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R S Rosenthal

Publications and source records attributed to R S Rosenthal.

At least 19 recordsLinked to original sources
PubMed2002

Enveloped virus inactivation by caprylate: a robust alternative to solvent-detergent treatment in plasma derived intermediates.

Solvent-detergent treatment, although used routinely in plasma product processing to inactivate enveloped viruses, substantially reduces product yield from the human plasma resource. To improve yields in plasma product manufacturing, a new viral reduction process has been developed using the fatty acid caprylate. As licensure of plasma products warrants thorough evaluation of pathogen reduction capabilities, the present study examined susceptibility of enveloped viruses to inactivation by caprylate in protein solutions with varied pH and temperature. In the immunoglobin-rich solutions from Cohn Fraction II+III, human immunodeficiency virus, Type-1, bovine viral diarrhea virus (BVDV), and pseudorabies virus were inactivated by caprylate concentrations of >/=9 mM, >/=12 mM, and >/=9 mM, respectively. Compared to solvent-detergent treatment, BVDV inactivation in Fraction II+III solution was significantly faster (20-60 fold) using 16 mM caprylate. Caprylate-mediated inactivation of BVDV was not noticeably affected by temperature within the range chosen manufacturing the immunoglobulin product. In Fraction II+III solutions, IgG solubility was unaffected by </=19 mM caprylate. In albumin solution from Cohn supernatant IV-1, 40 mM caprylate rapidly inactivated BVDV, demonstrating versatility in inactivating enveloped viruses potentially present in other protein solutions. Our data show that caprylate is a robust enveloped virus inactivating agent for immunoglobulins and albumin which may potentially be utilized for other proteins; viral inactivation was not adversely affected by protein content and the buffer composition conditions evaluated. Within the parameters examined, caprylate inactivation of enveloped viruses provided comparable activity or advantages relative to the current, standard solvent-detergent treatment.

Albumins↗
PubMed2001

Oncogenic Ras-induced proliferation requires autocrine fibroblast growth factor 2 signaling in skeletal muscle cells.

Constitutively activated Ras proteins are associated with a large number of human cancers, including those originating from skeletal muscle tissue. In this study, we show that ectopic expression of oncogenic Ras stimulates proliferation of the MM14 skeletal muscle satellite cell line in the absence of exogenously added fibroblast growth factors (FGFs). MM14 cells express FGF-1, -2, -6, and -7 and produce FGF protein, yet they are dependent on exogenously supplied FGFs to both maintain proliferation and repress terminal differentiation. Thus, the FGFs produced by these cells are either inaccessible or inactive, since the endogenous FGFs elicit no detectable biological response. Oncogenic Ras-induced proliferation is abolished by addition of an anti-FGF-2 blocking antibody, suramin, or treatment with either sodium chlorate or heparitinase, demonstrating an autocrine requirement for FGF-2. Oncogenic Ras does not appear to alter cellular export rates of FGF-2, which does not possess an NH(2)-terminal or internal signal peptide. However, oncogenic Ras does appear to be involved in releasing or activating inactive, extracellularly sequestered FGF-2. Surprisingly, inhibiting the autocrine FGF-2 required for proliferation has no effect on oncogenic Ras-mediated repression of muscle-specific gene expression. We conclude that oncogenic Ras-induced proliferation of skeletal muscle cells is mediated via a unique and novel mechanism that is distinct from Ras-induced repression of terminal differentiation and involves activation of extracellularly localized, inactive FGF-2.

Animals↗
PubMed2001

ERK1/2 is required for myoblast proliferation but is dispensable for muscle gene expression and cell fusion.

