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M Hoffman

Publications and source records attributed to M Hoffman.

At least 163 records · Page 9Linked to original sources
PubMed1995

Thrombin enhances monocyte secretion of tumor necrosis factor and interleukin-1 beta by two distinct mechanisms.

Thrombosis and disseminated intravascular coagulation (DIC) are common complications of infections. Abnormal activation of coagulation is due in part of expression of tissue factor on intravascular cells in response to cytokines, including interleukin-1 beta (IL1 beta ) and tumor necrosis factor (TNF). Both TNF and IL1 beta are thought to play significant roles in producing the pathologic manifestations of sepsis. Therefore, we examined the effects of thrombin on TNF and IL1 beta secretion of monocytes, and the ability of monocyte products to promote tissue factor expression by endothelial cells. Human monocytes were treated with thrombin or a thrombin receptor agonist peptide (SFLLRN), and/or bacterial lipopolysaccharide (LPS). The agonists were removed, and monocytes cultured 18 hours. The monocyte-conditioned supernatants were assayed for TNF and IL1 beta antigen, and for their ability to induce tissue factor expression on human umbilical vein endothelial cells and the Ea.hy endothelial cell line. Thrombin alone did not promote monocyte TNF or IL-1 beta secretion. However, thrombin enhanced LPS-induced TNF and IL1 secretion. Supernatants from monocytes exposed to LPS plus thrombin promoted greater tissue factor expression on endothelial cells than supernatants from those treated with LPS only. SFLLRN did not increase TNF secretion in response to LPS, but did enhance LPS-induced IL1 beta secretion and tissue factor-inducing activity. Neither SFLLRN nor active thrombin augmented the level of mRNA for TNF above that induced by LPS alone. However, both increased the LPS-induced level of IL1 beta message. Thus, thrombin enhanced LPS-induced TNF and IL1 beta secretion by monocytes. Unexpectedly, the effects on these two cytokines were mediated by different mechanisms. Enhancement of LPS-induced IL1 beta secretion was largely mediated via the tethered ligand type thrombin receptor and correlated with an increase in the steady state level of mRNA. By contrast, enhanced TNF required proteolytically active thrombin, but was not mediated by the tethered ligand receptor. These data demonstrate that physiologically relevant amounts of thrombin can synergize with endotoxin to stimulate monokine release. Thrombin could thereby play a role in the complex network of mediators involved in the pathophysiology of sepsis. We speculate that limiting thrombin activity during DIC could be a beneficial adjunct in the management of sepsis.

Cells, Cultured↗
PubMed1995

Monocyte chemoattractant activity of Ser195-->Ala active site mutant recombinant alpha-thrombin.

alpha-Thrombin is chemotactic for human monocytes with optimal activity between 10-100 nM. The mechanism by which this response is mediated remains a point of controversy. The purpose of this study was to compare the chemotactic activity of proteolytically inactive thrombin (active site Ser195-->Ala mutant or Phe-Pro-Arg-chloromethyl ketone-inactivated thrombin) to thrombin and the "tethered ligand" thrombin receptor agonist peptide SFLLRN (single-letter amino acid code). Monocyte chemotaxis was compared to an optimal concentration (10 nM, considered to be 100%) of formyl-Met-Leu-Phe (fMLP). Proteolytically inactive thrombin (38% of fMLP) had similar chemotactic activity to active thrombin (46% of fMLP) at a concentration of 100 nM. Chemotaxis to SFLLRN was comparable to that of a control hexapeptide (FSLNLR) which is not an agonist for the tethered ligand thrombin receptor. Cross-desensitization experiments showed that pretreatment of monocytes with either mutant or active thrombin reduced subsequent chemotaxis to both thrombin chemotaxins. Pretreatment with SFLLRN did not decrease subsequent chemotaxis to either form of thrombin. Calcium flux measurements showed that both active thrombin and SFLLRN induced a rapid increase in monocyte and platelet intracellular calcium concentration. However, there was no intracellular calcium change in response to mutant thrombin or FSLNLR. Likewise, active thrombin and SFLLRN induced a rapid net increase in polymerized actin, but mutant thrombin and FSLNLR did not. By contrast, both active and mutant thrombin induced a polarization of monocyte morphology and actin distribution. This polarization has been associated with directed migration in many cell types. SFLLRN, however, induced a symmetrical increase in polymerized actin. These results suggest that measurements of intracellular calcium and polymerized actin are not perfect surrogate tests for true chemotactic activity. These results show that thrombin proteolysis is not required for monocyte chemotaxis and may be mediated by interaction with a binding site other than the tethered ligand thrombin receptor.

