The KMT2A recombinome of acute leukemias in 2023

Chromosomal rearrangements of the human KMT2A/MLL gene are associated with de novo as well as therapy-induced infant, pediatric, and adult acute leukemias. Here, we present the data obtained from 3401 acute leukemia patients that have been analyzed between 2003 and 2022. Genomic breakpoints within the KMT2A gene and the involved translocation partner genes (TPGs) and KMT2A-partial tandem duplications (PTDs) were determined. Including the published data from the literature, a total of 107 in-frame KMT2A gene fusions have been identified so far. Further 16 rearrangements were out-of-frame fusions, 18 patients had no partner gene fused to 5'-KMT2A, two patients had a 5'-KMT2A deletion, and one ETV6::RUNX1 patient had an KMT2A insertion at the breakpoint. The seven most frequent TPGs and PTDs account for more than 90% of all recombinations of the KMT2A, 37 occur recurrently and 63 were identified so far only once. This study provides a comprehensive analysis of the KMT2A recombinome in acute leukemia patients. Besides the scientific gain of information, genomic breakpoint sequences of these patients were used to monitor minimal residual disease (MRD). Thus, this work may be directly translated from the bench to the bedside of patients and meet the clinical needs to improve patient survival.

The MLL recombinome of acute leukemias in 2017

Chromosomal rearrangements of the human MLL/KMT2A gene are associated with infant, pediatric, adult and therapy-induced acute leukemias. Here we present the data obtained from 2345 acute leukemia patients. Genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) were determined and 11 novel TPGs were identified. Thus, a total of 135 different MLL rearrangements have been identified so far, of which 94 TPGs are now characterized at the molecular level. In all, 35 out of these 94 TPGs occur recurrently, but only 9 specific gene fusions account for more than 90% of all illegitimate recombinations of the MLL gene. We observed an age-dependent breakpoint shift with breakpoints localizing within MLL intron 11 associated with acute lymphoblastic leukemia and younger patients, while breakpoints in MLL intron 9 predominate in AML or older patients. The molecular characterization of MLL breakpoints suggests different etiologies in the different age groups and allows the correlation of functional domains of the MLL gene with clinical outcome. This study provides a comprehensive analysis of the MLL recombinome in acute leukemia and demonstrates that the establishment of patient-specific chromosomal fusion sites allows the design of specific PCR primers for minimal residual disease analyses for all patients.

The association between time to disposition plan in the emergency department and in-hospital mortality of general medical patients

BACKGROUND

A perceived risk of time-limited emergency department (ED) assessment of patients is inadequate workup leading to inappropriate disposition. The aim of this study was to examine the association of time to disposition plan (TDP) on ED length of stay (LOS) and correlate this to mortality.

METHODS

A retrospective review of data collected from ED information systems at three hospitals was conducted between June 2008 and October 2009. Included patients were admitted to a general medical unit. Patients were excluded if admitted to intensive care, coronary care, a cardiac monitored bed or required surgery in first 24 h or had an expected LOS of <48 h. Multivariate regression analysis was used to identify independent associations with mortality.

RESULTS

A total of 10,107 patient episodes was analysed, of which 6768 patients (67.0%) had an ED LOS of ≥8 h. There was significant effect modification by ED LOS in the association of TDP and mortality. In the setting of longer ED LOS, a TDP of <4 h was associated with significantly higher mortality (OR 1.57, 95% CI: 1.28-1.92, P < 0.001), corrected for age, gender and triage category. This association was not significant when ED LOS was <8 h (OR 0.88, 95% CI: 0.60-1.27, P = 0.49).

CONCLUSIONS

In the setting of prolonged ED LOS, completing ED assessment and management within 4 h of presentation was associated with significantly higher mortality. Further prospective studies are required to understand the relationship between rapid decision making in the ED and patient safety.

