Non-Hodgkin's lymphoma

Lymphoid neoplasia is a complex area comprising multiple diseases with varied pathology, treatment, and outcome. The non-Hodgkin's lymphomas are reviewed here. Non-Hodgkin's lymphomas, collectively, represent the sixth most common cancer in the United States as well as the sixth most common cause of cancer deaths. The overall incidence of non-Hodgkin's lymphoma has risen steadily over the past four decades. Although some of this is attributable to human immunodeficiency virus (HIV)-associated lymphoma, HIV-associated disease accounts for only a small part of the increase in lymphoma. As our knowledge of normal as well as neoplastic lymphoid development has expanded on the basis of histopathology as well as adjunct cellular and molecular techniques, multiple classifications have been proposed to take these into account. The clinical relevance to our understanding of non-Hodgkin's lymphoma is the concept that various lymphoid cancers are counterparts of stages of normal lymphoid development. Stages of lymphoid development in terms of cell surface markers and immunoglobulin gene rearrangements have been well characterized. These are particularly applicable to the early B-cell development, which is antigen-independent and occurs in the bone marrow. Diseases correlating with these stages are largely acute lymphocytic and lymphoblastic leukemia/lymphoma and high-grade lymphomas, such as Burkitt's lymphomas. Much has been learned recently about subsequent antigen-dependent B-cell development in secondary lymphoid organs to improve our understanding of the corresponding stages of B-cell neoplasia. Many of these stages correlate with more recently described entities such as mantle cell and marginal zone lymphomas. Histologic study remains crucial in determining the subtype of NHLs, whereas immunohistochemistry, surface phenotype, and molecular studies are useful in selected cases. Although some lymphoma classifications may be better in terms of understanding the lymphoma biology, the working formulation remains useful to guide clinical decision making. Lymphomas classified as low grade are considered incurable with standard therapy when diagnosed, as is usual, at advanced stages. Different subtypes may have different median survivals, but the goal has typically been palliation, whereas experimental approaches are clearly needed. Intermediate and high-grade lymphomas are potentially curable with aggressive combination chemotherapy. Recent evidence suggests that CHOP chemotherapy is as effective as more complex regimens. Still, 40% to 50% of patients are cured. Prognostic factor analysis has allowed separation of subgroups with much better survival in whom CHOP is adequate versus those with much poorer survival in whom experimental approaches are rational. Additional subtypes of lymphomas have been described and characterized since the working formulation was developed, including mucosa-associated lymphoid tissue tumors (MALT-oma), mantle zone lymphoma, anaplastic large cell lymphoma and AILD-like T-cell lymphoma. Approaches to these entities are still being optimized. Newer approaches, including high-dose therapy with stem cell support, biologic agents, and newer chemotherapeutic agents are discussed, as are special situations such as localized lymphoma of certain sites and lymphoma in immunosuppressed patients.

Neoadjuvant and adjuvant chemotherapy for invasive bladder cancer

Patients with muscle-invasive transitional cell carcinoma of the bladder are at high risk of systemic relapse following primary therapy. Several randomized trials of neoadjuvant and adjuvant chemotherapy suggest that chemotherapy administered before or after primary therapy may improve the disease-free survival of patients with invasive bladder cancer. The effects of neoadjuvant and adjuvant chemotherapy on long-term survival remain controversial. Potential differences in the long-term outcome of patients treated with neoadjuvant and adjuvant chemotherapy are not known. The only randomized trial comparing these 2 approaches showed no difference in survival with short median follow-up. Treatment recommendations for an individual patient require consideration of the relative advantages and disadvantages of chemotherapy administered before or after primary therapy. Recommendations regarding the optimal treatment of patients with invasive bladder cancer await the results of ongoing randomized trials. Because the use of adjuvant and neoadjuvant chemotherapy in patients with invasive bladder cancer represents a promising but unproven approach, physicians should encourage patients with invasive bladder cancer to enroll in clinical trials.

