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Biomedical subjects

M Hoffman

Publications and source records attributed to M Hoffman.

At least 145 records · Page 8Linked to original sources
PubMed1996

The induction of p53 and WAF1/CIP1 in chronic lymphocytic leukemia cells treated with 2-chlorodeoxyadenosine.

The treatment of chronic lymphocytic leukemia includes the use of alkylating agents, steroids, and more recently nucleoside analogues. While prior studies have described potential mechanisms of 2-chlorodeoxyadenosine cytotoxicity including the accumulation of DNA strand breaks and induction of apoptosis or programmed cell death, the expression of p53 and its downstream target WAF1/CIP1 have not been examined. In this report we describe the induction of p53 and WAF1/CIP1 in the apoptotic chronic lymphocytic leukemia cells after exposure to 2-chlorodeoxyadenosine.

Antineoplastic Agents↗
PubMed1996

Newborn screening for HLA markers associated with IDDM: diabetes autoimmunity study in the young (DAISY).

Autoimmunity causing insulin-dependent diabetes mellitus (IDDM) begins in early childhood due to interactions between genes and unknown environmental factors that may be identified through follow-up of a large cohort of genetically susceptible children. Such a cohort has been established using a simple and rapid cord blood screening for HLA alleles. The DRB1 and DQB1 second exon sequences were co-amplified using the polymerase chain reaction and hybridized with single and pooled sequence-specific oligonucleotide probes. Four individual probes were used to detect the susceptibility alleles DRB1*03, DRB1*04, and DQB1*0302 as well as the usually protective DRB1*15/16 (DR2) alleles. In addition, pooled probes allow the distinction of DR3/3 from the DR3/x genotype (where x is neither DR2, 3, nor 4) and DR4/4 from DR4/x. Among 5000 newborns from the general Denver population, we have found the high-risk genotype (DRB1*03/ DRB1*04, DQB1*0302) to be present in 2.4% of non-Hispanic whites, 2.8% of Hispanics, and 1.6% of African Americans. The moderate-risk genotypes (DRB1*04, DQB1*0302/DRB1*04, DQB1*0302, DRB1*04, DQB1*0302/x, or DRB1*03/DRB1*03) are present in 17% of American non-Hispanic whites, 24% of Hispanics and in 10% of African Americans. These results demonstrate the feasibility of a large-scale newborn screening for genes associated with IDDM. The ultimate role for such a screening in future routine prediction and prevention of IDDM will depend on the availability of an effective and acceptable form of clinical intervention.

Asian People↗
PubMed1996

Stability study of nanoparticles of poly(epsilon-caprolactone), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide).

The objective was to evaluate the stability of nanoparticles prepared with poly(epsilon-caprolactone), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) polymers and stored at different temperatures and in different media. The stability parameters studied were molecular weight and crystallinity of the polymer, nanoparticle size and pH. The results show that the stability of polymeric nanoparticles depends on (i) the type of polymers with the following increasing order of polymer stability: PLA25GA50 < PLA37.5GA25 < PLA50 = PCL, (ii) the storage temperature: PCL and PLA50 nanoparticles can be kept at 4 degrees C and RT during one year, while PLA37.5GA25 and PLA25GA50 nanoparticles have to be stored at 4 degrees C, and (iii) the storage conditions: buffering or freeze-drying nanoparticles improves stability.

Biopolymers↗
PubMed1996

Urethral obstruction after anti-incontinence surgery in women: evaluation, methodology, and surgical results.

