Impact of 5 fluorouracil chemotherapy on gut inflammation, functional parameters, and gut microbiota.

Emerging evidence suggests that gut microbiota may influence the response to chemotherapy. We sought to characterize the effects of 5 fluorouracil (5FU) chemotherapy on colon inflammation and functional measures in colorectal cancer (CRC) and to further determine whether gut microbiota can influence this response. 50 C57BL/6 were randomized into four groups; Control + Vehicle (n = 10), Control + 5FU (n = 10), AOM/DSS + Vehicle (n = 15), and AOM/DSS + 5FU (n = 15). CRC was induced chemically by a single 10 mg/kg injection of azoxymethane (AOM) followed by two cycles (2% and 1%) of dextran sodium sulfate (DSS). Mice were then treated with 3 cycles of vehicle or 5FU (cycle 1: 40 mg/kg, cycle 2 + 3: 20 mg/kg). Functional tests (grip strength and run-to-fatigue) were performed prior to 5FU treatment (baseline) and at the completion of the second cycle of 5FU. Following the third 5FU cycle, mice were euthanized and the colon was evaluated for expression of inflammatory genes using RT-qPCR and stool samples were profiled using 16S rRNA sequencing. A second experiment used fecal microbiota transplantation from 5FU treated mice to control mice (n = 10-15/group) to determine whether 5FU associated changes in the microbiota could influence functional measures and colon inflammation. 5FU reduced grip strength (p < 0.05) and caused a trending decrease in run-to-fatigue performance in cancer mice (p = 0.06). Select intestinal inflammatory genes were significantly elevated with 5FU treatment and this was further exacerbated with cancer (p < 0.05). Microbiota analysis revealed increased dissimilarity and alterations in bacterial taxonomy in 5FU and AOM/DSS-treated mice (p < 0.05). Fecal transplant from 5FU treated mice reduced functional performance (p < 0.05) and altered select colon inflammatory markers (p < 0.05). This study provides evidence of an effect of 5FU on inflammatory responses and functional measures in a mouse model of CRC and suggests that gut microbes may play a role in some, but not all, 5FU related perturbations.

Susceptibility to HSV-1 infection and exercise stress in female mice: role of estrogen.

Exhaustive exercise has been associated with an increased risk for upper respiratory tract infections in mice and humans. We have previously shown (Brown AS, Davis JM, Murphy AE, Carmichael MD, Ghaffer A, Mayer EP. Med Sci Sports Exerc 36: 1290-1295, 2004) that female mice are better protected from the lethal effects of herpes simplex virus type 1 (HSV-1) infection, both at rest and following exercise stress, but little is known about possible mechanisms. This study tested the effects of estrogen on HSV-1 infection and macrophage antiviral resistance following repeated exhaustive exercise. Female mice were assigned to either exercise (Ex) or control (C): intact female (I-C or I-Ex), ovariectomized female (O-C or O-Ex), or ovariectomized estrogen-supplemented female (E-C or E-Ex). Exercise consisted of treadmill running to volitional fatigue ( approximately 125 min) for 3 consecutive days. Intact female mice had a later time to death than O and E (P < 0.05) and fewer deaths than both O and E (P < 0.05). Exercise stress was associated with increased time to sickness (P < 0.05) and symptom severity at days 6 and 12-21 postinfection (P < 0.05) and decreased macrophage antiviral resistance (P < 0.001) in all groups. E had increased symptom severity at days 6 and 13-21 postinfection (P < 0.05). Results indicate that intact female mice are better protected from the lethal effects of HSV-1 infection and that exercise stress had a similar negative impact in all groups. This protective effect was lost in ovariectomized mice, but it was not reinstated by 17beta-estradiol replacement. This indicates that other ovarian factors, alone or in combination with estrogen, are responsible for the protective effects in females.

PGC-1α4 gene expression is suppressed by the IL-6-MEK-ERK 1/2 MAPK signalling axis and altered by resistance exercise, obesity and muscle injury.