Polo-like kinase is a cell cycle-regulated kinase activated during mitosis

Previously, we demonstrated that expression of polo-like kinase (PLK) is required for cellular DNA synthesis and that overexpression of PLK is sufficient to induce DNA synthesis. We now report that the endogenous levels of PLK, its phosphorylation status, and protein kinase activity are tightly regulated during cell cycle progression. PLK protein is low in G1, accumulates during S and G2M, and is rapidly reduced after mitosis. During mitosis, PLK is phosphorylated on serine, and its serine threonine kinase function is activated at a time close to that of p34cdc2. The phosphorylated form of PLK migrates with reduced mobility on SDS-polyacrylamide gel electrophoresis, and dephosphorylation by purified protein phosphatase 2A converts it to the more rapidly migrating form and reduces the total amount of PLK kinase activity. Purified p34cdc2-cyclin B complex can phosphorylate PLK protein in vitro but causes little increase in PLK kinase activity.

Antisense oligodeoxyribonucleotide down-regulation of bcl-2 gene expression inhibits growth of the low-grade non-Hodgkin's lymphoma cell line WSU-FSCCL

The BCL-2 gene product is involved in preventing apoptosis. The t(14,18) chromosomal translocation, which results in a fusion messenger RNA containing the entire coding region of BCL-2 and a portion of the immunoglobulin heavy chain gene, is commonly found in follicular lymphoma and appears to play a role in lymphomagenesis by inhibiting cell death. We tested the hypothesis that downregulation of BCL-2 would decrease accumulation of follicular lymphoma cells by treating the t(14,18)-carrying follicular lymphoma cell line WSU-FSCCL in vitro with antisense oligodeoxyribonucleotides (ODNs) directed against BCL-2. We found dose-dependent, sequence-specific inhibition of cell accumulation by an antisense unmodified ODN directed at codons 2 to 7, which downregulated BCL-2 protein levels. This effect was near maximal at an ODN concentration of 40 micrograms/mL (6.9 mumol/L), with minimal toxicity by control sense, reverse, and mutated antisense ODN at the same concentration. The pre-B leukemia cell line REH showed no sequence-specific growth inhibition by the antisense ODN at these concentrations, and BCL-2 protein levels were not altered. These data suggest that WSU-FSCCL may be useful in a murine model to optimize antisense ODN for potential therapeutic utility.

Metabolic characterization of human non-Hodgkin's lymphomas in vivo with the use of proton-decoupled phosphorus magnetic resonance spectroscopy

Development of biological and clinical uses of in vivo 31P magnetic resonance spectroscopy has been hampered by poor anatomic localization of spectra and poor resolution of overlapping signals within phosphomonoester and phosphodiester regions of the spectrum. We applied 1H-decoupling and nuclear Overhauser enhancement to improve resolution of 31P magnetic resonance spectra accurately localized to 21 non-Hodgkin's lymphomas (NHL) by using three-dimensional chemical shift imaging. All 21 spectra had large phosphomonoester signals (26% of total phosphorus) that contained high amounts of phosphoethanolamine relative to phosphocholine. There were no signals from glycerophosphoethanolamine or glycerophosphocholine but only a broad signal from membrane phospholipids in the phosphodiester region (20% of phosphorus). Prominent nucleoside triphosphates (47% of phosphorus) and low inorganic phosphate (7% of phosphorus) indicate well-perfused tissue with viable cells. Mean intracellular pH was 7.23. These characteristics were similar in all grades and stages of NHL. By analogy with recently reported studies in cell lines in vitro, we hypothesize that the pattern of phospholipid metabolites observed in NHL in vivo is partly a manifestation of sustained activation of phospholipase C or D. The techniques we implemented permitted us to obtain more information about in vivo metabolism of NHL than has heretofore been available. This information is important for the establishment of appropriate experimental models and provides a basis from which to examine potential clinical uses of 31P magnetic resonance spectroscopy.

Prothymosin alpha: in search of a function

Prothymosin alpha is an acidic nuclear protein that is expressed at high levels in a wide variety of cell types. Accumulating data correlate prothymosin expression with alterations in the proliferative state of cells. Some data indicates that prothymosin may actually be necessary, if not sufficient, for proliferation, and that prothymosin may function in a c-myc associated pathway. Prothymosin is highly conserved through evolution suggesting a key function, however, that function remains unknown.

