Thrombopoietin, but not erythropoietin, directly stimulates multilineage growth of primitive murine bone marrow progenitor cells in synergy with early acting cytokines: distinct interactions with the ligands for c-kit and FLT3

Thrombopoietin (Tpo), the ligand for c-mpl, has been shown to be the principal regulator of megakaryocytopoiesis and platelet production. The ability of Tpo to potently stimulate the growth of committed megakaryocyte (Mk) progenitor cells has been studied in detail. Murine fetal liver cells, highly enriched in primitive progenitors, have been shown to express c-mpl, but little is known about the ability of Tpo to stimulate the growth and differentiation of primitive multipotent bone marrow (BM) progenitor cells. Here, we show that Tpo alone and in combination with early acting cytokines can stimulate the growth and multilineage differentiation of Lin- Sca-1+ BM progenitor cells. In particular, Tpo potently synergized with the ligands for c-kit (stem cell factor [SCF]) and flt3 (FL) to stimulate an increase in the number and size of clones formed from Lin- Sca-1+ progenitors. When cells were plated at 1 cell per well, the synergistic effect of Tpo was observed both in fetal calf serum-supplemented and serum-depleted medium and was decreased if the addition of Tpo to cultures was delayed for as little as 24 hours, suggesting that Tpo is acting directly on the primitive progenitors. Tpo added to SCF + erythropoietin (Epo)-supplemented methylcellulose cultures potently enhanced the formation of multilineage colonies containing granulocytes, macrophages, erythrocytes, and Mks. SCF potently enhanced Tpo-stimulated production of high-ploidy Mks from Lin- Sca-1+ progenitors, whereas the increased growth response obtained when combining Tpo with FL did not translate into increased Mk production. The ability of Tpo and SCF to synergistically enhance the growth of Lin- Sca-1+ progenitors was predominantly observed in the more primitive rhodamine 123(lo) fraction. Tpo also enhanced growth of Lin- Sca-1+ progenitors when combined with interleukin-3 (IL-3) and IL-11 but not with IL-12, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, or Epo. Epo, which has high homology to Tpo, was unable to stimulate the growth of Lin- Sca-1+ progenitors alone or in combination with SCF or FL, suggesting that c-mpl is expressed on more primitive stages of progenitors than the Epo receptor. Thus, the present studies show the potent ability of Tpo to enhance the growth of primitive multipotent murine BM progenitors in combination with multiple early acting cytokines and documents its unique ability to synergize with SCF to enhance Mk production from such progenitors.

The accuracy of dose localization for an image-guided frameless radiosurgery system

A compact X-band accelerator mounted on a robotic arm is under development for frameless stereotaxic radiosurgery. The therapy beam is aimed at the lesion by an imaging system comprised of two diagnostic x-ray cameras that view the patient during treatment. Patient position and motion are measured by the cameras and communicated in real time to the robotic arm for beam targeting and patient motion tracking. The tests reported here measured the pointing accuracy of the therapy beam and the present targeting and tracking capability of the imaging system. The results show that the system achieves the same level of targeting precision as conventional frame-based radiosurgery.

Myelotoxic effects of the bifunctional alkylating agent bizelesin on human, canine and murine myeloid progenitor cells