OBJECTIVES: To evaluate a group of women with voiding dysfunction and a low maximum flow rate (MFR) (less than or equal to 12 mL/s) after surgery for stress urinary incontinence (SUI); to establish diagnostic parameters indicating obstruction in an attempt to determine treatment selection; and to evaluate preliminary surgical results. METHODS: Eighteen women who underwent anti-incontinence surgery for SUI were diagnosed as having infravesical obstruction (IO). Thirteen women (group A [72%]) presented with clinically predominant symptoms of urgency, frequency, intermittency, and a variable vesical residual volume (RV), and five (group B [28%]) had as their most significant symptoms a high vesical RV and urinary tract infection that had been managed with intermittent catheterization (IC). The diagnosis of IO, suspected after clinical history, was established after physical examination and cystoscopic, cystographic and urodynamic investigations. RESULTS: Bladder instability was demonstrated in 6 group A patients (46%) and 1 group B patient (20%) (P = NS). Mean MFRs were 8.07 and 7.2 mL/s, respectively, in both groups (P = NS). Mean maximal voiding pressures (MVPs) were 20.23 and 5 cm H20, and mean RVs were 57.46 and 174 mL, respectively; both differences were statistically very significant (P <0.01 and P <0.001, respectively). High to normal MVPs occurred in 2 patients overall (11%). Bladder neck overcorrection, midurethral distortion, and postsurgical cystocele were demonstrated in both groups in 11 (85%), 0, and 2 (15%) patients in group A and 3 (60%), 2 (40%), and 3 (60%) patients in group B, respectively (P = NS). Patients in group A were treated surgically with cystourethrolysis and a repeated, less obstructive anti-incontinence operation. In group B 2 women (40%) had a similar surgical procedure; 1 (20%) underwent isolated urethrolysis; and 2 (40%) are currently maintained with IC. CONCLUSIONS: Among these 18 patients with voiding dysfunction after anti-incontinence surgery, a primary diagnosis of IO was established clinically. Only patients with a low MFR were selected for this study. Cytographic and endoscopic investigation as well as the presence of postsurgical cystocele assisted in establishing the diagnosis. The success rate with urethrolysis and resuspension was 60% for the 13 women with predominantly urgency, frequency, and the highest MVPs (20.23 +/- 9.67 cm H20 [group A) and 33% for the 5 women with urinary retention presenting the lowest MVPs (5.00 +/- 7.07 cm H20 [group A]) and 33% for the 5 women with urinary retention presenting the lowest MVPs (5.00 +/- 7.07 cm H20 [group B]). An added resuspension procedure is probably unnecessary in the latter group of patients and requires careful individual selection in the former group.

Adult↗
PubMed1996

Isolation of degradation-deficient mutants defective in the targeting of fructose-1,6-bisphosphatase into the vacuole for degradation in Saccharomyces cerevisiae.

The key regulatory enzyme in the gluconeogenesis pathway, fructose-1, 6-bisphosphatase (FBPase), is induced when Saccharomyces cerevisiae are grown in medium containing a poor carbon source. FBPase is targeted to the yeast vacuole for degradation when glucose-starved cells are replenished with fresh glucose. To identify genes involved in the FBPase degradation pathway, mutants that failed to degrade FBPase in response to glucose were isolated using a colony-blotting procedure. These vacuolar import and degradation-deficient (vid) mutants were placed into 20 complementation groups. They are distinct from the known sec, ups or pep mutants affecting protein secretion, vacuolar sorting and vacuolar proteolysis in that they sort CpY correctly and regulate osmotic pressure normally. Despite the presence of FBPase antigen in these mutants, FBPase is completely inactivated in all vid mutants, indicating that the c-AMP-dependent signal transduction pathway and inactivation must function properly in vid mutants. vid mutants block FBPase degradation by accumulating FBPase in the cytosol and also in small vesicles in the cytoplasm. FBPase may be targeted to small vesicles before uptake by the vacuole.

Carboxypeptidases↗
PubMed1996

Transmission of a procoagulant signal from tissue factor-bearing cell to platelets.

The goal of the current study was to examine the mechanism by which factor VIIa/tissue factor (TF) activity leads to platelet activation as the first step in initiation of coagulation. Adherent, endotoxin-treated monocytes were used as a cellular source of TF. The processes that led to platelet activation were rapid, since incubation of coagulation factors and platelets with TF for as little as 15 s initiated platelet activation. Further, direct contact between the TF source and platelets was not required since incubation of plasma levels of coagulation zymogens and inhibitors with TF generated the initiating signal for platelet activation. We hypothesized that thrombin generation on the cells that contained TF was the initiating signal for platelet activation. To test this hypothesis, factor VIIa, inhibitors, and different combinations of coagulation zymogens were incubated with TF-bearing cells. The supernatants were then transferred to a suspension of unactivated platelets with plasma concentrations of zymogen factors and inhibitors. Platelet activation was much more efficient when all the elements of the IIase complex (factors II, V and X) were preincubated with factor VIIa/TF than when only factor X was incubated with factor VIIa/TF. Finally, TF was incorporated into lipid vesicles containing phosphatidyl choline either with or without phosphatidyl serine. Vesicles without phosphatidyl serine have no IIase activity. Platelets were incubated with TF, coagulation zymogens and inhibitors. Platelet activation only occurred when the lipid vesicles could support IIase activity. We conclude that sufficient thrombin generation occurs on the TF-bearing cell (or TF-bearing vesicle) in the absence of platelets, to provide the procoagulant signal that leads to platelet activation. The activated platelet surface then provides sites for TF-activated factor IXa to recruit factor Xa to bind and assemble into functional Xase and IIase complexes.