Skeletal muscle satellite cells, which are found between the muscle fiber and the basal lamina, remain quiescent and undifferentiated unless stimulated to remodel skeletal muscle or repair injured skeletal muscle tissue. Quiescent satellite cells express c-met and fibroblast growth factor receptors (FGFR) 1 and 4, suggesting these receptors are involved in maintaining the undifferentiated quiescent state or involved in satellite cell activation. Although the signaling pathways involved are poorly understood, the mitogen activated protein kinase (MAPK) cascade has been implicated in the regulation of skeletal muscle growth and differentiation by FGFs. In this study, we investigated if activation of the Raf-MKK1/2-ERK1/2 signaling cascade plays a role in FGF-dependent repression of differentiation and proliferation of MM14 cells, a skeletal muscle satellite cell line. Inactivation ofthe Raf-MKK1/2-ERK1/2 pathway in myoblasts through the overexpression of dominant negative mutants of Raf-1 blocks ERK1/2 activity and prevents myoblast proliferation. Additionally, inhibition of MKK1/2 by treatment with pharmacological inhibitors also blocks FGF-mediated stimulation of ERK1/2 and blocks the G1 to S phase transition of myoblasts. Unexpectedly, we found that inactivation of the Raf-ERK pathway does not activate a muscle reporter, nor does inactivation of this pathway promote myogenic differentiation. We conclude that FGF-stimulated ERK1/2 signaling is required during the G1 phase of the cell cycle for commitment of myoblasts to DNA synthesis but is not required for mitosis once cells have entered the S-phase. Moreover, ERK1/2 signaling is not required either to repress differentiation, to promote skeletal muscle gene expression, or to promote myoblast fusion.

Animals↗
PubMed1998

The FGF receptor-1 tyrosine kinase domain regulates myogenesis but is not sufficient to stimulate proliferation.

Ligand-stimulated activation of FGF receptors (FGFRs) in skeletal muscle cells represses terminal myogenic differentiation. Skeletal muscle cell lines and subsets of primary cells are dependent on FGFs to repress myogenesis and maintain growth. To understand the intracellular events that transduce these signals, MM14 skeletal muscle cells were transfected with expression vectors encoding chimeric receptors. The chimeras are comprised of the PDGF beta receptor (PDGFbetaR) extracellular domain, the FGFR-1 intracellular domain, and either the PDGFbetaR or FGFR-1 transmembrane domain. The chimeric receptors were autophosphorylated upon PDGF-BB stimulation and are capable of stimulating mitogen-activated protein kinase activity. Activation of the tyrosine kinase domain of either chimera repressed myogenesis, suggesting intracellular responses regulating skeletal muscle differentiation are transduced by activation of the FGFR-1 tyrosine kinase. Unexpectedly, we found that activation of either chimeric receptor failed to stimulate cellular proliferation. Thus, it appears that regulation of skeletal muscle differentiation by FGFs requires only activation of the FGFR tyrosine kinase. In contrast, stimulation of proliferation may require additional, as yet unidentified, signals involving the receptor ectodomain, the FGF ligand, and heparan sulfate either alone, or in combination.

Animals↗
PubMed1998

Purification and characterization of the heteromeric transcriptional activator MvaT of the Pseudomonas mevalonii mvaAB operon.

The mvaAB operon of Pseudomonas mevalonii encodes HMG-CoA reductase (EC 1.1.1.88) and HMG-CoA lyase (EC 4.1.3.4), enzymes that catalyze the initial reactions of mevalonate catabolism in this organism. Expression of this operon is regulated by the constitutively expressed transcriptional activator protein MvaT that binds in vitro to an upstream regulatory element. Mevalonate is essential for activation of transcription in vivo, and in vitro data demonstrated that MvaT binds to the mvaAB cis-regulatory element in the absence of mevalonate with a Kd,app of 2 nM. Purification of MvaT enriched for two polypeptides of approximate molecular mass 15 kDa and 16 kDa, designated P15 and P16. MvaT, assayed by its DNA-binding activity, comigrated with P15 and P16 during DNA-affinity chromatography, size-exclusion chromatography, and sucrose density gradient centrifugation. P15 and P16 also comigrated during denaturing isoelectric focusing of purified MvaT. Treatment of MvaT with dimethylsuberimidate formed a 31-kDa polypeptide complex that contained N-terminal sequences from P15 and P16. The apparent association of P15 and P16 in solution and their copurification with MvaT activity strongly suggests that MvaT is comprised of these two subunits. Size-exclusion chromatography gave an estimated molecular mass for MvaT of 33 kDa. A partial DNA sequence of the P16 gene was obtained using PCR employing degenerate primers directed against the N-termini of P15 and P16. P16 appears to be comprised of at least 128 aminoacyl residues having a predicted molecular mass of 14.3 kDa.

Amino Acid Sequence↗
PubMed1996

Tolerance to appetite suppression induced by peptidoglycan.