Bizelesin is a potent synthetic derivative of the anticancer agent CC-1065 that preferentially alkylates and binds the minor grove of DNA. Preclinical animal studies have found bizelesin to be more toxic to beagle dogs than to rodents and that myelosuppression was the dose-limiting toxicity. This toxicity was dose- and time-dependent in all species. Due to the significant difference in the in vivo myelotoxicity between species, it was important to determine which one most closely resembles humans on a pharmacodynamic basis. Therefore, hematopoietic clonal assays were utilized to evaluate the effects of bizelesin on granulocyte-macrophage (CFU-gm) colony formation. Marrow cells were exposed in vitro to bizelesin (0.001-1000 nM) for 1 or 8 h and then assayed for colony formation. There was a 3-log difference in drug concentration at which 100% colony inhibition occurred (1 or 8 h) for murine CFU-gm versus human or canine CFU-gm. The IC70 value after an 8-h bizelesin exposure for human CFU-gm (0.006 +/- 0.002 nM) was 2220-times lower than for murine CFU-gm (13.32 +/- 8.31 nM). At any given concentration, an 8 h drug exposure resulted in greater colony inhibition than a 1 h exposure for all species (P < 0.05). Increasing exposure time from 1 to 8 h increased toxicity to human and canine CFU-gm much more than to murine CFU-gm. The clinically formulated drug solution was a more potent inhibitor of human colony formation than drug dissolved in DMSO. The IC70 value after a 1-h exposure was 1.7 times lower for human CFU-gm with formulated bizelesin (0.106 +/- 0.105 nM) than bulk drug in DMSO (0.184 +/- 0.044 nM). The results of these in vitro clonal assays were qualitatively consistent with those seen in whole animal studies, suggesting that bizelesin will be a potent myelosuppressive agent in the clinic. Since the dose-limiting toxicity in preclinical models is myelosuppression and the in vitro sensitivity of human and canine CFU-gm is similar, the canine maximum tolerated dose (MTD) is better than the murine MTD to determine a safe starting dose for phase I clinical trials.

Thrombopoietin, but not erythropoietin promotes viability and inhibits apoptosis of multipotent murine hematopoietic progenitor cells in vitro

The recently cloned c-mpl ligand, thrombopoietin (Tpo), has been extensively characterized with regard to its ability to stimulate the growth, development, and ploidy of megakaryocyte progenitor cells and platelet production in vitro and in vivo. Primitive hematopoietic progenitors have been shown to express c-mpl, the receptor for Tpo. In the present study, we show that Tpo efficiently promotes the viability of a subpopulation of Lin-Sca-1+ bone marrow progenitor cells. The ability of Tpo to maintain viable Lin-Sca-1+ progenitors was comparable to that of granulocyte colony-stimulating factor and interleukin-1, whereas stem cell factor (SCF) promoted the viability of a higher number of Lin-Sca-1+ progenitor cells when incubated for 40 hours. However, after prolonged (> 40 hours) preincubation, the viability-promoting effect of Tpo was similar to that of SCF. An increased number of progenitors surviving in response to Tpo had megakaryocyte potential (37%), although almost all of the progenitors produced other myeloid cell lineages as well, suggesting that Tpo acts to promote the viability of multipotent progenitors. The ability of Tpo to promote viability of Lin-Sca-1+ progenitor cells was observed when cells were plated at a concentration of 1 cell per well in fetal calf serum-supplemented and serum-depleted medium. Finally, the DNA strand breakage elongation assay showed that Tpo inhibits apoptosis of Lin-Sca-1+ bone marrow cells. Thus, Tpo has a potent ability to promote the viability and suppress apoptosis of primitive multipotent progenitor cells.

Association of mitochondrial DNA deletions and cochlear pathology: a molecular biologic tool

The purpose of these experiments was to develop a method of isolation, amplification, and identification of cochlear mitochondrial DNA (mtDNA) from minute quantities of tissue. Additionally, studies were designed to detect mtDNA deletions (mtDNA del) from the cochlea that previously have been amplified from other organ systems and tissues. MtDNA del have been associated with many pathologies, including neurological disorders, sensorineural hearing loss, ischemia, cardiomyopathies, and aging. DNA was extracted from rat and human tissues, and polymerase chain reaction was used to amplify mtDNA sequences. A 360 base pair (bp) cytochrome-b gene product and the highly conserved ND1-16S ribosomal ribonucleic acid regions found only in mtDNA were amplified from all tissues. Preliminary studies have identified a 4834 bp mtDNA del in aged rats and a corresponding 4977 bp mtDNA del in aged humans. Additionally, preliminary results in human archival temporal bone studies reveal the presence of the 4977-bp mtDNA deletion in two out of three patients with presbycusis. The deletion was not evident in age-matched control patients without a history of presbycusis. This technique of mtDNA identification makes it possible to investigate specific mtDNA defects from a single cochlea, promoting the study of hereditary hearing loss and presbycusis at a molecular biologic level.