Prostate-specific antigen messenger RNA is expressed in non-prostate cells: implications for detection of micrometastases

Prostate specific antigen (PSA) is generally believed to be expressed only by prostate epithelium. If this were true of PSA, RNA, then detecting PSA RNA in cells outside of the prostate would indicate metastasis. PCR can detect rare prostate cancer cells. To enhance sensitivity, we developed "nested primer" PCR to detect PSA RNA. With this method, PSA RNA is present in several non-prostate cell lines, including BG-1 (ovarian), SK-MES-1 (lung), and HL-60 (myeloid leukemia), and some normal blood. A low level of PSA RNA detectable by nested primer PCR is present in some cells of non-prostate origin and may interfere with sensitive methods to detect micrometastases. Transcripts of other genes thought to be organ specific may have similar limitations.

Pulsatile pelvic masses: options for evaluation and management of pelvic arteriovenous malformations

Three recent and previously unreported cases of pelvic arteriovenous malformation are presented. Two were surgically resected in conjunction with elective gynecologic surgery, and the third was embolized by retrograde femoral superselective coaxial catheterization. The causal significance of birth or surgical trauma is discussed, and guidelines for diagnostic angiographic imaging and therapeutic embolization are presented.

Treatment-related myelodysplastic syndrome following abdominopelvic radiotherapy for endometrial cancer

A patient with grade II endometrial adenocarcinoma underwent TAH/BSO. The tumor penetrated 50% of the myometrium. A lesion from the serosa of the sigmoid colon was removed and contained metastatic adenocarcinoma. Metastatic tumor was also found in the common iliac lymph nodes. Postoperatively the patient was treated with abdominopelvic radiotherapy to 30 Gy. The pelvis was boosted to a dose of 46.2 Gy. The vaginal apex was then treated with three applications of high-dose-rate brachytherapy to a total dose of 12 Gy. The patient was doing well with no evidence of recurrence 52 months following treatment when she was diagnosed with a myelodysplastic syndrome. Cytogenetic analysis revealed aberrations of chromosomes 5 and 7, which is highly suggestive of a treatment-related process. Myelodysplasia induced by radiotherapy alone is an unusual but recognized event.

[Hemodynamic impact of thrombolytic therapy in acute pulmonary thromboembolism]

PURPOSE

To evaluate pre and post-hemodynamic changes after thrombolytic therapy in patients with acute pulmonary embolism with multiple pulmonary segments compromised.

METHODS

Nine patients, 5 females, aged between 27 and 83 (mean 62 +/- 16) years, with the onset of symptoms preceding 7 days, were submitted to thrombolytic therapy, administered after baseline perfusion-ventilation lung scan, echodopplercardiography (ECO) and hemodynamic measurements with a Swan-Ganz thermodilution catheter. The same procedures were done after the thrombolytic infusion. Streptokinase (SK) was used in 7 (78%) cases and recombinant human tissue-type plasminogen activator (rt-PA, alteplase) in 2 with the following doses: SK-250,000 i.u. infusion over 30 min, then 100,000 i.v/h over 24 to 72 h and rt-PA-20 mg in bolus infusion, then 80 mg over 6 h. Thrombolytic was infused in pulmonary artery trunk in 8 (88%) cases and a peripheral vein in 1 (12%) case, until mean pulmonary artery pressure (PAP) reached 20 mmHg. All patients received i.v. heparin and oral anticoagulation after thrombolytic therapy.

RESULTS

A significant (p < 0.05) decrease in right atrial pressure (12 +/- 3 vs 8 +/- 2 mmHg), PAP (32 +/- 5 vs 19 +/- 2 mmHg), pulmonary vascular resistance (397 +/- 125 vs 87 +/- 24 dyne.s/cm5) and increase in cardiac output (3.4 +/- 0.5 vs 5.5 +/- 1.0 l/min) and stroke volume (30 +/- 5 vs 57 +/- 10 ml/beat) were observed after thrombolytic infusion. Two patients died as a result of pulmonary infection unrelated to the embolic event or thrombolysis. Minor bleeding complications occurred in two cases and major in one patient with orthopedic prosthesis.

