Effect of intravenous L-carnitine on growth parameters and fat metabolism during parenteral nutrition in neonates

To determine whether intravenous carnitine can improve nutritional indices, neonates requiring parenteral nutrition were randomized into carnitine treatment (n = 23) and control (n = 20) groups. Observed plasma lipid indices, carnitine and nitrogen balances, and plasma carnitine concentrations were not different in the prestudy period. Under standardized, steady-state conditions, 0.5 g/kg Intralipid was administered intravenously over 2 hr prior to carnitine administration, after infants received 7 days of 50 mumol/kg/day, and after a second 7 days of 100 mumol/kg/day of continuous intravenous L-carnitine as part of parenteral nutrition. Triglyceride (TGY), free fatty acid (FFA), acetoacetate (AA), beta-hydroxybutyrate (BOB), and plasma carnitine concentrations were measured prior to and at 2, 4, and 6 hr after the initiation of the lipid bolus. Twenty-four-hour urine collections for nitrogen and carnitine balance were obtained on days 7 and 14. Neonates receiving carnitine had significantly greater concentrations of plasma carnitine on days 7 and 14 (p less than 0.001). Greater nitrogen (p less than 0.05) and carnitine (p less than 0.001) balances and weight gain (week 2, p less than 0.05) were found in the carnitine-supplemented group when compared with controls. On day 14, (BOB + AA)/FFA ratios were significantly higher (p less than 0.05), and peak TGY concentrations and 6-hr FFA concentrations were significantly lower (p less than 0.05) in the treatment group. Carnitine supplementation was associated with modest increases in growth and nitrogen accretion possibly by enhancing the neonate's ability to utilize exogenous fat for energy.

Induction, accumulation, and persistence of sister chromatid exchanges in women with breast cancer receiving cyclophosphamide, adriamycin, and 5-fluorouracil chemotherapy

The induction, accumulation, and persistence of sister chromatid exchanges (SCEs) and high SCE frequency cells (HFCs) was measured in peripheral blood lymphocytes of women with breast cancer before chemotherapy and on multiple occasions during and after therapy. Chemotherapy consisted of i.v. infusion of cyclophosphamide, Adriamycin, and 5-fluorouracil, administered on day 1 of each of approximately six 21-day cycles. This treatment resulted in a highly significant induction of SCEs (1.8-fold, P less than 0.0001) and HFCs (5-fold, P less than 0.0001) measured in samples obtained 1 week after the first therapy. Accumulation of lesions leading to SCEs was measured by comparing samples surrounding the first and last rounds of therapy and was significant for both SCEs and HFCs in most comparisons. Persistence of lesions leading to SCEs was evaluated at multiple times until 9 months after completion of therapy, and both SCEs and HFCs remained significantly elevated throughout this time. Differences between donors were observed throughout the study, although they were not always consistent with time. Our results also indicate that the SCE frequency declines rapidly within a few weeks after treatment but that residual damage remains up to 9 months after the end of chemotherapy.

Experience with the Athena semi-automated karyotyping system

The traditional analysis and assembly of metaphase chromosomes into a karyogram is a slow and tedious process requiring intermediate photographic steps and manual manipulation of the chromosome images. Much of this task is highly repetitive and readily lends itself to partial automation. Semi-automated karyotyping systems now are being used increasingly in both clinical and research cytogenetic laboratories. Digital image processing techniques are used to capture, manipulate, and make an initial classification of chromosome images. The Athena system uses commercially available components based on a Macintosh II personal computer. Digital image processing procedures automatically isolate chromosome images from the metaphase and arrange them into a karyogram, using information about relative chromosome length, centromeric index, and banding pattern. The operator uses the intuitive graphics interface of the Macintosh computer to monitor each phase of the analysis, to resolve any problems in isolating chromosome images, and to rearrange the individual chromosome images while assembling the final karyogram. Athena is designed as a semi-automated karyotyping system that is easy to learn and has sufficient power and versatility for routine use in the analysis of human metaphase chromosomes.