Audit of an emergency biochemistry service

AIM

To examine a model for the evaluation of appropriateness of testing in an emergency biochemistry laboratory.

METHODS

A model was devised in which incoming emergency test requests were categorised as appropriate or inappropriate. Explicit criteria were used to define eight minor categories, which were chosen to reflect accurately current working practice within the hospital and laboratory. Five junior medical staff each undertook a prospective 24 hour assessment, during which time all incoming requests were monitored and categorised according to these criteria. Concordance between monitors was evaluated before and during assessments.

RESULTS

Of 509 requests, 384 (75%) were appropriate and 125 (25%) were inappropriate according to the criteria used to define categories. Inappropriate requests fell into three main groups: preoperative samples (43.2% (54/125) of all inappropriate requests), missed routine samples (33.6% (42/125)) and accelerated (priority) analyses (16% (20/125)). Various other reasons accounted for the remaining 7.2% (9/125).

CONCLUSION

This model may be used to obtain valid information about current clinical and laboratory practice. Strategies to reduce the number of inappropriate requests have been identified in order to reserve the emergency service for situations of true need.

Automated imaging and quantitation of tumor cells and CFU-GM colonies in microcapillary cultures: toward therapeutic index-based drug screening

Human colony forming units (CFUs) from both malignant and hematopoietic tissues can be assayed in vitro in microcapillary cultures, an alternative cloning system to the Petri dish methodology. For technical reasons, microcapillary culture may be ideally suited for new drug screening by therapeutic index. To achieve the high output required by screening programs, automated quantitation of CFUs is required. Toward this end, this paper reports the development of a prototype CapScan, an image analysis system that uses a novel axial laser illumination system to detect tumor cell colonies and, with technical modifications, CFU-granulocyte-macrophage (CFU-GM) colonies in microcapillary cultures. As currently configured, the CapScan can quantify colonies grown in a rack of 18 microcapillary cultures in 30 minutes or less. The sensitivity and detection specificity of tumor cell colonies is >90% with a coefficient of variance of 5-40%, dependent upon colony number. Over a range of colony numbers, CapScan and manual colony counts showed a linear correlation > -0.9, and yielded identical results in assays of doxorubicin inhibition of clonogenic P388 cells. As an additional advantage, the growth kinetics of individual colonies can also be monitored with the CapScan, making distinctions between cytotoxic and cytostatic drugs possible; colonies of freshly isolated human tumor cells can also be quantified. Thus, a microcapillary-based human tumor cloning assay that tests for resistance and/or sensitivity to chemotherapeutic agents may be useful in drug development programs and may also facilitate the development of chemotherapy for individual patient tumors, especially when tumor availability is limited.

Iatrogenic profound hypoalphalipoproteinaemia: an unrecognised cause of very low HDL cholesterol

A significant reduction in plasma high density lipoprotein (HDL) cholesterol is a recognised consequence of treatment with probucol. By contrast, fibrate therapy in general has the opposite effect. We report two cases where the combination of probucol and a fibrate led to profoundly reduced plasma levels of HDL cholesterol associated with very low levels of apolipoprotein A-I (apoA-I). In the first, bezafibrate was added to probucol, and in the second, probucol added to a combination of simvastatin and fenofibrate. In both cases, plasma levels of HDL and apoA-I returned towards normal after discontinuation of one or both drugs, indicating that the reduction was reversible.

HIMeg-1, a cell line derived from a CML patient, is capable of monocytic and megakaryocytic differentiation