CONCLUSION

Thrombolytic therapy exert desirable effects on hemodynamic abnormalities, achieving lungs scan and ECO improvement in patients with acute pulmonary embolism.

Heterogeneity of the aggregation response of human platelets to arginine vasopressin

Previous reports have alluded to variability in the aggregation response of normal human platelets to the neuropeptide arginine vasopressin (AVP). Since it has not been well documented, the current studies were undertaken to characterize this response. AVP (1-100 nM) produced a concentration-dependent aggregation response. Although the aggregation response to 100 nM AVP did not correlate with age or sex, there was a bimodal response distribution based on the presence or absence of a second wave of aggregation. In kinetic studies, the apparent km of AVP was 18.3 +/- 5.4 nM. There was a significant inverse relationship between the maximal aggregation response to 100 nM AVP and the km (r = -0.82). One hundred nanomolar AVP increased the intracellular calcium concentration of platelets by 406 +/- 120 nM in calcium free buffer and by 658 +/- 233 nM in the presence of 1.0 mM CaCl2. The aggregation response to 100 nM AVP correlated most strongly with the transmembrane influx of calcium (r = 0.84). In individuals whom 100 nM AVP was able to generate a second wave of aggregation, the selective protein kinase C inhibitor bis-indolylmaleimide significantly decreased the platelet aggregation response. Thus, there is significant heterogeneity in the aggregation response of normal human platelets to AVP. Based on our kinetic studies and the effects of PKC inhibition on the aggregation response to AVP, we would hypothesize that the variability of the aggregation response of normal human platelets to AVP is related to a polymorphism of the platelet AVP V1 receptor.

Application of brain cholinesterase reactivation to differentiate between organophosphorus and carbamate pesticide exposure in wild birds

Brain cholinesterase activity was measured to evaluate pesticide exposure in wild birds. Thermal reactivation of brain cholinesterase was used to differentiate between carbamate and organophosphorus pesticide exposure. Brain cholinesterase activity was compared with gas chromatography and mass spectrometry of stomach contents. Pesticides were identified and confirmed in 86 of 102 incidents of mortality from 29 states within the USA from 1986 through 1991. Thermal reactivation of cholinesterase activity was used to correctly predict carbamates in 22 incidents and organophosphates in 59 incidents. Agreement (P < 0.001) between predictions based on cholinesterase activities and GC/MS results was significant.

Lead poisoning of spectacled eiders (Somateria fischeri) and of a common eider (Somateria mollissima) in Alaska

Lead poisoning was diagnosed in four spectacled eiders (Somateria fischeri) and one common eider (Somateria mollissima) found dead or moribund at the Yukon Delta National Wildlife Refuge, Alaska (USA) in 1992, 1993, and 1994. Ingested lead shot was found in the lower esophagus of one spectacled eider and in the gizzard of the common eider. Lead concentrations in the livers of the spectacled eiders were 26 to 38 ppm wet weight, and 52 ppm wet weight in the liver of the common eider. A blood sample collected from one of the spectacled eiders before it was euthanized had a lead concentration of 8.5 ppm wet weight. This is the first known report of lead poisoning in the spectacled eider, recently listed as a threatened species by the U.S. Fish and Wildlife Service.

Insoluble Glucan Formation by Leuconostoc mesenteroides B-1355

Leuconostoc mesenteroides B-1355 produced at least three glucosyltransferases (GTFs). We previously identified GTF-2 as alternansucrase and GTF-3 as fraction L dextransucrase. We here show that GTF-1 is a previously unreported sucrase that synthesized water-insoluble dextran. Our evidence consisted of the following. (i) GTF-1 was a major component and GTF-2 was a minor component of culture supernatant fractions, but supernatant fractions actively synthesized water-insoluble glucan. (ii) GTF-1 and culture supernatants produced an unusual high-pressure liquid chromatography pattern of malto-oligosaccharides that was not reproduced by GTF-2-GTF-3 mixtures. (iii) GTF-2, GTF-3, and GTF-2-GTF-3 mixtures did not synthesize insoluble glucan from sucrose. Nearly all of the alternansucrase in young (less than 17-h) cultures was associated with the cells.

