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M Lozano

Publications and source records attributed to M Lozano.

At least 19 recordsLinked to original sources
PubMed2001

Transient ischaemic attack: a common initial manifestation of cardiac myxomas.

BACKGROUND AND AIMS: Cardiac myxomas may present clinically with many different features. Since highly effective treatments exist, it is important that they are diagnosed quickly in order to avoid further complications. Our aim was to determine the influence of neurological presentation in diagnosis and prognosis of cardiac myxomas. METHODS: We have reviewed the clinical charts of 28 patients diagnosed with cardiac myxomas seen at our centre in the last 20 years. RESULTS: Mean age at diagnosis in patients with neurological events was 49.22 years and 60.84 years in those without neurological manifestations (p = 0.0325). Most frequent presentations were: cardiac manifestations (92.8%), general manifestations (71.4%) and embolic events (39.3%). Nine patients (32.1%) presented with cerebral embolism; 7 of whom presented with transient ischaemic attacks (TIA), which was the first manifestation in 6 of them; 3 of them later suffered complete cerebral infarction with sequelae. Echocardiography confirmed diagnosis in 26 out of 27 patients in which it was performed. None of the patients presented neurological symptoms after surgery. CONCLUSION: The most frequent initial neurological manifestation in our series was TIA. Nevertheless, none of the patients were diagnosed after the first neurological symptom. Although the contribution of cardiac myxomas to the total amount of TIA is low, since surgery is highly effective and of low risk, and patients with neurological manifestations are younger, it is vital to consider the possibility of cardiac myxoma after a TIA of unknown origin.

Adult↗
PubMed2000

[Multinational European project and multicenter Spanish study of quality improvement of assistance on consultation-liaison psychiatry in general hospital: clinical profile in Spain].

BACKGROUND: In the frame of the European study on quality assurance in consultation liaison psychiatry and psychosomatics (supported by the BIOMED 1 program), the clinical < > of consultation-liaison psychiatry units pertaining to six Spanish general hospitals is analyzed. PATIENTS AND METHOD: A sample of 3. 608 consecutive patients referred to the consultation-liaison psychiatry units of five public general hospitals (Clínico of Zaragoza, Clínico of Barcelona, General of Alicante, Ramón y Cajal of Madrid, Princesa of Madrid) and one private gynecological hospital (Dexeus of Barcelona) was studied. The data were recorded with a standardized instrument (CL-BDoK-P), validated in a previous study. RESULTS: Consult request took place 10.6 days (on average) after the patients admission (< >), half the requests were urgent, and psychiatric consultants examined the patients 1.9 days (on average) after the request (< >). The most frequent reasons for referral were current psychiatric symptoms (50.3%), unexplained physical symptoms (15.2%), substance abuse (9.2%), psychiatric history (8.5%), suicide risk (6%) and coping with illness (5.8%). The main referral services were internal medicine (17.5%), traumatology (7.5%) and general surgery (7.3%). An important clinical activity is documented in patients frequently considered to be < >, with broad spectrum diagnostic and interventions processes and both in-hospital and out-patient follow-up. However, some problems were also detected in the clinical < >. CONCLUSIONS: The results outline the clinical importance of Spanish consultation-liaison psychiatry in the general hospital, but the possibility of improving its efficiency through the implementation of integrative models, organizational changes and modern models of < > is also emphasized.

Adult↗
PubMed2000

An association study of bipolar mood disorder (type I) with the 5-HTTLPR serotonin transporter polymorphism in a human population isolate from Colombia.

The short variant of a functional length polymorphism in the promoter region of the serotonin transporter has been associated with several behavioural and psychiatric traits, including bipolar mood disorder. The same short allele has also been implicated as a modifier of the bipolar phenotype. Here we evaluate the etiologic/modifier role of this polymorphism in a case (N=103) / control (N=112) sample for bipolar mood disorder (type I) collected from an isolated South American population. We did not detect an association between bipolar disorder and the 5-HTT promoter polymorphism in this sample. However, an excess of the short allele was seen in younger cases and in cases with psychotic symptoms. When combined with data from the literature, the increased frequency of the short allele in patients with psychotic symptoms was statistically significant.

