Characterization of the bone marrow niche in patients with chronic myeloid leukemia identifies CXCL14 as a new therapeutic option

Although tyrosine kinase inhibitors (TKIs) are effective in treating chronic myeloid leukemia (CML), they often fail to eradicate the leukemia-initiating stem cells (LSCs), causing disease persistence and relapse. Evidence indicates that LSC persistence may be because of bone marrow (BM) niche protection; however, little is known about the underlying mechanisms. Herein, we molecularly and functionally characterize BM niches in patients with CML at diagnosis and reveal the altered niche composition and function in these patients. Long-term culture initiating cell assay showed that the mesenchymal stem cells from patients with CML displayed an enhanced supporting capacity for normal and CML BM CD34+CD38- cells. Molecularly, RNA sequencing detected dysregulated cytokine and growth factor expression in the BM cellular niches of patients with CML. Among them, CXCL14 was lost in the BM cellular niches in contrast to its expression in healthy BM. Restoring CXCL14 significantly inhibited CML LSC maintenance and enhanced their response to imatinib in vitro, and CML engraftment in vivo in NSG-SGM3 mice. Importantly, CXCL14 treatment dramatically inhibited CML engraftment in patient-derived xenografted NSG-SGM3 mice, even to a greater degree than imatinib, and this inhibition persisted in patients with suboptimal TKI response. Mechanistically, CXCL14 upregulated inflammatory cytokine signaling but downregulated mTOR signaling and oxidative phosphorylation in CML LSCs. Together, we have discovered a suppressive role of CXCL14 in CML LSC growth. CXCL14 might offer a treatment option targeting CML LSCs.

Critical role of Lama4 for hematopoiesis regeneration and acute myeloid leukemia progression

Impairment of normal hematopoiesis and leukemia progression are 2 well-linked processes during leukemia development and are controlled by the bone marrow (BM) niche. Extracellular matrix proteins, including laminin, are important BM niche components. However, their role in hematopoiesis regeneration and leukemia is unknown. Laminin α4 (Lama4), a major receptor-binding chain of several laminins, is altered in BM niches in mice with acute myeloid leukemia (AML). So far, the impact of Lama4 on leukemia progression remains unknown. We here report that Lama4 deletion in mice resulted in impaired hematopoiesis regeneration following irradiation-induced stress, which is accompanied by altered BM niche composition and inflammation. Importantly, in a transplantation-induced MLL-AF9 AML mouse model, we demonstrate accelerated AML progression and relapse in Lama4-/- mice. Upon AML exposure, Lama4-/- mesenchymal stem cells (MSCs) exhibited dramatic molecular alterations, including upregulation of inflammatory cytokines that favor AML growth. Lama4-/- MSCs displayed increased antioxidant activities and promoted AML stem cell proliferation and chemoresistance to cytarabine, which was accompanied by increased mitochondrial transfer from the MSCs to AML cells and reduced reactive oxygen species in AML cells in vitro. Similarly, we detected lower levels of reactive oxygen species in AML cells from Lama4-/- mice post-cytarabine treatment. Notably, LAMA4 inhibition or knockdown in human MSCs promoted human AML cell proliferation and chemoprotection. Together, our study for the first time demonstrates the critical role of Lama4 in impeding AML progression and chemoresistance. Targeting Lama4 signaling pathways may offer potential new therapeutic options for AML.

Leukotriene signaling via ALOX5 and cysteinyl leukotriene receptor 1 is dispensable for in vitro growth of CD34+CD38- stem and progenitor cells in chronic myeloid leukemia

Tyrosine kinase inhibitors targeting the BCR-ABL oncoprotein in chronic myeloid leukemia (CML) are remarkably effective inducing deep molecular remission in most patients. However, they are less effective to eradicate the leukemic stem cells (LSC), resulting in disease persistence. Therefore, there is great need to develop novel therapeutic strategies to specifically target the LSC. In an experimental mouse CML model system, the leukotriene pathway, and specifically, the expression ALOX5, encoding 5-lipoxygenase (5-LO), has been reported as a critical regulator of the LSC. Based on these results, the 5-LO inhibitor zileuton has been introduced in clinical trials as a therapeutic option to target the LSC although its effect on primary human CML LSC has not been studied. We have here by using multiplex single cell PCR analyzed the expression of the mediators of the leukotriene pathway in bone marrow (BM) BCR-ABL⁺CD34⁺CD38^- cells at diagnosis, and found low or undetectable expression of ALOX5. In line with this, zileuton did not exert significant overall growth inhibition in the long-term culture-initiating cell (LTC-IC) and colony (CFU-C) assays of BM CD34⁺CD38^- cells from 7 CML patients. The majority of the single leukemic BCR-ABL⁺CD34⁺CD38^- cells expressed cysteinyl leukotriene receptors CYSLT1 and CYSLT2. However, montelukast, an inhibitor of CYSLT1, also failed to significantly suppress CFU-C and LTC-IC growth. These findings indicate that targeting ALOX5 or CYSLT1 signaling with leukotriene antagonists, introduced into the clinical practice primarily as prophylaxis and treatment for asthma, may not be a promising pharmacological strategy to eradicate persisting LSC in CML patients.

Assessment of bone marrow lymphocytic status during tyrosine kinase inhibitor therapy and its relation to therapy response in chronic myeloid leukaemia

PURPOSE

Tyrosine kinase inhibitors (TKIs) used in the treatment of chronic myeloid leukaemia have been reported to induce immunomodulatory effects. We aimed to assess peripheral blood (PB) and bone marrow (BM) lymphocyte status at the diagnosis and during different TKI therapies and correlate it with treatment responses.

METHODS

BM and PB samples were acquired from 105 first-line TKI-treated patients. Relative number of BM lymphocytes was evaluated from MGG-stained BM aspirates, and immunophenotypic analyses were performed with multicolour flow cytometry.

RESULTS

Early 3-month expansion of BM lymphocytes was found during all different TKIs (imatinib n = 71, 20 %; dasatinib n = 25, 21 %; nilotinib n = 9, 22 %; healthy controls n = 14, 12 %, p < 0.0001). Increased PB lymphocyte count was only observed during dasatinib therapy. The BM lymphocyte expansion was associated with early molecular response; patients with 3-month BCR-ABL1 <10 % showed higher lymphocyte counts than patients with BCR-ABL1 >10 % (23 vs. 17 %, p < 0.05). Detailed phenotypic analysis showed that BM lymphocyte expansion consisted of various lymphocyte subclasses, but especially the proportion of CD19+ B cells and CD3negCD16/56+ NK cells increased from diagnostic values. During dasatinib treatment, the lymphocyte balance in both BM and PB was shifted more to cytotoxic direction (increased CD8+CD57+ and CD8+HLA-DR+ cells, and low T regulatory cells), whereas no major immunophenotypic differences were observed between imatinib and nilotinib patients.

CONCLUSIONS

Early BM lymphocytosis occurs with all current first-line TKIs and is associated with better treatment responses. PB and BM immunoprofile during dasatinib treatment markedly differs from both imatinib- and nilotinib-treated patients.