Induced expression of a ubiquitin COOH-terminal hydrolase in acute lymphoblastic leukemia

To identify potential effector molecules of human B-cell differentiation, the acute lymphoblastic leukemia cells (Reh) were induced to terminal differentiation in vitro using the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate. Proteins of parent and differentiated Reh cells were mapped using powerful two-dimensional gel electrophoresis coupled with ultrasensitive silver stain. New protein (MW-pl; p34-5.3) spot was induced in the differentiated Reh cells. The NH2-terminal sequencing of this protein revealed 100% homology with the ubiquitin COOH-terminal hydrolase isozyme L1 (UCH-L1). The presence of UCH-L1 protein in the differentiated Reh cells but not in parent cells was confirmed by immunocytochemistry and Western blot. The cDNA for this enzyme was cloned from the differentiated Reh cells, and the UCH-L1 mRNA was detected in both parent and 12-O-tetradecanoylphorbol-13-acetate-induced cells. However, the message was more abundant in the differentiated cells than parent cells, indicating a posttranscriptional regulation. Until now, UCH-L1 was thought to be neuron-specific. The induced expression of UCH-L1 in differentiated Reh cells argues for a role of this enzyme, and the ubiquitin system, in B-cell differentiation.

Haloperidol blocks the uptake of [18F]N-methylspiroperidol by extrastriatal dopamine receptors in schizophrenic patients

We had previously demonstrated extrastriatal uptake of [18F]N-methylspiroperidol (18F-NMS) in the human brain. This study evaluates the effect of haloperidol on 18F-NMS binding in extrastriatal brain regions. Six schizophrenic patients on haloperidol underwent two PET scans with 18F-NMS at 12 h and at 6 days after haloperidol withdrawal. There was a significant increase in 18F-NMS uptake in striatal, thalamic, and temporal regions but not in frontal, occipital, or cerebellar regions, following drug withdrawal. Haloperidol's ability to block the uptake of 18F-NMS is an indication of the specificity of the radioligand's binding in these regions and supports the postmortem data demonstrating the presence of dopamine D2 receptors in the thalamus and temporal cortex of the human brain.

Comments on "Data truncation artifact reduction in MR imaging using a multilayer neural network"

A recent paper by Yan and Mao (see ibid., vol.12, no.1, p.73-7, 1993) provided the results of using a neural network based nonlinear prediction algorithm to extrapolate truncated magnetic resonance data. The extrapolation is intended to reduce the truncation artifacts that result when reconstructing an image from a limited k-space magnetic resonance data set using the discrete Fourier transform. When attempting to quantitatively compare Yan and Mao's method with the authors' own existing constrained modeling algorithm, the authors discovered a systematic error in Yan and Mao's analysis. With the error corrected, it was found that Yan and Mao's approach worked significantly better than they have reported and was more stable in the presence of noise.

Isolation of a morphologically and functionally distinct smooth muscle cell type from the intimal aspect of the normal rat aorta. Evidence for smooth muscle cell heterogeneity

Recent studies indicate that the neointima of injured rat arteries is composed of a subpopulation of smooth muscle cells (SMCs) distinct from medial smooth muscle cells. However, SMC diversity in normal adult aorta has remained elusive. This study characterizes two morphologically and functionally distinct SMC types isolated from different anatomic regions of the normal rat aorta. Rat aortic medial smooth muscle cells (MSMCs) were isolated from the media after removal of the intimal and adventitial cells. Rat aortic intimal smooth muscle cells (ISMCs) were isolated from the intimal aspect of everted rat aortas. The two cell types were characterized morphologically and immunohistochemically and were compared for their capacity to contract collagen gels in response to endothelin-1. MSMCs were spindle-shaped and grew in hills and valleys showing features previously described for vascular SMCs. Conversely, ISMCs displayed a polygonal and epitheloid shape, grew mainly as a monolayer, and had a higher proliferative rate. Both cell types expressed alpha-smooth muscle actin and were negative for Factor VIII-RAg. ISMCs produced large amounts of a laminin and type IV collagen-rich extracellular matrix which had a characteristic pericellular distribution. ISMCs, but not MSMCs, rapidly contracted collagen gels in response to endothelin-1. This study indicates that the normal rat aorta contains two types of SMCs located in anatomically distinct regions of the vessel wall. Because of their functional characteristics, the SMCs isolated from the intimal aspect of the aorta may play an important role in physiologic as well as pathologic conditions.