Probing the material properties and phase transitions of ferroelectric liquid crystals by determination of the Landau potential

The full Landau potential of several, widely varying ferroelectric liquid-crystalline materials has been experimentally determined. Tilt angle and polarisation data is analysed across the SmA to SmC transition for varying applied electric-field amplitudes, allowing the determination of all the coefficients of the generalised Landau model of ferroelectric liquid crystals. The materials investigated encompass different materials, including low-polarisation mixtures to high-polarisation single-component materials. The materials also possess a variation in the order of the SmA to SmC phase transition from strongly first order to strongly second order. The effects of both the polarisation and order of phase transition of the system are discussed with respect to the various terms of the generalised Landau model. Further, the mechanisms behind the difference between a first- and second-order phase transition are discussed with respect to the Landau potential and the second Landau coefficient b .

Quantitative experimental determination of the Landau-potential of chiral enantiomer doped ferroelectric liquid crystals

The full Landau potential was determined for a ferroelectric liquid crystal doped with varying concentrations of the chiral dopant R1011 and its enantiomer S1011. A multi-curve fitting procedure using temperature and electric field dependent tilt angle and polarization data was employed to the generalized Landau model of ferroelectric liquid crystals. From this analysis the three Landau coefficients as well as the polarization-tilt coupling parameters were obtained as a function of dopant concentration and configuration. It is shown that the two most varied parameters are those of the first Landau coefficient alpha and the (chiral) linear polarization-tilt coupling constant C. The effect on the first Landau term is equivalent for the two dopants of opposite handedness indicating its achiral nature, while the effect on the (chiral) bilinear coupling term differs for the R1011 and S1011 dopant, increasing and decreasing the coupling between tilt and polarization respectively. This difference in the bilinear coupling term quantifiably evidences that the R1011 dopant increases and S1011 dopant reduces the inherent chirality in this system.

Experimental determination of the full Landau potential of bent-core doped ferroelectric liquid crystals

The full Landau potential of a ferroelectric liquid crystal, doped with two different bent-core molecules at varying concentration, was determined experimentally. Using a multicurve fitting procedure, temperature and electric field dependent tilt angle and polarization measurements were analyzed according to the generalized Landau model of ferroelectric liquid crystals. From this analysis the three Landau coefficients as well as the polarization-tilt coupling parameters were obtained as a function of dopant concentration. It is shown that the two most varied parameters are those of the first Landau coefficient and the (chiral) linear polarization-tilt coupling constant. The results quantitatively verify the chiral induction capability of nonchiral bent-core shaped dopants and an observed increase in the electroclinic effect with increasing dopant concentration.

The twilight of national sovereignty

The institution envisaged in the Moscow Declaration, refined in the Atlantic Charter, and elaborated at Dunbarton Oaks, was called 'the United Nations'. The Preamble to its Charter began with the words 'We the peoples', and Articles 3 and 4 provided that its members should be states. The underlying assumption appeared to be that the words 'nation', 'people' and 'state' were interchangeable. To challenge that assumption may appear to be playing at word games, equivalent to doing the Times crossword. But since language is the vehicle by which we formulate and communicate our thinking, words have always been invested with a power, and certainly a life, of their own. Words have legal consequences. If the word 'A' is synonymous with 'B', then all the rights and obligations pertaining to an 'A' attach to a 'B', although that may not have occurred to us when we cheerfully used that label. Perhaps even more importantly, they have psychological consequences. If we can secure acceptance that 'B' means 'A', then all the legitimacy invoked by an 'A', is assumed by a 'B'. The argument that I want to advance is that those who drafted the Charter did so on the assumption that the wellbeing and the integrity of a people, or of a nation, are equivalent to the integrity and wellbeing of the specific state to which they are attached on a one-to-one basis. I want to go on to argue that that proposition was never wholly true, and that it is becoming increasingly remote from the real world. I decided to begin by attempting definitions of the three words, but I quickly discovered that the task, if achievable, would require greater leisure, not to mention a wiser head, than is available to me. The first conclusion I reached is that all three words have eel-like qualities. When you think that you have grasped a meaning, it slips through your fingers. Not only do meanings change from generation to generation but they change contemporaneously according to the purpose of those who use them.