Strength training improves muscle aerobic capacity and glucose tolerance in elderly

The primary aim of this study was to investigate the effect of short-term resistance training (RET) on mitochondrial protein content and glucose tolerance in elderly. Elderly women and men (age 71 ± 1, mean ± SEM) were assigned to a group performing 8 weeks of resistance training (RET, n = 12) or no training (CON, n = 9). The RET group increased in (i) knee extensor strength (concentric +11 ± 3%, eccentric +8 ± 3% and static +12 ± 3%), (ii) initial (0-30 ms) rate of force development (+52 ± 26%) and (iii) contents of proteins related to signaling of muscle protein synthesis (Akt +69 ± 20 and mammalian target of rapamycin +69 ± 32%). Muscle fiber type composition changed to a more oxidative profile in RET with increased amount of type IIa fibers (+26.9 ± 6.8%) and a trend for decreased amount of type IIx fibers (-16.4 ± 18.2%, P = 0.068). Mitochondrial proteins (OXPHOS complex II, IV, and citrate synthase) increased in RET by +30 ± 11%, +99 ± 31% and +29 ± 8%, respectively. RET resulted in improved oral glucose tolerance measured as reduced area under curve for glucose (-21 ± 26%) and reduced plasma glucose 2 h post-glucose intake (-14 ± 5%). In CON parameters were unchanged or impaired. In conclusion, short-term resistance training in elderly not only improves muscular strength, but results in robust increases in several parameters related to muscle aerobic capacity.

Low/negative expression of PDGFR-α identifies the candidate primary mesenchymal stromal cells in adult human bone marrow

Human bone marrow (BM) contains a rare population of nonhematopoietic mesenchymal stromal cells (MSCs), which are of central importance for the hematopoietic microenvironment. However, the precise phenotypic definition of these cells in adult BM has not yet been reported. In this study, we show that low/negative expression of CD140a (PDGFR-α) on lin⁻/CD45⁻/CD271⁺ BM cells identified a cell population with very high MSC activity, measured as fibroblastic colony-forming unit frequency and typical in vitro and in vivo stroma formation and differentiation capacities. Furthermore, these cells exhibited high levels of genes associated with mesenchymal lineages and HSC supportive function. Moreover, lin⁻/CD45⁻/CD271⁺/CD140a^low/− cells effectively mediated the ex vivo expansion of transplantable CD34⁺ hematopoietic stem cells. Taken together, these data indicate that CD140a is a key negative selection marker for adult human BM-MSCs, which enables to prospectively isolate a close to pure population of candidate human adult stroma stem/progenitor cells with potent hematopoiesis-supporting capacity.

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Comparative gene expression profiling identified MSC markers

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Primary adult bone marrow MSCs are CD140 (PDGFR-α) low/negative

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CD140a^low/− cells have typical in vitro and in vivo MSC properties

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Coculture with CD140a^low/− cells effectively expanded transplantable CD34⁺ HSCs

Expression of integrin α2 receptor in human cord blood CD34+CD38-CD90+ stem cells engrafting long-term in NOD/SCID-IL2Rγ(c) null mice

Human hematopoietic stem cells reside in the CD34+CD38-CD90+ population in cord blood and bone marrow. However, this cell fraction is heterogeneous, and the phenotype of the rare primitive stem cells remains poorly defined. We here report that primitive cord blood CD34+CD38-CD90+ stem cells, with the ability to reconstitute NOD/SCID-IL2Rγ(c) null (NSG) mice long-term, at 24 weeks after transplantation, can be prospectively isolated at an increased purity by using integrin α2 receptor as an additional stem cell marker. Using a limiting dilution transplantation assay, we found a highly significant enrichment of multilineage reconstituting stem cells in the CD34+CD38-CD90+ cell fraction expressing the integrin α2 receptor, with a frequency of 1/29 cells, as compared to a frequency of 1/157 in the corresponding integrin α2- cells. In line with this, long-term reconstituting stem cells within the cord blood CD34+CD38- cell population were significantly enriched in the integrin α2+ fraction, while stem cells and progenitors reconstituting short-term, at 8-12 weeks, were heterogeneous in integrin α2 expression. Global gene expression profiling revealed that the lineage-marker negative (Lin-) CD34+CD38-CD90+CD45RA- integrin α2+ cell population was molecularly distinct from the integrin α2- cell population and the more mature Lin-CD34+CD38-CD90-CD45RA- cell population. Our findings identify integrin α2 as a novel stem cell marker, which improves prospective isolation of the primitive human hematopoietic stem cells within the CD34+CD38-CD90+ cell population for experimental and therapeutic stem cell applications.

Expansion of highly differentiated CD8+ T-cells or NK-cells in patients treated with dasatinib is associated with cytomegalovirus reactivation

The tyrosine kinase inhibitor dasatinib exerts immunosuppressive effects on T-cells and NK-cells in vitro. However, in some dasatinib-treated leukemia patients, clonal lymphocytosis with large granular lymphocyte (LGL) morphology develops, and this is associated with enhanced therapeutic responses. To elucidate the mechanistic basis for this paradoxical observation, we conducted detailed phenotypic and functional analyses of T-cell and NK-cell populations from 25 dasatinib-treated leukemia patients. All tested patients with LGL expansions (15/16) were cytomegalovirus (CMV) immunoglobulin (IgG) seropositive with high frequencies of CMV-specific CD8(+) T-cells; 5/16 LGL patients also experienced symptomatic CMV reactivation during dasatinib therapy. Expanded T-cell and NK-cell populations exhibited late differentiated (CD27(-)CD57(+)) phenotypes; this was associated with a predisposition to apoptosis within the T-cell compartment and impaired NK-cell cytotoxicity. Only 3/9 non-LGL patients were CMV IgG seropositive. Dasatinib inhibited in vitro lymphocyte functions, similarly in LGL patients and controls. Notably, distinct CD8(high) and CD8(low) T-cell subsets were observed in LGL patients; this phenotypic dichotomy was also apparent in CMV-specific CD8(+) T-cell populations, and exhibited features consistent with antigen-driven activation. In addition, plasma levels of IP-10, IL-6, monokine induced by interferon-γ and interleukin-2R were significantly increased in LGL patients. These data provide evidence that dasatinib-associated LGL expansion is linked to CMV reactivation and suggest a potential mechanism for this phenomenon.

Pituitary function in patients with enlarged sella turcica and primary empty sella syndrome

The pituitary function in 20 patients with primary empty sella syndrome has been evaluated. The only endocrine symptom was secondary amenorrhoea in four patients. In half of the patients, pituitary function tests showed minor abnormalities, the most common being impaired growth hormone response to glucagon. In addition to the empty sella, other intracranial abnormalities such as pituitary tumour and hydrocephalus were found in four patients. Although commonly a benign condition, the empty sella may occasionally be associated with clinically important endocrine dysfunction, pituitary tumours and other intracranial abnormalities.

Critical role of thrombopoietin in maintaining adult quiescent hematopoietic stem cells

The role of cytokines in regulation of hematopoietic stem cells (HSCs) remains poorly understood. Herein we demonstrate that thrombopoietin (THPO) and its receptor, MPL, are critically involved in postnatal steady-state HSC maintenance, reflected in a 150-fold reduction of HSCs in adult Thpo(-/-) mice. Further, whereas THPO and MPL proved not required for fetal HSC expansion, HSC expansion posttransplantation was highly MPL and THPO dependent. The distinct role of THPO in postnatal HSC maintenance is accompanied by accelerated HSC cell-cycle kinetics in Thpo(-/-) mice and reduced expression of the cyclin-dependent kinase inhibitors p57(Kip2) and p19(INK4D) as well as multiple Hox transcription factors. Although also predicted to be an HSC viability factor, BCL2 failed to rescue the HSC deficiency of Thpo(-/-) mice. Thus, THPO regulates posttransplantation HSC expansion as well as the maintenance of adult quiescent HSCs, of critical importance to avoid postnatal HSC exhaustion.