Glucosyltransferase Mutants of Leuconostoc mesenteroides NRRL B-1355

Leuconostoc mesenteroides NRRL B-1355 produces dextrans and alternan from sucrose. Alternan is an unusual dextran-like polymer containing alternating α(1→6)/α(1→3) glucosidic bonds. Cultures were mutagenized with UV and ethyl methanesulfonate, and colony morphology mutants were selected on 10% sucrose plates. Colony morphology variants exhibited changes from parent cultures in the production of one or more glucosyltransferases (GTFs) and glucans. Mutants were characterized by measuring resistance of glucan products to dextranase digestion, by electrophoresis, and by high-pressure liquid chromatography of maltose acceptor products generated from sucrose-maltose mixtures. Some mutants produced almost pure fraction L dextran, and cultures exhibited a single principal GTF band on sodium dodecyl sulfate-acrylamide gels. Other mutants produced glucans enriched for alternan. Colony morphology characteristics (size, smoothness, and opacity) and liquid culture properties (clumpiness, color, and viscosity in 10% sucrose medium) were explained on the basis of GTF production. Three principal GTF bands were detected.

Induction of T cell differentiation and lymphomagenesis in the thymus of mice with severe combined immune deficiency (SCID)

Severe combined immune deficiency (SCID) mice have a defect in their recombinase system and cannot productively rearrange their immune receptor genes. Thus, SCID thymocytes are arrested at the immature "triple negative" phase, not expressing CD3, CD4, or CD8 surface markers. Whole body irradiation of SCID mice induced maturation of their thymocytes to the CD4+/CD8+ double positive, CD3+low stage of differentiation, and resulted in the generation of a thymic cortical region on histologic examination. No mature single positive T cells were detected in the thymus or the periphery. VDJ rearrangements of TCR-beta with restricted clonality were observed in the double positive cells from a given individual. The CD3 complex was expressed on some of these cells, but the cells failed to mobilize intracellular calcium after cross-linking with CD3 Abs. The double positive cells appeared several weeks after irradiation, persisted for many months in the thymus, and by 6 mo generally developed into metastatic lymphoma. Retroviral activation was undetectable in both the preneoplastic and transformed thymocytes. Thus, it appears that the earliest steps in T cell development can be induced in SCID mice by inducing DNA breaks with radiation. This system represents a model of early thymic development, preneoplasia, and neoplasia.

Assessment methods and clinical outcomes: chemical and microbial composition, formation, and maturation dynamics of pellicle, plaque, and calculus

Understanding the functional dynamics of the oral cavity helps researchers design methods to predict clinical outcomes. Most information about the oral cavities of companion animals must be drawn from animal studies designed to understand human oral disease and from human studies. Based upon functional criteria for any animal or experimental research study, supragingival plaque and calculus can be assessed within four to six weeks. Although longer studies may be more appealing, such study designs may compromise the oral soft tissue health of the animals and are complicated by oral cavity dynamics. Thus, they are less sensitive and predictive of longer term clinical outcomes. Additional research is necessary to relate tooth surface accumulation phenomena with oral soft tissue health.