Depletion of CD34+ CD4+ cells in bone marrow from HIV-1-infected individuals

Pancytopenia as a consequence of bone marrow abnormalities is commonly seen in HIV-infected individuals. To examine the effect that HIV-1 has on hematopoietic cells, we compared hematopoietic properties of bone marrow samples from HTV+ patients at various stages of disease with bone marrow samples from uninfected donors. While the absolute number of recovered CD34+ cells and the cloning efficiency of these cells did not differ significantly in HIV+ donors, the percentage of CD34+ CD4+ cells was significantly depleted in late-stage HIV+ patients. We observed a direct correlation between the numbers of CD34+ CD4+ cells in the bone marrow and the peripheral CD4 count. Further characterization of the CD34+ CD4+ subpopulation demonstrated that these cells expressed lower levels of HLA-DR on their surface compared with CD34+ CD4- cells, suggesting an immature phenotype. We also found evidence for expression of HIV-1 coreceptors CXCR-4 and CKR-5 message and protein in CD34+ bone marrow cells. While this finding suggested that hematopoietic cells might be susceptible to HIV infection at an early stage of maturation, thus affecting different cell lineages as they matured, we did not find any evidence for infection of HIV in these cells. These data suggest that HIV affects early hematopoietic progenitor cells either directly or indirectly, and in particular CD34+ CD4+ cells. This finding has important implications for disease pathogenesis and for application of gene therapy approaches that use CD34+ hematopoietic cells.

Melanocortin antagonists define two distinct pathways of cardiovascular control by alpha- and gamma-melanocyte-stimulating hormones

Melanocortin peptides and at least two subtypes of melanocortin receptors (MC3-R and MC4-R) are present in brain regions involved in cardiovascular regulation. In urethane-anesthetized rats, unilateral microinjection of alpha-melanocyte-stimulating hormone (MSH) into the medullary dorsal-vagal complex (DVC) causes dose-dependent (125-250 pmol) hypotension and bradycardia, whereas gamma-MSH is less effective. The effects of alpha-MSH are inhibited by microinjection to the same site of the novel MG4-R/MC3-R antagonist SHU9119 (2-100 pmol) but not naloxone (270 pmol), whereas the similar effects of intra-DVC injection of beta-endorphin (1 pmol) are inhibited by naloxone and not by SHU9119. Hypotensive and bradycardic responses to electrical stimulation of the arcuate nucleus also are inhibited by ipsilateral intra-DVC microinjection of SHU9119. gamma-MSH and ACTH(4-10), but not alpha-MSH, elicit dose-dependent (0.1-12.5 nmol) pressor and tachycardic effects, which are much more pronounced after intracarotid than after intravenous administration. The effects of gamma-MSH (1.25 nmol) are not inhibited by the intracarotid injection of SHU9119 (1.25-12.5 nmol) or the novel MC3-R antagonist SHU9005 (1.25-12.5 nmol). We conclude that the hypotension and bradycardia elicited by the release of alpha-MSH from arcuate neurons is mediated by neural melanocortin receptors (MC4-R/MC3-R) located in the DVC, whereas the similar effects of beta-endorphin, a peptide derived from the same precursor, are mediated by opiate receptors at the same site. In contrast, neither MC3-R nor MC4-R is involved in the centrally mediated pressor and tachycardic actions of gamma-MSH, which, likely, are mediated by an as yet unidentified receptor.