Evaluation of aminoglycoside disposition in patients previously treated with cisplatin

The alterations in aminoglycoside disposition in patients previously treated with cisplatin were determined by reviewing the medical records of 37 cancer patients. The patients received 44 courses of an aminoglycoside antibiotic (gentamicin, n = 27; amikacin, n = 14; and tobramycin, n = 3). The mean (SD) half-life of 171 (120) min was greater than our previously published mean aminoglycoside half-life in children with cancer who were not receiving cisplatin. Twenty-five of 44 courses were completed without an aminoglycoside dosage reduction and only 5 courses were discontinued because of delayed aminoglycoside elimination. There was no significant difference in the duration of aminoglycoside therapy between the group that had a dosage reduction and the group that did not [6.6 (2.3) versus 5.8 (2.9) days, p = 0.42, respectively]. Multiple linear regression analysis of patient variables identified serum creatinine and cumulative cisplatin dose as the best predictors of aminoglycoside half-life (r2 = 46.0%, p less than 0.001). The only predictor of aminoglycoside clearance was serum creatinine (r2 = 35.2%, p less than 0.001). Patients previously treated with cisplatin are at greater risk for delayed aminoglycoside elimination. Prior administration of cisplatin is not an absolute contraindication to the use of aminoglycoside antibiotics. When clinically indicated, patients who have previously received cisplatin and have apparently normal renal function should be treated cautiously with standard doses of aminoglycoside antibiotics, and pharmacokinetic monitoring should be routinely performed.

Plasma carnitine concentration and lipid metabolism in infants receiving parenteral nutrition

The relationships among plasma total carnitine concentration, postnatal age, and fatty acid metabolism were evaluated in 57 infants receiving parenteral nutrition. Concentrations of plasma carnitine, triglycerides, free fatty acids, acetoacetate, and beta-hydroxybutyrate were determined before and at 2 and 4 hours from the beginning of a standardized 2-hour lipid infusion. Plasma carnitine concentrations declined with increasing postnatal age. There were no significant differences in gestational age or triglyceride concentrations between infants less than or equal to 4 weeks of age and those greater than 4 weeks of age, whereas free fatty acid concentrations were lower and acetoacetate and beta-hydroxybutyrate concentrations were higher in the younger infants. Infants less than or equal to 4 weeks of age were further grouped according to plasma carnitine concentration greater than 13 nmol/ml (group 1) and less than or equal to 13 nmol/ml (group 2) and were then compared with infants greater than 4 weeks of age (group 3). There were no significant differences in triglyceride concentrations among the three groups; free fatty acids, acetoacetate, and beta-hydroxybutyrate concentrations for group 2 patients were similar to those of group 1 patients or fell between values for group 1 and group 3 patients. These results demonstrate decreasing plasma carnitine concentrations and possibly for more than 4 weeks.

Cytogenetic response to 1,2-dicarbonyls and hydrogen peroxide in Chinese hamster ovary AUXB1 cells and human peripheral lymphocytes

Mutagenic 1,2-dicarbonyls have been reported to occur in coffee and other beverages and in various foods. We have measured the induction of sister-chromatid exchanges (SCEs) and endoreduplicated cells (ERCs) to determine the genotoxicity of various 1,2-dicarbonyl compounds in Chinese hamster ovary (CHO) AUXB1 cells and human peripheral lymphocytes. The 1,2-dicarbonyls glyoxal, methylglyoxal and kethoxal each induced highly significant increases in both SCEs and ERCs in AUXB1 cells. Glyoxal and kethoxal induced SCEs but not ERCs in human peripheral lymphocytes. In addition, hydrogen peroxide induced highly significant levels of SCEs and ERCs in AUXB1 cells. Bisulfite, which reacts with carbonyl groups to form addition products, significantly reduced the frequency of SCEs and the proportion of ERCs when glyoxal, methylglyoxal, kethoxal and diacetyl were administered to AUXB1 cells. In addition, bisulfite blocked the formation of ERCs, but not SCEs, induced by hydrogen peroxide. These in vitro results suggest that 1,2-dicarbonyls may play an important role in the genotoxicity of some foods and beverages.

