Characterization and quantitation of primitive hematopoietic progenitor cells present in peripheral blood autografts

In this report, we assess the content of primitive hematopoietic progenitor cells (HPC) that circulate transiently in the peripheral blood (PB) of cancer patients (group A) who received a PB stem-cell-mobilizing regimen that included high-dose chemotherapy (HD-CTX) of 7 g/m2 cyclophosphamide followed by a combination of recombinant hematopoietic growth factors (C-HGF), including either interleukin-3 (IL-3) plus granulocyte-colony stimulating factor (G-CSF), IL-3 plus granulocyte-macrophage colony-stimulating factor (GM-CSF), or a recombinant GM-CSF/IL-3 fusion protein (PIXY-321). These data were compared to the HPC content of PB obtained from a similar group of cancer patients that had not received such a mobilization regimen (group B). Monoclonal antibody staining and fluorescence-activated cell sorting (FACS) were used to identify and isolate cell populations enriched for more differentiated HPC (CD34+HLA-DR+) and more primitive HPC (CD34+HLA-DR-). The content of CD34+HLA-DR+ and CD34+HLA-DR- cells in the PB of group A patients was significantly greater than that observed in the PB of group B patients. In addition, HD-CTX plus C-HGF mobilization resulted in the appearance of greater numbers of PB colony-forming units-granulocyte/macrophage, -granulocyte/erythroid/macrophage/megakaryocyte, and -megakaryocyte (CFU-GM, CFU-GEMM, and CFU-Mk), and burst-forming units-erythroid and -megakaryocyte (BFU-E and BFU-Mk) than those observed in the PB of group B patients (p < 0.01). CD34+HLA-DR- cells isolated from the PB of group A patients were capable of initiating long-term hematopoiesis in vitro, which persisted for 10 weeks, while CD34+HLA-DR- cells obtained from the PB of group B patients were capable of sustaining long-term hematopoiesis in vitro for only 4 weeks. As determined by a limiting dilution analysis of group A PB CD34+HLA-DR- cells, the frequency of cells capable of giving rise to hematopoietic progenitor cells (pre-CFC) after 2 weeks in liquid culture was 4.3% (range 1.0-8.3%). Pre-CFC constituted 0.01% (range 0.001-0.02%) of group A PB mononuclear cells, and 151 pre-CFC were calculated to be present in 1 mL mobilized PB (range 20-310/mL). These results suggest that peripheral blood mononuclear cells (PBMC) collected by leukapheresis following HD-CTX plus C-HGF mobilization contain not only differentiated HPC but also more primitive HPC.

A simplified method for single-cell RT-PCR that can detect and distinguish genomic DNA and mRNA transcripts

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The ability of diphenylpiperazines to prevent neuronal death in dorsal root ganglion neurons in vitro after nerve growth factor deprivation and in vivo after axotomy

The mechanism of neuroprotection by the calcium channel antagonist flunarizine against neuronal death is unknown. We investigated the ability of other calcium channel antagonists (cinnarizine, nimodipine, nicardipine, diltiazem, and verapamil), calmodulin antagonists, and calpain inhibitors to prevent neuronal death in rat dorsal root ganglion neurons in vitro after nerve growth factor (NGF) deprivation and the ability of cinnarizine and diltiazem to protect in vivo after axotomy. In vitro, only neurons treated with cinnarizine or flunarizine were protected from death after withdrawal. In vivo, cinnarizine, but not diltiazem, protected dorsal root ganglion neurons in rats after unilateral sciatic nerve crush. Intracellular calcium concentration ([Ca2+]i) was evaluated with fura 2 after NGF deprivation in vitro. Neurons "committed to die" 24 h after NGF deprivation displayed a decline in [Ca2+]i before visible morphological deterioration consistent with cell death. The influx of extracellular calcium was not necessary to produce neuronal death. Neurons deprived of NGF gradually lost the ability to respond to elevated external potassium with an increase in [Ca2+]i during the first 24 h after trophic factor deprivation. After 24 h, neurons deprived of NGF could not be rescued by readministration of NGF. Neurons protected from cell death with diphenylpiperazines maintained their response to high external potassium, suggesting continued membrane integrity. We speculate that diphenylpiperazines may protect sensory neurons via an unknown mechanism that stabilizes cell membranes.

Enhanced cancer growth in mice administered daily human-equivalent doses of some H1-antihistamines: predictive in vitro correlates

BACKGROUND

Present studies of drug-induced tumor growth promotion have evolved from earlier investigations into the mechanism of action of N,N-diethyl-2-[4-(phenylmethyl)phenoxy[ethanamine.HCl, a tamoxifen derivative which potently inhibits lymphocyte mitogenesis in vitro and stimulates tumor growth in vivo. It is thought that potency to bind to intracellular histamine receptors (HIC), some of which are on cytochromes P450, may correlate with tumor growth-promoting activity.

PURPOSE

We assessed the effectiveness of five in vitro assays in predicting in vivo tumor growth stimulation by the H1-antihistamines loratadine, astemizole, cetirizine, hydroxyzine, and doxylamine.

METHODS

Potency of each agent was ranked 1-5 in each of the following in vitro assays: 1) inhibition of [3H]histamine binding to microsomal HIC, 2) inhibition of histamine binding to microsomal P450, 3) inhibition of the P450-catalyzed demethylation of aminopyrine, 4) inhibition of lymphocyte mitogenesis, and 5) stimulation of tumor colony formation. An overall rank score was assigned to each drug and correlated with tumor growth stimulation in vivo. Two laboratories conducted in vivo studies in a blinded fashion. Female C57BL and C3H mice were given a subcutaneous injection on day 1 of syngeneic B16F10 melanoma cells (5 x 10(5)) or C-3 fibrosarcoma cells (1 x 10(5)), respectively. Mice were randomly assigned to treatment groups, then received a single, daily intraperitoneal injection of an estimated human-equivalent dose (or range of doses) of antihistamine or vehicle control for 18-21 days before being killed. Tumors were surgically removed and wet weights compared statistically among groups.

RESULTS

The cumulative potency of each drug in affecting tumor growth or growth mechanisms in the five in vitro assays ranked as follows: Loratidine and astemizole ranked highest and were equally potent, followed in decreasing order by hydroxyzine, doxylamine, and cetirizine. A significant correlation (r = .97; P < .02) was observed between the rank order of potency of the antihistamines in all five in vitro assays and the rank order to enhance tumor growth in vivo: Loratidine and astemizole significantly (P < .001) promoted the growth of both melanoma and fibrosarcoma, hydroxyzine significantly (P < .001) promoted the growth of melanoma, while doxylamine and cetirizine did not promote the growth of either tumor.

CONCLUSION

Data demonstrate that the in vitro assays predicted the propensity of each H1-antihistamine to stimulate cancer growth in vivo.