Actins↗
PubMed1995

The monocyte monolayer assay: a noninvasive technique for predicting the severity of in utero hemolysis.

To test the noninvasive monocyte monolayer assay in predicting hemolytic severity in utero, we studied 18 patients from two institutions with significant erythrocyte alloantibodies. Serum samples were obtained from each patient. Each subject donated a serum sample during her pregnancy. Monocytes were harvested from a single healthy donor and grown in monolayer culture. Erythrocytes with the appropriate antigens were sensitized with maternal serum and incubated with the monocyte monolayers. Erythrophagocytosis was scored as a percentage of the positive control. Perinatal outcomes were assessed post hoc and cases were classified as unaffected or mildly, moderately, or severely affected using standard definitions. Prenatal management was conducted without knowledge of the results. Six of the 18 patients had severe disease and one of the 18 had moderately severe disease. At a cutoff level of 20, the assay generated the following results: sensitivity was 7 of 7 (100%), specificity was 10 of 11 (90.9%), positive predictive value was 7 of 8 (87.5%), and negative predictive value was 10 of 10 (100%). The monocyte monolayer assay appears to be a useful, noninvasive modality for predicting the severity of hemolytic disease in utero.

Erythroblastosis, Fetal↗
PubMed1995

The effects of proprioceptive ankle disk training on healthy subjects.

According to research, proprioceptive training enables injured subjects to reduce proprioceptive deficits and increase postural control. However, the effects of proprioceptive training have not been researched in healthy subjects. This study investigated the effects of Biomechanical Ankle Platform System (BAPS) training on postural sway of healthy subjects (N = 28). Subjects were pretested and posttested using the Kistler force platform while performing a single limb stance. The subjects stood on their dominant leg with the opposite hip and knee held in a self-selected position. Subjects trained the dominant leg three times per week for 10 weeks on the BAPS. Experimental subjects showed significant improvements in both the medial-lateral and anterior-posterior parameters of postural sway when compared with a control group. In conclusion, 10 weeks of proprioceptive ankle disk training significantly decreased postural sway in both the medial-lateral and anterior-posterior directions.

Adolescent↗
PubMed1995

HIV test counselling at a tertiary hospital.

A questionnaire was distributed to 64 of the 78 interns working at a teaching hospital in Cape Town in August 1992 to examine their attitudes and practice in respect of HIV test counselling. The questionnaire was completed by 61 interns. Thirteen per cent of those who responded counselled all patients, 49% counselled some patients and 38% counselled no patients. Thirty-four per cent stated that they felt that pre-test counselling was always necessary and 57% that post-test counselling was always necessary. The most frequently stated reasons for not counselling patients were language barriers, time constraints, feelings of incompetence on the part of the intern and the fact that the patient was too ill. It is recommended that standard counselling procedures be established in each ward and formal under- and postgraduate counselling training for medical students and interns be instituted.

Adult↗
PubMed1994

Human monocytes support factor X activation by factor VIIa, independent of tissue factor: implications for the therapeutic mechanism of high-dose factor VIIa in hemophilia.

High doses of recombinant factor VIIa are useful in managing bleeding in hemophiliacs with inhibitors. Whether this therapeutic effect of factor VIIa is dependent on tissue factor (TF) is a matter of debate. We examined the ability of freshly isolated human monocytes (which lack TF) to support the activation of coagulation-factor X by factor VIIa. The rate of factor-X activation by factor VIIa was accelerated in the presence of monocytes compared with the rate of X activation in solution. This activation of factor X on monocytes was saturable with a K1/2 of about 400 to 600 pmol/L factor VIIa. The rate of activation was not inhibited by an excess of inhibitory anti-TF antibody or a Gla-containing fragment of prothrombin. In contrast to monocytes, an endothelial cell line did not support activation of factor X by factor VIIa. Our findings suggest that at least one cell type can accelerate activation for factor X by factor VIIa in the absence of TF. This activity requires higher concentrations of factor VIIa than does the TF mechanism. The concentrations of VIIa required are of a similar order of magnitude to those required for a therapeutic effect of VIIa in bleeding hemophiliacs with inhibitors.

Cells, Cultured↗
PubMed1994

Reticulated platelet counts in patients undergoing autologous bone marrow transplantation: an aid in assessing marrow recovery.