AIM: PGC-1α4 is a novel regulator of muscle hypertrophy; however, there is limited understanding of the regulation of its expression and role in many (patho)physiological conditions. Therefore, our purpose was to elicit signalling mechanisms regulating gene expression of Pgc1α4 and examine its response to (patho)physiological stimuli associated with altered muscle mass. METHODS: IL-6 knockout mice and pharmacological experiments in C2C12 myocytes were used to identify regulation of Pgc1α4 transcription. To examine Pgc1α4 gene expression in (patho)physiological conditions, obese and lean Zucker rats with/without resistance exercise (RE), ageing mice and muscle regeneration from injury were examined. RESULTS: In IL-6 knockout mice, Pgc1α4mRNA was ~sevenfold greater than wild type. In C2C12 cells, Pgc1α4mRNA was suppressed ~70% by IL-6. Suppression of Pgc1α4 by IL-6 was prevented by MEK-ERK-MAPK inhibition. RE led to ~260% greater Pgc1α4mRNA content in lean rats. However, obese Zucker rats exhibited ~270% greater Pgc1α4mRNA than lean, sedentary with no further augmentation by RE. No difference was seen in IL-6mRNA or ERK-MAPK phosphorylation in Zucker rats. Aged mice demonstrated ~50% lower Pgc1α4mRNA and ~fivefold greater ERK-MAPK phosphorylation than young despite unchanged Il-6mRNA. During muscle regeneration, Pgc1α4 content is ~30% and IL-6mRNA >threefold of uninjured controls 3 days following injury; at 5 days, Pgc1α4 was >twofold greater in injured mice with no difference in IL-6mRNA. CONCLUSION: Our findings reveal a novel mechanism suppressing Pgc1α4 gene expression via IL-6-ERK-MAPK and suggest this signalling axis may inhibit Pgc1α4 in some, but not all, (patho)physiological conditions.

Estrogen status and skeletal muscle recovery from disuse atrophy.

Although estrogen loss can alter skeletal muscle recovery from disuse, the specific components of muscle regrowth that are estrogen sensitive have not been described. The primary purpose of this study was to determine the components of skeletal muscle mass recovery that are biological targets of estrogen. Intact, ovariectomized (OVX), and ovariectomized with 17beta-estradiol replacement (OVX+E2) female rats were subjected to hindlimb suspension for 10 days and then returned to normal cage ambulation for the duration of recovery. Soleus muscle mass returned to control levels by day 7 of recovery in the intact animals, whereas OVX soleus mass did not recover until day 14. Intact rats recovered soleus mean myofiber cross-sectional area (CSA) by day 14 of recovery, whereas the OVX soleus remained decreased (42%) at day 14. OVX mean fiber CSA did return to control levels by day 28 of recovery. The OVX+E2 treatment group recovered mean CSA at day 14, as in the intact animals. Myofibers demonstrating central nuclei were increased at day 14 in the OVX group, but not in intact or OVX+E2 animals. The percent noncontractile tissue was also increased 29% in OVX muscle at day 14, but not in either intact or OVX+E2 groups. In addition, collagen 1a mRNA was increased 45% in OVX muscle at day 14 of recovery. These results suggest that myofiber growth, myofiber regeneration, and extracellular matrix remodeling are estrogen-sensitive components of soleus muscle mass recovery from disuse atrophy.

Time course of hypertrophic adaptations of the anterior latissimus dorsi muscle to stretch overload in aged Japanese quail.

The purpose of this study was to determine if aged Japanese quail demonstrated an altered time course of change in the morphology of the anterior latissimus dorsi (ALD) muscle during the first two weeks of hypertrophy induced by stretch overload. The left wing of adult (12 weeks of age) and aged (90 weeks of age) birds were weighted with 10% of their body weight; the right wing served as the intra-animal control. Thirteen to sixteen birds from each age group were killed after 7 and 14 days of stretch overload. Total fiber number was quantified by counting all the fibers in a transverse section from the mid-belly of the ALD muscle. The aged ALD retained the ability to increase the mass and total fiber number of the stretched ALD after 7 (82%, 16%) and 14 (102%, 19%) days of stretch overload. However, there was a main effect of age on the capacity to increase muscle mass and total fiber number after stretch overload. These results suggest that aging diminishes the increase and alters the time course of adaptation in fiber number and myofibrillar mass of the stretch overloaded ALD during the first two weeks of stretch overload.

Serum response factor mRNA induction in the hypertrophying chicken patagialis muscle.

Gene expression in the stretched chicken patagialis (Pat) muscle has not been extensively examined. This study's purpose was to determine the Pat muscle's expression pattern of serum response factor (SRF), skeletal alpha-actin, and MyoD mRNAs after 3 days (onset of stretch), 6 days (end of first week of rapid growth), and 14 days (slowed rate of stretch-induced growth) of stretch. SRF mRNA demonstrated two species (B1 and B2), with B2 being more prevalent in the predominantly fast-twitch Pat muscle, compared with the slow-tonic muscle. Stretch overload increased B1 and B2 SRF mRNA concentrations, and the increase in B1 SRF mRNA concentration was greater at day 6 compared with days 3 or 14. MyoD mRNA concentration was greater in 3-day-stretched Pat muscles, compared with days 6 or 14. Skeletal alpha-actin mRNA concentration was not changed during the study. Gel mobility shift assays demonstrated that SRF binding with serum response element 1 of the skeletal alpha-actin promoter had no altered binding patterns from 6-day-stretched Pat nuclear extracts. It appears that SRF and MyoD mRNAs are induced in the stretch-overloaded Pat muscle but at different time points.