Distinct roles of integrins alpha6 and alpha4 in homing of fetal liver hematopoietic stem and progenitor cells

Homing of hematopoietic stem cells (HSCs) into the bone marrow (BM) is a prerequisite for establishment of hematopoiesis during development and following transplantation. However, the molecular interactions that control homing of HSCs, in particular, of fetal HSCs, are not well understood. Herein, we studied the role of the alpha6 and alpha4 integrin receptors for homing and engraftment of fetal liver (FL) HSCs and hematopoietic progenitor cells (HPCs) to adult BM by using integrin alpha6 gene-deleted mice and function-blocking antibodies. Both integrins were ubiquitously expressed in FL Lin(-)Sca-1(+)Kit(+) (LSK) cells. Deletion of integrin alpha6 receptor or inhibition by a function-blocking antibody inhibited FL LSK cell adhesion to its extracellular ligands, laminins-411 and -511 in vitro, and significantly reduced homing of HPCs to BM. In contrast, the anti-integrin alpha6 antibody did not inhibit BM homing of HSCs. In agreement with this, integrin alpha6 gene-deleted FL HSCs did not display any homing or engraftment defect compared with wild-type littermates. In contrast, inhibition of integrin alpha4 receptor by a function-blocking antibody virtually abrogated homing of both FL HSCs and HPCs to BM, indicating distinct functions for integrin alpha6 and alpha4 receptors during homing of fetal HSCs and HPCs.

Laminin isoforms in development and disease

The members of the laminin family of heterotrimers are major constituents of all basement membranes, sheet-like extracellular structures, present in almost all organs. The laminins bind to cell surface receptors and thereby tightly connect the basement membrane to the adjacent cell layer. This provides for the specific basement membrane functions to stabilize cellular structures, to serve as effective physical barriers, and furthermore, to govern cell fate by inducing intracellular signalling cascades. Many different types of diseases involve basement membranes and laminins. Metastasizing solid tumors must pass through basement membranes to reach the vascular system, and various microbes and viruses enter the cells through direct interaction with laminins. Furthermore, whereas mutations in one specific laminin chain lead to a muscular disorder, mutations of other laminin chains cause skin blistering and kidney defects, respectively. This review summarizes recent progress concerning the molecular mechanisms of laminins in development and disease. The current knowledge may lead to clinical treatment of lamininopathies and may include stem-cell approaches as well as gene therapy.

Contribution of alpha6 integrins to hematopoietic stem and progenitor cell homing to bone marrow and collaboration with alpha4 integrins

The laminin receptor integrin alpha6 chain is ubiquitously expressed in human and mouse hematopoietic stem and progenitor cells. We have studied its role for homing of stem and progenitor cells to mouse hematopoietic tissues in vivo. A function-blocking anti-integrin alpha6 antibody significantly reduced progenitor cell homing to bone marrow (BM) of lethally irradiated mice, with a corresponding retention of progenitors in blood. Remarkably, the anti-integrin alpha6 antibody profoundly inhibited BM homing of long-term multilineage engrafting stem cells, studied by competitive repopulation assay and analysis of donor-derived lymphocytes and myeloid cells in blood 16 weeks after transplantation. A similar profound inhibition of long-term stem cell homing was obtained by using a function-blocking antibody against alpha4 integrin, studied in parallel. Furthermore, the anti-integrin alpha6 and alpha4 antibodies synergistically inhibited homing of short-term repopulating stem cells. Intravenous injection of anti-integrin alpha6 antibodies, in contrast to antibodies against alpha4 integrin, did not mobilize progenitors or enhance cytokine-induced mobilization by G-CSF. Our results provide the first evidence for a distinct functional role of integrin alpha6 receptor during hematopoietic stem and progenitor cell homing and collaboration of alpha6 integrin with alpha4 integrin receptors during homing of short-term stem cells.

Laminin isoform-specific promotion of adhesion and migration of human bone marrow progenitor cells

Laminins are alphabetagamma heterotrimeric extracellular proteins that regulate cellular functions by adhesion to integrin and nonintegrin receptors. Laminins containing alpha4 and alpha5 chains are expressed in bone marrow, but their interactions with hematopoietic progenitors are unknown. We studied human bone marrow cell adhesion to laminin-10/11 (alpha5beta1gamma1/alpha5beta2gamma1), laminin-8 (alpha4beta1gamma1), laminin-1 (alpha1beta1gamma1), and fibronectin. About 35% to 40% of CD34(+) and CD34(+)CD38(-) stem and progenitor cells adhered to laminin-10/11, and 45% to 50% adhered to fibronectin, whereas they adhered less to laminin-8 and laminin-1. Adhesion of CD34(+)CD38(-) cells to laminin-10/11 was maximal without integrin activation, whereas adhesion to other proteins was dependent on protein kinase C activation by 12-tetradecanoyl phorbol-13-acetate (TPA). Fluorescence-activated cell-sorting (FACS) analysis showed expression of integrin alpha6 chain on most CD34(+) and CD34(+)CD38(-) cells. Integrin alpha6 and beta1 chains were involved in binding of both cell fractions to laminin-10/11 and laminin-8. Laminin-10/11 was highly adhesive to lineage-committed myelomonocytic and erythroid progenitor cells and most lymphoid and myeloid cell lines studied, whereas laminin-8 was less adhesive. In functional assays, both laminin-8 and laminin-10/11 facilitated stromal-derived factor-1alpha (SDF-1alpha)-stimulated transmigration of CD34(+) cells, by an integrin alpha6 receptor-mediated mechanism. In conclusion, we demonstrate laminin isoform-specific adhesive interactions with human bone marrow stem, progenitor, and more differentiated cells. The cell-adhesive laminins affected migration of hematopoietic progenitors, suggesting a physiologic role for laminins during hematopoiesis.

Glucocorticoids down-regulate the extracellular matrix proteins fibronectin, fibulin-1 and fibulin-2 in bone marrow stroma

Glucocorticoids regulate hematopoietic cell interactions with the bone marrow microenvironment, but the molecules involved in the regulation are still largely unknown. We have studied the effect of glucocorticoids on mRNA expression and protein synthesis of the major extracellular matrix adhesion protein fibronectin and three other extracellular proteins, fibulin-1, fibulin-2 and nidogen-1, in mouse bone marrow cultures and in a hematopoiesis supporting the stromal MC3T3-G2/PA6 cell line. Glucocorticoids suppressed mRNA expression and protein synthesis of fibronectin, fibulin-1 and fibulin-2, but not nidogen-1, in adherent cells of bone marrow cultures, as shown by Northern blot analysis and immunoprecipitation. mRNA levels of all four proteins were down-regulated by dexamethasone in MC3T3-G2/PA6 cells, indicating a direct glucocorticoid effect on cells synthesizing extracellular matrix proteins. Dexamethasone down-regulated fibronectin mRNA rapidly, within 2 h of treatment, in the stromal cells. This effect did not require mRNA or protein synthesis, as shown by Northern blot analysis after treatment by actinomycin D and cycloheximide. Interferon-alpha, which also has been reported to modulate haematopoietic cell-matrix interactions, did not affect mRNA expression of the proteins in MC3T3-G2/PA6 cells. Our results indicate that glucocorticoids down-regulate expression of several mesenchymal-type extracellular matrix molecules in bone marrow, but with a variable effect on different proteins. Thus one mechanism by which glucocorticoids regulate haematopoiesis may be by altering the relative proportions of extracellular matrix proteins.