Immunocytochemical detection of breast cancer cells in marrow and peripheral blood of patients undergoing high dose chemotherapy with autologous stem cell support

Detection of small numbers of breast cancer cells is important in staging the disease and can be helpful in assessing the efficacy of purging regimens prior to autologous stem cell infusion. Immunohistochemical methods are potentially useful and broadly applicable for this purpose since they are simple to perform, sensitive, and may be quite specific. We have used a combination of four monoclonal antibodies [260F9, 520C9, 317G5 (Baxter Corp); BrE-3 (Dr. R. Ceriani)] against tumor cell surface glycoproteins in a sensitive immunocytochemical assay to identify breast tumor cells in bone marrow and peripheral blood. Immunostained cytospin preparations were fixed prior to staining to preserve cytological details of immunopositive cells. After immunostaining, slides were counterstained with hematoxylin to confirm the identify of labeled cells. In cytocentrifuge experiments in which small numbers of CAMA human breast tumor cells were added to bone marrow mononuclear cells, a linear relationship between the number of tumor cells added and the number of tumor cells detected was obtained over a broad range of tumor cell concentrations. The probability of detecting tumor cells was dependent on the number of cytocentrifuge slides examined. When ten slides (5 million cells) were examined, the probability of detecting tumor at a concentration of 4 tumor cells per million bone marrow mononuclear cells was 98%. In clinical specimens, tumor cells were detected in marrow aspirates from 73 of 240 (30%) patients undergoing autologous transplantation, including 70 (37%) of 190 patients with clinical stage IV disease, 0 of 7 patients with clinical stage III disease, and 3 of 43 (7%) patients with clinical stage II disease. Seventy-three of 657 peripheral blood specimens from 26 of 155 patients (17%) contained breast cancer cells with counts ranging from 1 to 97 tumor cells per million leukocytes. Tumor cells were most frequently found in the blood of patients with stage IV disease [21 of 107 (20%)] but were also found in a substantial number [5 of 44 (11%)] of patients with stage II disease. Positive selection of CD34-positive hematopoietic progenitor cells as well as negative purging methods such as incubation with 4-hydroxyperoxy-cyclophosphamide (4-HC) were evaluated with respect to tumor cell depletion. Selection of CD34-positive progenitor cells from bone marrow or peripheral blood resulted in log reduction of 1 to > 4 tumor cells reinfused at autologous transplantation. A lesser log reduction (up to 1) was demonstrated following 4-HC purging. We conclude that properly performed and controlled immunocytochemical staining of bone marrow and peripheral blood cytospins is a sensitive and simple way to detect and quantitate breast cancer cells in hematopoietic specimens harvested for autotransplantation and that CD34-positive progenitor cell selection results in significant reduction in the number of breast cancer cells reinfused with marrow or peripheral blood stem cells.

Estimation of body composition changes during weight cycling by bioelectrical impedance analysis in rats

The effects of body weight cycling (WC) in rats on body composition (BC) and feeding efficiency were studied. The usefulness of estimating BC by bioelectrical impedance analysis (BIA) was also examined. Female Sprague-Dawley rats were divided into high-fat ad libitum feeding, either noncycling or cycling, or restricted feeding (75% of control feed) cycling groups. Control rats were fed a regular laboratory ad libitum diet and did not cycle. All rats were killed at the end of week 61. A BIA unit was used at each stage of WC to obtain resistance and reactance readings. Final BC was determined by chemical analysis. On the basis of the final chemical analysis and BIA measurements, an equation was established and applied to estimate BC at each stage of WC: fat-free mass (g) = 0.38 x body wt (g) + 13.8 x [length (cm)2/resistance] + 70.9 (r = 0.95, P < 0.001). High-fat ad libitum feeding induced rapid body weight and fat gains as well as an elevated feeding efficiency and an internal fat-to-subcutaneous fat ratio, regardless of whether the rats cycled. This change in fat mass was clearly detected by the BIA. Although rats fed restricted diets had similar body weights as did control rats, they had a significantly higher internal fat-to-subcutaneous fat ratio. Thus, not only the amount of food but also the composition of the diet is important for proper weight management. The BIA method is capable of detecting the body fat mass change during WC.