Integrin signaling's potential for mediating gene expression in hypertrophying skeletal muscle.

Overloaded skeletal muscle undergoes dramatic shifts in gene expression, which alter both the phenotype and mass. Molecular biology techniques employing both in vivo and in vitro hypertrophy models have demonstrated that mechanical forces can alter skeletal muscle gene regulation. This review's purpose is to support integrin-mediated signaling as a candidate for mechanical load-induced hypertrophy. Research quantifying components of the integrin-signaling pathway in overloaded skeletal muscle have been integrated with knowledge regarding integrins role during development and cardiac hypertrophy, with the hope of demonstrating the pathway's importance. The role of integrin signaling as an integrator of mechanical forces and growth factor signaling during hypertrophy is discussed. Specific components of integrin signaling, including focal adhesion kinase and low-molecular-weight GTPase Rho are mentioned as downstream targets of this signaling pathway. There is a need for additional mechanistic studies capable of providing a stronger linkage between integrin-mediated signaling and skeletal muscle hypertrophy; however, there appears to be abundant justification for this type of research.

Hypertrophy and proliferation of skeletal muscle fibers from aged quail.

The purpose of this study was to determined whether fibers in the anterior latissimus dorsi (ALD) muscle from aged Japanese quail have decreased hypertrophic or proliferative responses to 30 days of stretch overload compared with fibers from adult birds. Two groups of quail were studied, 12-wk-old quail (adult; n = 16) and 90-wk-old quail (aged; n = 16). The left wing of each bird was overloaded with a weight corresponding to 10% of the bird's body weight, and the right wing served as the intra-animal control. Quails were killed after 30 days of stretch overload. Total fiber number was quantified by counting all the fibers in a transverse section from the midbelly of the ALD muscle. ALD muscles in aged quails retained the capacity to increase their muscle mass (145%), total fiber number (49%), and fiber cross-sectional area (54%) in response to stretch overload. The ALD muscle in aged quail had a significantly lower increase in muscle mass (33%) and mass corrected for nonmuscle tissue (36%) compared with the ALD from young adult birds. Age had no effect on fiber type distribution shifts with stretch. These results suggest that although muscles in old birds have a substantial ability to adapt to enlarge, stretch-induced hypertrophy is attenuated in muscles from old quail.

SRF protein is upregulated during stretch-induced hypertrophy of rooster ALD muscle.

Serum response element 1 has previously been reported to be necessary and sufficient for activation of the skeletal alpha-actin promoter during hypertrophy of the anterior latissimus dorsi (ALD) muscle of roosters [J. A. Carson, R. J. Schwartz, and F. W. Booth. Am. J. Physiol. 270 (Cell Physiol. 39): C1624-C1633, 1996]. Serum response factor (SRF) protein is the transcription factor that binds as a homodimer to serum response element 1 and activates the skeletal alpha-actin promoter. An increased expression of exogenous SRF protein in replicating C2C12 myoblasts induced a three- to fourfold activation of the skeletal alpha-actin promoter (L. Wei, W. Zhou, J. D. Croissant, F.-E. Johansen, R. Prywes, A. Balasubramamyan, and R. J. Schwartz. J. Biol. Chem. 273: 30287-30294, 1998). Thus we hypothesized that SRF protein concentration would be increased during hypertrophy of skeletal muscle. In the present study, 10% of the rooster's body weight was attached to the left wing to induce enlargement of the ALD muscle compared with the contralateral muscle. With Western analysis, a significant increase in SRF protein per gram of wet weight of the ALD muscle was noted at 7 and 13 days of hypertrophy. Furthermore, the increase in SRF protein occurred in both crude nuclear protein and cytoplasmic fractions in 7-day stretched ALD muscles. This is the first report showing increased protein concentration for a transcription factor whose regulatory element in the skeletal alpha-actin promoter has previously been shown to be required for the transduction of a hypertrophy signal in overloaded skeletal muscle of an animal.

RhoA expression during recovery from skeletal muscle disuse.