IMPLICATION

These in vitro tests may prove valuable to screen potential tumor growth promoters.

A hydrodynamic interpretation of crisis in sickle cell anemia

The occurrence of crisis events in patients with sickle cell disease is associated with an increase in blood plasma viscosity, the hydrodynamic consequences of which are examined here. A mathematical model of the flow of sickle cells in capillaries predicts that for moderate increases in plasma viscosity, a regime of multivalued solutions for blood velocities is encountered, and the likely physical response is a precipitous drop to the lowest velocity solution. This behavior results from the coupling of the hydrodynamics with sickle erythrocyte rheology and oxygen transport to the surrounding tissue; no such catastrophe is predicted for normal erythrocytes. The type of velocity changes predicted by the model strongly suggest that plasma viscosity changes may play an important role in initiating or exacerbating crisis.

In vitro study of osteoblastic cells from patients with idiopathic osteoporosis and comparison with cells from non-osteoporotic controls

We have examined bone cells derived from iliac crest trabecular explants of 30 patients with idiopathic osteoporosis and 45 control subjects in order to determine whether intrinsic abnormalities in osteoblast function may contribute to the decreased bone formation observed in this disease. Bone cells isolated from all subjects expressed several in vitro characteristics of the osteoblast phenotype including adenylate cyclase responsiveness to parathyroid hormone (PTH) and prostaglandin E1 (PGE1), basal and 1,25(OH)2D3-stimulated alkaline phosphatase activity and osteocalcin production. Results were compared amongst three subject groups; young controls less than 40 years old, older controls over 40 years old, and osteoporotics. Osteoporotic cells were found in general to be fully active in vitro. There were no differences between osteoporotic and control cells in their basal levels of adenylate cyclase, or alkaline phosphatase, in their growth rates, or cell morphology. The cyclic AMP (cAMP) response to PTH was significantly lower in osteoporotic cells (71%, p < 0.01) and older control cells (64%, p < 0.005) relative to the response in cells from younger controls, suggesting that the decreased responsiveness in osteoporotic cells was due to subject age rather than the osteoporotic state. At the same time, the cAMP responses to PGE1 and cholera toxin were similar in cells from all three subject groups. The response to forskolin was reduced to about 40% in osteoporotic cells compared with controls, but this was not mirrored by similar differences in the responses to PTH, PGE1 or cholera toxin, suggesting that the availability of catalytic subunits is not rate-limiting in these cells. 1,25(OH)2D3-stimulated osteocalcin production was 220% higher in osteoporotics than in older controls, but the numbers tested were small and the difference did not reach significance. The one significant abnormality we observed in osteoporotic cells was in alkaline phosphatase activity: 1,25(OH)2D3-stimulated alkaline phosphatase activity was twofold higher in osteoporotics than in younger (p < 0.05), older (p < 0.05) and pooled controls (p < 0.025). The significance of this finding is unknown, but we postulate that it may reflect an intrinsic abnormality in osteoblast function in patients with idiopathic osteoporosis.

Further study on the magnesium-mediated change in physical state of phospholipid modulates mitochondrial F0-F1-ATPase activity

We have postulated that magnesium may play a role in altering the lipid fluidity of the bilayers, which would induce a change of conformation of the F0-ATPase portion (buried in the lipid core) of mitochondrial F0-F1-ATPase. Such change could be transmitted to the soluble F1 portion, resulting in higher enzymatic activity. The assumption was further supported by the results presented in the following: (1) A conformational difference for the F0-ATPase-containing proteoliposomes induced by the magnesium effect could be detected using a fluorescent probe acrylodan; (2) H(+)-translocation activity of F0-ATPase-incorporated proteoliposomes with magnesium, monitoring by fluorescence quenching of 9-aminoacridine or the bulk phase pH change, was higher than that without magnesium; (3) The magnesium effect on the reconstituted F0-F1-ATPase activity was greatly enhanced when the reconstitution was carried out in the presence of oligomycin sensitivity conferring protein (OSCP, a main component of the connecting link between the F1 and F0 sector of F0-F1-ATPase).

A single B1 subunit mapped to mouse chromosome 7 may be a common component of Na channel isoforms from brain, skeletal muscle and heart

A beta 1 subunit associated with one or more isoforms of brain voltage-sensitive Na channels has previously been cloned, sequenced and expressed. Northern and Western blot analyses have suggested that homologues to this protein are expressed in skeletal muscle and heart. Here, reverse transcriptase-polymerase chain reaction (RT-PCR)/cloning reveals that transcripts encoding identical beta 1 subunit ORFs are expressed in adult rat brain, skeletal muscle and heart. Heterologous co-expression of beta 1 with brain (RIIA) and skeletal muscle (mu 1) alpha subunits caused a stabilization of normal, rapidly inactivating (mode 1) gating relative to anomalous, non-inactivating (mode 2) states and a negative shift in steady state inactivation. Chromosome mapping of the beta 1 subunit showed a single locus (Scn1b) in mouse chromosome 7 1.8 cM (+/- 1.2 cM) distal to D19F11S1h and 0.9 cM (+/- 0.9 cM) proximal to Pkca. This locus is in the region of the mouse mutant "quivering," characterized by a variety of neurological disorders and muscle paralysis. A mutation in a single beta 1 subunit forming functional complexes with multiple Na channel isoforms could underlie these deficits.

In vivo administration of recombinant methionyl human stem cell factor expands the number of human marrow hematopoietic stem cells

A growing number of in vitro studies suggest that recombinant human stem cell factor (SCF) is capable of augmenting the proliferative capacity of human hematopoietic progenitor cells (HPC) and stem cells (HSC). We further evaluated this biologic effect by analyzing the response of bone marrow (BM) HPCs and HSCs to the administration of SCF in eight patients with locally advanced or metastatic breast cancer who were enrolled in an ongoing phase I study. SCF was administered for 14 days by daily subcutaneous injection at dosages of 10, 25, or 50 micrograms/kg/d. BM CD34+ HLA-DR+ and CD34+ HLA-DR- CD15- cells, previously shown by our laboratory to be enriched for various classes of differentiated and primitive HPCs, respectively, were quantitated in BM samples on day 0 (pretreatment) and day 15 (posttreatment). These CD34+ HLA-DR+ and CD34+ HLA-DR- CD15- cells were then isolated by cell-sorting and assayed for several classes of HPCs, including the high--proliferative potential colony-forming cell (HPP-CFC), the burst-forming unit--megakaryocyte (BFU-MK), and the long-term BM culture--initiating cell (LTBMC-IC). SCF administration resulted in a 3.3-fold (range, 1.4- to 18.8-fold; P = .018) increase in the absolute numbers of CD34+ cells, a 3.7-fold (range, 1.2- to 8.2-fold; P = .028) increase in the absolute numbers of CD34+ HLA-DR+ cells, and a 2.4-fold (range, 1.1- to 29.3-fold; P = .010) increase in the absolute numbers of CD34+ HLA-DR- CD15- cells. Following the infusion of SCF, a statistically significant increase in the absolute numbers of HPP-CFC (P = .018), BFU-MK (P = .046), CFU-granulocyte, erythrocyte, monocyte, megakaryocyte (CFU-GEMM: P = .043), BFU-erythrocyte (BFU-E; P = .043), CFU-granulocyte, macrophage (CFU-GM; P = .045), and CFU-megakaryocyte (CFU-MK; P = .028) per milliliter of marrow was observed. Stromal cell-free LTBMCs supplemented with SCF and interleukin-3 (IL-3), initiated with CD34+ HLA-DR- CD15- cells obtained on day 0, produced viable cells for 9.6 weeks, compared with 11.5 weeks for LTBMCs initiated with CD34+ HLA-DR- CD15- cells obtained on day 15. Cumulative cellular production by LTBMCs initiated with day 15 CD34+ HLA-DR- CD15- cells was statistically greater than that by day 0 LTBMCs (P = .031). These same cultures produced CFU-GM for 6.3 weeks (day 0) versus 9 weeks (day 15).(ABSTRACT TRUNCATED AT 400 WORDS)