In vivo cytogenetic effects of cooked food mutagens

Using a variety of in vivo cytogenetic endpoints, we have investigated the effects of several compounds formed during the cooking of meat. C57Bl/6 mice were used to test for an increase in the frequency of sister-chromatid exchanges (SCEs), chromosomal aberrations, and micronucleated erythrocytes by 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx), and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). MeIQx and DiMeIQx did not induce SCEs in mouse bone marrow cells. PhIP induced sister-chromatid exchanges, but not chromosomal aberrations in bone marrow. In peripheral blood lymphocytes, PhIP did induce aberrations at 100 mg/kg, the highest dose tested. PhIP induced a low but significantly increased frequency of micronuclei in normochromatic but not polychromatic erythrocytes in bone marrow and peripheral blood. However, dose responses were not observed. With the exception of the SCEs induced by PhIP, these results contrast with observations made in vitro, where these compounds were found to have significant genotoxicity in mammalian cells and a very high mutation frequency in prokaryotic systems.

Cytogenetic response to coffee in Chinese hamster ovary AUXB1 cells and human peripheral lymphocytes

We have investigated the genotoxic effects of three different brands and three types of coffee (freshly brewed regular, instant regular and freshly brewed decaffeinated) in two mammalian systems: the Chinese hamster ovary (CHO) AUXB1 cell line and human peripheral lymphocytes. Sister-chromatid exchanges (SCEs) and endoreduplicated cells (ERCs) were used as the endpoints. Coffee was prepared according to the manufacturer's suggestions, and after cooling, administered to cultured cells at dilutions ranging up to 11% that of full-strength coffee. Each brand and type of coffee induced significant levels of SCEs and ERCs in AUXB1 cells. SCEs, but not ERCs, were induced in human peripheral lymphocytes. Bisulfite, which complexes with carbonyls and reduces their genotoxicity, significantly diminished the number of SCEs and ERCs found after administration of coffee. Catalase and peroxidase, enzymes that destroy hydrogen peroxide activity, had no significant effect upon the SCE and ERC frequencies in AUXB1 cultures treated with freshly brewed regular coffee. These experiments indicate that different brands and types of coffee have sufficient genotoxic activity to increase SCEs and ERCs at levels only a fraction of those normally consumed. 1,2-Dicarbonyls alone and peroxides alone do not appear to be responsible for the majority of SCEs and ERCs that were observed to be induced by dilute coffee.

Hepatic drug clearance in children: studies with indocyanine green as a model substrate

For several drugs metabolized by the liver, higher dosages (mg/kg body weight) are required in children to attain serum concentrations comparable to those in adults. Indocyanine green (ICG), a commonly used model substrate for hepatic elimination of high intrinsic clearance drugs, has been extensively evaluated in adults but not in children. We evaluated the disposition of ICG in 115 children with leukemia and nine healthy adult volunteers. The mean (SD) ICG plasma clearance (CLp) for all 115 children (age 0.9-17.8 years) was significantly greater (p = 0.0006) than for adults [14.8 (7.8) versus 10.6 (2.4) mL/min/kg]. When clearances from only children less than 10 years of age (N = 85) were compared with those from adults, the difference was even greater [15.6 (7.3) versus 10.6 (2.4) mL/min/kg; p = 0.0001]. However, when ICG CLp was normalized to body surface area, values for children did not differ significantly from adults [378 (204) versus 422 (102) mL/min/m2]. These data provide insight as to why dosage (mg/kg) requirements of certain drugs are higher in children.