We have characterized HIMeg-1, a subclone of the promegakaryoblastic cell line HIMeg, in terms of its capability of proliferation and differentiation when it is exposed to various agents. We observed that phorbol 12-myristate 13-acetate (PMA) arrested HIMeg-1 growth and induced expression of monocytic surface antigens CD11c and CD14, but not the megakaryocytic surface antigen CD14a. In addition, PMA treatment of HIMeg-1 led to rapid activation of mRNA expression of egr-1, a transcription factor involved in regulating differentiation of hematopoietic progenitor cells. On the other hand, treatment of HIMeg-1 with the activated peripheral blood lymphocyte-conditioned medium (PBL-CM) resulted in greatly enhanced incorporation of 3H-thymidine into newly synthesized DNA. This enhanced 3H-thymidine incorporation appears to be specific to HIMeg-1 since the same concentrations of PBL-CM had little effect on the growth of the megakaryoblastic leukemia cell line SAM-1. The PBL-CM-induced DNA synthesis in HIMeg-1 was associated with activation of CD41a and CD41b surface antigen expression and down-regulation of expression of the erythroid marker glycophorin A and the early myeloid surface antigen CD33. HIMeg-1 capable of responding differentially to PMA and PBL-CM by changing its growth rate as well as its differentiation patterns will provide an ideal model to study the underlying mechanism regulating lineage restriction of hematopoietic progenitor cells.

Nephrotoxicity of ionic and nonionic contrast media in 1196 patients: a randomized trial. The Iohexol Cooperative Study

The incidence of nephrotoxicity occurring with the nonionic contrast agent, iohexol, and the ionic contrast agent, meglumine/sodium diatrizoate, was compared in 1196 patients undergoing cardiac angiography in a prospective, randomized, double-blind multicenter trial. Patients were stratified into four groups: renal insufficiency (RI), diabetes mellitus (DM) both absent (N = 364); RI absent, DM present (N = 318); RI present, DM absent (N = 298); and RI and DM both present (N = 216). Serum creatinine levels were measured at -18 to 24, 0, and 24, 48, and 72 hours following contrast administration. Prophylactic hydration was administered pre- and post-angiography. Acute nephrotoxicity (increase in serum creatinine of > or = 1 mg/dl 48 to 72 hours post-contrast) was observed in 42 (7%) patients receiving diatrizoate compared to 19 (3%) patients receiving iohexol, P < 0.002. Differences in nephrotoxicity between the two contrast groups were confined to patients with RI alone or combined with DM. In a multivariate analysis, baseline serum creatinine, male gender, DM, volume of contrast agent, and RI were independently related to the risk of nephrotoxicity. Patients with RI receiving diatrizoate were 3.3 times as likely to develop acute nephrotoxicity compared to those receiving iohexol. Clinically severe adverse renal events were uncommon (N = 15) and did not differ in incidence between contrast groups (iohexol N = 6; diatrizoate N = 9). In conclusion, in patients undergoing cardiac angiography, only those with pre-existing RI alone or combined with DM are at higher risk for acute contrast nephrotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiparasitic and antiproliferative effects of indoleamine 2,3-dioxygenase enzyme expression in human fibroblasts

Studies were carried out to evaluate the proposed role of indoleamine 2,3-dioxygenase (INDO) induction in the antimicrobial and antiproliferative effects of gamma interferon (IFN-gamma) in human fibroblasts. The INDO cDNA coding region was cloned in the pMEP4 expression vector, containing the metallothionein (MTII) promoter in the sense (+ve) or the antisense (-ve) orientation. Human fibroblasts (GM637) stably transfected with the sense construct expressed INDO activity after treatment with CdCl2 or ZnSO4, but cells transfected with the antisense construct did not. The growth of Chlamydia psittaci was strongly inhibited in INDO +ve cells but not in INDO -ve cells after treatment with Cd2+ or Zn2+. The inhibition correlated with the level of INDO activity induced and could be reversed by the addition of excess tryptophan to the medium. The growth of Toxoplasma gondii was also strongly inhibited in INDO +ve cells but not in INDO -ve cells after treatment with Cd2+. Expression of Cd(2+)-induced INDO activity also inhibited thymidine incorporation and led to cytotoxicity in INDO +ve cells but not in INDO -ve cells. Thus, the induction of INDO activity by IFN-gamma may be an important factor in the antimicrobial and antiproliferative effects of IFN-gamma in human fibroblasts.

Regional and supraregional biochemistry services in Scotland: a survey of hospital laboratory users

AIM

To ascertain the views of Scottish hospital laboratory users on aspects of regional and supraregional biochemical services offered by the Institute of Biochemistry at Glasgow Royal Infirmary.