Age of Onset↗
PubMed2000

Effects of the addition of second-messenger effectors to platelet concentrates separated from whole-blood donations and stored at 4 degrees C or -80 degrees C.

BACKGROUND: Platelet concentrates (PCs) are currently stored at 22 degrees C under continuous agitation. Because of the potential risk of the overgrowth of bacteria in case of contamination, PC shelf life is limited to 5 days. A mixture of second-messenger effectors is being evaluated to determine if it has benefits for cold liquid storage and cryopreservation of platelets. STUDY DESIGN AND METHODS: PCs separated from whole-blood donations by the buffy coat method were randomly assigned (n = 6 each) to be stored for 5 days at 22 degrees C under continuous agitation or at 4 degrees C after treatment with a platelet storage medium (ThromboSol, LifeCell Corp. ). PCs were also cryopreserved with 6-percent DMSO (final concentration) or with ThromboSol plus 2-percent DMSO (final concentration) (TC). After storage, platelets were analyzed by flow cytometry, transmission electron microscopy, and aggregation and perfusion techniques. RESULTS: Cold liquid storage of ThromboSol-treated platelets resulted in a lower binding of coagulation factor Va on the platelet surface than on platelets stored at 22 degrees C. In transmission electron microscopy, a conversion to spherical morphology was seen in the case of cold liquid storage. No difference between ThromboSol-treated platelets stored at 4 degrees C and platelets stored at 22 degrees C was seen in perfusion studies. Cryopreservation in the presence of TC prevented the reduction in glycoprotein Ib and IV expression on platelet surface that is seen in 6-percent DMSO-cryopreserved platelets. Platelets cryopreserved in TC covered, by thrombus, a significantly greater percentage of the perfused surface after the freezing and thawing process. CONCLUSION: ThromboSol-treated PCs separated from whole-blood donations by the buffy coat method, stored at 4 degrees C for 5 days, or cryopreserved in the presence of TC, maintained in vitro functional activity comparable to that achieved by current methods of storage, although discoid morphology was not preserved during cold liquid storage with ThromboSol.

Bacteria↗
PubMed2000

Alterations in cytoskeletal organization and tyrosine phosphorylation in platelet concentrates prepared by the buffy coat method.

BACKGROUND: Numerous morphologic and biochemical changes occurring during platelet storage may result in the impairment of platelet function. STUDY DESIGN AND METHODS: The effect of preparation and storage conditions on platelet function was analyzed through evaluation of cytoskeletal organization and signaling mechanisms involved in the activation of platelets by thrombin. Samples of platelets prepared by the buffy coat method were obtained before and after the platelet concentrates were prepared during storage for 1, 3, and 5 days. Thrombin-induced aggregation was monitored, and changes in the organization of proteins in the cytoskeleton were analyzed by gel electrophoresis. For the analysis of tyrosine phosphorylation, proteins were transferred to nitrocellulose membranes and probed with a specific antibody. RESULTS: The aggregation and the cytoskeletal organization induced by thrombin activation were markedly impaired immediately after preparation of platelet concentrates, although they normalized after the first 24 hours of storage and decreased progressively after 3 days of storage. Results in tyrosine phosphorylation paralleled those obtained with cytoskeletal organization, except for samples obtained immediately after processing to obtain platelet concentrates. CONCLUSION: These data indirectly suggest that the stress induced by the preparation method has an activating effect on platelet function that may imply a delayed platelet response to further stimuli. This effect may result in a deficient redistribution of signaling molecules within platelets.

Blood Platelets↗
PubMed2000

CDP is a repressor of mouse mammary tumor virus expression in the mammary gland.

