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M Lieberman

Publications and source records attributed to M Lieberman.

At least 19 recordsLinked to original sources
PubMed1992

Magnesium homeostasis in cardiac cells.

Several aspects of Mg2+ homeostasis were investigated in cultured chicken heart cells using the fluorescent Mg2+ indicator, FURAPTRA. The concentration of cytosolic Mg2+ ([Mg2+]i) is 0.48 +/- 0.03 mM (n = 31). To test whether a putative Na/Mg exchange mechanism controls [Mg2+]i below electrochemical equilibrium, we manipulated the Na+ gradient and assessed the effects on [Mg2+]i. When extracellular Na+ was removed, [Mg2+]i increased; this increase was not altered in Mg-free solutions, but was attenuated in Ca-free solutions. A similar increase in [Mg2+]i, which was dependent upon extracellular Ca2+, was observed when intracellular Na+ was raised by inhibiting the Na/K pump with ouabain. These results do not provide evidence for Na/Mg exchange in heart cells, but they suggest that Ca2+ can modulate [Mg2+]i. In addition, removing extracellular Na+ caused a decrease in intracellular pH (pHi), as measured by pH-sensitive microelectrodes, and this acidification was attenuated when Ca2+ was also removed from the solution. These results suggest that Ca2+ and H+ interact intracellularly. Since changes in the Na+ gradient can also alter pHi, we questioned whether pH can modulate [Mg2+]i. pHi was manipulated by the NH4Cl prepulse method. NH4(+)-evoked changes in pHi, as measured by the fluorescent indicator BCECF, were accompanied by opposite changes in [Mg2+]i; [Mg2+]i changed by -0.16 mM/unit pH. These NH4(+)-evoked changes in [Mg2+]i were not caused by movements of Mg2+ or Ca2+ across the sarcolemma or by changes in cytosolic Ca2+. Additionally, pHi was manipulated by changing extracellular pH (pHo).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Unexpected effects of the severe combined immunodeficiency mutation on murine lymphomagenesis.

Strain C.B17 scid/scid (SCID) mice, which lack functional T and B lymphocytes, show heightened susceptibility to the induction of thymic lymphomas by x-irradiation. Susceptibility is highest in thymus-chimeric SCID-BL mice (thymectomized SCID mice bearing a C57BL thymus graft). All SCID-BL lymphomas originate in the cells of the thymic graft (C57BL type) and lack murine leukemia virus expression. Both SCID and SCID-BL lymphomas are phenotypically CD4-8+ and/or CD4+8+, but only the SCID-BL tumors express CD3. Injection of C57BL or BALB/c bone marrow into irradiated SCID-BL mice prevents lymphoma development, but SCID marrow is completely ineffective. The results suggest that the scid condition enhances the activity of a putative lymphomagenic agent induced in the bone marrow by x-irradiation and that C57BL thymic cells are highly sensitive targets. Moreover, the failure of SCID bone marrow to protect against lymphomagenesis vs. the efficacy of marrow from immunocompetent donors points to involvement of T or B lineage cells in this process.

Animals↗
PubMed1992

Differentiation of CD3-4-8- thymocytes in short-term thymic stromal cell culture.

We have investigated the ability of a heterogeneous thymic stromal cell (HTSC) culture system to promote in vitro differentiation of CD3-4-8- thymocytes. Culture of purified murine CD3-4-8- thymocytes on HTSC for 1 d resulted in the appearance of CD4+8+ cells, which did not occur when the sorted cells were maintained in medium alone. It is remarkable that when the culture period was extended to 2 d, CD3-4-8- progenitors differentiated further to CD4+8- and CD4-8+ cells, which also expressed high levels of TCR-CD3. This rapid differentiation on stroma in vitro appears to outpace parallel development in vivo. The differentiation potential of a subset of CD3-4-8- thymocytes that express high levels of a marker of normal and neoplastic thymic progenitors, the 1C11 antigen, was examined next. 1C11hiCD3-4-8- cells also gave rise to CD4-8+ and CD4+8+ populations after 1 d of culture on HTSC. Extending the culture period to 2 d resulted in a significant percentage of CD3-expressing cells that were CD4+8+, CD4+8- and CD4-8+ cells. These results suggest that in the in vitro HTSC culture system, various subsets of immature thymocytes can differentiate into all the mature phenotypes of cells normally found in the adult mouse thymus. This may provide a novel and rapid assay for thymic progenitors.