Blood Coagulation↗
PubMed1996

Biochemical and mutational analysis of the histidine residues of staphylococcal enterotoxin A.

The goal of this study was to examine the role of histidine residues in the biological activities of staphylococcal enterotoxin A (SEA). Carboxymethylated SEA was unable to stimulate murine T-cell proliferation but was resistant to monkey stomach lavage fluid degradation, suggesting that native conformation was intact. Site-directed mutagenesis of the histidine residues of SEA was subsequently performed. SEA-H44A (SEA with histidine 44 replaced with alanine), SEA-H44D, SEA-H50A, SEA-H50D, SEA-H114A, SEA-H114D, SEA-H187A, and SEA-H187D retained superantigen and emetic activities, whereas SEA-H225A and SEA-H225D were defective in the ability to stimulate T-cell proliferation. These mutants were unable to compete with SEA for binding to Raji cells, suggesting that the defect in SEA-H225A and SEA-H225D is due to impaired major histocompatibility complex class II binding. SEA-H225D provoked an emetic response in monkeys only if fed at high doses, while SEA-H225A did not provoke an emetic response at low or high doses. In comparison, SEA-H61A and SEA-H61D were defective in emetic activity but not in the ability to stimulate murine T-cell proliferation. Overall, these studies show that the carboxy-terminal histidine at residue position 225 of SEA is important for both the superantigen and emetic activities of this enterotoxin. Histidine 61 appears to be important for emetic activity but not for superantigen activity, consistent with the hypothesis that the two activities are separable in staphylococcal enterotoxins.

Animals↗
PubMed1996

Cellular interactions in hemostasis.

Coagulation reactions normally occur on cell membranes in vivo. Using a cell-based in vitro model system, we have shown that where a factor is located, not simply how much is activated, is critically important in determining its role in hemostasis. Factor Xa activated on a tissue factor (TF)-bearing cell is not equivalent to factor Xa activated on a platelet surface. Factor IX and factor VIII are required for hemostasis because they combine to generate factor Xa on the platelet surface. Factor X activation by factor VIIa/TF does not compensate for a lack of factor IX or VIII because the factor Xa activated by VIIa/TF is located on the wrong surface for efficient thrombin generation.

Blood Coagulation↗
PubMed1996

Role of the beta 3-adrenergic receptor locus in obesity and noninsulin-dependent diabetes among members of Caucasian families with a diabetic sibling pair.

Obesity and insulin resistance are important risk factors for the development of noninsulin-dependent diabetes (NIDDM) and are prevalent among predisposed first degree relatives of diabetic individuals. Recent molecular screening and analysis of a common missense mutation of the beta 3-adrenergic receptor gene suggested this locus as a strong candidate for increased obesity, earlier age of diabetes onset, and insulin resistance. To test the hypothesis that the beta 3-adrenergic receptor locus affects diabetes susceptibility, obesity as measured by body mass index, and components of the insulin resistance syndrome, we examined the role of this region in families ascertained for two or more NIDDM siblings. Linkage analysis was conducted using both parametric and nonparametric analyses, including multipoint sibling pair analysis. We found no evidence for linkage to NIDDM as a dichotomous trait and no evidence for linkage to body mass index, waist/hip ratio, insulin levels, or glucose levels as quantitative traits or to reported age of onset among NIDDM individuals. The Trp64 Arg missense mutation was present in 11% of the population. The mutation was not associated with NIDDM, and Arg64 carriers did not have earlier NIDDM onset, higher body mass index, or higher waist/hip ratio than Trp64 homozygotes. Among relatives, Arg64 carriers had significantly lower fasting glucose levels and lower waist/hip ratios than Trp64 homozygotes, but no characteristics of the insulin resistance syndrome. We conclude that the beta 3-adrenergic receptor locus does not play an important role in NIDDM susceptibility or in the insulin resistance syndrome among members of families with a strong predisposition to NIDDM.

Adult↗
PubMed1996

Sequence variants in the sulfonylurea receptor (SUR) gene are associated with NIDDM in Caucasians.