Mouse mammary tumor virus (MMTV) transcription is highest in the lactating mammary gland but is detectable in a variety of other tissues. Previous results have shown that MMTV expression is suppressed in lymphoid and other tissues through the binding of the homeodomain-containing repressor special AT-rich binding protein 1 to a negative regulatory element (NRE) in the MMTV long terminal repeat (LTR). Another homeoprotein repressor, CCAAT displacement protein (CDP), also binds to the MMTV NRE, but a role for CDP in MMTV transcriptional suppression has not yet been demonstrated. In this paper, we show that the level of CDP decreases during development of the mammary gland and that this decline in CDP level correlates with the known increase in MMTV expression observed during mammary gland differentiation. Moreover, CDP overexpression was able to suppress MMTV LTR-reporter gene activity up to 20-fold in transient-transfection assays of mouse mammary cells. To determine if this effect was due to direct binding of CDP to the promoter-proximal NRE, we performed DNase I protection assays to map two CDP-binding sites from +835 to +845 and +920 to +931 relative to the first base of the LTR. Mutations engineered into each of these sites decreased CDP binding to the proximal NRE, whereas a combination of these mutations further reduced binding. Subsequently, each of these mutations was introduced into the full-length MMTV LTR upstream of the luciferase reporter gene. Analysis of stable transfectants of LTR constructs showed that CDP binding site mutations in the proximal NRE elevated reporter gene expression two- to sixfold compared to wild-type LTR constructs. Thus, MMTV expression increases during mammary gland development, in part due to decreased CDP levels and CDP binding to the LTR. Together, these experiments provide the first evidence that CDP acts as a repressor of MMTV transcription in the mammary gland.

Animals↗
PubMed2000

C3H mouse mammary tumor virus superantigen function requires a splice donor site in the envelope gene.

Mouse mammary tumor virus (MMTV) encodes a superantigen (Sag) that is required for efficient milk-borne transmission of virus from mothers to offspring. The mRNA used for Sag expression is controversial, and at least four different promoters (two in the long terminal repeat and two in the envelope gene) for sag mRNA have been reported. To determine which RNA is responsible for Sag function during milk-borne MMTV transmission, we mutated a splice donor site unique to a spliced sag RNA from the 5' envelope promoter. The splice donor mutation in an infectious provirus was transfected into XC cells and injected into BALB/c mice. Mice injected with wild-type provirus showed Sag activity by the deletion of Sag-specific T cells and induction of mammary tumors in 100% of injected animals. However, mice injected with the splice donor mutant gave sporadic and delayed T-cell deletion and a low percentage of mammary tumors with a long latency, suggesting that the resulting tumors were due to the generation of recombinants with endogenous MMTVs. Third-litter offspring of mice injected with wild-type provirus showed Sag-specific T-cell deletion and developed mammary tumors with kinetics similar to those for mice infected by nursing on MMTV-infected mothers, whereas the third-litter offspring of the splice donor mutant-injected mice did not. One of the fifth-litter progeny of splice donor mutant-injected mice showed C3H Sag activity and had recombinants that repaired the splice donor mutation, thus confirming the necessity for the splice donor site for Sag function. These experiments are the first to show that the spliced sag mRNA from the 5' envelope promoter is required for efficient milk-borne transmission of C3H MMTV.

Animals↗
PubMed2000

Metastatic osteosarcoma presenting as a small-bowel polyp. A case report and review of the literature.

Gastrointestinal metastases of osteosarcoma are an extraordinarily rare event and, as far as we can determine, have been reported previously only 5 times; these cases represent an unusual pattern of progression. We describe a 21-year-old man with an osteosarcoma of the right tibia that was removed 4 years previously. Two years later, the patient showed lung metastases. At his most recent presentation, he complained of abdominal pain, nausea, vomiting, and anorexia. Radiologic examination revealed an abdominal mass close to the jejunum and 3 nodules in the liver. One metastasis was an ulcerated and pedunculated polypoid mass located in the mucosa of the bowel, and the other involved the entire thickness of the jejunum. This unusual phenomenon represents an alteration in the natural history of osteosarcoma as a result of increased long-term survival.

Adult↗
PubMed2000

Thrombin facilitates primary platelet adhesion onto vascular surfaces in the absence of plasma adhesive proteins: studies under flow conditions.