Long-term exercise training and retirement in genetically obese rats: effects on food intake, feeding efficiency and carcass composition

Short-term physical exercise (EX) can reduce body weight and fat gain in obese humans and animals. However, the beneficial effects of physical exercise are not long-lasting. In this study, the effects of long-term physical exercise and retirement from exercise (R) on body weight, body composition and fat distribution were examined in genetically obese (OB) and lean (LE) female rats. Fifty OB and 45 LE rats, four weeks old, were divided into EX (swimming, 2h/day, 5 days/week) or sedentary (SD) groups. At the end of the 28th week of treatment, EX groups were further divided into continued EX or R groups for another 11-12 weeks. It was found that at the end of the 28th week EX had reduced the rate of weight gain in OB and LE rats. Percentage body fat was only reduced in OBEX rats and this was achieved by a significant reduction of subcutaneous fat mass. At the end of the 40th week, EX had further reduced the weight gain, fat mass and body fat percentage in OBEX rats while only body fat percentage was reduced in the LEEX group. Retirement from exercise reversed these phenomena. Thus there were no differences between OBSD and OBEX-R rats in body weight, fat mass and percentage body fat. However, the OBEX-R group had a significantly higher amount of internal fat than the other two OB groups. Therefore, exercise, even long-term to cover the entire fat cell proliferation period, still only exerted temporary beneficial effects in OB rats. After retirement, the beneficial effects all disappeared rapidly.(ABSTRACT TRUNCATED AT 250 WORDS)

The Denver II: A Major Revision and Restandardization of the Denver Developmental Screening Test

Since the Denver Developmental Screening Test was first published 23 years ago, it has been utilized worldwide and restandardized in more than a dozen countries. Concerns raised through the years by test users about specific items and features of the Denver Developmental Screening Test, coupled with a need for more current norms, have prompted a major revision and restandardization of the test. For the revision, 336 potential items were administered to more than 2000 children. The average number of times each item was administered was 540. Using regression analysis, composite norms for the total sample and norms for subgroups (based on gender, ethnicity, maternal education, and place of residence), were used to determine new age norms. The final selection of the 125 Denver II items was based on the following criteria: ease of administration and scoring, item appeal to child and examiner, item test-retest and inter-rater reliability, minimal "refusal" scores, minimal "no opportunity" scores, minimal subgroup differences, and a smooth step-like progression of ages at which 90% of children could perform the tasks. The major differences between the Denver II and the Denver Developmental Screening Test are: 1) an 86% increase in language items; 2) two articulation items; 3) a new age scale; 4) a new category of item interpretation to identify milder delays; 6) a behavior rating scale; and 7) new training materials.

Studies in human lactation: milk composition and daily secretion rates of macronutrients in the first year of lactation

Time-dependent changes in milk composition and secretion from pregnancy through greater than or equal to 6 mo of exclusive breast-feeding were studied in 13 multiparous women. Concentrations and secretion rates of lipid, lactose, protein, sodium, chloride, potassium, total calcium, ionized calcium, magnesium, glucose, citrate, inorganic phosphate, creatinine, and urea and pH were analyzed longitudinally from day 6 until weaning commenced. The composition of the antepartum secretion was related to the permeability of the junctional complexes between mammary cells. Significant increases in lactose, glucose, pH, and ionized calcium and significant decreases in protein, sodium, potassium, chloride, and calcium concentrations were observed between 1 and 6 mo. Significant differences among individuals, which persisted through lactation, were observed for the concentrations of sodium, potassium, chloride, and inorganic phosphate. The amount of lactose, ionized calcium, and magnesium transferred to the infant was also characteristic of each mother-infant pair. Our data imply that lactation performance is determined in the first month postpartum.