Rationale for the selection of the dose regimen of ‘Zendra’ used in the CLASS-I study

P195

Clomethiazole (CMZ; ‘Zendra’) is a neuroprotective drug that enhances GABA-A receptor activity. Two clinical trials in stroke patients (pts) were performed: 92CM01 (n=17) and CLASS (CLomethiazole Acute Stroke Study; n=678 on CMZ). In CLASS, a post-hoc analysis showed that CMZ appeared to improve outcome in pts with clinical signs suggestive of a large stroke. Dosing for the pivotal trial, CLASS-I, was based on information from these previous studies. In 92CM01, a loading dose of 6 mg/kg given over 15 min followed by a maintenance dose of 69 mg/kg to 24 h was the maximum CMZ dose that could be given without excessive sedation. In this study, plasma sampling from each pt allowed for individual kinetic modelling. In CLASS, the same dose regimen was used. One sample for drug analysis was taken from each pt at the end of the 24-h infusion. In total, 619 CLASS pts were eligible for a population kinetic evaluation. The clearance estimates in both studies were in the same range. Therefore, the pharmacokinetic parameter estimates from study 92CM01 could be used to simulate the plasma concentrations according to a 2-compartment model for different dosing regimens. According to the protocols, CMZ infusion should be temporarily interrupted if pts become excessively sedated. In CLASS, there were 218 infusion interruptions in 158 pts. CMZ kinetics did not differ between pts who had interruptions and those who did not. There was a delay in the occurrence of excessive sedation, with the majority of interruptions seen between 10 and 24 h. Pts with clinical signs suggesting a large stroke were particularly susceptible to sedation in CLASS, a new dose regimen was needed to reduce excessive sedation in these pts. For CLASS-I the adjusted dosage regimen was calculated as a total CMZ dose of 68 mg/kg, given as a 15 min loading dose, followed by two maintenance doses over 7.75 and 16 h respectively. This should avoid high plasma concentrations during the second half of the infusion period. Taking into account treatment interruptions, CLASS-I pts are predicted to receive an average dose of 63 mg/kg, the same as was actually received by such pts in CLASS. ‘Zendra’ is a trademark, the property of the AstraZeneca group of companies

Association of extracellular matrix proteins fibulin-1 and fibulin-2 with fibronectin in bone marrow stroma

Extracellular matrix (ECM) molecules, together with growth factors and stromal cells, regulate haematopoietic cell development in bone marrow (BM). We report here expression of ECM proteins fibulin-1 and fibulin-2 in mouse BM. In other tissues, fibulin-1 and fibulin-2 associate with fibronectin and other ECM proteins. Fibulin-2 has also been found to adhere to cells via beta3 integrins. We studied the association of fibulins with fibronectin in BM stroma. By confocal microscopy, fibulin-1 and fibulin-2 immunostainings were co-localized with fibronectin in the adherent layer of long-term BM cultures. In cell adhesion assays using recombinant proteins, mouse fibulin-2 adhered to human erythroid-megakaryocytic leukaemia cell line HEL. This adhesion was mediated by beta3 integrins. However, HEL cells did not adhere to human fibulin-2. We therefore studied a possible species-specific cell-adhesive activity of mouse fibulin-2 by using mouse megakaryocytes, obtained by culture of BM cells in the presence of thrombopoietin. These megakaryocytes did not adhere to mouse fibulin-2. Our findings suggested that the functional role of fibulin-1 and fibulin-2 in BM stroma is related to binding to the major cell adhesion protein fibronectin, whereas adhesion of mouse fibulin-2 to human cells containing the integrin beta3 chain is not related to an apparent physiological function of the protein.

cDNA cloning and embryonic expression of mouse nuclear pore membrane glycoprotein 210 mRNA

BACKGROUND

In embryonic kidneys, mesenchymal cells convert into epithelium in response to an induction by the tip of the ureter bud. Metanephric mesenchyme can also be induced to convert into epithelium in vitro. It is a model system to identify genes that could be important for epithelial development.

METHODS

By differential screening of a cDNA library made from mesenchymes induced in transfilter cultures by embryonic spinal cord for 24 hours, we selected cDNA clones representing genes that were preferentially expressed in 24-hour-induced mesenchyme and not in uninduced mesenchyme. The sequence of one clone was determined and used to obtain the sequence of a complete open reading frame. By Northern blotting and in situ hybridization, the expression of the mRNA in embryonic kidneys was determined.

RESULTS

We report the sequence and expression pattern of a marker for the 24-hour-induced state, mouse nuclear pore membrane glycoprotein 210 (mPOM210). The deduced 1886 amino acid sequence shows a 95% identity to the sequence of rat gp210. Northern blotting revealed a single 7.5 kb mRNA in 24-hour-induced mesenchyme, whereas message levels were fourfold to fivefold lower in uninduced mesenchyme. In situ hybridization of in vivo development confirmed the preferential expression of mPOM210 in epithelial cells. In the kidney, expression was seen in both the epithelium derived from the ureteric tree and the mesenchyme-derived epithelium. In other tissues of 13-day-old embryos, expression was also confined to the epithelium. In nervous tissues, the olfactory epithelium and walls of the lateral ventricle were the most prominently stained. Weak expression was seen in the heart.

CONCLUSIONS

mPOM210 mRNA is an early marker for developing epithelial cells. Furthermore, our results suggest that nuclear pore membrane proteins could be more cell-type specific than previously anticipated.

Characterization of bone marrow laminins and identification of alpha5-containing laminins as adhesive proteins for multipotent hematopoietic FDCP-Mix cells

Laminins are extracellular matrix glycoproteins that influence the phenotype and functions of many types of cells. Laminins are heterotrimers composed of alpha, beta, and gamma polypeptides. So far five alpha, three beta, and two gamma polypeptide chains, and 11 variants of laminins have been proposed. Laminins interact in vitro with mature blood cells and malignant hematopoietic cells. Most studies have been performed with laminin-1 (alpha1beta1gamma1), and its expression in bone marrow is unclear. Employing an antiserum reacting with most laminin isoforms, we found laminins widely expressed in mouse bone marrow. However, no laminin alpha1 chain but rather laminin alpha2, alpha4, and alpha5 polypeptides were found in bone marrow. Our data suggest presence of laminin-2 (alpha2beta1gamma1), laminin-8 (alpha4beta1gamma1), and laminin-10 (alpha5beta1gamma1) in bone marrow. Northern blot analysis showed expression of laminin alpha1, alpha2, alpha4, and alpha5 chains in long-term bone marrow cultures, indicating upregulation of laminin alpha1 chain expression in vitro. Laminins containing alpha5 chain, in contrast to laminin-1, were strongly adhesive for multipotent hematopoietic FDCP-mix cells. Integrin alpha6 and beta1 chains mediated this adhesion, as shown by antibody perturbation experiments. Our findings indicate that laminins other than laminin-1 are functional in adhesive interactions in bone marrow.