The in vitro and in vivo effects of stem cell factor on human hematopoiesis

The c-kit ligand or stem cell factor (SCF) and the c-kit ligand receptor (KR) are thought to play pivotal roles in the regulation of human hematopoiesis. When added to interleukin 3 (IL-3) and/or granulocyte-macrophage colony stimulating factor (GM-CSF), SCF has an especially profound effect on the in vitro proliferation of several classes of primitive hematopoietic progenitor cells including the burst forming unit megakaryocyte (BFU-MK), the high proliferative potential colony forming cell (HPP-CFC) and the long-term bone marrow culture-initiating cell (LTBMC-IC). These primitive hematopoietic progenitor cells are present in a CD34+HLA-DR- fraction of marrow which has in vivo marrow populating ability and thereby resembles the pluripotent hematopoietic stem cell. Furthermore, the CD34+HLA-DR- marrow subpopulation which expresses KR contains virtually all of the marrow BFU-MK, HPP-CFC and LTBMC-IC, indicating that the human stem cell is KR positive. The addition of SCF, IL-3 and GM-CSF to suspension cultures initiated with CD34+HLA-DR- cells results in an exponential expansion of the numbers of hematopoietic progenitor cells. Large numbers of such progenitor cells generated ex vivo may be useful as transfusion products for the treatment of chemotherapy induced cytopenias. The therapeutic potential of the in vivo administration of SCF has also been evaluated in a phase I trial of recombinant methionyl SCF. SCF administration led to an increase in both differentiated and primitive hematopoietic progenitor cells within the marrow. Such studies suggest that in vivo SCF administration may be useful for improving the quality of bone marrow grafts to be used either for autologous or allogeneic bone marrow transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)

In patients receiving dopamine infusions for treatment of shock do free radicals convert dopamine to 6-hydroxydopamine?

Free hydroxyl radicals react with dopamine in vitro to produce the neurotoxin 6-hydroxydopamine (6-OHDA). If 6-OHDA were produced in vivo it could destroy central and/or peripheral neurons. Free radicals are produced in patients with cardiovascular or toxic shock. These patients are often treated with intravenous dopamine infusions. Using a newly developed method for measuring 6-OHDA in biological samples, we have examined blood from 15 patients receiving dopamine infusions for treatment of shock. 6-OHDA neither binds to nor elutes from either alumina or ion-exchange resins; therefore we used ODA-silica (Sep-Pak) to prepare samples for HPLC analysis with electrochemical detection. 6-OHDA disappeared rapidly from whole blood or serum at room temperature but was stable at -70 degrees C in an HClO4 extract. Recovery from Sep-Pak was 95% and detection limit 10 nmol/L. We repeated the experiments that showed in vitro hydroxyl radical conversion of dopamine to 5- and 6-OHDA. We detected neither 5- nor 6-OHDA in plasma samples from patients receiving dopamine infusions at 10-28 micrograms kg-1 min-1. Plasma dopamine in these patients was 1-5 mumol/L. We conclude that any 6-OHDA produced by hydroxyl radical attack in vivo is rapidly scavenged by endogenous substances containing sulfhydryl groups.

Role of cyclic GMP in the mediation of circadian rhythmicity of the adenylate cyclase-cyclic AMP-phosphodiesterase system in Euglena

Cyclic AMP (cAMP) and cyclic GMP (cGMP) are two second messengers that have been proposed to act as a dualistic system in biological regulation. To determine if cGMP plays a role in the mediation of circadian rhythmicity of the adenylate cyclase (AC)-cAMP-phosphodiesterase (PDE) system in the achlorophyllous ZC mutant of the unicellular flagellate Euglena, the levels of cAMP and cGMP were monitored in synchronized cell populations, and the effects of the cGMP analog 8-bromo-cGMP (8-Br-cGMP) and the cGMP inhibitor 6-anilinoquinoline-5,8-quinone (LY 83583) on the activity of AC and PDE, as well as on the level of cAMP, were measured in vivo. A bimodal, 24-hr rhythm of cGMP content was found in both dividing and nondividing cultures in either a 12-hr:12-hr light-dark cycle or constant darkness. The peaks and troughs of the cGMP rhythm occurred 2 hr in advance of those of the cAMP rhythm that has been reported previously. The addition of 8-Br-cGMP at different circadian times increased the cAMP level in vivo by two to five times, whereas LY 83583 reduced the amplitude of the cAMP rhythm so that it disappeared. The effects of 8-Br-cGMP on the activity of AC and PDE were circadian phase-dependent and consistent with the changes in cAMP content. These findings suggest that cGMP may serve as an upstream effector that mediates the cAMP oscillation by regulation of the AC-cAMP-PDE system.

The change of C-fos expression in ovariectomized rats following electroacupuncture treatment--an immunohistochemistry study

The roles of electroacupuncture (EA) in regulating the function of ovulation in rat have been investigated; however, the systematic study for the involvement of neural population of central nervous system (CNS) in acupuncturing the ovariectomized rat for promoting functional recovery has not been well understood. The present research was designed to examine, by C-fos immunocytochemistry, the distribution of Fos labelled neuron in CNS after acupuncturing the point of "Zhong-Ji (RN3)", "Guan-Yuan (RN4)", "San-Ying-Jiao (SP6)" and "Zi-Gong (EXCA1)" in ovariectomized rat. The area occupied by Fos protein labelled neuron, two hours after ovariotomy, was detected in medial preoptic nucleus (MPN), lateral preoptic nucleus (LPN), suprachiasmatic nucleus (SCN), paraventricular nucleus of the hypothalamus (PANH), medial amygdala nucleus (MAN), periventricular nucleus of the hypothalamus (PVNH), ventromedial nucleus of the hypothalamus (VNH), and arcuate nucleus (AR). The C-fos immunoreactive labelled neurons disappeared two weeks later following ovariotomy. The rat, recovering for two weeks after ovariotomy, received EA, and many specific Fos labelled cell were observed in LPN, PVNH, VNH, SCN and especially in AR, PANH and MPN, but not any labelled neuron could be found in MAN. No obvious C-fos expression was shown in these areas in the control group and EA group without ovariotomy. These results indicate that the above structures involved in regulating the function of hypothalamus-pituitary-ovarian axis and EA could modulate this function through effects on the above nuclei.