The use of the Markov process in describing the natural course of diabetic retinopathy

The natural course of early diabetic retinopathy in young subjects with insulin-dependent diabetes mellitus was evaluated during 693 patient visits for 259 subjects during a mean of 2.4 years. Diabetic retinopathy is considered a progressive disease among people with insulin-dependent diabetes mellitus (type I). Improvement of early retinopathy has not been recognized as a part of the natural course. In our experience, 25% of observations in subjects with early diabetic retinopathy (grades 2 and 3) showed improvement. Thus, 28 of 174 observations of diabetic retinopathy improved from grade 2 to grade 1, and 34 of 79 observations improved from grade 3 to grades 2 or 1. Markov chains indicate that 25% of observations of diabetic retinopathy will change from grade 1 to grade 5 or 6 in 17.0 years and 25% will change from grade 2 to grade 5 or 6 in 16.0 years. Future studies of diabetic retinopathy should consider a matrix of estimated transition probabilities, depending on the population, to judge probabilities of transition between states of retinopathy.

Growth of Listeria monocytogenes at refrigeration temperatures

The growth of three strains of Listeria monocytogenes at refrigeration temperatures (-0.5 to 9.3 degrees C) in chicken broth and/or UHT milk was determined using a rocking temperature gradient incubator. Minimum growth temperatures ranged from -0.1 to -0.4 degree C for the three strains. Lag times of 1-3 d and 3 to greater than 34 d were observed with incubation at 5 and 0 degrees C respectively. Corresponding generation times ranged from 13-24 h at 5 degrees C and 62-131 h at 0 degree C. The type of culture medium had an influence on both the rate and extent of growth. Incubation of cultures at 4 degrees C before inoculation caused a marked reduction in the lag time when compared with cultures which had been previously incubated at 30 degrees C.

Studies in human lactation: milk volumes in lactating women during the onset of lactation and full lactation

After validation of test-weighing procedures milk volumes produced by 13 multiparous Caucasian women were followed longitudinally through the first year of lactation. All practiced exclusive breast-feeding for at least 5 mo. Milk transfer to the infant was low on days 1 and 2 and increased rapidly to 498 +/- 129 g/d (means +/- SD) on day 5 and then more slowly to 753 +/- 89 g/d during months 3-5. There was a characteristic milk volume for each mother-infant pair that was significantly related neither to milk yield on days 4-6 nor to birth weight. It was, however, strongly related to infant weight at 1 mo, suggesting that infant and/or maternal factors coming into play during the first month of life are strong determinants of subsequent milk transfer to the infant.

Chromosome aberrations in individuals occupationally exposed to ethylene oxide, and in a large control population

Chromosome aberration frequencies in 61 employees potentially exposed to ethylene oxide (ETO) were compared with those in unexposed control groups. We studied 3 worksites with differing historical ambient levels of ETO. Within worksites, groups were classified as high potential exposed, low potential exposed, or controls. Further control groups including an off-site community control group were added to give a total of 304 control individuals. Blood samples were drawn several times over a 24-month period. Aberrations were analyzed in 100 cells per sample after culture for 48-51 h. Worksites I, II and III respectively represented increasing levels of potential ETO exposure. At worksites I and II, no consistent differences in aberration frequencies were found among groups. At worksite III aberration frequencies in potentially exposed individuals were significantly increased compared with controls. The frequencies of cells with aberrations were 5.6% for the 2 individuals in the high potential exposure category and 2.6% for 23 persons in the low potential exposure group. The overall frequency of cells with aberrations in the matched control individuals was 1.4%. In the total control group of 304 individuals we found significant increases in aberrations associated with smoking and with increasing age. We have also reported previously an association between sister-chromatid exchange (SCE) frequency and ETO exposure (Stolley et al., 1984). When aberration frequencies were compared with levels of SCEs there was only a weak overall association. The correlation was found in potentially exposed but not in control groups, and for any individual, one observation could not be used to predict the other.