BACKGROUND AND OBJECTIVE: The effect of local and circulating thrombin on platelet adhesion onto vascular surfaces was explored in the absence of plasma adhesive proteins using flow conditions. DESIGN AND METHODS: To study the local effects of thrombin, denuded rabbit aorta segments were incubated with thrombin concentrations of 0.001, 0.01 and 0.1 U/mL. To evaluate the effects of circulating thrombin, the same concentrations were added to perfusates consisting of washed platelets and washed red blood cells suspended in a human albumin solution (5%). In some experiments, purified von Willebrand's factor (vWF) (Haemate-P) was added to the perfusates (0. 8 U/mL of vWF, final concentration). A humanized chimeric antibody to the GPIIb-IIIa complex (Reopro) was used to determine the role of this glycoprotein on platelet adhesion under the conditions described. The effect of blocking GPIb was also assessed. Perfusions were carried out at 800 s(-1) for 10 min. The interaction of platelet with the vessel surface was morphometrically evaluated and expressed as percentage of surface coverage (%SC). Changes in the surface expression of the major platelet antigens were also analyzed by flow cytometry. RESULTS: Incubation of subendothelial surfaces with thrombin enhanced platelet deposition with respect to control levels (increases in SC of 64%, 79% and 86% with 0.001, 0.01 and 0.1 U/mL of thrombin, respectively). Low concentrations of thrombin (0.001 and 0.01 U/mL) incorporated in the perfusates resulted in a similar pro-adhesive effect (increases in SC of 64% and 71%, respectively) while the highest concentration (0.1 U/mL) failed to produce a pro-adhesive effect due to the augmented formation of platelet aggregates with subsequent thrombocytopenia (15+/-1 vs. 160+/-5x10(9) plt/L in the perfusates). Similar results were obtained when VWF was present in the perfusate. Reduction of platelet deposition by blockade of GPIIb-IIIa (to 5.3+/-0.7%) was partially restored by thrombin. Blockade of GPIb prevented platelets from adhering even when thrombin was present (%SC of 2.0+/-0.8%). No significant changes in the distribution of platelet membrane glycoproteins during perfusion experiments were detected. INTERPRETATION AND CONCLUSIONS: Our results suggest that thrombin facilitates primary platelet adhesion onto vascular surfaces even in the absence of plasma adhesive proteins. This effect seems to be mainly dependent on the GPIb/vWF axis.

Animals↗
PubMed1999

Modifications in accessibility of membrane glycoproteins, binding of specific ligands and coagulation factor V during the activation of platelets in blood emerging from bleeding time wounds.

Dual color flow cytometric techniques were applied to micro-aliquots of whole blood obtained from bleeding time (BT) wounds. Modifications in platelet activation markers (P-selectin [CD62P]) and lysosomal related protein (UMPS [CD63]), presence of membrane glycoproteins (GPIb [CD42b], GPIIb-IIIa [CD41a], GDIV [CD36], binding of von Willebrand factor (vWF), fibrinogen (Fg) and factor V [FV]) were analyzed in normal donors (n = 10) and in a severe von Willebrand patient (type 3) von Willebrand disease [vWD]). Samples of blood (20 microl) were sequentially removed from BT wound edges for up to 5 min and fixed with paraformaldehyde. Antigens were detected using the corresponding tagged monoclonal antibodies (moAbs) and quantitative results were referred to those found on platelet samples obtained from venous blood obtained from the same individuals. A progressive increase in % of platelets positive for activation dependent antigens (CD62 from 7 +/- 2 to 48 +/- 19% and CD63 from 9 +/- 1 to 44 +/- 8%; initial vs. 4 min) was observed. Accessibility of GPIIb-IIIa epitopes on platelets from BT wounds remained slightly above levels observed in venous blood platelets, despite a progressive increase in the presence of platelets positive for Fgn. Binding of MoAb to GPIV increased at late stages of BT. A moderate decrease in the binding of a moAb to GPIb was observed on platelets obtained at late stages of the BT (14 +/- 9% and 20 +/- 6% at 4 and 5 min, respectively). This apparent decrease in GPIb epitopes paralleled an increased presence of platelets positive for vWF (26 +/- 12 and 38 +/- 15%). Binding of moAb to GPIb always remained above basal levels in platelets obtained from BTs performed in the patient with type 3 vWD. FV levels on platelets coming from the BT persisted at background levels in all the individuals and at all times studied.