Protein kinase C couples membrane excitation to acetylcholine receptor gene inactivation in chick skeletal muscle

The signaling pathway connecting membrane depolarization and gene activity in skeletal muscle remains largely unknown. Using transcription elongation (run-on) analysis we have found that electrical stimulation of denervated chick skeletal muscle in vivo rapidly and selectively results in inactivation of acetylcholine receptor (AChR) subunit genes. We have studied the possible involvement of protein kinase C (PKC) in this response and have observed that electrical stimulation increases the activity of PKC in the nucleus by over two orders of magnitude within 10 min; phorbol esters, within minutes after intramuscular application, block AChR subunit genes in the absence of electrical activity; and the activity-triggered gene inactivation is blocked by the protein kinase inhibitor staurosporine or by enzyme depletion resulting from chronic pretreatment of muscle with phorbol esters. We conclude that PKC is an integral component of the pathway coupling membrane excitation and AChR gene control.

Evaluation of biological response modifiers in the enhancement of tumor uptake of technetium-99m labeled macromolecules. A preliminary report

Imaging tumors with radioactive monoclonal antibodies remains attractive but continues to be challenging. With the hypothesis that the use of biological response modifiers (BRMs) may augment the tumor uptake, technetium-99m(99mTc)-labeled tumor necrosis factor (TNF) and nuclear histone specific TNT-1-F(ab')2 were evaluated in tumor bearing mice given a single dose of interferon (IFN). Ukrain or pokeweed mitogen as BRMs. As early as 1.5 h post injection (p.i.) of the radioactive macromolecules, the absolute tumor uptake (% administered dose/g) of each agent was enhanced (e.g., TNF, control = 1.8 +/- 0.4, Ukrain = 3.2 +/- 0.5, P = 0.006) and tumor to muscle ratios were elevated (e.g., TNF, control a 4.1 +/- 2.2, interferon 8.3 +/- 2.7, P = 0.01). The absolute tumor uptake remained practically unchanged at 4 h p.i. Generally with BRMs, the blood clearance was rapid and tumor/blood ratios and tumor/muscle ratios were higher than in the control group, increasing to greater than 200% for IFN as a BRM. The early enhancement in tumor uptake of macromolecules, leading to excellent delineation of tumors by scintigraphy is highly encouraging and warrants further studies to explore the full potential of BRMs.

Effect of stem cell factor on colony growth from acquired and constitutional (Fanconi) aplastic anemia

The aim of this study was to evaluate the effect of stem cell factor (SCF) on the in vitro growth of bone marrow hematopoietic progenitors from patients with acquired severe aplastic anemia (AA) or Fanconi's anemia (FA). For this purpose, we studied 11 patients with acquired AA (5 at diagnosis, 6 after ALG treatment), 12 patients with FA, and nine normal controls. Bone marrow cells were plated in vitro for colony-forming unit granulocyte-macrophage (CFU-GM) (in the presence of granulocyte-macrophage colony-stimulating factor [GM-CSF]), and for burst-forming unit-erythroid (BFU-E) and CFU-granulocyte, erythroid, monocyte, megakaryocyte (CFU-GEMM) colonies (in the presence of erythropoietin and interleukin-3 [IL-3]), with or without 20 ng/mL of SCF. In normal controls, SCF enhanced the growth of CFU-GM colonies from 103 to 263 (median), of BFU-E from 168 to 352, and of GEMM colonies from 6 to 38/10(5) cells plated. In patients with acquired AA, SCF induced a significant enhancement of BFU-E growth (8 to 29; P = .01) and allowed the formation of GEMM colonies that were not scored in baseline culture conditions (0 to 8; P = .01). CFU-GM growth was enhanced (4 to 20), but not significantly (P = .3). This was true both for patients at diagnosis and after antilymphocyte globulin treatment. By contrast, 10 of 12 FA patients grew no CFU-GM, BFU-E, or CFU-GEMM colonies, with or without SCF. In two FA patients (one transfusion-dependent and one transfusion-independent), an enhancement of CFU-GM and/or BFU-E was observed. The lack of response of hematopoietic progenitor cells from FA patients to GM-CSF+SCF or IL-3+SCF was not dependent on a defective expression of cytokine receptor messenger RNAs. Northern blot analysis showed in marrow cells from acquired AA and FA patients the presence of normal transcripts for alpha- and beta-chains of GM-CSF/IL-3 receptor and for c-kit protein. In conclusion, SCF promotes the in vitro growth of hematopoietic progenitors in patients with acquired AA, but not in patients with FA, pointing out the intrinsic nature of the defect in the latter disorder.

Stimulation of malignant growth in rodents by antidepressant drugs at clinically relevant doses

Tricyclic antidepressants, such as amitriptyline (Elavil), and the nontricyclic agent, fluoxetine (Prozac), bind to growth-regulatory intracellular histamine receptors, associated with anti-estrogen binding sites in microsomes and nuclei. The prototype anti-estrogen binding site/intracellular histamine receptor ligand, N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine HCl, inhibits normal cell proliferation in vitro but stimulates tumor growth in vivo. Because of their structural similarity to N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine HCl, we carried out studies to determine whether amitriptyline and fluoxetine stimulate tumor growth and/or development in rodents at concentrations relevant to the treatment of human depression (equivalent human dose range, approximately 100-150 mg/day for amitriptyline and approximately 20-80 mg/day for fluoxetine). All experiments were performed blinded. In studies of growth stimulation of transplantable syngeneic tumors, groups of mice were inoculated s.c. with C-3 fibrosarcoma cells or given i.v. or s.c. injections of B16f10 melanoma cells, followed 24 h later by daily i.p. injections of saline, amitriptyline, or fluoxetine. Tumor latency (fibrosarcoma), aggregate tumor weight (s.c. injected melanoma), or time to death from pulmonary metastasis (i.v. injected melanoma) was determined; drug-induced stimulation of DNA synthesis in C-3 fibrosarcoma cells in vitro was correlated with tumor growth acceleration in vivo. In a mammary carcinogenesis model, the effects of chronic saline, amitriptyline, or fluoxetine administration on the rate and frequency of development of mammary tumors in rats fed dimethylbenzanthracene (DMBA) were compared. Eight of 20 amitriptyline- or fluoxetine-treated mice developed fibrosarcoma tumors by day 5, as compared to none of 20 saline controls (P less than 0.002). Similarly, 20 of 21 DMBA-treated rats receiving the antidepressant drugs developed 33 mammary tumors by week 15 as compared to 5 tumors in 4 of 7 DMBA-treated rats receiving saline (P less than 0.001). For both models, tumor latency decreased 30-40% and, in the DMBA model, tumor frequency increased greater than 2-fold in the antidepressant-treated rats as compared to controls. Stimulation of fibrosarcoma growth in vivo correlated with a corresponding bell-shaped drug-induced increase in DNA synthesis in vitro. While the median time to death from pulmonary metastases did not differ among groups given i.v. injections of melanoma cells, a significant (P less than 0.01) stimulation of growth of s.c. injected melanoma was observed in mice receiving the antidepressants.(ABSTRACT TRUNCATED AT 400 WORDS)