Laminin isoforms and epithelial development

Several different approaches suggest that basement-membrane assembly is important for epithelial development. Basement membranes contain isoforms of collagen IV, proteoglycans, and noncollagenous glycoproteins such as the laminins and nidogens. The expression and role of laminins for epithelial morphogenesis is reviewed. Laminins are large heterotrimeric proteins composed of alpha, beta, and gamma chains. Many major epithelial laminins and their receptors have been identified recently, and the extracellular protein-protein interactions that drive basement-membrane assembly are beginning to be understood. Three laminin alpha-chains are typically made by epithelial, alpha 1, alpha 3, and alpha 5. Three major epithelial heterotrimers can at present be distinguished--laminin-1 (alpha 1 beta 1 gamma 1), laminin-5 (alpha 3 beta 3 gamma 2), and laminin-10 (alpha 5 beta 1 gamma 1)--but other heterotrimers may exist in epithelia. Laminins containing either alpha 1 or alpha 3 chains are largely limited to epithelia, whereas the alpha 5 is also found in endothelial and muscle basement membranes, particularly in the adult. Some epithelial cell types express several laminin alpha-chains, so it is relevant to test how the different laminins affect epithelial cells. Laminins interact with integrin type of receptors on the cell surface, but binding to other proteins has also recently been demonstrated. Two important recent discoveries are the identification of dystroglycan as a major laminin receptor in muscle and epithelia, and nidogen as a high-affinity laminin-binding protein important for basement-membrane assembly. Antibody perturbation experiments suggest that these protein-protein interactions are important for epithelial morphogenesis.

Expansion of the nonadherent myeloid cell population by monoclonal antibodies against tenascin-C in murine long-term bone marrow cultures

Tenascin-C, a predominantly mesenchymal extracellular matrix protein, has a restricted distribution in adult tissues. It has previously been shown that this protein is expressed in the bone marrow. In this paper we show that murine myeloid and lymphoid long-term bone marrow cultures differ in their expression of tenascin-C splice variants. In the adherent stromal layer of myeloid cultures, the 260-kDa polypeptide encoded by the 8-kb mRNA was the major splice variant, whereas in the stromal layer of lymphoid cultures both the shorter 210-kDa polypeptide encoded by the 6-kb mRNA and the 260-kDa polypeptide were abundantly expressed. However, in both culture systems the larger 260-kDa tenascin-C polypeptide was the major isoform secreted in the culture supernatant. This finding is in agreement with previous reports indicating that the smaller 210-kDa isoform is preferentially deposited in the stroma, whereas the alternatively spliced segment in the 260-kDa tenascin-C may contain anti-adhesive domains. Glucocorticoids in myeloid long-term bone marrow cultures and in the MC3T3-G2/PA6 cell line downregulated the expression of tenascin-C. In the present study we observed that this was due primarily to downregulation of the 8-kb major splice variant of the tenascin-C mRNA. We also studied the possible role of tenascin-C in the bone marrow by using antibodies against tenascin-C in long-term bone marrow cultures. We found that three monoclonal antibodies against the carboxyterminal type III fibronectin repeats of tenascin-C (TNCfn 7-8) increased the number of the non-adherent myeloid cells in myeloid long-term bone marrow cultures. It has recently been suggested that the TNCfn 6-8 domain of tenascin-C binds to the alpha8beta1 integrin. Using Northern blotting, we found that the integrin alpha8 subunit was expressed in adherent cells in bone marrow cultures, raising the possibility that tenascin-C acts in bone marrow cultures by binding to the alpha8beta1 integrin.

Expression of laminin alpha 1, alpha 5 and beta 2 chains during embryogenesis of the kidney and vasculature

Laminins, found predominantly in basement membranes, are large glycoproteins consisting of different subsets of alpha, beta and gamma chain subunits. To resolve conflicting data in the literature concerning coexpression of alpha 1 and beta 2 chains, expression of alpha 1 chain was studied with two different antisera against the E3 fragment of laminin alpha 1 chain. Expression of the alpha 1 chain was seen in several types of epithelial basement membranes throughout development, but its expression in rat glomerular basement membranes and some other types of epithelial basement membranes occurred only during early stages of development. By contrast, beta 2 chains were detected by immunofluorescence only during advanced stages of glomerulogenesis and vascular development. By Northern and Western blots, beta 2 chains were detected somewhat earlier, but in situ hybridization revealed that beta 2 chain was also confined to vasculature during the earlier stages. It thus seems that, in the tissues studied here, the expression of alpha 1 and beta 2 chains was mutually exclusive. To explore whether the newly described alpha 5 chain is expressed in locations lacking alpha 1 chain, expression of alpha 5 chain was studied by Northern blots and in situ hybridization. The alpha 5 chain was not uniformly expressed in all embryonic epithelial cell types but was present mainly in epithelial sheets which produce very little alpha 1 chain. There also appeared to be a developmental trend, with alpha 1 chain appearing early and alpha 5 later, in maturing epithelial sheets. The alpha 5 chain could be a major alpha chain of the adult glomerular basement membrane.

Integrin alpha 6B beta 1 is involved in kidney tubulogenesis in vitro

Laminin-1 has previously been shown to be of major importance for the development of kidney tubules. Antibodies against fragments E8 and E3 of laminin-1 perturb kidney development in vitro. We here studied expression of integrins alpha 6 beta 1 and alpha 6 beta 4, two known laminin receptors, during kidney development. Integrin beta 1 subunit could be detected by immunofluorescence on all cell types of embryonic mouse kidney, but we could not detect integrin beta 4 subunit in embryonic kidney by immunofluorescence or by in situ hybridization. The presence of integrin alpha 6 subunit in all epithelia of embryonic kidney was demonstrated by immunofluorescence and by in situ hybridization. RT-PCR showed that alpha 6B is the major splice variant in embryonic kidney. During in vitro conversion of nephrogenic mesenchyme to epithelial tubules, a strong increase in the expression of the 6 kb mRNA for alpha 6 integrin subunit was seen by northern blotting at the onset of epithelial morphogenesis, on day two of culture. Immunoprecipitation of extracts from embryonic kidney with antibodies against alpha 6 subunit yielded bands corresponding to the expected size of beta 1 integrin subunit but not of beta 4 subunit. Monoclonal antibodies against either alpha 6 or beta 1 subunit but not against E-cadherin blocked kidney tubulogenesis in vitro. This suggests that integrin alpha 6B beta 1 is involved in kidney tubulogenesis in vitro. Another possibility is that the antibodies against integrin alpha 6 and beta 1 subunit cause abnormal signalling by the integrin.

Ameliorative effect of allopurinol on nonbacterial prostatitis: a parallel double-blind controlled study

PURPOSE

Nonbacterial prostatitis is a common problem in young men. It is a disease that is often recurrent and each episode lasts for several months. Different causative mechanisms of the disease have been discussed, including identified and unidentified microorganisms, stone formation and psychological factors. We have demonstrated in a previous study that urinary reflux (as shown by a high creatinine concentration in prostatic fluid) occurs to a varying extent into the prostatic ducts, and this reflux has been related to prostatic pain and urate concentration in expressed prostatic secretion.

