross loosening of the femoral component. The back-scatter scanning electron microscopic examination of serial sections and biomechanical testing of the post-mortem specimens demonstrated focal cement fracture around implants that were otherwise rigidly fixed. In eight cases from which tissue was available, histology showed a histiocytic reaction with evidence of particulate polymethylmethacrylate. We consider that this local fragmentation was the stimulus for local osteolysis in an otherwise stable cemented femoral component.

Biomechanical Phenomena↗

PubMed1990

Expression of a class I MHC transgene: regulation by a tissue-specific negative regulatory DNA sequence element.

In vivo patterns of expression of a miniature swine class I major histocompatibility gene, PD7, were analyzed both in situ in the pig, and in transgenic mice. Structural analysis of PD7 DNA sequences revealed that PD7 is highly homologous to the pig gene PD1, which encodes a classical transplantation antigen. Despite the extensive homology, PD7 is expressed in situ at markedly lower levels than PD1 in nearly all tissues. Introduction of PD7 into mice results in a pattern of PD7 expression in the transgenic animals that parallels that observed in situ in the pig. Comparison of two lines of PD7 transgenic mice, which differ only in the extent of 5' flanking sequence, reveals the presence of a silencer element. The silencer activity is tissue specific: differences in PD7 expression are observed only in lymphoid tissues and skin. Skin from both lines of transgenics mediates graft rejection, but the rate of rejection correlates with the level of PD7 expression.

Amino Acid Sequence↗

PubMed1989

EGF-induced neuritogenesis and correlated synthesis of plasma membrane gangliosides in cultured embryonic chick CNS neurons.

Epidermal growth factor (EGF), over a low range of concentrations (165-825 pM), induced neuritogenesis in post-mitotic chick CNS precursor neurons cultured in a serum-free medium, without the addition of other growth factors. Antibody to EGF blocks the neurite-promoting activity of EGF. Similarly, neuritogenesis of cultured chick CNS neurons in medium supplemented with 20% fetal bovine serum is blocked by antibody to EGF, even though serum may contain other neuronotrophic bioactive proteins and steroids. Quantitatively, the only major gangliosides of the undifferentiated post-mitotic neurons are GD3 and GD2. GD3 as well as its biosynthetic precursor, GM3, undergo active biosynthesis in serum-free medium as evidenced by their vigorous labeling by radioactive galactose supplied in the culture medium. When the undifferentiated neurons in serum-free medium are exposed to EGF, the ensuing generation of neurite plasma membrane coincides with initiation of biosynthesis of the sialosyl gangliotetraosyl ceramide species of gangliosides (GD1A, GD1B, GT1B, GQ1B). Antibody to EGF simultaneously inhibits biosynthesis of these gangliosides as well as inhibition of neuritogenesis. These findings indicate that EGF may be a primary neurite-inducing growth factor for post-mitotic embryonic CNS neurons and that gangliosides, particularly those of the sialosyl gangliotetraosyl ceramide species, characterize the plasma membrane of CNS neurons during neuritogenesis.

Animals↗

PubMed1989

Radiation therapy in the treatment of difficult giant cell tumors.

Thirteen patients with giant cell tumors of bone have been treated by radiation therapy because surgery was not feasible or unacceptably disfiguring. Seven patients were treated for primary giant cell tumors of the bone, four for recurrent disease, and three for metastasis (one presented with both distant metastasis and local recurrence after primary surgery). The follow-up time ranged from 18 months to 13 years, with a mean of 6.5 years. All patients except one are alive. Local control was achieved in 11 patients (85%). One patient whose tumor was located in the sacrum had no gross response and at 5 months was subjected to a partial sacrectomy. A second patient had local regrowth 1 year after treatment; salvage surgery was successful. There have been no long-term complications of radiation therapy. This study confirms that for patients with giant cell tumor of bone, radiation therapy offers an effective alternative to complex or difficult surgery and constitutes a good treatment method to medically inoperable patients.

Adolescent↗

PubMed1989

Cementless total hip arthroplasty: femoral remodeling and clinical experience.

Cementless fixation of arthroplasty components has proved to be viable. The physiology of ingrowth is increasingly understood, and many of the factors influencing this phenomenon have been elucidated. The effect of ingrowth fixation on bone remodeling is less understood. The effects of varying ingrowth surfaces and the distribution of these surfaces influence remodeling and are critical to clinical success. Clinical studies with femoral components of different design show that while both yield good clinical results and exhibit similar remodeling patterns, the degree of remodeling may be influenced by design criteria.

Acetabulum↗

PubMed1989

Hand-held and automated sonomammography. Clinical role relative to X-ray mammography.