Bone marrow harvest for marrow transplantation: effect of multiple small (2 ml) or large (20 ml) aspirates

The aim of this study was to evaluate the yield of nucleated cells and CFU-GM and the T cell composition in bone marrow harvested by means of multiple small (2 ml) or large (20 ml) aspirations. Eleven marrow donors were studied: each donated 1000 ml of bone marrow in two aliquots of 500 ml for an HLA identical sibling transplant. In six cases the first 500 ml were harvested by means of multiple 2 ml aspirations (A) and the second 500 ml by means of 20 ml aspirations (B). In five cases the opposite was done: 20 ml aspirates first (C) and 2 ml afterwards (D). From each 500 ml aliquot a sample was taken for enumeration of nucleated cells and CD3+ lymphocytes and for CFU-GM growth. Small volume aspirations (groups A and D) yielded more nucleated cells (p = 0.02), more CFU-GM (p = 0.03) and fewer CD3+ cells (p = 0.1) when compared with large volume aspirations (groups B and C). This study shows that marrow harvesting by means of multiple small volume aspirations minimizes the dilution with peripheral blood and results in greater numbers of cells and hemopoietic progenitors.

The role of ions and second messengers in circadian clock function

The fact that single cells can exhibit circadian rhythmicity simultaneously in quite different processes, such as those of photosynthesis, bioluminescence, and cell division, suggests that membrane-bound compartmentalization is important for temporal organization. Since these rhythms, as well as others, are known to be affected by changes in the ionic environment and are probably membrane-bound systems, it is not surprising that transmembrane ion transport or flux has been proposed to be a key feature of the underlying circadian oscillator(s). Likewise, signal transduction along the entrainment pathway leading to the clock, among the elements, or "gears," of the timing loop itself, and within the output pathway between the oscillator and its "hands" likely is mediated by ions and second messengers. In this overview, we examine the theoretical and experimental evidence supporting the possible roles of intracellular free calcium and cyclic AMP in these capacities, particularly in view of the fact that oscillations in the concentrations of both species have been proposed to form the basis of pacemaker activity and other biological rhythms.

Long-term marrow culture in patients with aplastic anemia compared with marrow transplant recipients and normal controls

Patients with severe aplastic anemia (SAA; n = 46) were studied in long-term bone marrow culture (LTBMC) systems and compared with allogeneic marrow transplant (BMT) recipients (n = 16) (within 30 days following BMT) and normal control patients (n = 12). SAA patients were divided in two groups: transfusion-dependent (Tx-D) SAA patients (group A; n = 15) and transfusion-independent (Tx-I) patients after treatment with antilymphocyte globulin (group B; n = 31). Cultures were analyzed at three levels: stromal layer (SL) formation (score: 0, no SL; 1, half confluent SL; and 2, confluent SL), number of nucleated cells in suspension, and growth of CFU-GM colonies. SL formation was rapid and complete in SAA patients, groups A and B (mean score on day 14: 1.3 and 1.4), similar to controls (mean score on day 14: 1.3), whereas an impairment of SL formation was seen in BMT recipients (mean score on day 14: 1.0). The number of nucleated cells in suspension increased significantly on day 7 of culture in controls (7.6-fold), significantly more than in BMT and SAA patients, and declined thereafter. Colony formation was also significantly increased on day 7 in Tx-I SAA patients, BMT recipients, and normal controls (4-, 5-, and 16-fold, respectively), lasting respectively 2, 3, and 4 weeks. Increments of colony formation were also obtained in Tx-D SAA patients, but in the first week of culture only.

IN CONCLUSION

1) a significant impairment of SL formation was seen in BMT recipients, but not in SAA patients; 2) a significant increment of granulocyte-macrophage colony-forming units (CFU-GM) growth can be obtained in patients with marrow failure early after starting long-term culture; 3) the number of CFU-GM grown in these culture conditions from Tx-I SAA patients parallels the number of progenitors from early post-BMT recipients; and 4) progenitor cells from Tx-D SAA patients are not only reduced in numbers, but also exhibit a poor ability to survive in LTBMC.

Intracellular histamine and liver regeneration: high affinity binding of histamine to chromatin, low affinity binding to matrix, and depletion of a nuclear storage pool following partial hepatectomy

We have demonstrated in rat hepatocytes that 3H-histamine binds specifically to novel low (microM) and high (nM) affinity sites, designated "HIC" to denote their intracellular location. Low affinity HIC sites are associated with microsomes, while both low and high affinity HIC sites are associated with the nucleus. A growth-regulatory action of intracellular histamine at HIC, independent of the rise in cytosolic calcium, has been demonstrated in mitogen-stimulated lymphocytes. We now report that the high affinity HIC sites in liver cell nuclei are associated exclusively with chromatin, while only low affinity sites are found in the residual material containing the nuclear matrix. Moreover, hepatocyte nuclei contain histamine (approximately 1 ng/mg protein), unaffected by incubation for up to 18 hours with the histidine decarboxylase inhibitor, alpha-FMH, suggesting a slow rate of turnover typical of a storage pool. A decrease in nuclear histamine parallels a rise in DNA synthesis in the first 24 hours after partial hepatectomy. Our findings support a role for a nuclear pool of pre-formed histamine in the mediation of liver regeneration.