MATERIALS AND METHODS

We performed a paralled double-blind controlled study of the objective and subjective effects of allopurinol on patients with nonbacterial prostatitis. Twenty patients received placebo, 18 received 300 mg. allopurinol daily and 16 received 600 mg allopurinol daily for 240 days. All patients began medication at the same time regardless of whether the disease was in an active state. No side effects were noted in the treatment groups.

RESULTS

Significant effects were noted on the concentrations of serum urate, urine urate, expressed prostatic secretion urate, expressed prostatic secretion xanthine and subjective discomfort.

CONCLUSIONS

Allopurinol has a significant, positive effect on nonbacterial prostatitis. It is safe and worthy of trial for all at least a 3-month period at each episode to relieve the symptoms of nonbacterial prostatitis.

Regulation of mesenchymal extracellular matrix protein synthesis by transforming growth factor-beta and glucocorticoids in tumor stroma

We have here studied the composition and regulation of stromal extracellular matrix components in an experimental tumor model. Nude mice were inoculated with WCCS-1 cells, a human Wilms' tumor cell line. In the formed tumors the stroma was found to contain mesenchymal extracellular matrix proteins such as tenascin-C, fibulins-1 and 2 and fibronectin, but no nidogen. Nidogen was confined to basement membranes of tumor blood vessels. Since glucocorticoids have been shown to downregulate tenascin-C expression in vitro, we tested whether dexamethasone can influence biosynthesis of extracellular matrix components during tumor formation in vivo. A downregulation of tenascin-C mRNA and an upregulation of fibronectin mRNA expression by dexamethasone was noted. Transforming growth factor-beta 1 mRNA levels were unaffected by the dexamethasone treatment. Glucocorticoids can thus downregulate tenascin-C synthesis although local stimulatory growth factors are present. The competition between a negative and a positive extrinsic factor on synthesis of stromal extracellular matrix components was studied in a fibroblast/preadipocyte cell line. Transforming growth factor-beta 1 stimulated tenascin-C synthesis but did not affect fibronectin or fibulin-2 synthesis. Dexamethasone at high concentrations could completely suppress the effect of transforming growth factor-beta 1 on tenascin-C mRNA expression. Transforming growth factor-beta 1 could in turn overcome the downregulation of tenascin-C mRNA expression caused by a lower concentration of dexamethasone. We therefore suggest that the limited expression of tenascin-C in part is due to a continuous suppression by physiological levels of glucocorticoids, which can be overcome by local stimulatory growth factors when present in sufficient amounts.

Role of mesenchymal nidogen for epithelial morphogenesis in vitro

Recent biochemical studies suggested that the extracellular matrix protein nidogen is a binding molecule linking together basement membrane components. We studied its expression and role during development. By immunofluorescence and northern blotting, nidogen was found early during epithelial cell development of kidney and lung. Yet, in situ hybridization revealed that nidogen was not produced by epithelium but by the adjacent mesenchyme in both organs. Binding of mesenchymal nidogen to epithelial laminin may thus be a key event during epithelial development. This is supported by antibody perturbation experiments. Antibodies against the nidogen binding site on laminin B2 chain perturbed epithelial development in vitro in embryonic kidney and lung. Mesenchymal nidogen could be important for early stages of epithelial morphogenesis.

Quantification of effect delay and acute tolerance development to morphine in the rat

In this study the effect delay and the development of acute tolerance to morphine's antinociceptive effect were investigated in the rat. The antinociceptive response induced after three different short infusions of morphine was measured by using the electrical stimulation vocalization method. Three treatment groups received morphine hydrochloride over 10, 60 and 180 min, targeting maximal plasma concentrations of 25 microM at the end of the infusion. The maximal concentrations of morphine obtained for the three groups were 29.4 +/- 3.7, 26.7 +/- 4.7 and 28.9 +/- 7.3 microM, respectively. Both an effect delay and acute tolerance were observed. For each group, the peak effects were 248 +/- 82, 337 +/- 116 and 303 +/- 49% above base line, at 35, 65 and 90 min after the start of the infusions. A pharmacokinetic-pharmacodynamic model with separate effect and tolerance compartments (the ET-model) well described the antinociceptive response over time. The antinociceptive effect was best described by using a linear model, whereas acute tolerance was best described by using an Emax model. The rates of drug equilibration between the plasma and the effect compartment (ke0) and the plasma and the tolerance compartment (kt0), expressed as half-lives, were 34 +/- 2 and 48 +/- 4 min, respectively. High concentrations were required for the acute tolerance to develop (TC50 of 17 microM).

Downregulation of tenascin expression by glucocorticoids in bone marrow stromal cells and in fibroblasts

Tenascin, a predominantly mesenchymal extracellular matrix (ECM) glycoprotein has a rather restricted tissue distribution, but until now factors that inhibit its expression have not been identified. Glucocorticoids are known to be beneficial for establishment of myelopoiesis in long-term bone marrow cultures. Tenascin was found to be expressed in the bone marrow, and glucocorticoids were found to affect bone marrow tenascin expression. Both tenascin mRNAs and the mRNA of another ECM protein, laminin B1 chain, were drastically downregulated by glucocorticoids during initiation of bone marrow cultures. However, in already established long-term cultures glucocorticoids did not affect laminin B1 chain mRNA levels although tenascin mRNAs continued to be downregulated. Studies with a stromal cell line (MC3T3-G2/PA6) and fibroblasts (3T3) suggested that glucocorticoids act directly on the stromal cells that produce tenascin. In 3T3 cells this downregulation occurred within 12 h of glucocorticoid-treatment, suggesting that glucocorticoids acted through cis regulatory elements of the tenascin gene. We suggest that glucocorticoids in part regulate hematopoiesis by modifying the ECM. Furthermore, downregulation of tenascin expression by glucocorticoids may in part explain the restricted tissue distribution of tenascin in other tissues.

Modeling of tolerance development and rebound effect during different intravenous administrations of morphine to rats

The development of tolerance and the rebound effect to the antinociceptive effect of morphine were investigated and correlated with morphine pharmacokinetics. Five i.v. regimens, including a bolus dose (35 mumol/kg), 2 constant rate infusions (2.5 and 4.2 mumol/hr) over 4 days, 1 saline bolus dose and 1 glucose infusion were followed for 8 days. Clearance (CL) was estimated as 148 +/- 58 ml/min*kg after the bolus dose and 108 +/- 32 ml/min*kg during infusion (N.S.). Tolerance developed during the first day of morphine infusion and no antinociceptive effect could be measured from the third day. After cessation of the infusions, rebound hyperalgesia, significant for the higher infusion rate (P < .05), was observed. No hyperalgesia was detected after the bolus dose. A pharmacodynamic model with separate effect and tolerance compartments was used to describe the antinociceptive effect over time. The rates of equilibration of drug between the blood and effect compartment and the blood and tolerance compartment, expressed in half-lives, were estimated as 25 +/- 8 min and 26 +/- 6 hr, respectively. It is apparent from these results that an i.v. bolus dose of morphine causes less tolerance than constant rate infusions of morphine. With the presented model it is possible to quantify the rate and extent of tolerance development of morphine.