METHODS

A questionnaire was circulated asking questions or inviting opinions under various headings, including current patterns of usage of the services provided, availability of information on specimen collection requirements and reference ranges, current arrangements for transport of specimens, turnaround times for delivery of reports, layout and content of request and report forms, quantity and quality of interpretive advice, potential changes in laboratory services, and overall impression of the services provided. Opportunities were provided for free text comment. The questionnaire was circulated in 1992 to heads of department in 23 Scottish hospital biochemistry laboratories.

RESULTS

Twenty one replies were received. Services used widely included trace metals/vitamins (n = 20) and specialised endocrine tests (n = 19). Other services also used included specialised lipid tests (n = 13), toxicology (n = 12), thyroid function tests (n = nine), and tumour markers (n = eight). Fifteen laboratories used one or more of the services at least weekly. Most (n = 20) welcomed the idea of a handbook providing information on specimen collection and reference ranges. Nine identified loss of specimens as a problem. Other perceived problems included the absence of reference ranges from report forms, quantity and quality of interpretive advice, and turnaround times of some tests. Overall impressions of the service(s) offered were very good (n = 12); adequate (n = seven); poor (n = one).

CONCLUSIONS

Useful information was obtained about patterns of use and transport arrangements. Areas identified as requiring follow up included provision of information, alternative ways of communicating reports, and improvement in quantity and quality of interpretive advice.

On-call duties in chemical pathology: a survey of junior medical staff in the UK

To ascertain the extent of variation in out-of-hours duties among trainees in chemical pathology in the UK questionnaires were sent to 81 junior medical staff in 1992. Replies were received from 63 (78%). Although most had participated in an advisory rota, only 41 (65%) had participated in an analytical rota. Nine (14%) had participated in specialist analytical rotas, while 13 (21%) had experience of multidisciplinary rotas and only eight (13%) had experience of rotas involving clinical responsibility. Only 10 (16%) regularly reviewed their work on call with their senior medical staff. There was no single method of requesting tests out of hours in the trainees' laboratories and there was also considerable variation with respect to the tests available out of hours. It is concluded that sufficient variation exists in the on-call experience gained by junior medical staff in chemical pathology to raise concern about the quality of training in out-of-hours work.

In vitro characterization of the myelotoxicity of cyclopentenyl cytosine

We studied the toxicity of a new experimental anticancer drug, cyclopentenyl cytosine (CPE-C), to human and murine hematopoietic progenitor cells in vitro. Due to CPE-C's in vivo myelotoxicity, it was important to characterize its potential adverse effects on human marrow cells during preclinical development of the drug. Marrow cells were exposed to CPE-C for either 1 h prior to addition in clonal assays or continuously during their culture period. The inhibitory effects of CPE-C on myeloid (CFU-gm) and erythroid (CFU-e, BFU-e) colony formation were concentration- and time-dependent, with continuous CPE-C exposure being significantly more inhibitory than 1-h exposure. The results of both exposure experiments were combined to investigate colony inhibition as a function of overall drug exposure (concentration x time, AUC) and data analyzed by the nonlinear Emax equation. Human and murine CFU-gm had similar AUC-response curves and IAUC70 values (i.e., AUC at 70% colony inhibition) of 40.8 and 41.9 microM h, respectively. In contrast, murine CFU-e and BFU-e were more sensitive to CPE-C, having lower IAUC70 values (both, 21.1 microM h) than human CFU-e and BFU-e (107.8 and 33.0 microM h, respectively). This difference was most prominent with the late erythroid progenitor, CFU-e, in that the human cells were 5 times more resistant to inhibition by CPE-C. CPE-C was myelotoxic in vitro to human and murine marrow cells and toxicity correlated with overall drug exposure.