Use of an isolated in situ canine lung perfusion model to evaluate dopamine clearance by the lung

An isolated in situ lung perfusion model was used to assess dopamine clearance by the lungs in 12 dogs. The preparation consisted of a closed perfusion system in situ, in which systemic arterial blood supply was interrupted. Blood flow to the lungs was maintained at presurgery flow rates. The inflow was restricted to the lungs by the pulmonary arteries and outflow was limited to the pulmonary veins. Pulmonary artery pressure, temperature and pO2 were maintained at physiological levels. After confirmation of a stable base line, one of 3 doses (1, 2, or 5 micrograms/kg/min) of dopamine was infused over 30 min to achieve steady-state blood concentrations, then blood samples were drawn at specified times during and after the infusion. Dopamine plasma concentrations were analyzed by high performance liquid chromatography with electrochemical detection. Dose-dependent disposition of dopamine was observed in both plasma concentration-time profiles and in clearance (20.3 +/- 9.6 ml/min/kg at 5 micrograms/kg/min vs. 41.6 +/- 19.1 ml/min/kg at 1 micrograms/kg/min, P = 0.038). A sham experiment revealed that the blood in this experimental preparation contributed less than 10% to the total clearance of dopamine. This study revealed that our isolated in situ model is an excellent method to evaluate the role of the lungs in drug removal. Furthermore, it confirmed that the lungs contribute to the clearance of dopamine from the body.

Circadian rhythmicity in the activities of adenylate cyclase and phosphodiesterase in synchronously dividing and stationary-phase cultures of the achlorophyllous ZC mutant of Euglena gracilis

Key factors in the adenosine 3′,5′-cyclic monophosphate (cyclic AMP) metabolic pathway are two enzymes responsible for its generation and degradation, namely, adenylate cyclase (AC) and phosphodiesterase (PDE). In LD: 12,12 (12 h light, 12 h dark), these enzymes were found to undergo bimodal, circadian variation of activity in both dividing and nondividing cultures of the photosynthesis-deficient, achlorophyllous ZC mutant of Euglena gracilis Klebs (Z). Maximal AC activity occurred 2 h after the onset of the light interval (CT 02) and at the beginning of darkness (CT 12–14); these times corresponded to the acrophase profile for the rhythmic changes in cyclic AMP content that have been previously reported. The activity of PDE also exhibited a daily oscillation, but with an inverse phase pattern. Both the AC and PDE activity rhythms persisted after the cultures were transferred from LD: 12,12 to constant darkness. The activity of AC was activated significantly in vivo by forskolin at the trough phase (CT 20), while that of PDE was inhibited by 3-isobutyl-1-methyl-xanthine (IBMX) at its peak phase. These results indicate that the rhythms of both AC and PDE may be the main factors generating the circadian oscillations of cyclic AMP content in Euglena, which appear to be under control of an endogenous pacemaker.

Response of CFU-GM to increasing doses of rhGM-CSF in patients with aplastic anemia

The aim of this study was to test whether large amounts of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) are capable of promoting the growth of hemopoietic progenitors from patients with marrow failure. For this purpose 0.1, 100, 1000, 10,000 and 20,000 ng/ml of rhGM-CSF were added to 10(5) light-density (adherent cell-depleted) bone marrow cells from 9 normal controls and from 52 patients with aplastic anemia, 25 cases of which were transfusion-dependent (Tx-D) aplastic anemia (AA) and 27 of which were transfusion-independent (Tx-I) aplastic anemia (AA). A dose-dependent increase of granulocyte-macrophage colony-forming units (CFU-GM) was observed in healthy donors, from 81 to 247 colonies at 0.1 and 1000 ng/ml of rhGM-CSF, with a plateau thereafter. Tx-I AA patients showed the best increase of CFU-GM in response to colony-stimulating factor, from 0.1 to 32.7 mean colonies at 0.1 and 20,000 ng/ml of rhGM-CSF, and the increment was greater when compared to controls. The ratio of CFU-GM grown from these patients and controls was 1:810 at 0.1 ng/ml of rhGM-CSF and 1:7.9 at 20,000 ng/ml. Eleven patients were studied at diagnosis; there was no in vitro response to rhGM-CSF (0 and 1.8 mean colonies/10(5) cells at 0.1 and 10,000 ng/ml). Overall, Tx-D AA patients showed minimal increments of CFU-GM growth at very high doses of rhGM-CSF. Two suggestions come from this study: 1) maturation of CFU-GM from recovering AA patients appears to require larger doses of GM-CSF than normal controls, and 2) very high doses of rhGM-CSF have little or no effect on CFU-GM growth in AA patients. This may be relevant for clinical studies designed to improve hemopoiesis in patients with marrow failure.

In vitro response of T cells from aplastic anemia patients to antilymphocyte globulin and phytohemagglutinin: colony-stimulating activity and lymphokine production

The aim of the present study was to compare the response of bone marrow (BM) lymphocytes from patients with aplastic anemia (AA) or normal controls to increasing doses of antilymphocyte globulin (ALG) or phytohemagglutinin (PHA). For this purpose BM T-enriched cells from 11 AA patients and 9 normal individuals were incubated with ALG (0-1000 micrograms/ml) or PHA (0%-10%) for 1 day, and the supernatants were tested for suppression/enhancement of granulocyte-macrophage colony-forming unit (CFU-GM) growth and for release of granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma) assayed with the enzyme-amplified sensitivity immunoassay (EASI). The production of colony-stimulating activity (CSA) by T cells primed with ALG and tested in the absence of exogenous GM-CSF correlated with the dose of ALG in priming cultures up to 14% EG (100% EG = CFU-GM growth with 30 ng/ml of GM-CSF). The amount of GM-CSF in the supernatants paralleled their capacity to sustain CFU-GM growth (up to 3.5 ng/ml of GM-CSF). Production of CSA or GM-CSF from T cells primed with PHA was significantly lower. Supernatants of PHA-primed T cells, when added to normal BM cells in the presence of exogenous GM-CSF, produced a dose-dependent inhibition of CFU-GM growth (down to 13% +/- 10% EG). The same supernatants contained detectable amounts of IFN-gamma and TNF-alpha (21 +/- 6.7 IU/ml and 4.6 +/- 2.9 ng/ml, respectively). IFN-gamma production from severe AA (SAA) T cells in response to PHA was significantly superior to the IFN-gamma production from normal T cells (21 +/- 6.7 IU/ml vs 9.5 +/- 7.1 IU/ml, p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Severe aplastic anemia (SAA): response to cyclosporin A (CyA) in vivo and in vitro

The aim of the present study was to test the effect of cyclosporin A (CyA) in vitro on CFU-GM growth from patients with severe aplastic anemia (SAA). For this purpose, bone marrow (BM) cells from 9 SAA patients and 5 healthy individuals were incubated with or without CyA and then cultured for CFU-GM growth in the presence of exogenous recombinant human GM-CSF (30 ng/ml). SAA patients were tested before or after treatment with CyA, or after treatment with antilymphocyte globulin (ALG). In 3 patients responding to CyA, the addition of CyA in vitro enhanced colony growth from 13 +/- 10 to 40 +/- 20/10(5) BM cells (p = 0.01) - the median increment of colony formation was 2.4-fold. In 5 ALG responders, CyA produced no increment of CFU-GM growth (from 14 +/- 26 to 15 +/- 16/10(5) BM cells, p = 0.1). CyA did not enhance significantly CFU-GM growth in normal controls (from 57 +/- 45 to 58 +/- 81/10(5) BM cells, p = 0.9). In conclusion, it would appear that some patients with SAA can respond to CyA in vivo and in vitro, and ALG responders are not necessarily among these. This is in keeping with different mechanisms of action of CyA and ALG and possibly with the existence of distinct pathogenetic pathways in SAA.