Statistical analyses for in vitro cytogenetic assays using Chinese hamster ovary cells

It is a widely held view that objective statistical criteria are needed for the evaluation of genetic toxicity assays. This paper presents statistical methods for the analysis of data from in vitro sister chromatid exchange (SCE) and chromosome aberration tests that use Chinese hamster ovary cells. For SCEs, an extensive study of solvent control results demonstrated that there is a substantial interday component of variability in the data, and that a Poisson sampling model is applicable to data generated via the protocol of Galloway et al [1985]. Consequently, a trend test for evidence of a dose response is proposed for such SCE data. As an illustration of this statistical method, analysis of data previously considered to be negative [Gulati et al, 1985] indicates that di(2-ethyl-hexyl) phthalate induces a weak, but reproducible, SCE dose response in CHO cells. Monte Carlo methods are used to show that the trend test is more sensitive than four other statistical procedures considered for the analysis of Poisson-distributed SCEs. A similar trend test for dose response in proportions is proposed for chromosome aberration data, where the percent of cells with chromosome aberrations is the response of interest. Sensitivity (or power) studies indicate that three doses and a control with 50 cells/dose point is a reasonable design for an in vitro SCE study that uses the Galloway et al protocol. For in vitro chromosome aberrations, however, three doses and a control with 100 cells/dose point appears to produce too insensitive an assay; an increase to 200 cells/dose point in the Galloway et al protocol seems worthy of serious consideration.

Development of a standard protocol for in vitro cytogenetic testing with Chinese hamster ovary cells: comparison of results for 22 compounds in two laboratories

A major problem of cytogenetics testing in mammalian cells is lack of agreement of results among laboratories. Our objective was to develop a sensitive in vitro test protocol that was applicable to large-scale chemical screening and yielded comparable results in two laboratories. We used sister chromatid exchange (SCE) and chromosome aberration (CAb) tests in Chinese hamster ovary (CHO) cells. The initial protocol used standard cell densities, medium, batch of rat liver S9 for metabolic activation; positive, negative, and solvent controls; staining and scoring techniques; and fixation times. Treatment without S9 was for 8-12 hr (CAb) or 26 hr (SCE), and with S9 for 2 hr in serum-free medium. Bromodeoxyuridine (BrdUrd) (10 microM) was added to SCE cultures only, 2 hr after addition of the test chemical. Doses were based on the 50% toxicity level in a preliminary test of cell survival 24 hr after treatment. One hundred cells (CAb) or 50 cells (SCE) were scored from each control and from five dose levels. Five clastogens were tested in the first two-laboratory comparison: mitomycin-C, triethylenemelamine, N-methyl-N'-nitro-N-nitrosoguanidine, cyclophosphamide, and benzo(alpha)pyrene. There was quite good agreement between laboratories. Seventeen compounds were then tested "blind" in the two laboratories. As testing proceeded, some discrepancies occurred between the laboratories, and the protocol was modified in attempts to improve the resolution of marginal responses and make dose selection more consistent. The preliminary test for cell survival was omitted. A 10(5) dose range in a half-log series was tested, and cells were scored at the highest dose at which sufficient mitotic cells were obtained, and at the next two lower doses. By delaying fixation times, SCE and CAb were scored at doses that inhibited cell cycle progression. This protocol gave comparable results in the two laboratories in many cases and by testing up to a maximum dose, limited by solubility and/or toxicity, should detect a high proportion of clastogens and SCE inducers.

Studies on human lactation. I. Within-feed and between-breast variation in selected components of human milk

Within-feed and between-breast differences in the concentrations of sodium, potassium, chloride, calcium, magnesium, lipid, protein, lactose, glucose, urea nitrogen, creatinine, zinc, and copper were examined in milk samples from 10 women. The average lipid content doubled in the interval from the beginning of the feed to the end. The composition of the aqueous phase of milk, as determined by the major osmotically active constituents, did not vary significantly within the feed. For these components as well as for lipid a small mid-feed sample of milk gave the same mean composition as the pooled, pumped contents of one breast suggesting that such a sample is adequate for determination of milk composition in population studies. Sporadic, inconsistent differences in the composition of the milk from the right and left breasts were observed. It is suggested that mastitis may contribute to these differences. It is recommended that samples routinely be taken from both breasts and analyzed for sodium and chloride to rule out episodes of mastitis or other local phenomena which sporadically alter milk composition.