Animals↗
PubMed1992

Quick-freezing of cultured cardiac cells in situ with special attention to the mitochondrial ultrastructure.

A new method has been developed which allows quick-freezing in situ of primary, cardiac cell cultures grown to confluence on gas-permeable membranes (Petriperm dishes). Small pieces of the growth substratum, with rhythmically beating myocardial cells, were slam-frozen, without cryoprotectants, against the surface of a helium-cooled copper block at approximately 16 K. The quality of the cellular cryopreservation, as judged by ultrastructural criteria, was studied in freeze-substituted specimens processed for transmission electron microscopy. The ultrastructure of cryofixed cardiac cells was compared with that of unfrozen, chemically fixed samples. The severity of cryodistortions increased progressively with increasing distance from the point of first impact. Of particular interest were the dramatic alterations of the mitochondrial ultrastructure. The concept that the reticular and the outer mitochondrial membranes are intimately and strongly associated was clearly demonstrated. Optimally frozen material revealed cryopreserved ultrastructure of high quality. The method described appears to offer an ideal model system for correlating the information gained by phase-contrast microscopy of living cell cultures with the ultrastructure of the same samples fixed in situ by chemical or physical techniques. Cryofixation would be particularly useful for studying dynamic cellular processes associated with physiological and pathophysiological conditions, e.g. metabolic inhibition, anoxia and substrate deprivation.

Animals↗
PubMed1992

Intracellular pH modulates cytosolic free magnesium in cultured chicken heart cells.

To assess the role of pH in cellular Mg homeostasis, cytosolic pH (pHi) was manipulated by the NH4Cl prepulse technique; pHi, cytosolic Mg2+ (Mgi), and cytosolic Ca2+ (Cai) were measured fluorometrically in single cultured embryonic chicken heart cells loaded with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF), FURAPTRA, and fura-2, respectively. The basal values obtained were as follows: pHi = 7.21 +/- 0.10 (n = 7), [Mg]i = 0.51 +/- 0.08 mM (n = 9), [Ca]i = 126 +/- 15 nM (n = 7). When cells were perfused with 10 mM NH4Cl solution for 5 min, a transient alkalinization (0.53 U) of the cytosol was accompanied by a transient decrease (0.12 mM) in [Mg]i and a transient increase (59 nM) in [Ca]i; these changes approached control levels within 5 min. Upon removal of NH4Cl, a transient acidification (0.89 U) of the cytosol was accompanied by a transient increase (0.10 mM) in [Mg]i and a transient increase (125 nM) in [Ca]i; again, these changes returned toward control levels within 5 min. No significant changes in total cell Mg or Ca were observed during these manipulations. NH4Cl-evoked changes in [Mg]i were not altered significantly by either Mg-free or Ca-free conditions. Changes in [Mg]i were inversely correlated with changes in pHi and were not secondary to changes in [Ca]i. The results suggest that pHi modulates Mgi, probably by affecting cytosolic Mg binding and/or the transport of Mg across subcellular organelles.

Ammonium Chloride↗
PubMed1991

Growth of primary T-cell non-Hodgkin's lymphomata in SCID-hu mice: requirement for a human lymphoid microenvironment.