Physiologically realistic peptidoglycan (PG) fragments, derived from Neisseria gonorrhoeae, were shown previously to dose-dependently suppress food consumption and body weight gain in rats following single intraperitoneal injections. The present study, examining the effects of repeated daily injection of PG, provides additional support to our underlying hypothesis, i.e., that soluble PG fragments contribute to the loss of appetite commonly associated with bacterial infections. An initial intraperitoneal injection of purified, soluble, macromolecular, extensively O-acetylated PG fragments (S-O-PG) (240 micrograms/kg of body weight) decreased overnight food consumption in male Lewis rats (150 g) by approximately 35% relative to animals receiving diluent alone (P < 0.05). However, subsequent daily injections of S-O-PG resulted in progressively smaller effects on food consumption until, by the fourth day, rats were completely nonresponsive (tolerant) to S-O-PG-induced hypophagia. Rats that developed tolerance to the effects of S-O-PG on appetite were also tolerant to three other known hypophagic agents, lipopolysaccharide (LPS), muramyl dipeptide, and interleukin-1, when challenged one day after establishment of S-O-PG tolerance. Similarly, rats developed tolerance to repeated injections of muramyl dipeptide or LPS and were cross-tolerant to S-O-PG when challenged 1 day later. However, 30 days after establishment of S-O-PG tolerance, rats remained nonresponsive to S-O-PG but regained full responsiveness to LPS-mediated hypophagia. Thus, at least two mechanisms of tolerance to S-O-PG hypophagia exist: an early tolerance which is nonspecific and a late tolerance which is specific for S-O-PG. Late, but not early, tolerance to S-O-PG-mediated suppression of appetite was associated with an increase in specific anti-PG antibody activity as measured in an enzyme-linked immunosorbent assay.

Acetylation↗
PubMed1994

Peptidoglycan fragments decrease food intake and body weight gain in rats.

We hypothesized that peptidoglycan (PG) fragments decrease appetite in rats. Male Lewis rats (150 g; n > or = 7) received intraperitoneal (i.p.) injections of purified soluble PG fragments that had been treated with polymyxin B-agarose to remove residual endotoxin. Food consumption and body weight gain were determined at intervals after injection. Single i.p. injections of macromolecular extensively O-acetylated PG (S-O-PG) and non-O-acetylated PG fragments (24 to 240 micrograms/kg) reduced food intake and body weight gain in a dose-dependent fashion during the first 12 h after injection. Low-molecular-weight disaccharide peptide monomers with nonreducing 1,6-anhydro-N-acetylmuramic acid ends and muramyl dipeptide (MDP; 1.6 mg/kg) were also appetite and weight gain suppressants, albeit at least 10-fold less potent than S-O-PG; however, muramidase-derived monomers and peptide cross-linked dimers with reducing muramic acid ends were inactive. Appetite suppression was not limited to the Lewis rat strain since another strain, F344, exhibited similar decreases in food intake after injection of S-O-PG or MDP. Oral administration of MDP or S-O-PG, at concentrations 3 and 20 times higher, respectively, than those that were active i.p., failed to elicit a hypophagic response. We conclude that soluble PG fragments are potent suppressants of food consumption and body weight gain in rats and that, although macromolecular PG is more potent than low-molecular-weight fragments, neither O-acetylation nor glycosidic linkage of PG fragments is required for activity. We speculate that PG fragments may contribute to loss of appetite during bacterial illness.

Acetylation↗
PubMed1993

Blood clearance and organ localization of Candida albicans and E coli following dual infection in rats.

Immunosuppressed prematures, cancer patients, and transplant recipients are susceptible to bacterial or fungal sepsis or both. This report evaluates whether the ability of the reticuloendothelial system (RES) to remove blood-borne viable radiolabeled 35S Escherichia coli and 3H-Leucine Candida albicans is adversely affected by a dual intravenous challenge of these organisms. Male Sprague Dawley rats (n = 150) weighing 175 to 180 g were placed in 5 experimental groups (n = 30). Group I received intravenous (IV) C albicans (10(7)/mL), group II received E coli (10(9)/mL), group III received a dual injection of C albicans and E coli, group IV received Candida 1 hour prior to E coli, and group V received E coli 1 hour prior to fungi. At 1, 4, and 24 hours, tissue samples (50 to 100 mg) of liver, spleen, kidneys, and lungs were processed for liquid scintillation counting. Organ distribution of bacteria and fungi was calculated and expressed as mean percent +/- SD of labeled organisms. The liver trapped 72% +/- 10% and the lungs 1.1% +/- 0.3% of E coli (group II) (P < .001). The organ distribution of Candida (group I), however, was similar in liver and lungs (42.5% +/- 10% and 41.4% +/- 6.4%, respectively). Liver localization of E coli was unaffected by simultaneous or staggered fungal injection (groups III, 4, and V). Lung distribution of E coli following dual injection (group III) was significantly higher than controls (group II) (3.6% +/- 0.7% v 1.1% +/- 0.3%; P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Initial organ localisation of blood-borne Candida albicans in a rat model of disseminated candidosis.