Pharmacokinetics and pharmacodynamics of morphine-3-glucuronide in rats and its influence on the antinociceptive effect of morphine

In this study the pharmacokinetics and pharmacodynamics of morphine-3-glucuronide (M3G) were investigated in rats after i.v. administration as a bolus dose (86.7 mumol kg-1) and as a constant rate infusion (2.9 mumol h-1) over 5 days. After the bolus dose, the clearance (Cl) was 12.1 +/- 0.6 ml min-1*kg, the volume of distribution at steady state (Vss) 1.68 +/- 0.89 l kg-1, the half-life of the first phase 13.2 +/- 1.8 min and the half-life of the second phase 11.6 +/- 7.7 h. After the constant rate infusion, Cl was 10.5 +/- 1.7 ml min-1*kg. The antagonistic effect of M3G on the antinociceptive effect of a bolus dose of morphine (35 mumol kg-1) was tested during steady state concentrations of M3G on day 4 and to M3G naïve rats. No antinociceptive, hyperalgesic or withdrawal effects were observed as a result of M3G administration, but a significantly lower antinociceptive effect of morphine was found in the M3G infusion group compared to the control group. Systemically administered M3G antagonized the antinociceptive effect of morphine, but this cannot be the only explanation to the tolerance development observed after morphine administration.

Estimation of unbound concentrations of morphine from microdialysate concentrations by use of nonlinear regression analysis in vivo and in vitro during steady state conditions

The unbound concentration of morphine in striatum of rats was estimated during a constant rate infusion of morphine 14 mumol/h*kg, by use of the microdialysis technique and nonlinear regression analysis. The concentrations in plasma of morphine and its metabolite, morphine-3-glucuronide, were 4.2 +/- 1.4 microM and 7.7 +/- 4.0 microM, respectively, during the constant rate infusion. The corresponding estimated unbound concentrations of morphine in striatum varied between 0.06 and 0.11 microM. No morphine-3-glucuronide was detected in the brain dialysates. The unbound concentration in striatum was lower than expected based on unbound plasma concentrations and could be an indication of active transport from the brain. Five different equations were tested to find the best empirical description of the relationship between microdialysate concentration and perfusion rate by nonlinear regression analysis. The equations were validated by a serum in vitro study, where three unbound concentrations of morphine estimated from microdialyis were compared to estimates obtained from equilibrium dialysis. The precision of the parameter estimates obtained from the five equations was tested by Monte Carlo simulations. One of the equations (Eq. 4) was selected in preference to the others, because of the good agreement with the estimated unbound concentration obtained by equilibrium dialysis in vitro, and good precision of the parameter estimates. The method described in this paper is valuable when estimating the unbound concentration of drug from microdialysate concentrations during steady state conditions. Furthermore, the method is easily accessible when working in the pharmacokinetic and pharmacodynamic field.

Laminin isoforms and their receptors in the developing kidney

Epithelial cells have a polarized morphology, with distinct basal, lateral, and apical cell surfaces. It would be of considerable interest to know how the polarized morphology develops during embryogenesis. Both the tubular and glomerular epithelial cells of the kidney develop from mesenchymal stem cells during embryogenesis. A unique conversion of nonpolar cells to polarized epithelial cells thus occurs in the embryonic kidney. This conversion also occurs in vitro if the mesenchymal cells are properly induced. Organ cultures of mesenchymal cells from the mouse embryonic kidney have therefore been much used to study the development of epithelial cell polarity. We have used this model system to study the role of basement membrane glycoproteins in development. The results obtained suggest that laminins are particularly important for epithelial cell development. There are many different types of laminins. Developing kidney tubule cells synthesize a laminin isoform with the chain composition A-B1-B2, and it seems to promote development by interacting with specific integrin receptors on the cell surface. The mesenchymal stem cells also produce laminin B chains, but not the A chain, and they also lack the integrin receptor that interacts with A-B1-B2 laminin.

Differential expression of laminin A and B chains during development of embryonic mouse organs

Laminin is a large glycoprotein of basement membranes. The best described laminin from a mouse tumor contains three polypeptide chains (A, B1 and B2), but there is recent evidence that some cell types produce laminin isoforms lacking the A chain. We have here studied the occurrence of the isoforms during mouse organogenesis. In all tissues studied, the A chain mRNA and polypeptide were more weakly expressed than those of the B chains. Laminin A chain polypeptides showed a much more restricted tissue distribution than the B chains. Laminin A chain polypeptide was mainly detected in basement membranes of epithelial cells, suggesting that this chain is important for morphogenesis of epithelial sheets. Most endothelial basement membranes and all embryonic mesenchyme matrices studied seemed to lack the A chain even though they contained B chains. Several of the cells producing laminin devoid of A chain seem to produce other polypeptides that become complexed to the B chains. With an anti-laminin antiserum, which in immunoblots reacts only with A and B polypeptide chains, additional polypeptides of 160 and 190 × 10(3) Mr were co-precipitated from all tissues studied. In developing heart, a polypeptide of 300 × 10(3) Mr was co-precipitated in addition. Our data suggest that these laminin-associated polypeptides are not formed by a differential splicing of the known A chain mRNA. Northern blotting of poly (A)+ RNA showed only 10kb A chain transcripts but no truncated forms. We conclude that several cell types in the mouse embryo produce laminin variants that lack the 400 × 10(3) Mr A chain. Since a major cell binding site of laminin contains parts of the A chain, the variants should differ in biological function from laminin containing this A chain.

A genomic clone encoding a novel proliferation-dependent histone H2A.1 mRNA enriched in the poly(A)+ fraction

Replication-dependent histone mRNAs are prime examples of nonpolyadenylated mRNAs. We isolated and characterized cDNAs and a genomic clone for a replication-dependent histone H2A.1 mRNA which segregated into the poly(A)+ fraction during mRNA isolation through an oligo(dT)-cellulose column. However, the results of sequencing of the genomic clone suggested that the mRNA did not contain a poly(A) tail. Instead, the genomic sequence revealed a nonterminal oligo(A) tract directly upstream from the typical 3'-terminal hairpin loop of replication-dependent histone mRNAs. The nonterminal oligo(A) tract consisted of 14 adenylate residues interrupted by one guanylate residue (A4GA10). We concluded that this short oligo(A) stretch mediated binding of the mRNA to oligo(dT) even after stringent washes with 0.1 M NaCl, indicating that rather short oligo(A) sequences can ensure binding to oligo(dT)-cellulose. The cDNA and genomic clones contained an AAATAAG sequence at the end of the coding region. It has been suggested that this sequence contains a polyadenylation signal in some yeast and mouse transcripts, but it does not function as a polyadenylation signal in the histone transcript described in this paper.

Transient and locally restricted expression of laminin A chain mRNA by developing epithelial cells during kidney organogenesis

Three polypeptide chains, A, B1, and B2, have been described for mouse laminin, a basement membrane protein. We studied expression of laminin A, B1, and B2 mRNA in the developing mouse kidney. Induction of kidney mesenchyme differentiation in vitro led to an increased expression of B1 and B2 chain mRNA on day 1 of development. In contrast, expression of A chain mRNA increased on day 2, when epithelial cell polarization begins. Laminin A mRNA and polypeptide were expressed only by epithelia during in vivo development as well. Some polarized cell types producing basement membrane (endothelium, some adult epithelia) lacked the A chain mRNA and polypeptide, although they did express B chains. Laminin with the 400 kd A chain is therefore a transient form appearing at specific sites of kidney morphogenesis, whereas isoforms with a different A chain or without it have a more widespread distribution.