Molecular cloning of a novel receptor tyrosine kinase, tif, highly expressed in human ovary and testis

Using a combination of polymerase chain reaction and conventional cDNA library screening approaches, we have cloned and characterized a putative receptor tyrosine kinase termed tif. The extracellular domain of tif has an immunoglobulin-like loop and a fibronectin type III structure. The intracellular domain contains a tyrosine kinase domain. Compared with ryk, a ubiquitously expressed receptor tyrosine kinase, tif expression is tissue-specific with human ovary and testis containing the highest amount of tif mRNA. Many other tested human tissues such as heart, liver, pancreas and thymus do not contain detectable levels of tif mRNA. The molecular cloning and characterization of tif cDNA will facilitate the identification of a potential ligand(s) for the putative receptor and the study of its biological role.

In vivo-in vitro correlation of myelotoxicity of 9-methoxypyrazoloacridine (NSC-366140, PD115934) to myeloid and erythroid hematopoietic progenitors from human, murine, and canine marrow

BACKGROUND

9-Methoxypyrazoloacridine (PZA) is an anticancer agent that shows selectivity of action for carcinomas over leukemias. It also has nearly equal potency against cycling and quiescent or hypoxic and normoxic target cells. Phase I trials of PZA in humans are nearing completion.

PURPOSE

This study was conducted to determine (a) if PZA is directly inhibitory to hematopoietic cells and, if it is, to characterize the inhibition pharmacodynamically, (b) whether species-specific differences in direct toxicity could explain differences in myelosuppression in mice, dogs, and humans, and (c) whether in vitro data correlate with in vivo myelosuppression data.

METHODS

In vitro clonogenic assays of hematopoietic progenitors of myeloid and erythroid lineages from human, canine, and murine femoral marrow were used to measure the direct toxicity of PZA. Results from these assays were compared on an area-under-the-curve (AUC) basis to clinical myelosuppression data.

RESULTS

On the basis of maximum tolerated concentrations, canine hematopoietic progenitors are most susceptible to PZA, followed by human and then murine progenitors. We found no difference in susceptibility to PZA toxicity between the human progenitors of myeloid and erythroid lineages. Both concentration and duration of exposure contribute to the in vitro toxicity of PZA. In contrast to antimetabolites, the in vitro toxicity of PZA could be minimized at a given AUC by lowering drug concentration and prolonging the period of exposure. On an AUC basis, the in vitro data are consistent with limited in vivo myelosuppression data from preclinical models and correlate with neutropenia data from a phase I trial.

CONCLUSIONS

PZA directly inhibits hematopoietic progenitors, an action that is responsible for the myelosuppression observed in humans. Human marrow appears able to compensate for the loss of up to 35% of its myeloid progenitors, in that peripheral neutrophil counts remain unchanged at that level of loss. Although in vivo studies show that prolonged infusion reduces myelosuppression at a given total dose in both rodent and canine models, pharmacokinetic differences make it unlikely that this approach will benefit human patients.

IMPLICATIONS

The in vitro data quantitatively predict the AUCs at maximum tolerated dose in preclinical models and human patients. Thus, in vitro clonogenic assays of myelotoxic agents can provide data that make both preclinical toxicology testing and clinical trial planning and interpretation more efficient and accurate.

Q-switched ruby laser treatment of benign pigmented lesions in Chinese skin

The Q-switched ruby laser has been demonstrated as an effective choice of treatment for a range of benign pigmented lesions. Its wavelength of 694 nm enables deep penetration of the skin allowing the treatment of both epidermal and dermal lesions. However, this wavelength is selectively absorbed by melanin thereby enabling efficient targeting of the lesion's melanocytes. By utilising a Q-switched pulsewidth of 25 nanoseconds, thermal conduction into surrounding tissues is minimised. Lesions such as nevus of Ota, chloasma, lentigines and cafe au lait have been successfully treated with energy densities ranging from 6 to 12 J/cm2. Four case histories are described in this report. The clinical evidence indicates that pigmented lesions in Chinese skin must be treated with energy densities higher than those used in Caucasian skin to minimise the incidence of hyper-pigmentation. Typically, lesions require a small number of treatments, usually within the range one to six, to effect complete removal. The technique is easy to apply, with no need for anaesthesia, in many cases.