The rat was evaluated as an experimental model for disseminated candidosis by quantitating blood clearance and initial organ localisation of 3H-leucine-labelled Candida albicans after intravenous injection into the tail or portal vein. Viable or formalin-killed blastoconidia or viable blastoconidia with germ tubes were injected into experimental animals. Blood and tissue samples were obtained up to 24 h after injection and processed for liquid scintillation counting (to determine the distribution of labelled yeasts) and quantitation of viable organisms. Yeasts were cleared rapidly after intravenous (i.v.) injection by either route, i.e., < 5% of the radioactivity was detected in the blood after 5 min. The liver and lung were the major organs that sequestered blood-borne yeasts 1 h after tail vein injection (42.5 SD 15% and 41.4 SD 6.4% of labelled yeasts injected, respectively). However, injections via the portal vein resulted in trapping of the yeasts predominantly by the liver. Recovery of radioactivity and viable yeasts from all organs except the kidneys decreased with time. Overall, the results indicated that the rat might serve as a reliable model for short-term studies on organ distribution and thus contribute to our understanding of tissue trophism in candidosis.

Animals↗
PubMed1991

Impaired clearance and organ localization of Candida albicans in obstructive jaundice.

Sepsis is a major cause of morbidity and mortality in infants with cholestatic jaundice. This may be attributed to altered host defense mechanisms. Fungal infection frequently occurs in immunocompromised patients. This study evaluates the effect of biliary obstruction on blood clearance and organ localization of radiolabeled viable Candida albicans. Male Sprague-Dawley rats (140 to 150 g) were placed in 2 groups. Group I (n = 30) were sham-operated controls. Group II (n = 90) underwent ligation and division of the distal common bile duct (CDL). At 1, 2, and 3 weeks following CDL, 10(7) cells/mL radiolabeled viable C albicans were injected via the tail vein. The final distribution of the organisms was calculated and expressed as the mean percent of radiolabeled organisms per gram and per total organ. Blood clearance of C albicans was similarly rapid in both groups. However, there was a significant decrease in the trapping of fungi by the rat liver Kupffer cells (20.3% +/- 7.9% v control 42.5% +/- 15%; P greater than .001), and increased pulmonary localization of bacteria 3 weeks following CDL (53.6% +/- 13.2% v control 41.4% +/- 6.4%). The significant decrease in liver trapping and increased lung localization of C albicans in CDL rats, may result in systemic reemergence of fungi and play a role in the susceptibility to fungal infection in jaundiced subjects.

Animals↗
PubMed1990

Somnogenic, pyrogenic, and hematologic effects of bacterial peptidoglycan.

Bacterial infections and certain muramyl peptides elicit a variety of pathophysiological effects including increases in body temperature and slow-wave sleep. Bacterial cell wall peptidoglycan is composed of muramyl peptides. To investigate the ability of isolated bacterial cell walls to enhance slow-wave sleep, rabbits were injected intravenously with cell walls isolated from Staphylococcus aureus or with soluble peptidoglycan prepared from Neisseria gonorrhoeae. These injections increased slow-wave sleep, electroencephalographic delta-wave amplitudes, and body temperature, reduced rapid-eye-movement sleep, and induced neutrophilia and lymphopenia. The somnogenic and pyrogenic effects of S. aureus cell walls developed within 1 h and persisted throughout the recording period. Injections of N. gonorrhoeae peptidoglycan induced similar effects but of larger magnitude and shorter duration. We conclude that peptidoglycan is a bacterial component that mediates the increased sleep observed during infectious disease.

Animals↗
PubMed1989

Somnogenic activity of O-acetylated and dimeric muramyl peptides.