Human viral gastroenteritis

During the last 15 years, several different groups of fastidious viruses that are responsible for a large proportion of acute viral gastroenteritis cases have been discovered by the electron microscopic examination of stool specimens. This disease is one of the most prevalent and serious clinical syndromes seen around the world, especially in children. Rotaviruses, in the family Reoviridae, and fastidious fecal adenoviruses account for much of the viral gastroenteritis in infants and young children, whereas the small caliciviruses and unclassified astroviruses, and possibly enteric coronaviruses, are responsible for significantly fewer cases overall. In addition to electron microscopy, enzyme immunoassays and other rapid antigen detection systems have been developed to detect rotaviruses and fastidious fecal adenoviruses in the stool specimens of both nonhospitalized patients and those hospitalized for dehydration and electrolyte imbalance. Experimental rotavirus vaccines have also been developed, due to the prevalence and seriousness of rotavirus infection. The small, unclassified Norwalk virus and morphologically similar viruses are responsible for large and small outbreaks of acute gastroenteritis in older children, adolescents, and adults. Hospitalization of older patients infected with these viruses is usually not required, and their laboratory diagnoses have been limited primarily to research laboratories.

Effect of hydration on methotrexate plasma concentrations in children with acute lymphocytic leukemia

Hydration and urinary alkalinization are used with high-dose methotrexate (HDMTX) to minimize renal toxicity resulting from methotrexate (MTX) precipitation in the kidney tubules. The effect of two hydration and alkalinization schedules on MTX plasma concentrations were evaluated in 100 children with acute lymphocytic leukemia (ALL) following two courses of MTX, 2 g/m2. The mean 21- and 44-hour MTX plasma concentrations were significantly lower in the group receiving the greater hydration and alkalinization schedule: 0.79 (0.90 SD) v 1.39 (1.99 SD) mumol/L for 21-hour MTX plasma concentrations, P = .01; and 0.18 (0.38 SD) v 0.25 (0.50 SD) mumol/L for 44-hour MTX plasma concentrations, P = .01. Although the overall incidence of toxic events was similar in both groups, the incidence of severe toxicity was reduced in the group that received the greater hydration and alkalinization, 6% v 16%. This study demonstrated that the amount of hydration and alkalinization can affect MTX plasma concentrations. Optimizing the hydration and alkalinization schedule is important for minimizing the incidence of severe toxicity associated with HDMTX.

Comparison of the Abbott and Ortho enzyme immunoassays and cell culture for the detection of respiratory syncytial virus in nasopharyngeal specimens

A comparison of the Abbott Laboratories and the Ortho Diagnostic Systems Respiratory Syncytial Virus (RSV) Enzyme Immunoassays (EIA) and HEp-2 cell culture for the detection of RSV in 81 nasopharyngeal (NP) specimens from pediatric patients with lower respiratory tract infection was carried out. The sensitivity and specificity of the Abbott test compared to confirmed infection was 92.3% and 100.0%, respectively. The sensitivity and specificity of the Ortho test was 87.5% and 80.3%, respectively. We found the Abbott EIA test to be sensitive, specific, rapid, and easy to perform.

Phase II testing of melphalan in children with newly diagnosed rhabdomyosarcoma: a model for anticancer drug development

We describe events that led to successful testing of melphalan, one of the nitrogen mustard compounds, in children with newly diagnosed, poor-risk rhabdomyosarcoma (RMS). Preclinical studies with xenografts of human RMS, growing in the flanks of immune-deprived mice, had indicated superior oncolytic activity by melphalan compared with other agents commonly used to treat this tumor. However, in a conventional phase II trial, melphalan failed to produce partial responses in 12 of 13 heavily pretreated patients with recurrent tumors. Subsequent comparison of the drug's pharmacokinetics in mice and patients indicated that its poor clinical performance was not the result of interspecies differences in drug disposition. Therefore, we elected to retest melphalan in untreated patients, before they were enrolled in a phase III study. Of 13 children who received the drug for 6 weeks, ten had partial responses, confirming the significant antitumor activity seen in the xenograft system. These findings illustrate the inherent limitations of phase II drug trials in previously treated patients and suggest a useful paradigm for the development of antineoplastic drugs.