Effect of bumetanide on tubuloglomerular feedback in Necturus maculosus

A non-invasive technique was developed to measure single-nephron glomerular blood flow (SNGBF) in Necturus maculosus. Erythrocytes labelled with rhodamine, a fluorescent dye, were injected systemically and the frequency at which labelled cells entered an arteriole was measured. Frequency was converted to flow by measuring the concentration of labelled erythrocytes in whole blood. Dependence of SNGBF on flow rate in early distal tubules was used to assess tubuloglomerular feedback (TGF). SNGBF decreased with increasing flow in the early distal tubule in a pattern typical of TGF; SNGBF decreased 25% at the highest flow rates. SNGBF increased when bumetanide was added to the perfusate, but the TGF response to flow rate persisted. IC50 (concentration that produces half-maximal inhibition) was 2.4 x 10(-10), 9.8 x 10(-10) and 1.2 x 10(-9) M bumetanide at distal perfusion rates of 5, 10 and 20 nl min-1 respectively. These results are consistent with modulation of SNGBF according to the rate of luminal entry of NaCl into early distal tubule cells. This transport rate depends on the luminal concentration of NaCl, which is tubular flow rate-dependent; NaCl and bumetanide compete.

Familial and sporadic medullary thyroid carcinoma: clinical and immunohistological findings

We have studied the clinical and thyroid immunohistological features of 19 patients with sporadic medullary thyroid carcinoma and 16 patients with the hereditary syndrome multiple endocrine neoplasia 2a (MEN 2a). Both groups were identified by family screening using serum calcitonin determinations before and after pentagastrin stimulation. Pheochromocytoma and hyperparathyroidism were associated both with multiple endocrine neoplasia 2a and some cases of sporadic medullary thyroid carcinoma. Hereditary medullary thyroid carcinoma was invariably associated with C-cell hyperplasia, but C-cell hyperplasia was also associated with some sporadic tumours. All tumours were positive for calcitonin and carcinoembryonic antigen (by immunohistological staining) (CEA) and most tumours stained for somatostatin. C-cell hyperplasia also stained for calcitonin, CEA and somatostatin. We conclude that sporadic and familial medullary thyroid carcinoma cannot always be discriminated by clinical or immunohistological methods. Family screening is essential in the diagnosis of hereditary medullary thyroid carcinoma.

Late expression of M and N antigens on glycophorin A during erythroid differentiation

The M/N blood groups are carried by the major human red cell sialoglycoprotein, glycophorin A. O-glyosidic carbohydrate is needed for the activity, but the M/N specificity is due to amino acid replacements in the NH2-terminal portion of the molecule. We have used monoclonal antibodies specific for M and N blood groups to study their expression during normal erythropoiesis. Here we report that the M/N blood group activities are very weakly or not at all expressed before the polychromatic normoblast stage. Using polyclonal anti-glycophorin A antiserum, it was shown that glycophorin A molecules are already abundantly present on the earliest morphologically recognizable erythroid precursor, the proerythroblast. These findings can be explained by our previous observation that the O-glycosylation of glycophorin A gradually increases during erythroid maturation.

A method for simultaneous study of the karyotype, morphology, and immunologic phenotype of mitotic cells in hematologic malignancies

A major problem in the cytogenetic analysis of hematologic neoplasms has been an inability to identify the cell from which the chromosomes were obtained. We describe a procedure that allows simultaneous analysis of karyotype and cell cytology in mitotic cells. The method differs from conventional cytogenetic analysis in that after mild hypotonic treatment, the cells are cytocentrifuged onto glass slides. In mitotic cells, this procedure often results in adequate spread of the chromosomes within the intact cell membrane. The cytoplasmic structure also remains intact, so that cytologic preparations are of good quality. Morphologic and immunologic identification of mitotic cells can be done using routine hematologic stains, such as Giemsa or Sudan black B, and various antisera using immunofluorescence techniques. The chromosomes can be simultaneously analyzed either without banding on slides stained with Giemsa or with Q-banding on slides stained with immunofluorescence techniques. Identification of numerical and structural karyotype aberrations thus is possible in morphologically identified cells.

Differentiation of human erythroid cells is associated with increased O-glycosylation of the major sialoglycoprotein, glycophorin A

Glycophorin A, the major human erythrocyte sialoglycoprotein, is found exclusively on cells of the erythroid lineage. The amino acid sequence is known, and glycophorin A isolated from mature erythrocytes contains a single N-glycosidic and 15 O-glycosidic oligosaccharides. Monoclonal antibodies against erythrocyte glycophorin A reacted weakly with erythroid precursors while a monospecific rabbit antiserum reacted strongly with immature and mature red cells. Glycophorin A was isolated from cells representing various stages of erythropoiesis in normal bone marrow, from blood cells of neonates with erythroblastosis fetalis, and from the erythroleukemic cell lines K562 and HEL before and after induced differentiation. Analysis of the oligosaccharides showed less O-glycosylation of glycophorin A in erythroid precursors. The degree of glycosylation increased concomitantly with differentiation.

Chromosome abnormalities in 16 Finnish patients with Burkitt's lymphoma or L3 acute lymphocytic leukemia

Eleven patients with Burkitt's lymphoma (BL), i.e., small noncleaved non-Hodgkin's lymphoma, and 5 patients with Burkitt-type acute lymphocytic leukemia (ALL-L3) were selected for chromosome study. Two of the 16 patients had no B-cell markers, but the erythrocyte marker--glycophorin A--was present on the surface of the leukemic blasts. The critical breakpoint at 8q24 was detected in 14 of the 16 patients, whereas this aberration was not detected in any of the 134 patients belonging to other subgroups of non-Hodgkin's lymphoma or ALL that we studied during the same period. In addition to the t(8;14)(q24;q32), the following translocations with the breakpoint at 8q24 were seen: t(2;8)(p11;q24), t(8;11)(q24;q13) in BL, and t(2;8;14)(p11 or p12;q24;q32) in ALL. Additional aberrations seen more than once were trisomy #7 and abnormalities in chromosomes #1, #11, and #13.

Expression of spectrin in normal and malignant erythropoiesis

Spectrin is a major constituent of the erythrocyte membranoskeleton. The occurrence of spectrin during normal and malignant erythropoiesis was investigated by immunofluorescence using a monospecific rabbit anti-human spectrin antiserum. The expression of spectrin was correlated to the presence of glycophorin A, which is an early and specific marker for erythroid cells. The expression of spectrin during normal erythroid differentiation coincided with that of glycophorin A. Both markers were already present in the proerythroblasts. Spectrin was also found in leukaemic cells from patients with acute erythroleukaemia and erythroid blast crisis of chronic myelogenous leukaemia. In a large panel of human haematopoietic cell lines only those with erythroid phenotype (K 562 and HEL) stained positively for spectrin. It is concluded that spectrin appears early in the erythroid maturation. It is expressed both in normal and malignant erythroid precursors. Spectrin can be used as a marker for erythroid blasts in the diagnosis of erythroleukaemias.