Induction of T cell differentiation and lymphomagenesis in the thymus of mice with severe combined immune deficiency (SCID)

Severe combined immune deficiency (SCID) mice have a defect in their recombinase system and cannot productively rearrange their immune receptor genes. Thus, SCID thymocytes are arrested at the immature "triple negative" phase, not expressing CD3, CD4, or CD8 surface markers. Whole body irradiation of SCID mice induced maturation of their thymocytes to the CD4+/CD8+ double positive, CD3+low stage of differentiation, and resulted in the generation of a thymic cortical region on histologic examination. No mature single positive T cells were detected in the thymus or the periphery. VDJ rearrangements of TCR-beta with restricted clonality were observed in the double positive cells from a given individual. The CD3 complex was expressed on some of these cells, but the cells failed to mobilize intracellular calcium after cross-linking with CD3 Abs. The double positive cells appeared several weeks after irradiation, persisted for many months in the thymus, and by 6 mo generally developed into metastatic lymphoma. Retroviral activation was undetectable in both the preneoplastic and transformed thymocytes. Thus, it appears that the earliest steps in T cell development can be induced in SCID mice by inducing DNA breaks with radiation. This system represents a model of early thymic development, preneoplasia, and neoplasia.

Phospholipase C-gamma 1 can induce DNA synthesis by a mechanism independent of its lipase activity

Inositol phospholipid-specific phospholipase C (PLC) is involved in several signaling pathways leading to cellular growth and differentiation. Our previous studies reported the induction of DNA synthesis in quiescent NIH 3T3 cells after microinjection of PLC and the inhibition of serum- or Ras-stimulated DNA synthesis by a mixture of monoclonal antibodies to PLC-gamma 1. In the course of our investigation of anti-PLC-gamma 1 monoclonal antibodies, we found that each antibody exerts different inhibitory effects on the phosphatidylinositol-hydrolyzing activity of PLC-gamma 1 and that the inhibition of enzymatic activity does not correlate with the inhibition of DNA synthesis observed in the microinjection assay. PLC-gamma 1 with defective enzymatic activity was synthesized by substituting phenylalanine for histidine within the PLC-gamma 1 catalytic domain at amino acids 335 and 380, and mutant enzymes were expressed using a vaccinia expression system. The mutant enzymes were purified and microinjected into quiescent NIH 3T3 cells to evaluate their mitogenic activity. A moderate induction of DNA synthesis occurred after injection of mutant PLC-gamma 1. This mitogenic activity was inhibited by an antibody (alpha E 8-4) that does not significantly inhibit PLC-gamma 1 enzyme activity, which indicates that something else has to be inhibited. Furthermore, the partial induction of DNA synthesis observed with mutant PLC-gamma 1 was increased to levels seen with wild-type PLC-gamma 1 by coinjection of mutant PLC-gamma 1 with two second messengers, diacylglycerol and inositol trisphosphate. These results suggest that the mitogenic activity of PLC-gamma 1 does not exclusively result from the enzymatic activity of the lipase and that another activity inherent to the PLC-gamma 1 molecule can also induce DNA synthesis in quiescent cells.

[Diagnosis of papillary muscle rupture in acute myocardial infarction by transesophageal Doppler echocardiography]

Three patients, two females, ages ranging from 62 to 78 years were studied, evolving with hypotension, acute pulmonary edema and cardiogenic shock. One had anterior myocardial infarction, and in two, infero-posterior. Due to severe hemodynamic instability and necessity of vasoactive drug therapy to maintain adequate arterial pressure, coronary angiography was performed in two, showing total occlusion of the circumflex artery and severe mitral regurgitation. In one case, angioplasty on the circumflex artery was successfully achieved. No hemodynamic improvement was observed, however. Doppler echocardiography depicted mild to moderate mitral regurgitation in the three cases. Transesophageal echo confirmed the clinical suspicion of papillary muscle rupture: total rupture of antero-lateral papillary muscle in one patient, as well as total and partial rupture of the postero-medial papillary muscle in the other two patients. Two patients were submitted to mitral valve replacement, and the surgical findings confirmed the transesophageal echo conclusions. One of them died in the immediate pos-operative period, whereas the other was discharged from the hospital and is doing well. The third patient died before operation. Differential diagnosis of acute mitral regurgitation due to papillary muscle dysfunction or rupture was not possible by left ventriculography or by transthoracic echo. Transesophageal echo was the only exam to clearly confirm papillary muscle rupture, as should be done promptly after clinical suspicion of this severe condition arises.