Increased risk of leukemia relapse with high-dose cyclosporine A after allogeneic marrow transplantation for acute leukemia

Eighty-one patients with acute myeloid leukemia (ANLL, n = 44) or acute lymphoblastic leukemia (ALL, n = 37), aged 10 to 50 years were randomized to receive 1 mg/kg per day (n = 41, group A) or 5 mg/kg per day (n = 40, group B) of cyclosporine A (CyA) from day -1 to day +20 after bone marrow transplant (BMT). All patients received CyA orally thereafter. All patients were prepared with cyclophosphamide (CY) 120 mg/kg and fractionated total body irradiation (TBI), and received unfractionated BM from an HLA-identical sibling. The two groups were comparable for diagnosis, disease status, French-American-British (FAB) classification, WBC count at diagnosis, cytogenetic abnormalities, extramedullary disease before BMT, donor/recipient age and sex, number of cells infused, and number of days with intravenous (IV) CyA. Median follow-up for surviving patients in group A was 983 v 632 days in group B. Patients in group A had lower serum levels of CyA (295 v 686 ng/mL, P = .004), lower bilirubin levels (1.9 v 2.6 mg/dL, P = .07), lower creatinine levels (0.9 v 1.4 mg/dL, P = .06), and a lower proportion of CD8+ cells in the peripheral blood (PB) within day +21 (19% v 28%, P = .07). First day to 0.5 x 10(9)/L neutrophils was comparable in the two groups (13 v 14 days; P = .1). In a Cox model, the actuarial risk of acute graft-v-host disease (GVHD) grade II+, after stratification for age (less than 20 years greater than) was significantly lower in group B patients (0.54, P = .04). The actuarial risk of developing chronic GVHD was comparable (P = .9). Actuarial transplant-related mortality (TRM) at 240 days was 28% and 26% (P = .8) in group A and B: the major cause of death was GVHD in group A (P = .02) and multiorgan toxicity in group B (P = .07). The actuarial risk of relapse at 2 years overall was 20% in group A and 52% in group B (P = .001); it was 9% v 43%, respectively, for patients in first remission (P = .0001) and 48% v 63% for patients in non-first complete remission (CR) (P = .1). Actuarial 2-year disease-free survival (DFS) in group A and B was 58% v 32% (P = .02) for all patients, 71% v 35% (P = .01), in first remissions, and 30% v 23% (P = .2) in advanced disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Myocardial adrenergic changes at two stages of heart failure due to adriamycin treatment in rats

Changes in myocardial norepinephrine (NE) levels, turnover, uptake, and release in rats were examined at two stages of cardiac dysfunction induced by adriamycin (ADR) given intraperitoneally in six equal doses over a period of 2 wk for a cumulative dose of 15 mg/kg. At 3 wk posttreatment, ADR-treated animals showed no changes in left ventricular systolic pressure (LVSP), aortic systolic pressure (ASP), and aortic diastolic pressure (ADP) but left ventricular end-diastolic pressure (LVEDP) was significantly higher. At 6 wk posttreatment, LVSP, ASP, and ADP were significantly lower and LVEDP remained elevated. Animals in both ADR-treated groups showed signs of congestive heart failure as indicated by ascites, congestive liver, and elevated LVEDP. Structural changes typical of ADR cardiomyopathy were more pronounced in the 6-wk group. In vivo hemodynamic as well as in vitro muscle function response to different concentrations of epinephrine was depressed in its duration as well as extent in both 3- and 6-wk ADR-treated groups. Myocardial NE levels were increased in the 3-wk group but were depressed in the 6-wk group. NE turnover was faster in both 3- and 6-wk ADR groups, uptake was increased only in the 6-wk group, and release was unchanged. These data show increased cardiac sympathetic tone at both stages of ADR-induced congestive heart failure.

Cyclosporin A and chronic graft versus host disease

One hundred and seventeen patients undergoing allogeneic bone marrow transplantation (BMT) for severe aplastic anemia (n = 18) or leukemia (n = 99) who were alive on day +180, were analysed for the incidence and severity of chronic graft-versus-host disease (cGVHD), developing before or after discontinuation of cyclosporin A (CSA). All patients received CSA for GVHD prophylaxis for 94 to greater than 988 days post-BMT. cGVHD developed in 74 patients (63%) before CSA discontinuation (de novo n = 12, progression from acute GVHD n = 42, following resolution of acute GVHD n = 20). CSA was discontinued in 112 patients: electively (n = 80), because of toxicity (n = 8), or following relapse of leukemia (n = 24). In five patients CSA was never discontinued. After discontinuation of CSA, progression or de novo cGVHD was seen in 25 patients, with a significant difference in patients treated for more or less than 150 days (8% vs 41%, p = 0.0007). In 15 patients CSA had to be re-instituted and in 14 it could be discontinued a second time. Overall 111/117 (94%) patients have finally discontinued CSA. In conclusion cGVHD will progress or appear de novo in 41% of patients receiving CSA for less and in 8% of those receiving CSA for more than 150 days respectively, indicating that the drug should be administered for at least 5 months post-BMT. Most patients (94%) will eventually become CSA independent.

Long-term effects of physiologic concentrations of dexamethasone on human bone-derived cells

Bone cells derived from human trabecular explants display osteoblastic features. We examined the modulation of alkaline phosphatase activity and cAMP production as the result of exposing trabecular explants to physiologic concentrations of dexamethasone for 4 weeks during cellular outgrowth and subculture. Cells treated with dexamethasone were observed to grow generally more slowly than control cells. Cells appeared larger and more polygonal, and staining for alkaline phosphatase was more intense in the dexamethasone-exposed cultures. There was a progressive increase in cellular PTH responsiveness with increasing duration of exposure of cells to dexamethasone. Cells grown for 6 weeks in 3 x 10(-8) M dexamethasone had a 10-fold increase in PTH-stimulated cyclic AMP accumulation. Dexamethasone-treated cells also had a significantly increased alkaline phosphatase activity. 1,25-(OH)2D3-stimulated alkaline phosphatase activity was increased approximately 20-fold. cAMP responses were significantly increased to PTH (21.7-fold), PGE1 (2.67-fold), and forskolin (4.81-fold), but not to cholera toxin. Dexamethasone-treated cells also had a mean decrease in 1,25-(OH)2D3-stimulated osteocalcin production to 26.2% of control values (p less than 0.001). Hydrocortisone treatment gave rise to similar effects but of smaller magnitude than those of dexamethasone. Testosterone did not have a significant effect on alkaline phosphatase activity or cAMP production. Skin fibroblasts showed a significant enhancement of alkaline phosphatase activity in response to dexamethasone, but of a much smaller magnitude than in bone cells. The phenotypic changes induced by long-term culture in dexamethasone are consistent with the promotion of a more differentiated osteoblastic phenotype.