Thiazole orange (TO) is a fluorescent dye that is commonly used for flow cytometric measurement of erythrocytic reticulocytes. This technique has also been validated for counting "reticulated" platelets, as a measure of bone marrow thrombopoietic activity. Patients with an established diagnosis of idiopathic thrombocytopenic purpura (ITP) have been reported to have a three- to five-fold increase in the percent of circulating reticulated platelets. The current study was conducted to determine if platelet reticulocyte counts predicted recovery of bone marrow thrombopoietic activity following autologous bone marrow transplantation. We found an increase in the percent of circulating reticulated platelets preceding recovery of the platelet count; then, as the patients' platelet counts rose, the percent reticulated platelets fell. In patients with prolonged thrombocytopenia, a persistent increase in the proportion of reticulated platelets suggested a consumptive process, as opposed to failure of engraftment. Moderate transfusion of platelet concentrates did not interfere with the ability of the platelet reticulocyte measurements to detect increased thrombopoietic activity. Platelet transfusions did obscure any decrease in the proportion of reticulated platelets. Our results show that platelet reticulocyte counts could be useful in monitoring the recovery of marrow function following autologous bone marrow transplantation.

Adult↗
PubMed1994

Molecular screening of the glucokinase gene in familial type 2 (non-insulin-dependent) diabetes mellitus.

The glucokinase locus has been implicated by linkage studies in several Caucasian pedigrees with early onset, autosomal dominant diabetes, and mutations have been identified in a large number of these pedigrees. Although mutations have been reported in some pedigrees with late onset Type 2 (non-insulin-dependent) diabetes mellitus, linkage studies of typical familial Type 2 diabetes did not suggest a major role for this locus. Nonetheless, linkage studies were consistent with the hypothesis that mutations of the glucokinase gene were responsible for the pathogenesis of Type 2 diabetes in a minority of pedigrees or one gene in a polygenic disorder. To systematically address this hypothesis, we examined 60 diabetic members of 18 pedigrees ascertained for two or more Type 2 diabetic siblings and eight unrelated diabetic spouses. Initially, the coding regions from each of the 11 glucokinase exons were examined by the sensitive technique of single strand conformation polymorphism analysis to screen for single nucleotide substitutions. Subsequently, we also sequenced each exon from an affected member of the single pedigree in which a glucokinase allele was most likely to segregate with diabetes. Single strand conformation polymorphism analysis detected only three variants, none of which altered the amino acid sequence. No coding or splice site mutations were detected. Likewise, no additional mutations were detected upon direct sequence analysis. However, additional screening of promoter and 3' untranslated regions detected a variant pattern in the untranslated region of exon 10 which appeared to segregate with diabetes and impaired glucose tolerance in one pedigree.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

EEG detection of nontonic-clonic status epilepticus in patients with altered consciousness.

Subtypes of status epilepticus (SE) without tonic-clonic convulsions (nontonic-clonic SE) present as altered consciousness sometimes with subtle motor activity and are important to consider in the differential diagnosis of patients with unexplained altered consciousness. Other patients may have altered consciousness with intermittent ictal activity on electroencephalography (EEG) that represents probable SE, but have other medical conditions that may be contributing to altered consciousness. EEG is the only reliable way to make the diagnosis of nontonic-clonic SE and we make emergency EEG available on a 24-h basis at our hospital. To determine how often definite or probable nontonic-clonic SE was detected by EEG we prospectively collected data on all cases where physicians ordered EEG to evaluate altered consciousness or possible SE. Out of 198 cases with altered consciousness but no clinical convulsions, 74 (37%) showed EEG and clinical evidence of definite or probable nontonic-clonic SE. Forty-two episodes (57%) were probable or definite complex partial SE, 29 (39%) were probable or definite subtle generalized SE, and three (4%) were myoclonic SE. In 23 SE cases altered consciousness was the only clinical sign at the time of diagnosis; subtle motor activity was present in 36 others. Neither clinical signs nor prior history predicted which patients showed SE on EEG. Nontonic-clonic SE followed a cerebral infarction in 16 cases. Contrary to other reports, we found no relationship between duration of SE and EEG pattern. Subtle generalized SE occurred most commonly in the setting of a diffuse brain injury rather than evolving from convulsive SE. This study demonstrates that nontonic-clonic SE is a common finding in patients with unexplained altered consciousness and EEG is necessary in the evaluation of these patients.

Adolescent↗
PubMed1994

The detection of post-traumatic angle recession by gonioscopy in a population-based glaucoma survey.