Antibodies, Monoclonal↗
PubMed1999

Platelet concentrates prepared and stored under currently optimal conditions: minor impact on platelet adhesive and cohesive functions after storage.

BACKGROUND: The effect on platelets of two standard methods of platelet concentrate (PC) preparation was studied by flow cytometry. The findings were correlated with those obtained in an experimental in vitro perfusion model. STUDY DESIGN AND METHODS: PCs were prepared from whole blood by the platelet-rich plasma (PRP) or buffy coat (BC) method and placed on a flatbed platelet agitator at 22 degrees C for up to 5 days. Platelet glycoproteins (GP)lbalpha, GPIIb/IIIa, and GPIV, p-selectin and lysosomal integral membrane protein, and the binding of von Willebrand factor, fibrinogen, fibronectin, and coagulation factor Va were measured with the corresponding specific conjugated antibodies. Perfusions were carried out in an annular chamber with citrated blood depleted of platelets and white cells by filtration, to which samples from PCs were added. RESULTS: PRP-PC production provoked intense platelet activation. In contrast, in BC-derived PCs, platelet activation was milder, and only a significant increase in bound fibrinogen was seen. After 1 day of storage, differences between the methods that had been observed immediately after separation had almost disappeared. During the remaining storage period, increases in activation-dependent antigens and in procoagulant activity were measured. Of the studied platelet GPs, only GPIIIb/ IIIa decreased by 25 percent in PRP-PCs. Differences in covered surface were not significant in perfusion studies performed on Day 0 and after 5 days of storage in PRP-PCs (26.8 +/- 6.9 vs. 20.5 +/- 5.8) or BC-PCs (23.8 +/- 11 vs. 24.8 +/- 10.2). CONCLUSION: Platelet activation occurred during the separation and storage of PCs prepared by both methods, and it was higher in PRP-PCs only in samples obtained immediately after preparation. Despite these changes, platelet adhesive and cohesive functions were similar in both types of PCs and remained basically unchanged after storage.

Blood Platelets↗
PubMed1999

Expression of mouse mammary tumor virus superantigen mRNA in the thymus correlates with kinetics of self-reactive T-cell loss.

Mouse mammary tumor virus (MMTV) encodes a superantigen (Sag) that is expressed at the surface of antigen-presenting cells in conjunction with major histocompatibility complex (MHC) type II molecules. The Sag-MHC complex is recognized by entire subsets of T cells, leading to cytokine release and amplification of infected B and T cells that carry milk-borne MMTV to the mammary gland. Expression of Sag proteins from endogenous MMTV proviruses carried in the mouse germ line usually results in the deletion of self-reactive T cells during negative selection in the thymus and the elimination of T cells required for infection by specific milk-borne MMTVs. However, other endogenous MMTVs are unable to eliminate Sag-reactive T cells in newborn mice and cause partial loss of reactive T cells in adults. To investigate the kinetics of Sag-reactive T-cell deletion, backcross mice that contain single or multiple MMTVs were screened by a novel PCR assay designed to distinguish among highly related MMTV strains. Mice that contained Mtv-17 alone showed slow kinetics of reactive T-cell loss that involved the CD4(+), but not the CD8(+), subset. Deletion of CD4(+) or CD8(+) T cells reactive with Mtv-17 Sag was not detected in thymocytes. Slow kinetics of peripheral T-cell deletion by Mtv-17 Sag also was accompanied by failure to detect Mtv-17 sag-specific mRNA in the thymus, despite detectable expression in other tissues, such as spleen. Together, these data suggest that Mtv-17 Sag causes peripheral, rather than intrathymic, deletion of T cells. Interestingly, the Mtv-8 provirus caused partial deletion of CD4(+)Vbeta12(+) cells in the thymus, but other T-cell subsets appeared to be deleted only in the periphery. Our data have important implications for the level of antigen expression required for elimination of self-reactive T cells. Moreover, these experiments suggest that mice expressing endogenous MMTVs that lead to slow kinetics of T-cell deletion will be susceptible to infection by milk-borne MMTVs with the same Sag specificity.