A retrospective analysis of 73 patients who had undergone X-ray mammography (XRM), automated sonomammography (ASM), and hand-held sonomammography (HSM) was performed to evaluate the clinical role of both types of sonomammography (SM) relative to XRM. The results were classified on the basis of mammographic and sonographic findings. Clinical and/or surgical proof was obtained in all 73 patients. The SM was complementary to XRM, depending on the radiographic breast density. When comparison was made between ASM (4.5 MHz) and the HSM (7.5 MHz), the pathologic condition was better identified by HSM in 86% of the cases. Moreover, in no cases was ASM better than HSM.

Adult↗

PubMed1989

Anabolic sialosylation of gangliosides in situ in rat brain cortical slices.

Radiolabeling of the sialic acid residues of gangliosides was examined in thin slices of rat brain cerebral cortex incubated under physiologic conditions in the presence of either [14C]N-acetyl-mannosamine (ManNAc) or cytidine 5'-monophosphoryl-[14C]N-acetyl-neuraminic acid (CMP-NeuAc). CMP-NeuAc is the direct donor substrate in the transfer of sialic acid to gangliosides by sialosyl transferases (SATs), including ectosialosyl transferases at the cell surface. ManNAc must be internalized by the neural cells (neuronal or glial) where it serves as an obligate precursor for the biosynthesis of the NeuAc moiety of intracellular CMP-NeuAc, via multiple reactions in the cytosol and nucleus. When exogenous [14C]ManNAc was supplied, there appeared to be a 2-h lag period before label was incorporated measurably into ganglioside sialic acid. That was followed by rapid ganglioside labeling continuing up to 6 h. There was high incorporation into ganglioside GM1. Labeling by ManNAc was inhibited by monensin, a monovalent cationophore that blocks anabolic transport in medial and trans Golgi. Extracellular CMP-NeuAc was not internalized by the cells. CMP-[14C]NeuAc labeling of gangliosides had no lag period, reached a maximum within 2 h, and then began to level. The label distribution among gangliosides was high in GD3, but quite low in GM1. CMP-NeuAc labeling was not inhibited by 10(-7) M monensin. These findings support a model in which ManNAc labels gangliosides by an intracellular route involving monensin-sensitive, Golgi-associated SATs. In this intracellular system, the major labeled products are gangliosides of the gangliotetraosyl series (GM1, GD1a, etc.).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Postradiation multicentric osteosarcoma.

The oncogenic effects of radiation are well-established. Osteosarcomas and fibrosarcomas are the two most common histologic types of secondary sarcoma. In this article a case of postradiation osteosarcoma is presented in which four discrete foci of sarcomatous transformation have occurred in the tibia and fibula after irradiation for a rhabdomyosarcoma of the calf 8 years earlier. A review of the literature reveals no similar case. Although synchronous, multifocal osteosarcoma without prior radiation has been described, this case differs in clinical, radiographic, and pathologic features; it best fits the description of postradiation multicentric osteosarcoma.

Bone Neoplasms↗

PubMed1988

Endogenous glycosphingolipid acceptor specificity of sialosyltransferase systems in intact Golgi membranes, synaptosomes, and synaptic plasma membranes from rat brain.

Preparations highly enriched in Golgi complex membranes, synaptosomes, and synaptic plasma membranes (SPM) by marker enzyme analysis and electron microscopic morphology were made from the brains of 28-day-old rats. These were incubated with cytidine 5'-monophosphate-N-acetyl[14C]neuraminic acid (CMP-NeuAc) in a physiologic buffer, without detergents. Glycolipid sialosyltransferase activities (SATs) were measured by analyzing incorporation of radiolabeled NeuAc into endogenous membrane gangliosides. Golgi SAT was diversified in producing all the various molecular species of labeled gangliosides [2.64 pmol of NeuAc transferred (mg of protein)-1 h-1]. Synaptosomal SAT exhibited a lower activity [0.66 pmol (mg of protein)-1 h-1], but it was highly specific in its labeling pattern, with a marked preference for labeling NeuAc alpha 2----8NeuAc alpha 2----3Gal beta 1----4Glc beta 1----1 Cer (GD3 ganglioside). SPM prepared from the synaptosomes retained the GD3-related SAT (or SAT-2), and the total specific activity increased [1.41 pmol (mg of protein)-1 h-1], which suggests that the location of the synaptosomal activity is in the SPM. These results indicate that SAT activity in Golgi membranes differs from that in synaptosomes with regard to endogenous acceptor substrate specificity and SAT activity of synaptosomes should be located in the synaptosomal plasma membrane. This SAT could function as an ectoenzyme in concert with ecto-sialidase to modulate the GD3 and other ganglioside population in situ at the SPM of the central nervous system.

Brain↗