Simultaneous identification and banding of human chromosome material in somatic cell hybrids

We have developed a method that identifies human chromosomes in human x hamster somatic cell hybrids and simultaneously bands these same metaphases. Other methods generally require separate slides for banding and detection of human chromosome material, making the precise characterization of human material difficult. Our procedure involves denaturing metaphase chromosomes, followed by in situ hybridization of biotinylated whole human DNA. Fluoresceinated avidin is then bound to the biotinylated DNA, staining the human chromosomes yellow-green when excited with UV light. Chromosome banding is achieved by staining the slides with DAPI and actinomycin D. The fluorescein and DAPI excite maximally at 488 and 355 nm and emit at 520 and 450 nm, respectively. This permits identification of the human material at one excitation wavelength and visualization of the banding patterns at another wavelength. With this procedure, we have successfully identified both intact and broken human chromosomes, as well as human material involved in human x hamster translocations. The results indicate that this procedure is more accurate and considerably more rapid than previous methods and can be routinely employed for the cytogenetic analysis of human x rodent hybrids.

Genotoxicity of compounds from cooked beef in repair-deficient CHO cells versus Salmonella mutagenicity

A series of compounds isolated on the basis of their mutagenicity in the Ames/Salmonella reversion assay were previously identified in fried beef and chemically synthesized for further evaluation. In this study three of these compounds were tested for genotoxic effects in the UV5 line of Chinese hamster ovary (CHO) cells, which is deficient in nucleotide excision repair. Both 2-amino-3,4-dimethyl-imidazo]4,5-f]quinoline (MeIQ) and 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) gave very weak responses for cell killing, hprt mutation induction and sister chromatid exchange. These effects occurred at doses in the range of 100-800 micrograms/ml (approximately solubility limit), and dose-dependent increases were not observed. Induction of chromosomal aberrations did not occur with either compound. Nor did either of these compounds produce differential cytotoxicity in normal CHO cells versus UV5 cells, indicating that potentially repairable DNA damage was not responsible for the observed cell killing. In contrast to these results, 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP), which constitutes greater than 90% of the mass of bacterial mutagens in beef, was strongly positive for all endpoints at doses in the range 1-3 micrograms/ml. PhIP also gave marked differential cytotoxicity (ratio of 6) and cell survival curves that were strongly dependent on repair capacity. Because PhIP is 50- to 300-fold less mutagenic than MeIQ and MeIQx in Salmonella TA1538, these results point to major differences between the bacterial and mammalian assays in terms of the relative potency of these food-related compounds.

Influence of concomitant aspirin or prednisone on methotrexate synovial fluid concentration

Methotrexate (MTX) is currently being used in the treatment of patients with rheumatoid arthritis. The purpose of this study was to investigate the effect of two classes of drugs, steroids and salicylates, on MTX synovial fluid concentrations. A novel canine model of monoarticular inflammation was used, in which each animal served as its own control with both inflamed and normal knees in the same animal. After the 6-week immunization process, animals in each group received either no drug (control), prednisone or aspirin (low dose and high dose) for 1 week before MTX. On the day of the study, each animal was given i.v. MTX, and serial serum and synovial fluid samples were obtained. Laboratory, histologic and clinical observations supported the presence of monoarticular inflammation. The end-of-infusion synovial MTX concentration in inflamed knees was significantly greater than in normal knees (P less than .05), but, 2 hr after the end of infusion, they were not different. The end-of-infusion ratio of synovial fluid MTX concentration to serum MTX concentration (both total and unbound) was significantly lower in the prednisone group than in the other treatment groups (P less than .05). The end-of-infusion ratio of the MTX synovial concentration in the inflamed knee compared with the normal knee at 2 hr was significantly lower in the prednisone group than in the other three treatment groups (P less than .05). These results have therapeutic implications for the use of MTX in treating rheumatoid arthritis.