Animals↗
PubMed1999

Captopril administration reduces thrombus formation and surface expression of platelet glycoprotein IIb/IIa in early postmyocardial infarction stage.

Long-term administration of the angiotensin-converting enzyme inhibitor captopril in survivors of myocardial infarction (MI) reduces the risk of cardiovascular death, recurrence of MI, and unstable angina, suggesting that captopril may possess antithrombotic properties that have not been clearly elucidated. We assessed the short-term antithrombotic effects of captopril on platelet aggregation, platelet-subendothelium interaction, and the expression of major glycoproteins on platelet surface. A double-blind study was carried out in 25 patients with MI. Blood samples were taken before (baseline) and 12 days after treatment in both the control and captopril groups. Platelet aggregation was tested by conventional aggregometry using common activating agents. Platelet interaction with deeply damaged subendothelial surface was evaluated in a perfusion model, with blood maintained under flow conditions. Deposition of platelets was quantified by using computer-assisted morphometric techniques on histological sections, and it was expressed as a percentage of total vessel surface covered by platelets (CS) and as a ratio between large aggregates (T) and surface covered by platelets (100XT/CS). Glycoprotein expression was measured using flow cytometric techniques. Aggregometric responses showed no significant variations; however, in the captopril group, 100XT/CS decreased after 12 days of treatment (100XT/CS: 36+/-12.1% captopril versus 64+/-8.0% baseline; P=0.005). This parameter was also significantly decreased from that found in control group patients (100XT/CS:67=/-4.5%, P=0.008). Flow cytometry showed a 30% reduction in glycoprotein IIb/IIIa expression (P=0.02). Captopril reduced the formation of large aggregates in a perfusion system, which might be related to a down-regulation of glycoprotein IIb/IIIa complex on the platelet surface. These results suggest that captopril exerts an antiplatelet effect that may contribute to its beneficial action in MI.

Aged↗
PubMed1998

[Platelet count and mean platelet volume in the Spanish population].

BACKGROUND: Platelet counts between 150 x 10(9)/l and 400 x 10(9)/l are considered as normal in the adult population. However in Spain it is not unusual to find lower counts in healthy people. SUBJECTS AND METHODS: We have studied platelet counts in 1,430 prospective healthy platelet donors. In 93 we measured mean platelet volume (MPV) in a blood sample collected in citrate (1:4 v/v) in order to avoid the platelet swelling induced by EDTA. Complete blood counts were performed on a Bayer-Technicon H*1. A reference range of 95% was calculated for platelet count and MPV, and the relationship between platelet count and sex, age, hemoglobin and MPV was studied. RESULTS: Mean (SD) platelet count (in x 10(9)/l) in men (195 [42]; n = 1,053) is lower (p < or = 0.0005) than in women (213 [47]; n = 377). The reference range in men is 123-295, in women 137-319 and in both 125 to 300. The mean (SD) for MPV (in fl) is 9.6 (0.7) (no significant differences between sexes) and the reference range is 7.8-11. There is an inverse linear relationship between the circulating platelets and their MPV measured in citrate at high concentration (r = -0.282, p = 0.006, n = 93) and in EDTA (r = -0.364, p < or = 0.0005, n = 1,430) and also between platelet count and Hb levels (r = -0.166, p < or = 0.0005). CONCLUSIONS: The mean of platelet count in women is higher than in males in a sample of Spanish population. There is an inverse linear relationship between platelet count and their MPV measures measured in citrate at high concentration and in EDTA. The reference range for platelet count seems to be lower than in other populations of North European origin.

Adult↗
PubMed1998

Detection of Enterocytozoon bieneusi in two human immunodeficiency virus-negative patients with chronic diarrhea by polymerase chain reaction in duodenal biopsy specimens and review.