Multicenter trial of ionic versus nonionic contrast media for cardiac angiography. The Iohexol Cooperative Study

Contrast agents used for cardiac angiography are different in regard to ionicity, osmolality and physiologic effects. The nonionic contrast media have been shown to have less toxic effects and a better safety profile than do higher osmolar agents. To better assess this risk, clinically stable patients undergoing cardiac angiography were stratified according to the presence of diabetes mellitus, and level of serum creatinine, and then randomized to receive either iohexol (Omnipaque 350) or sodium meglumine diatrizoate (Renografin 76). All adverse events that occurred during and immediately after angiography were tabulated. A multivariate model was used to identify patients at increased risk for adverse outcome. The 1,390 patients were randomized to iohexol (n = 696) or diatrizoate (n = 694). Significant differences were found in the number of patients with contrast media-related adverse (iohexol vs diatrizoate: 10.2 vs 31.6%; p < 0.001) and cardiac adverse (7.2 vs 24.5%; p < 0.001) events. Severe reactions and the need for treatment were more frequent with diatrizoate than with iohexol, but there was no difference in the incidence of death. The presence of New York Heart Association classification 3 or 4 and serum creatinine > or = 1.5 mg/dl predicted a higher incidence of adverse events as a result of contrast media alone. Use of iohexol is associated with a lower incidence of all types of adverse events during cardiac angiography than is diatrizoate.

Effects of sample collection and handling on concentration of osteocalcin in equine serum

A commercially available radioimmunoassay kit for measurement of human osteocalcin was validated for use in horses. For accurate measurement of equine serum osteocalcin, blood samples may be collected at a temperature between 20 and 25 C, then centrifuged within 90 minutes; serum may be stored at -20 C in plastic tubes for up to 26 weeks. Serum may be thawed and refrozen up to 5 times without significant change in measured equine serum osteocalcin concentration. Assay sensitivity was 0.16 ng/ml. Recovery of bovine osteocalcin standard added to equine serum was linear. Intra-assay coefficient of variation (x 100) for 2 equine serum pools was 6.9 (mean +/- SD, 13.9 +/- 1.0 ng/ml) and 7.5 (10.6 +/- 0.8 ng/ml) %. Interassay coefficient of variation for 3 equine serum pools measured in 12 assays was 12.5 (16.1 +/- 2.0 ng/ml), 12.7 (11.5 +/- 1.5 ng/ml), and 24.6 (3.0 +/- 0.7 ng/ml) %. Dilutional parallelism was documented by assaying pooled equine serum at 4 dilutions and correcting the mean result for dilution. Significant change was not observed in equine serum osteocalcin concentration for various time-of-day blood sample collections in horses housed under continuous lighting.

Megakaryocytopoiesis and platelet production: does stem cell factor play a role?

Megakaryocytopoiesis, resulting in the production and release of platelets, is a multistage procession of cellular differentiation and maturation which is regulated by a constellation of cytokines. Since thrombocytopenia is a frequent dose-limiting toxicity of chemotherapy, newly-identified cytokines have been actively investigated for their potential megakaryocyte/platelet-promoting properties. Stem cell factor (SCF, also known as mast cell growth factor, Steel factor or Kit ligand) has been found to synergize with GM-CSF, IL-6, IL-3, IL-11 or Epo to increase the numbers of megakaryocyte-containing colonies (i.e., CFU-Meg, BFU-Meg, CFU-GMM, CFU-GEMM). On the other hand, SCF increased the number of megakaryocytes per colony in the presence of IL-3, GM-CSF or IL-6. SCF also stimulated the proliferation of specific megakaryocytic cell lines (i.e., CMK, M-07e). SCF did not, however, alter megakaryocyte markers or increase cell ploidy. Thus, SCF appears to expand the committed myeloid progenitor compartments, rather than increase the rate of megakaryocyte maturation or the number of platelets released. We describe studies in which SCF stimulated murine CFU-Meg alone and in the presence of IL-3. However, a decrease in cultured cell plating density resulted in ablation of this SCF-stimulation of CFU-Meg colonies. CFU-Meg colony stimulation by SCF was dose dependent, even under serum-free conditions. The effects of SCF in other in vitro and in vivo animal model systems are reviewed.