We reasoned that the SCID-hu mouse could provide an appropriate lymphoid or stromal microenvironment to support the growth of primary human lymphoma. Heterotransplantation of nine cases of primary T-cell non-Hodgkin's lymphoma (NHL) into untreated SCID mice and SCID mice reconstituted with human fetal thymus, spleen, and liver (SCID-hu) resulted in the development of lymphoid tumors in five (56%) cases. Two clonal T-cell NHL grew after a mean of 90 days after injection of primary lymphoma cell suspensions into the thymus xenografts in SCID-hu mice and failed to grow in a variety of sites in SCID mice, except for small tumors that developed after a long (157-day) latency period after intracranial injection of tumor cell suspensions into weanling SCID mice. Successful serial transplantation of NHL in SCID and SCID-hu mice required the presence of a human lymphoid or tumor microenvironment, and was enhanced by pretreating the SCID mice with 175 rad radiation and antiasialo antisera. Analysis of the primary and transplanted T-cell tumors showed identical patterns of T-cell surface markers by flow cytometry and immunophenotyping of fixed tissue sections, and, in one case, reactivity with a specific monoclonal antibody to V beta 5.1. Genotyping of the transplanted tumors showed T-cell receptor gene rearrangements identical to those present in the primary tumors. In one case, the presence of Epstein-Barr virus-positive B cells in association with the primary tumor resulted in the growth of a lymphoblastoid B-cell neoplasm in addition to the malignant T-cell lymphoma after transplantation of tumor fragments to SCID mice. The data support the hypothesis that a human lymphoid microenvironment enhances the growth of T-cell NHL in SCID mice. The SCID-hu thymus graft provides an apparently unique microenvironment that supports the growth of primary T-cell NHL, and can be used to study the interaction between lymphoma cells, nontransformed lymphoid cells, and the surrounding stromal microenvironment in vivo.

Animals↗
PubMed1991

Adenine nucleotide degradation in cultured chick heart muscle cells.

Cultured chick heart muscle cells degrade ATP during metabolic inhibition via ADP to AMP. Whether AMP is primarily deaminated to IMP or dephosphorylated to adenosine depends on the 'metabolic block' (glycolysis vs. oxidative phosphorylation). Inhibition of glycolysis (deoxyglucose) results in an inosine/adenosine ratio greater than 1 in the supernatant, whereas the nucleoside ratio is less than or equal to 1 during inhibition of oxidative phosphorylation (hypoxia, rotenone). EHNA, a blocker of adenosine deaminase, has little effect on inosine release during metabolic inhibition, consistent with the reported low activity of adenosine deaminase in cardiac muscle cells. The amount of adenosine and inosine released can be largely attenuated by two nucleoside carrier inhibitors, nitrobenzyl-thioinosine and dipyridamole, which suggests that nucleosides are produced intracellularly and subsequently released. These results indicate that the amount of inosine or adenosine released from the cardiomyocyte during impaired energy metabolism (e.g. ischemia) can be controlled by the metabolic state of the cell.

Adenine↗
PubMed1991

Structural and elemental characterization of heart cells grown in a collagen matrix.

A novel preparation of spontaneously contracting heart cells embedded in a collagen strand provides an ideal experimental system for correlative structure-function experiments that utilize the techniques of electron microscopy, quantitative electron probe x-ray microanalysis (EPXMA) and imaging. Heart cells grown within the strand for 1 day possess the subcellular content and distribution of physiologically relevant elements--Na, Mg, P, S, Cl, K, and Ca--found in intact heart cell preparations. The presence of junctional specializations between, and organized myofibrils within, the majority of cells after 1 day in culture also establishes that the collagen matrix promotes vigorous cell development as well as maintains physiological integrity. EPXMA, combined with ultrastructural analyses, provides elemental content data on a cell-by-cell basis. In studies presented here, viable cells, comprising over 80% of the strand cell population, could be distinguished easily from those which had been functionally compromised, not only by aberrant structure but also by altered subcellular compartmentation of Na, K, Cl, and Ca. Within individual viable cells, compartmental differences in element content were notable especially between mitochondria and cytoplasm. However, nuclear euchromatin, but not heterochromatin, appeared approximately identical to cytoplasm in elemental and water content. In such cells, the cytoplasmic K:Na ratio was maintained at a high level (approximately 15:1). The results with respect to K, Na, and other elements demonstrated the integrity of membrane transport mechanisms regulating the movement and distribution of ions and the maintenance of ionic homeostasis in cells of the strand preparation.

Animals↗
PubMed1991

Apparent affinity of the Na/K pump for ouabain in cultured chick cardiac myocytes. Effects of Nai and Ko.