BACKGROUND: Blunt trauma is responsible for most eye injuries in urban populations. Anterior chamber angle recession has been reported to be the most common sign of previous blunt trauma to the eye. The cumulative lifetime prevalence of post-traumatic angle recession has not been reported previously, and the relation between angle recession and glaucoma in a population-based setting is unknown. METHODS: As part of a population-based glaucoma survey, gonioscopy was performed on 987 (82.7%) of 1194 inhabitants of the village of Mamre, near Cape Town, South Africa, who were 40 years of age or older. RESULTS: Some degree of angle recession was identified in one eye of 60 people and in both eyes of 86 people. Men were affected more than three times as often as women in the fifth, sixth, and seventh decades. The cumulative lifetime prevalence of angle recession in this community was 14.6%. The prevalence of glaucoma in people with angle recession was 5.5% (8/146). Of 87 eyes with 360 degrees of angle recession, only 7 (8.0%) had glaucoma. Excessive alcohol consumption was significantly related to the presence of angle recession in women (P < 0.001). The prevalence of monocular blindness due to trauma was 2.5% (25/987). CONCLUSION: Although the importance of the study may be limited to this community, the findings suggest that future population-based studies of ocular trauma should include gonioscopy on all individuals examined. Secondary glaucomas, especially those related to trauma, should be screened for in developing countries when trying to establish the prevalence of potential visual loss from glaucoma.

Adult↗
PubMed1994

HIV-infected macrophages as efficient stimulator cells for detection of cytotoxic T cell responses to HIV in seronegative and seropositive vaccine recipients.

The induction of CD8+ CTL responses is a goal of most HIV-1 vaccine trials, but such potentially protective effector responses have been difficult to evaluate, particularly in these vaccine prevention trials, due to technical obstacles. We report a method to evaluate CTL responses based on the ability to infect autologous macrophages with a monocytotropic strain of HIV-1, and to use these cells as efficient stimulators. This approach does not require the addition of exogenous cytokines, allows detection of class I-restricted CTLs against multiple HIV-1 gene products, and circumvents the problem, often detected using other stimulator cells, of high levels of lytic activity against target cells expressing vaccinia and/or EBV antigens. Adherent monocyte-derived macrophages were infected with HIV-1 Ba-L, and used within 2-3 weeks as autologous stimulators. Fresh PBMCs were cultured with the infected macrophages, harvested after 1 week, replated with fresh infected macrophages and filler cells, and tested after 5-7 days for cytolytic activity. CD8+ CTL responses specific for HIV-1 envelope were detected at an E:T ratio as low as 5:1 in two of four HIV-1-uninfected recipients of an HIV vaccine regimen that included a recombinant live vaccinia virus. Cytotoxic T lymphocyte activity could be detected > 1 year following vaccination. Similar lytic activity was detected with cryopreserved responder cells. In two HIV-1-infected individuals participating in a blinded therapeutic vaccination trial, the use of infected macrophages as in vitro stimulators permitted detection of the presence of envelope and gag-specific CTLs. No responses were observed in nonimmunized, uninfected controls. Thus, HIV-1-infected macrophages can stimulate in vitro the repertoire of primed HIV-reactive CD8+ precursors from seronegative and seropositive participants in HIV-1 vaccine trials, and should facilitate the identification of potentially effective candidate HIV vaccines.

AIDS Vaccines↗
PubMed1994

Platelet procoagulant complex assembly in a tissue factor-initiated system.

The aim of this study was to examine the assembly of the factor IXa/VIIIa (Xase) and factor Xa/Va (IIase) complexes on the platelet surface in a system designed to mimic tissue factor-initiated coagulation. The experimental system contained tissue factor-bearing monocytes, unactivated platelets, and plasma concentrations of factors V, VIII, IX, X, prothrombin, tissue factor pathway inhibitor (TFPI), antithrombin III (ATIII), and small amounts of factor VIIa. The time courses of platelet activation, coagulation factor binding and thrombin generation were compared. In this system, thrombin generation by the combination of monocytes and platelets was synergistic compared to each cell type alone. Platelet activation and thrombin generation were minimal in the absence of prothrombin or factor X. After a lag period, platelet activation began, followed by progressive binding of factors Va and VIIIa. This was followed by factor IXa and Xa binding and the onset of thrombin generation. Unexpectedly, a transient early increase in platelet-associated factor IX and X was also seen, that was due to release from platelets. The amount of factor IX bound to isolated activated platelets was increased by addition of factor VIIIa, or by activation of factor IX to IXa. In contrast, factor VIIIa binding was not altered by the presence of factor IX or IXa. We conclude that in a tissue factor-initiated system, assembly of the procoagulant complexes on the platelet surface begins after platelet activation occurs. Platelet activation requires thrombin generation in the vicinity of the tissue factor bearing cells. The cofactors Va and VIIIa bind to the platelets and facilitate subsequent binding of factors IXa and Xa to form functional procoagulant complexes.