Slow-wave sleep-promoting factors in brain and urine were identified as muramyl peptides (MPs), the building blocks of bacterial cell wall peptidoglycan. In this study, structural variations of MPs that occur naturally in bacterial peptidoglycan were investigated for somnogenic activity. Monomeric and dimeric MPs were isolated and purified from Neisseria gonorrhoeae and Actinomadura sp. strain R39. The structures of these MPs were verified by fast atom bombardment mass spectroscopy and tandem mass spectroscopy. After intracerebroventricular administration of MPs, electroencephalograms and brain temperatures of rabbits were recorded for 6 h and were analyzed to determine durations of slow-wave sleep, rapid-eye-movement sleep, and wakefulness. The 6-O acetylation of muramic acid enhanced the somnogenic effects of certain monomeric MPs relative to their non-O-acetylated (but otherwise identical) counterparts. Two monomeric MPs containing an unsubstituted amide (i.e., Iso-Gln) were inactive, thus confirming previous results showing that amidation of a variety of MPs can block somnogenic activity. Two peptide-cross-linked MP dimers tested had no effect on slow-wave sleep, although a third peptide-cross-linked MP containing a 1,6-anhydro muramyl end on one of its monomeric subunits, a structure that enhances somnogenic potency of un-cross-linked monomers, was somnogenic. Two dimers connected by glycosidic bonds and containing an Iso-Gln moiety were inactive. Two other glycosidically linked dimers that also contained an Iso-Gln moiety, but were of lower molecular weight, were somnogenic. In summary, 6-O acetylation of muramic acid in somnogenic MPs enhances activity, and as a class, peptide-linked dimeric MPs tend to be less active than their constituent monomers.

Acetylation↗
PubMed1987

Fast atom bombardment mass spectrometry and tandem mass spectrometry of biologically active peptidoglycan monomers from Neisseria gonorrhoeae.

Fast atom bombardment mass spectrometry (FABMS) and tandem mass spectrometry (MS/MS) were employed to define the structures of Neisseria gonorrhoeae peptidoglycan monomers that were of interest because of their abilities to mediate diverse biological reactions ranging from arthritogenicity to somogenicity. FABMS-determined molecular weights of individual components present in several different enzymatically derived classes of gonococcal monomers revealed that each of these classes was a complex mixture of up to 13 distinct peptidoglycan fragments. These ranged from the predominant disaccharide tetrapeptides possessing reducing or nonreducing 1,6-anhydro-N-acetylmuramic acid ends to relatively minor constituents containing glycine or asparagine in addition to traditional peptidoglycan amino acids, i.e. alanine, glutamic acid, and diaminopimelic acid. FABMS of high performance liquid chromatography-purified monomers yielded some sequence information; however, analysis even of unfractionated peptidoglycan mixtures using a JEOL HX110/HX110 tandem mass spectrometer operating at 10 kV provided unambiguous primary sequence data for the peptidoglycan monomers and defined the position of glycine in four compounds as well as the location of O-acetyl substituents (present on some compounds) on C-6 of the N-acetylmuramic acid residue.

Amino Acid Sequence↗
PubMed1987

Bacterial peptidoglycans as modulators of sleep. I. Anhydro forms of muramyl peptides enhance somnogenic potency.

Chemically defined muramyl peptides (MPs), derived primarily from enzymatic digests of Neisseria gonorrhoeae peptidoglycan, were used to define the structural determinants of MP-mediated somnogenic activity. One of these, i.e. N-acetylglucosaminyl-N-acetyl-1,6-anhydro-N-acetylmuramyl-alanyl-glutamy l- diaminopimelyl-alanine, was structurally identical to the major naturally occurring MP previously detected in mammalian brain and urine. The somnogenic potency of this MP was similar to that of the corresponding disaccharide pentapeptide containing an additional alanine at the C-terminus and the analogous anhydro-muramic acid-containing monosaccharide tetrapeptide lacking the glucosamine moiety. Infusion of as little as 1 pmol of these highly active MPs increased significantly the percentage of slow-wave sleep in experimental animals. In fact, each of 5 anhydro-muramyl disaccharide peptides tested was somnogenic at a dose of 10 pmol or less and, as far as tested, the activity was affected only slightly by the length or composition of the peptide side chain. However, none of a matched set of analogous MPs, differing only in replacement of the anhydro-muramyl end by a hydrated muramic acid residue, was somnogenic at this dose. A modified form of the hydrated muramyl tripeptide containing a free amide on the diaminopimelic acid residue was completely inactive in amounts up to 1000 pmol. Together, the current data suggested: that the anhydro-muramic acid end (but not the glucosamine moiety) is essential for maximal somnogenic potency; and that amidation of carboxyl groups on the peptide-side chain may block MP-mediated somnogenic activity.

Anhydrides↗