Intestinal microsporidiosis has been associated traditionally with severely immunocompromised patients with AIDS. We describe two new cases of intestinal microsporidiosis due to Enterocytozoon bieneusi in human immunodeficiency virus-negative adults. Both patients presented with chronic nonbloody diarrhea, and one had intestinal lymphangiectasia as well. Intestinal microsporidiosis was diagnosed by evaluation of stool samples, and the specific species was determined by use of polymerase chain reaction (PCR) in duodenal biopsy specimens. To our knowledge, this is the first report of confirmation of E. bieneusi in the intestinal epithelium of HIV-negative individuals by use of PCR in duodenal biopsy specimens. Cases of intestinal microsporidiosis in HIV-negative individuals reported in the English-language literature are reviewed. These two new cases along with those described previously corroborate the need to evaluate for microsporidia in HIV-negative individuals with unexplained diarrhea.

Adult↗
PubMed1998

Mutational and functional analysis of the C-terminal region of the C3H mouse mammary tumor virus superantigen.

The mouse mammary tumor virus (MMTV) encodes within the U3 region of the long terminal repeat (LTR) a protein known as the superantigen (Sag). Sag is needed for the efficient transmission of milk-borne virus from the gut to target tissue in the mammary gland. MMTV-infected B cells in the gut express Sag as a type II transmembrane protein that is recognized by the variable region of particular beta chains (Vbeta) of the T-cell receptor (TCR) on the surface of T cells. Recognition of Sag by particular TCRs results in T-cell stimulation, release of cytokines, and amplification of MMTV infection in lymphoid cells that are needed for infection of adolescent mammary tissue. Because the C-terminal 30 to 40 amino acids of Sag are variable and correlate with recognition of particular TCR Vbeta chains, we prepared a series of C-terminal Sag mutations that were introduced into a cloned infectious MMTV provirus. Virus-producing XC rat cells were used for injection of susceptible BALB/c mice, and these mice were monitored for functional Sag activity by the deletion of C3H MMTV Sag-reactive (CD4+ Vbeta14+) T cells. Injected mice also were analyzed for mutant infection and tumor formation in mammary glands as well as milk-borne transmission of MMTV to offspring. Most mutations abrogated Sag function, although one mutation (HPA242) that changed the negative charge of the extreme C terminus to a positive charge created a weaker Sag that slowed the kinetics of Sag-mediated T-cell deletion. Despite the lack of Sag activity, many of the sag mutant viruses were capable of sporadic infections of the mammary glands of injected mice but not of offspring mice, indicating that functional Sag increases the probability of milk-borne MMTV infection. Furthermore, although most viruses encoding nonfunctional Sags were unable to cause mammary tumors, tumors were induced by such viruses carrying mutations in a negative regulatory element that overlaps the sag gene within the LTR, suggesting that loss of Sag function may be compensated, at least partially, by loss of transcriptional suppression in certain tissues. Together these results confirm the importance of Sag for efficient milk-borne transmission and indicate that the entire C-terminal region is needed for complete Sag function.

Amino Acid Sequence↗
PubMed1998

Platelet-leukocyte activation during hemodialysis detected with a monoclonal antibody to leukocyte integrin CD11b.

Platelet activation is commonly monitored with a battery of monoclonal antibodies against different platelet epitopes with controversial results. The transient expression of platelet markers and their role mediating interactions with other cells could easily explain these discrepancies. The present study has evaluated whether the analysis of a leukocyte activation antigen (CD11b) could provide more reliable results than detection of platelet activation markers. Cytometric techniques with specific monoclonal antibodies were used to compare the reliability of platelet and leukocyte markers to detect activation. Modifications in the presence of platelet glycoproteins GPIb (CD42b), GPIIIa (CD41) and GPIV (CD36), expression of specific platelet markers (P-selectin (CD62P) and lysosomal protein (CD63)) and leukocyte integrin (CD11b) were assessed during hemodialysis. Platelet antigens remained in uremic patients at levels similar or slightly above those detected in a group of healthy subjects. Modifications of platelet antigens during hemodialysis produced inconclusive results. However, numbers of leukocytes expressing CD11b increased progressively during hemodialysis (17.2 +/- 5.1% at 15 min and 21.3 +/- 6.6% at 2 h, p < 0.05, vs. baseline 6.9 +/- 0.2%). The hemodialysis procedure caused an increased formation of leukocyte-platelet aggregates. Detection of leukocyte CD11b may be a useful marker of overall cellular activation during the hemodialysis procedure.

Aged↗