NIDDM is a common heterogeneous disorder, the genetic basis of which has yet to be determined. The sulfonylurea receptor (SUR) gene, now known to encode an integral component of the pancreatic beta-cell ATP-sensitive potassium channel, IKATP, was investigated as a logical candidate for this disorder. The two nucleotide-binding fold (NBF) regions of SUR are known to be critical for normal glucose regulation of insulin secretion. Thus, single-strand conformational polymorphism analysis was used to find sequence changes in the two NBF regions of the SUR gene in 35 NIDDM patients. Eight variants were found; and three were evaluated in two Northern European white populations (Utah and the U.K.): 1) a missense mutation in exon 7 (S1370A) was found with equal frequency in patients (n = 223) and control subjects (n = 322); 2) an ACC-->ACT silent variant in exon 22 (T761T) was more common in patients than in control subjects (allele frequencies 0.07 vs. 0.02, P = 0.0008, odds ratio (OR) 3.01, 95% CI 1.54-5.87); and 3) an intronic t-->c change located at position -3 of the exon 24 splice acceptor site was also more common in patients than in control subjects (0.62 vs. 0.46, P < 0.0001, OR 1.91, 95% Cl 1.50-2.44). The combined genotypes of exon 22 C/T or T/T and intron 24 -3c/-3c occurred in 8.9% of patients and 0.5% of control subjects (P < 0.0001, OR 21.5, 95% CI 2.91-159.6). These results suggest that defects at the SUR locus may be a major contributor to the inherited basis of NIDDM in Northern European Caucasians.

ATP-Binding Cassette Transporters↗
PubMed1996

Differentiating agents do not induce a true hairy cell phenotype in B-CLL cells in vitro.

B-Chronic lymphocytic leukemia (B-CLL) and hairy cell leukemia (HCL) are both differentiated B-cell lymphoproliferative disorders. Prior studies have suggested that phorbol esters and the macrocyclic lactone Bryostatin-1, which are both protein kinase-C activators, can induce the differentiation of B-CLL cells into HCL cells in vitro, as evidenced by morphology, phenotype and TRAP activity. The differentiating effect of all-trans retinoic acid on B-CLL cells has been less extensively studied. We studied the effects of incubating adherence purified B-CLL cells with phorbol myristic acetate (PMA), all-trans retinoic acid (ATRA), and Bryostatin-1. None of these agents induced a true HCL phenotype (CD5-, CD11c/CD25 coexpression) under the conditions studied.

Acid Phosphatase↗
PubMed1996

A functional tethered ligand thrombin receptor is present on human hematopoietic progenitor cells.

The processing of inflammatory signals occurs through a variety of mechanisms; the recent descriptions of the tethered ligand receptor for thrombin (JA Hoxie et al., J Biol Chem 268:13756, and TK Vu et al., Cell 64:1057) provide a novel route and mechanism for cellular activation after inflammation and thrombosis. Using standard flow-cytometric techniques, it has been shown that the tethered ligand receptor is found on a number of terminally differentiated hematopoietic cells including platelets, lymphocytes, and monocytes. In this paper, we show that the CD34+ subset of hematopoietic stem cells bears the tethered ligand receptor on its surface; in addition, stimulation of this receptor with the agonist peptide SFLLRN results in a dose-dependent increase in intracellular calcium levels. We also show that culturing bone marrow mononuclear cells in the presence of thrombin or the tethered ligand receptor agonist peptide results in a statistically significant increase in colony-forming units-erythroid and -granulocyte/macrophage (CFU-E and CFU-GM). Although more work is needed to establish the exact mechanism of this effect, our results suggest that activation of the tethered ligand thrombin receptor may modulate the proliferative responses of CD34+ hematopoietic progenitor cells.

Antigens, CD↗
PubMed1996

[Bactericide activity of sulbactam before bacteria belonging to the Acinetobacter calcoaceticus-Acinetobacter baumannii complex].

BACKGROUND: To evaluate the bactericidal activity of colistin, imipenem and sulbactam against 24 Acinetobacter calcoaceticus-Acinetobacter baumannii complex isolations. METHODS: Bactericidal activity was estimated by using killing curves method. The concentrations employed were: colistin 4 mg/l, imipenem 8 mg/l and sulbactam 8 and 32 mg/l. RESULTS: Colistin was bactericidal in 24 isolations after 6 hours of incubation. When we used 8 mg/l of imipenem we detected bactericidal activity at the susceptible strains (MIC < or = 4 mg/l). We found bactericidal effect in 15 of 18 strains susceptible to sulbactam when we used 8 mg/l in killing curves after 24 hours of incubation. Using 32 mg/l we detected the same effect in 18 strains with MIC < or = 8 mg/l. CONCLUSIONS: Considering the high incidence of resistance in Acinetobacter spp. to several antibiotics including imipenem, we consider that sulbactam could be an excellent therapeutic alternative because it presents bactericidal activity in susceptible strains.