Effects of anticoagulants upon sister-chromatid exchanges, cell-cycle kinetics, and mitotic index in human peripheral lymphocytes

The effects of 3 blood anticoagulants, heparin, acid citrate dextrose (ACD), and ethylenediaminetetraacetic acid (EDTA) were investigated using human peripheral lymphocytes. Three different endpoints were examined: sister-chromatid exchange (SCE), cell kinetics index (CKI), and mitotic index (MI). SCEs were significantly increased in cells treated with EDTA, while the CKI and MI were significantly decreased in cultures treated with either ACD or EDTA when compared to cultures treated with heparin. These results suggest that anticoagulants may produce undesired effects upon cultured cells and indicate that the type of anticoagulant should be considered carefully prior to commencing cytogenetic studies using human peripheral lymphocytes.

Pharmacokinetics of anticancer drugs in children

Interpatient pharmacokinetic variability normally observed in adults is often of even greater magnitude in paediatric patients because of age-related maturation of physiological processes responsible for drug disposition. Several antineoplastic agents have shown age-related changes, including alterations in volume of distribution, hepatic (doxorubicin, cyclophosphamide), and renal (bleomycin, methotrexate) clearances. These differences in pharmacokinetics as a function of age alter systemic exposure to chemotherapy, and may alter the efficacy and toxicity profile for standard doses of antineoplastic drugs. The relationship of systemic exposure to toxicity has been most clearly defined for methotrexate. Clinical monitoring of methotrexate serum concentrations, and adjustment of folinic acid dosages and duration of rescue based on methotrexate disposition is now routine. More recently, pharmacodynamic data have been published for high-dose methotrexate, epipodophyllotoxins, cisplatin, and cytarabine (cytosine arabinoside), indicating a relation between drug disposition and toxicity or efficacy. Collectively, these data suggest that the pharmacokinetics of many anticancer drugs in children is different from adults, and that variability in drug disposition may have an important influence on toxicity or efficacy.

Enhanced lipid utilization in infants receiving oral L-carnitine during long-term parenteral nutrition

Fourteen infants requiring long-term total parenteral nutrition but able to tolerate small quantities of enteral feedings were randomized into carnitine treatment and placebo control groups. All infants had received nutritional support devoid of carnitine. Plasma carnitine levels and observed plasma lipid indices were not different before supplementation. Under standardized, steady-state conditions, 0.5 g/kg fat emulsion (intralipid) was administered intravenously over 2 hours both before and after infants received 7 days of continuous nasogastric or gastric tube L-carnitine (50 mumol/kg/day) or placebo. Plasma triglyceride, free fatty acid, acetoacetate, beta-hydroxybutyrate, and carnitine concentrations were observed at 0 (start of lipid infusion), 2, and 4 hours for pre- and post-treatment periods, and in addition at 6 and 8 hours after carnitine supplementation. Infants receiving carnitine had significantly greater beta-hydroxybutyrate plasma concentrations (P less than 0.05) and carnitine (P less than 0.001) at 0, 2, 4, 6, and 8 hours, and greater plasma acetoacetate concentrations (P less than 0.05) at 2, 4, 6, and 8 hours, compared with controls. Twenty-four-hour urinary carnitine excretion was very low for both groups before supplementation; after supplementation, excretion was higher (P less than 0.05) in the carnitine group. No significant differences were found between groups for plasma triglyceride or free fatty acid concentrations at any observation period. This study demonstrated enhanced fatty acid oxidation, as evidenced by increased ketogenesis, with L-carnitine supplementation in infants receiving long-term total parenteral nutrition.