Effect of antilymphocyte globulin (ALG) on bone marrow T/non-T cells from aplastic anaemia patients and normal controls

The aim of this study was twofold: (a) to test the effect of antilymphocyte globulin (ALG) on bone marrow (BM) T/non-T cells, and (b) to look for a possible differential response of cells from severe aplastic anaemia (SAA) patients and controls. For this purpose bone marrow T/non-T cells from normal individuals (n = 7) or aplastic patients (SAA, n = 13) were kept in liquid culture with or without ALG. Supernatants were then tested for enhancement/suppression on colony forming unit, granulocyte-macrophage (CFU-GM) growth (in the presence of exogenous recombinant granulocyte-macrophage colony stimulating factor (rGM-CSF)), or for their ability to support CFU-GM growth (in the absence of exogenous rGM-CSF). Supernatants from SAA T cells suppressed CFU-GM growth of normal bone marrow cells in 5/12 patients (mean expected growth (EG) 71 +/- 16%), but not after incubation with ALG (mean 110 +/- 29% EG, P = 0.03). No inhibition could be obtained with the supernatants from untreated normal T cells. Significant enhancement was seen with ALG treated versus untreated SAA T cells (142 +/- 28% EG v. 105 +/- 61% EG, P = 0.01) and with ALG treated versus untreated SAA non-T cells (165 +/- 26% EG v. 105 +/- 23% EG, P = 0.01), but not in controls. Supernatants from SAA and control T/non-T cells were capable of promoting colony formation in the absence of rGM-CSF (colony-stimulating activity (CSA) production): 16 +/- 14% for SAA-T cells and 19 +/- 18% EG for non-T cells (100% = 30 ng rGM-CSF/ml). The addition of ALG increased CSA production in T cells to 37 +/- 23% EG (P = 0.04) and in non-T cells to 40 +/- 13% EG (P = 0.04). Similar results could be obtained in controls.

IN CONCLUSION

(a) ALG interacts in vitro with bone marrow T and non-T cells from SAA patients, down-regulating the production of negative lymphokines and enhancing the release of haemopoietins; (b) the latter, but not the former effect, can be shown also with cells from normal controls. The two effects are not mutually exclusive, and are likely to provide maximal benefit in vivo.

Active sliding between cytoplasmic microtubules

Microtubules are versatile cellular polymers that play a role in cell shape determination and mediate various motile processes such as ciliary and flagellar bending, chromosome movements and organelle transport. That a sliding microtubule mechanism can generate force has been demonstrated in highly ordered structures such as axonemes, and microtubule-based force generation almost certainly contributes to the function of mitotic and meiotic spindles. Most cytoplasmic microtubule arrays, however, do not exhibit the structural regularity of axonemes and some spindles, and often appear disorganized. Yet many cellular activities (such as shape changes during morphogenesis, axonal extension and spindle assembly) involve highly coordinated microtubule behaviour and possibly require force generated by an intermicrotubule sliding mechanism, or perhaps use sliding to move microtubules rapidly into a protrusion for stabilization. Here we show that active sliding between cytoplasmic microtubules can occur in microtubule bundles of the amoeba Reticulomyxa. A force-producing mechanism of this sort could be used by this organism to facilitate the extension of cell processes and to generate the dynamic movements of the cytoplasmic network.

Changes in the levels of translatable glutaminase mRNA during onset and recovery from metabolic acidosis

The amount of the mitochondrial glutaminase present within rat kidney is increased 5-fold during chronic metabolic acidosis. This adaptive response is due to a corresponding increase in the relative rate of glutaminase synthesis. Poly(A+) RNA was purified from the kidneys of control, 7-day acidotic, and 2-day recovered rats and then fractionated by electrophoresis on a low melting temperature agarose gel. Translation of the fractionated RNA in a rabbit reticulocyte lysate yields a 72,000-dalton protein that is specifically precipitated by anti-glutaminase IgG. The level of this protein is at least 3-fold greater in the translation products of the fractionated poly(A+) RNA derived from the acidotic vs. control or recovered rats. Therefore, the 72,000-dalton product of translation is the apparent precursor to the 68,000- and 65,000-dalton proteins that are contained in the mitochondrial glutaminase. From its relative electrophoretic mobility, the size of the glutaminase mRNA was estimated to be approximately 6.5 kilobases. The relative levels of translatable glutaminase mRNA were determined by using unfractionated poly(A+) RNA prepared from rats at various times following onset and recovery from acidosis. The observed increase occurred gradually, requiring 7 days to reach a maximal induction of 4.2-fold. The increase could be due to the increased transcription of a stable mRNA (t1/2 approximately 3 days). However, 2 days of recovery was sufficient to return the level of translatable glutaminase mRNA to normal. Thus, the selective inactivation or the altered stability of the glutaminase mRNA must also contribute to the regulation of the glutaminase gene expression.

The effect of metabolic acidosis on the synthesis and turnover of rat renal phosphate-dependent glutaminase

Regulation of the mitochondrial phosphate-dependent glutaminase activity is an essential component in the control of renal ammoniagenesis. Alterations in acid-base balance significantly affect the amount of the glutaminase that is present in rat kidney, but not in brain or small intestine. The relative rates of glutaminase synthesis were determined by comparing the amount of [35S]methionine incorporated into specific immunoprecipitates with that incorporated into total protein. In a normal animal, the rate of glutaminase synthesis constitutes 0.04% of the total protein synthesis. After 7 days of metabolic acidosis, the renal glutaminase activity is increased to a value that is 5-fold greater than normal. During onset of acidosis, the relative rate of synthesis increases more rapidly than the appearance of increased glutaminase activity. The increased rate of synthesis reaches a plateau within 5 days at a value that is 5.3-fold greater than normal. Recovery from chronic acidosis causes a rapid decrease in the relative rate of glutaminase synthesis, but a gradual decrease in glutaminase activity. The former returns to normal within 2 days, whereas the latter requires 11 days. The apparent half-time for glutaminase degradation was found to be 5.1 days and 4.7 days for normal and acidotic rats respectively. These results indicate that the increase in renal glutaminase activity associated with metabolic acidosis is due primarily to an increase in its rate of synthesis. From the decrease in activity that occurs upon recovery from acidosis, the true half-life for the glutaminase was estimated to be 3 days.