The measured apparent affinity (K0.5) of the Na/K pump for ouabain has been reported to vary over a wide range. In a previous report we found that changing Nai could alter apparent affinity by at least an order of magnitude and that the model presented predicted this variability. To increase our understanding of this variability, isolated cells or two- to three-cell clusters of cardiac myocytes from 11-d embryonic chick were used to measure the effects of Nai and Ko on the K0.5 of the Na/K pump for ouabain. Myocytes were whole-cell patch clamped and Na/K pump current (Ip) was measured in preparations exposed to a Ca-free modified Hank's solution (HBSS) that contained 1 mM Ba, 10 mM Cs, and 0.1 mM Cd. Under these conditions there are no Ko-sensitive currents other than Ip because removal of Ko in the presence of ouabain had no effect on the current-voltage (I-V) relation. The I-V relation for Ip showed that in the presence of 5.4 mM Ko and 51 mM Nai, Ip has a slight voltage dependence, decreasing approximately 30% from 0 to -130 mV. Increasing Nai in the patch pipette from 6 to 51 mM (Ko = 5.4 mM) caused Ip to increase from 0.46 +/- 0.07 (n = 5) to 1.34 +/- 0.08 microA/cm2 (n = 13) with a K0.5 for Nai of 17.4 mM and decreased the K0.5 for ouabain from 18.5 +/- 1.8 (n = 4) to 3.1 +/- 0.4 microM (n = 3). Similarly, varying Ko between 0.3 and 10.8 mM (Nai = 24 mM) increased Ip from 0.13 +/- 0.01 (n = 5) to 0.90 +/- 0.05 microA/cm2 (n = 5) with a K0.5 for Ko of 1.94 mM and increased K0.5 for ouabain from 0.56 +/- 0.14 (n = 3-6) to 10.0 +/- 1.1 microM (n = 6). All of these changes are predicted by the model presented. A qualitative explanation of these results is that Nai and Ko interact with the Na/K pump to shift the steady-state distribution of the Na/K pump molecules among the kinetic states. This shift in state distribution alters the probability that the Na/K pump will be in the conformation that binds ouabain with high affinity, thus altering the apparent affinity. In intact cells, the measured apparent affinity represents a combination of all the rate constants in the model and does not equate to simple first-order binding kinetics.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

The SCID-hu mouse: a small animal model for HIV infection and pathogenesis.

The SCID-hu mouse is a heterochimeric small animal model designed to support hematopoietic differentiation and function in vivo. Multiple organs of the human hematolymphoid system have been successfully engrafted into the immunodeficient C.B-17 scid scid mouse, including fetal liver, thymus, lymph node, and skin. Co-implantation of human fetal liver and human fetal thymus results in long-term, multilineage human hematopoiesis in vivo. Mature human lymphocytes within the SCID-hu mouse are phenotypically and functionally normal. HIV infection of the SCID-hu mouse reflects a tropism similar to that found in humans: only human organs with CD4+ cells are infected. Viral replication can thereafter be monitored with assays that are safe, reproducible, and quantitative. Given this small animal model, it is now possible to study systematically the infective process of HIV and to address questions about the efficacy of novel antiviral compounds or vaccines in vivo.

Animals↗
PubMed1990

An immunodominant murine lymphoma cell surface heterodimer marks thymic progenitor subsets.