Prevalence of Coxsackie B virus antibodies in patients with juvenile dermatomyositis

A number of viruses have been implicated as being the cause of various forms of myositis, including acute transient myositis, chronic polymyositis, and dermatomyositis. However, the cause of juvenile dermatomyositis (JDM) has remained elusive. Our study of serum samples taken within 4 months of the onset of disease in 12 children with JDM showed that 83% had detectable titers of complement-fixing (CF) antibody to 1 or more coxsackie B viral antigens. Detectable titers were found in only 25% of age-, sex-, and date-matched control sera taken from 24 patients with juvenile rheumatoid arthritis (JRA), and in 25% of serum samples taken from 2,192 "normal" children who had been hospitalized because of viral syndromes. Titers of CF antibody to coxsackie B1, B2, and B4 were positive in 58%, 50%, and 58%, respectively, of the JDM patients. In matched JRA controls, the respective values were 8%, 13%, and 8%. There were no significant antiviral titers and no significant differences in the results of tests for 13 other viral CF antigens, hepatitis B surface antigen, and Mycoplasma pneumoniae CF antigen in the JDM patient sera compared with the JRA patient sera. When titers of neutralizing antibody were determined, 58%, 58%, and 67% of the JDM patients were positive for coxsackie B2, B4, and B5, respectively, whereas 16%, 26%, and 21%, respectively, of the JRA controls were positive for the 3 antigens. These data suggest that the host response to coxsackie B virus might be related to the pathophysiology of JDM.

Retinol-binding protein and prealbumin: useful measures of protein repletion in critically ill, malnourished infants

Plasma prealbumin (PA) and retinol-binding protein (RBP) concentrations were serially measured in 25 critically ill, malnourished infants requiring parenteral nutrition to determine if these visceral protein markers are useful in assessing acute protein repletion. Significant increases in both proteins (p less than 0.05) were noted as early as 5 to 7 days after institution of parenteral nutrition and continued significantly above baseline values through 2 weeks of observation. Gestational development (in infants less than 4 weeks old) and mean protein intake influenced visceral protein responses. Appropriate for gestational age neonates had more rapid and quantitatively greater PA responses (p less than 0.05) than small for gestational age neonates. Small for gestational age neonates never exceeded baseline RBP responses. Average protein intake of less than or equal to 2 g/kg/day resulted in PA and RBP concentrations below baseline and significantly lower than infants on higher protein intakes (p less than 0.05), at the end of 2 weeks. Average calorie intake of greater than 100 cal/kg/day had no differential influence on PA or RBP when compared with infants on less calories. Prealbumin values correlated with RBP values observed simultaneously (r = 0.588, p less than 0.0001). We conclude that PA and RBP are useful measures of protein repletion in critically ill infants requiring parenteral nutrition.

Determination of the baseline sister chromatid exchange frequency in human and mouse peripheral lymphocytes using monoclonal antibodies and very low doses of bromodeoxyuridine

We measured the frequency of sister chromatid exchanges (SCEs) in human and mouse peripheral lymphocytes using doses of bromodeoxyuridine (BrdU) ranging from 30 nM to 100 microM (human) and from 10 nM to 10 microM (mouse). Heparinized peripheral blood was obtained from five healthy nonsmokers and from six C57B1/6 male mice. The blood was stimulated with PHA (human) or lipopolysaccharide (LPS, mouse) and grown for the first of two cell cycles in BrdU. Metaphase chromosomes were denatured and exposed to a monoclonal antibody reactive to single-stranded DNA containing BrdU. A second antibody was used to label the first antibody with fluorescein, and propidium iodide was used as a counterstain. Second-division metaphases were thus differentially stained red to indicate DNA content and yellow-green to indicate the presence of BrdU. The results indicate that the baseline SCE frequency in human and mouse peripheral lymphocytes is 3.6 and 2.4 SCEs per cell per generation, and that in the human these frequencies are invariant at the lowest BrdU levels. This suggests that SCEs are an integral part of DNA replication, even in the absence of agents known to induce SCEs. The distribution of SCEs per chromosome was analyzed and found to be Poisson-distributed in all 24 murine cultures and in 25 of 36 human cultures. The distribution of SCEs per chromosome may be due to either species-specific chromosome packaging or to karyotypic differences between the species.