Megakaryocyte colony-stimulating factor (Meg-CSF) is a unique cytokine specific for the megakaryocyte lineage

The regulation of megakaryocytopoiesis and platelet production has not yet been clearly elucidated. Several cytokines have been shown to be capable of producing megakaryocyte colonies from bone marrow [i.e. Interleukin (IL)-3, granulocyte-macrophage (GM)-colony-stimulating factor (CSF), erythropoietin (Epo)]. In addition, other activities have been reported to stimulate megakaryocyte precursors, yet a megakaryocyte-CSF (Meg-CSF) has not been purified to homogeneity and IL-3, GM-CSF and/or Epo often contaminate purification attempts which could account for the activities. A Meg-CSF has been isolated from the urine of patients with aplastic anaemia and purified by sequential ultrafiltration, cation exchange, G-50 chromatography, preparative PAGE, chromatofocusing and cation exchange HPLC. The activity of this material is 2-4 x 10(4) CFU-Meg/mg as measured in a murine marrow, serum-containing assay. This activity also stimulates CFU-Meg in the absence of adherent accessory cells and in serum-free cultures, indicative of the direct stimulation on CFU-Meg. Immunoassays, colony forming assays, and proliferation assays demonstrate that purified Meg-CSF has no GM-CSF, IL-3, M-CSF, G-CSF or IL-1 alpha, -3, -6, -9 and -11. In confirmation of these results, neutralizing antibody to IL-6 also did not abrogate Meg-CSF activity. Therefore the previously-reported megakaryocyte colony-stimulating activity in purified aplastic anaemia patient urine is due to a unique cytokine: Meg-CSF.

The self-management of skills by persons with mental retardation

The transition of persons with mental retardation to less restrictive environments is often hindered by difficulties in managing their own behavior in the absence of external controls. This observation has led to an upsurge of interest in the advantages of teaching self-management skills to persons with mental retardation. This article reviews evidence about the effects of self-management training on the acquisition, maintenance, and generalization of skills. The analyses show that self-management training has been useful in promoting the maintenance of behavior change first effected by external control procedures, but that a dearth of evidence and a number of methodological problems preclude convincing conclusions about its value in promoting generalization. The empirical evidence also suggests that the effectiveness of these procedures may depend upon the cognitive and linguistic abilities of the persons receiving self-management training. Finally, the design of much of the empirical research does not enable the disentanglement of the specific effects of self-management training from those arising from the concurrent application of external control procedures. Carefully controlled componential studies of the effects of self-management training and external control procedures are sorely needed.

Exogenous reinfection with multidrug-resistant Mycobacterium tuberculosis in patients with advanced HIV infection

BACKGROUND

In the United States there have been recent outbreaks of multidrug-resistant tuberculosis. These outbreaks have primarily involved persons infected with the human immunodeficiency virus (HIV).

METHODS

We collected clinical information on 17 patients seen at a New York City hospital who had repeatedly positive cultures for Mycobacterium tuberculosis. Analysis of restriction-fragment--length polymorphisms (RFLPs) was performed on serial isolates of M. tuberculosis obtained from these patients.

RESULTS

Six patients had isolates that remained drug-susceptible, and the RFLP patterns of these isolates did not change over time. Eleven patients had isolates that became resistant to antimicrobial agents. The RFLP patterns of the isolates from six of these patients remained essentially unchanged (two strains showed one additional band) despite the development of drug resistance. In five other patients, however, the RFLP patterns of the isolates changed dramatically at the time that drug resistance was detected. The change in the RFLP pattern of the isolate from one patient appeared to be the result of contamination during processing in the laboratory. In the remaining four patients, all of whom had advanced HIV disease, the clinical and microbiologic evidence was consistent with the presence of active tuberculosis caused by a new strain of M. tuberculosis.

CONCLUSIONS

Resistance to antituberculous drugs can develop not only in the strain that caused the initial disease, but also as a result of reinfection with a new strain of M. tuberculosis that is drug-resistant. Exogenous reinfection with multidrug-resistant M. tuberculosis can occur either during therapy for the original infection or after therapy has been completed.