mAb 1C11 was raised against the cells of retrovirus-negative, radiation-induced thymomas of C57BL/Ka mice. MAb 1C11 binds to radiation- and RadLV-induced C57BL/Ka lymphomas, to lymphomas of other mouse strains and to B-lineage tumors. The 1C11 Ag is expressed on a subpopulation of normal thymocytes that is enriched in immature cells. After fractionated x-irradiation, this percentage increases gradually during the preleukemic period, hence mAb 1C11 appears to identify a transformation-related cell surface molecule. This conclusion is supported by experiments demonstrating that flow microfluorimetry-sorted, 1C11-expressing preleukemic thymocytes progress rapidly to full neoplasia following intrathymic injection, whereas nonexpressing cells do not. Most of day-14 fetal thymocytes are as strongly positive as thymic lymphomas for the 1C11 Ag whereas Ag-activated T cell lines express moderate levels. Multiparameter flow microfluorimetry analysis shows that 1C11 is expressed predominantly on CD3-/lo thymic blast cells of three phenotypically defined subsets: CD4-8-, CD4-8+, and CD4+8+, all of which contain thymic progenitors. By immunohistochemical staining, the Ag is also found in association with epithelial cells on a variety of normal, nonlymphoid tissue, but is not detectable on heart tissue. The 1C11 antibody immunoprecipitates a disulfide-linked heterodimeric protein of 85/37 kDa and the antigenic determinant is located on the H chain of the molecule. When analyzed by SDS-PAGE under nonreducing conditions, the molecule exists as a 130-kDa protein. Enzymatic digestion of the heterodimer indicates that the H chain, but not the L chain, has at least three N-linked glycosylation sites. We propose that this novel cell surface glycoprotein may be associated with processes of differentiation and lymphomagenesis.

Animals↗
PubMed1990

Israeli cephalometric standards compared to Downs and Steiner analyses.

A sample consisting of 40 young Israeli adolescents, 18 males and 22 females, was examined cephalometrically. The subjects were classified as Angle Class I, with less than three millimeters of crowding and an orthognathic profile. Steiner and Downs analyses were performed for all subjects. Each analysis was done both manually and by using a computer. The computerized results were processed and subjected to statistical tests. The Israeli sample is characterized by a convex profile, a retrusive mandible, a steep mandibular plane and protrusive incisors.

Adolescent↗
PubMed1990

Na/K pump current in aggregates of cultured chick cardiac myocytes.

Spontaneously beating aggregates of cultured embryonic chick cardiac myocytes, maintained at 37 degrees C, were voltage clamped using a single microelectrode switching clamp to measure the current generated by the Na/K pump (Ip). In resting, steady-state preparations an ouabain-sensitive current of 0.46 +/- 0.03 microA/cm2 (n = 22) was identified. This current was not affected by 1 mM Ba, which was used to reduce inward rectifier current (IK1) and linearize the current-voltage relationship. When K-free solution was used to block Ip, subsequent addition of Ko reactivated the Na/K pump, generating an outward reactivation current that was also ouabain sensitive. The reactivation current magnitude was a saturating function of Ko with a Hill coefficient of 1.7 and K0.5 of 1.9 mM in the presence of 144 mM Nao. The reactivation current was increased in magnitude when Nai was increased by lengthening the period of time that the preparation was exposed to K-free solution prior to reactivation. When Nai was raised by 3 microM monensin, steady-state Ip was increased more than threefold above the resting value to 1.74 +/- 0.09 microA/cm2 (n = 11). From these measurements and other published data we calculate that in a resting myocyte: (a) the steady-state Ip should hyperpolarize the membrane by 6.5 mV, (b) the turnover rate of the Na/K pump is 29 s-1, and (c) the Na influx is 14.3 pmol/cm2.s. We conclude that in cultured embryonic chick cardiac myocytes, the Na/K pump generates a measurable current which, under certain conditions, can be isolated from other membrane currents and has properties similar to those reported for adult cardiac cells.

Animals↗
PubMed1990

Intracellular sodium affects ouabain interaction with the Na/K pump in cultured chick cardiac myocytes.