Acinetobacter↗
PubMed1995

Factors IXa and Xa play distinct roles in tissue factor-dependent initiation of coagulation.

Tissue factor is the major initiator of coagulation. Both factor IX and factor X are activated by the complex of factor VIIa and tissue factor (VIIa/TF). The goal of this study was to determine the specific roles of factors IXa and Xa in initiating coagulation. We used a model system of in vitro coagulation initiated by VIIa/TF and that included unactivated platelets and plasma concentrations of factors II, V, VIII, IX, and X, tissue factor pathway inhibitor, and antithrombin III. In some cases, factor IX and/or factor X were activated by tissue factor-bearing monocytes, but in some experiments, picomolar concentrations of preactivated factor IX or factor X were used to initiate the reactions. Timed samples were assayed for both platelet activation and thrombin activity. Factor Xa was 10 times more potent than factor IXa in initiating platelet activation, but factor IXa was much more effective in promoting thrombin generation than was factor Xa. In the presence of VIIa/TF, factor X was required for both platelet activation and thrombin generation, while factor IX was only required for thrombin generation. We conclude that VIIa/TF-activated factors IXa and Xa have distinct physiologic roles. The main role of factor Xa that is initially activated by VIIa/TF is to activate platelets by generating an initial, small amount of thrombin in the vicinity of platelets. Factor IXa, on the other hand, enhances thrombin generation by providing factor Xa on the platelet surface, leading to prothrombinase formation. Only tiny amounts of factors IX and X need to be activated by VIIa/TF to perform these distinct functions. Our experiments show that initiation of coagulation is highly dependent on activation of small amounts of factors IXa and Xa in proximity to platelet surfaces and that these factors play distinct roles in subsequent events, leading to an explosion of thrombin generation. Furthermore, the specific roles of factors IXa and Xa generated by VIIa/TF are not necessarily reflected by the kinetics of factor IXa and Xa generation.

Blood Coagulation↗
PubMed1995

Inhibition of platelet-derived growth factor-BB-induced fibroblast proliferation by plasmin-activated alpha 2-macroglobulin is mediated via an alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein-dependent mechanism.

alpha 2-Macroglobulin (alpha 2M) is a potentially important regulator of platelet-derived growth factor-BB (PDGF-BB)-stimulated cell growth due to our previous observation that PDGF-BB binds to alpha 2M noncovalently (Bonner, J. C., Goodell, A. L., Lasky, J. A., and Hoffman, M. R. (1992) J. Biol. Chem. 267, 12837-12844). We examined the in vitro effect of native and plasmin-activated (receptor-recognized) alpha 2M on the PDGF-BB-induced proliferation of mouse Swiss 3T3 and rat lung fibroblasts. Nondenaturing polyacrylamide gel electrophoresis showed that plasmin converted alpha 2M to its electrophoretically "fast" form at a 2:1 molar ratio and that 125I-PDGF-BB bound both alpha 2M and alpha 2M-plasmin. PDGF-BB-induced growth was not affected by native alpha 2M (0.3 microM) or plasmin (0.6 microM). The combination of plasmin and alpha 2M (2:1 molar ratio) inhibited PDGF-BB-induced cell proliferation 80-90%. Complexes of PDGF-BB.alpha 2M purified by gel filtration chromatography retained growth promoting activity, but the PDGF-BB.alpha 2M-plasmin complex did not. Preincubation of fibroblasts (37 degrees C for 24 h) with alpha 2M-plasmin did not change 125I-PDGF-BB binding or affect gene expression of the 6.5-kilobase PDGF-alpha receptor or 5.2-kilobase PDGF-beta receptor mRNA. However, preincubation with alpha 2M-plasmin (0-4 degrees C for 4 h) increased 125I-PDGF-BB binding 2-fold, and this increase was blocked by a receptor-associated protein antagonist of the alpha 2M-receptor/low density lipoprotein receptor-related protein. The receptor-associated protein antagonist blocked 125I-alpha 2M-methylamine binding, inhibited PDGF-BB-alpha 2M-plasmin uptake from fibroblast-cultured supernatants, and abolished the inhibitory effect of alpha 2M-plasmin on PDGF-stimulated growth. These data suggest that inhibition of PDGF-stimulated proliferation by alpha 2M-plasmin is mediated in part by clearance of PDGF-BB-alpha 2M-plasmin through the lipoprotein receptor-related protein.

Animals↗