Blood Coagulation Factors↗
PubMed1994

Evaluation of human immunodeficiency virus type 1 (HIV-1)-specific cytotoxic T-lymphocyte responses utilizing B-lymphoblastoid cell lines transduced with the CD4 gene and infected with HIV-1.

Analysis of major histocompatibility complex-restricted cytotoxic T lymphocytes (CTL) capable of killing human immunodeficiency virus type 1 (HIV-1)-infected targets is essential for elucidating the basis for HIV-1 disease progression and the potential efficacy of candidate vaccines. The use of primary CD4+ T cells with variable infectivity as targets for such studies has significant limitations, and immortal autologous cells with high levels of CD4 expression that can be consistently infected with HIV-1 would be of much greater utility. Therefore, we transduced Epstein-Barr-virus-transformed B-lymphoblastoid cell lines (LCL) with a retroviral vector, LT4SN, containing the human CD4 gene. Stable LCL in which more than 95% of cells expressed membrane CD4 were obtained. Aliquots were infected with HIV-1, and, after 4 to 7 days, nearly all of the cells contained cytoplasmic gag and produced high levels of p24 antigen. The ability of major histocompatibility complex-restricted CD8+ CTL to lyse such HIV-1-infected CD4-transduced LCL (LCL-CD4HIV-1) was evaluated. These autologous targets were lysed by CTL generated from an HIV-1-uninfected vaccinee over a broad range of effector-to-target ratios. Similarly, the LCL-CD4HIV-1 were efficiently lysed by fresh circulating CTL from HIV-1-infected individuals, as well as by CTL activated by in vitro stimulation. Both HIV-1 env- and gag-specific CTL effectors lysed LCL-CD4HIV-1, consistent with the cellular expression of both HIV-1 genes. The LCL-CD4HIV also functioned as stimulator cells, and thus are capable of amplifying CTL against multiple HIV-1 gene products in HIV-1-infected individuals. The ability to produce HIV-1-susceptible autologous immortalized cell lines that can be employed as target cells should enable a more detailed evaluation of vaccine-induced CTL against both homologous and disparate HIV-1 strains. Furthermore, the use of LCL-CD4HIV-1 should facilitate the analysis of the range of HIV-1 gene products recognized by CTL in seropositive persons.

AIDS Vaccines↗
PubMed1994

Severe inflammatory upper airway stenosis in ulcerative colitis.

Severe upper airway stenosis was diagnosed in a 23 year old woman who presented with hoarseness, cough and dyspnoea 8 yrs after initial diagnosis of ulcerative colitis. The respiratory symptoms worsened over the next few months, the patient eventually developing dysphagia and ultimately severe upper airway obstruction. The narrowest site was the glottis, which was severely stenosed by inflammatory swellings. Systemic corticosteroids led to rapid clinical improvement and restoration of normal airway patency within a few months. Ulcerative colitis is frequently associated with extraintestinal inflammatory manifestations. In the respiratory tract these usually take the form of chronic bronchitis, which occasionally develops into bronchiectasis. This case confirms that the inflammation can also involve the larynx and large airways.

Adult↗
PubMed1994

2-Chlorodeoxyadenosine is an active salvage therapy in advanced indolent non-Hodgkin's lymphoma.

PURPOSE: To determine the response rate to 2-chlorodeoxyadenosine (2-CdA; cladribine) in patients with advanced indolent non-Hodgkin's lymphoma (NHL) who fail to respond to or progress after a response to standard chemotherapy drugs. PATIENTS AND METHODS: Twenty-one patients were treated with at least one cycle of 2-CdA 0.1 mg/kg/d by continuous infusion for 5 or 7 days. RESULTS: The overall response rate (complete response [CR] and partial response [PR]) was nine of 21 patients (43%; 95% confidence interval, 22% to 64%). Unmaintained durable responses (longest follow-up, 29+ months) have been observed. The treatment was well tolerated by all patients. The major toxicity was related to myelosuppression (predominantly neutropenia) and immunosuppression with infection. CONCLUSION: The purine analog 2-CdA is an active salvage therapy in pretreated patients with indolent NHL, and deserves further assessment in untreated patients and in combination with other chemotherapy agents.

Adolescent↗