Whether a given dose of ouabain will produce inotropic or toxic effects depends on factors that affect the apparent affinity (K0.5) of the Na/K pump for ouabain. To accurately resolve these factors, especially the effect of intracellular Na concentration (Nai), we have applied three complementary techniques for measuring the K0.5 for ouabain in cultured embryonic chick cardiac myocytes. Under control conditions with 5.4 mM Ko, the value of the K0.5 for ouabain was 20.6 +/- 1.2, 12.3 +/- 1.7, and 6.6 +/- 0.4 microM, measured by voltage-clamp, Na-selective microelectrode, and equilibrium [3H]ouabain-binding techniques, respectively. A significant difference in the three techniques was the time of exposure to ouabain (30 s-30 min). Since increased duration of exposure to ouabain would increase Nai, monensin was used to raise Nai to investigate what effect Nai might have on the apparent affinity of block by ouabain. Monensin enhanced the rise in Na content induced by 1 microM ouabain. In the presence of 1 microM [3H]ouabain, total binding was found to be a saturating function of Na content. Using the voltage-clamp method, we found that the value of the K0.5 for ouabain was lowered by nearly an order of magnitude in the presence of 3 microM monensin to 2.4 +/- 0.2 microM and the magnitude of the Na/K pump current was increased about threefold. Modeling the Na/K pump as a cyclic sequence of states with a single state having high affinity for ouabain shows that changes in Nai alone are sufficient to cause a 10-fold change in K0.5. These results suggest that Nai reduces the value of the apparent affinity of the Na/K pump for ouabain in 5.4 mM Ko by increasing its turnover rate, thus increasing the availability of the conformation of the Na/K pump that binds ouabain with high affinity.

Animals↗
PubMed1990

Intracellular pH regulation in cultured embryonic chick heart cells. Na(+)-dependent Cl-/HCO3- exchange.

The contribution of Cl-/HCO3- exchange to intracellular pH (pHi) regulation in cultured chick heart cells was evaluated using ion-selective microelectrodes to monitor pHi, Na+ (aiNa), and Cl- (aiCl) activity. In (HCO3- + CO2)-buffered solution steady-state pHi was 7.12. Removing (HCO3- + CO2) buffer caused a SITS (0.1 mM)-sensitive alkalinization and countergradient increase in aiCl along with a transient DIDS-sensitive countergradient decrease in aiNa. SITS had no effect on the rate of pHi recovery from alkalinization. When (HCO3- + CO2) was reintroduced the cells rapidly acidified, aiNa increased, aiCl decreased, and pHi recovered. The decrease in aiCl and the pHi recovery were SITS sensitive. Cells exposed to 10 mM NH4Cl became transiently alkaline concomitant with an increase in aiCl and a decrease in aiNa. The intracellular acidification induced by NH4Cl removal was accompanied by a decrease in aiCl and an increase in aiNa that led to the recovery of pHi. In the presence of (HCO3- + CO2), addition of either amiloride (1 mM) or DIDS (1 mM) partially reduced pHi recovery, whereas application of amiloride plus DIDS completely inhibited the pHi recovery and the decrease in aiCl. Therefore, after an acid load pHi recovery is HCO3o- and Nao- dependent and DIDS sensitive (but not Ca2+o dependent). Furthermore, SITS inhibition of Na(+)-dependent Cl-/HCO3- exchange caused an increase in aiCl and a decrease in the 36Cl efflux rate constant and pHi. In (HCO3- + CO2)-free solution, amiloride completely blocked the pHi recovery from acidification that was induced by removal of NH4Cl. Thus, both Na+/H+ and Na(+)-dependent Cl-/HCO3- exchange are involved in pHi regulation from acidification. When the cells became alkaline upon removal of (HCO3- + CO2), a SITS-sensitive increase in pHi and aiCl was accompanied by a decrease of aiNa, suggesting that the HCO3- efflux, which can attenuate initial alkalinization, is via a Na(+)-dependent Cl-/HCO3- exchange. However, the mechanism involved in pHi regulation from alkalinization is yet to be established. In conclusion, in cultured chick heart cells the Na(+)-dependent Cl-/HCO3- exchange regulates pHi response to acidification and is involved in the steady-state maintenance of pHi.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1990

Craniographic examination of the condylar angle and the maxillary incisal palatal angle in Bedouin skulls.

Craniographic registrations were used to examine 25 Bedouin skulls. The skulls were divided into three groups according to the anatomy and position of the maxillary incisor. Correlations between condylar guidance angle, maxillary incisal palatal angle, attrition, and flaring were investigated. No correlation was found between the condylar and maxillary incisal palatal angles. In the presence of severe attrition and/or flaring, the maxillary incisal palatal angle was reduced and mild reduction was also found in the condylar guidance angle. A strong correlation was found between the level of attrition and flaring.

Cephalometry↗