Functional overload and anabolic steroid administration induce signaling pathways that regulate skeletal muscle RhoA expression. The purpose of this study was to determine RhoA and associated protein expression at the onset of disuse and after a brief period of reloading. Male Sprague-Dawley rats were randomly assigned to cage control (Con), 3 days of hindlimb suspension (Sus), or 3 days of hindlimb suspension with 12 h of reloading (12-h Reload). The reloading stimuli consisted of 12 h of resumed normal locomotion after 3 days of hindlimb suspension. Plantaris muscle-to-body weight (mg/g) ratio decreased 17% from Con with Sus but returned to Con with 12-h Reload, increasing 13% from Sus. Sus decreased RhoA protein concentration 46%, whereas 12-h Reload induced a 24% increase compared with Sus. The ratio of cytosolic- to membrane-associated RhoA protein was not changed with either Sus or 12-h Reload. RhoA mRNA concentration was decreased 48% by Sus, and 12-h Reload induced a 170% increase from Sus. beta(1)-Integrin protein, a transmembrane protein associated with RhoA activation, was not altered by Sus but increased 155% with 12-h Reload. Although beta(1)-integrin mRNA was not altered by Sus, it increased 70% from Con with 12-h Reload. Rho family member Cdc42 protein associated with the muscle membrane was decreased 60% with Sus, and 12-h Reload induced a 172% increase compared with Sus. In conclusion, decreased RhoA protein expression and mRNA abundance are early adaptations to disuse but recover rapidly after normal locomotion is resumed.

Myogenic regulatory factors during regeneration of skeletal muscle in young, adult, and old rats.

Myogenic factor mRNA expression was examined during muscle regeneration after bupivacaine injection in Fischer 344/Brown Norway F1 rats aged 3, 18, and 31 mo of age (young, adult, and old, respectively). Mass of the tibialis anterior muscle in the young rats had recovered to control values by 21 days postbupivacaine injection but in adult and old rats remained 40% less than that of contralateral controls at 21 and 28 days of recovery. During muscle regeneration, myogenin mRNA was significantly increased in muscles of young, adult, and old rats 5 days after bupivacaine injection. Subsequently, myogenin mRNA levels in young rat muscle decreased to postinjection control values by day 21 but did not return to control values in 28-day regenerating muscles of adult and old rats. The expression of MyoD mRNA was also increased in muscles at day 5 of regeneration in young, adult, and old rats, decreased to control levels by day 14 in young and adult rats, and remained elevated in the old rats for 28 days. In summary, either a diminished ability to downregulate myogenin and MyoD mRNAs in regenerating muscle occurs in old rat muscles, or the continuing myogenic effort includes elevated expression of these mRNAs.

Carbohydrate ingestion influences skeletal muscle cytokine mRNA and plasma cytokine levels after a 3-h run.

Sixteen experienced marathoners ran on treadmills for 3 h at approximately 70% maximal oxygen consumption (Vo(2 max)) on two occasions while receiving 1 l/h carbohydrate (CHO) or placebo (Pla) beverages. Blood and vastus lateralis muscle biopsy samples were collected before and after exercise. Plasma was analyzed for IL-6, IL-10, IL-1 receptor agonist (IL-1ra), IL-8, cortisol, glucose, and insulin. Muscle was analyzed for glycogen content and relative gene expression of 13 cytokines by using real-time quantitative RT-PCR. Plasma glucose and insulin were higher, and cortisol, IL-6, IL-10, and IL-1ra, but not IL-8, were significantly lower postexercise in CHO vs. Pla. Change in muscle glycogen content did not differ between CHO and Pla (P = 0.246). Muscle cytokine mRNA content was detected preexercise for seven cytokines in this order (highest to lowest): IL-15, TNF-alpha, IL-8, IL-1beta, IL-12p35, IL-6, and IFN-gamma. After subjects ran for 3 h, gene expression above prerun levels was measured for five of these cytokines: IL-1beta, IL-6, and IL-8 (large increases), and IL-10 and TNF-alpha (small increases). The increase in mRNA (fold difference from preexercise) was attenuated in CHO (15.9-fold) compared with Pla (35.2-fold) for IL-6 (P = 0.071) and IL-8 (CHO, 7.8-fold; Pla, 23.3-fold; P = 0.063). CHO compared with Pla beverage ingestion attenuates the increase in plasma IL-6, IL-10, and IL-1ra and gene expression for IL-6 and IL-8 in athletes running 3 h at 70% Vo(2 max) despite no differences in muscle glycogen content.

Pediatric gastroesophageal reflux: age-specific indications for operation.

Pediatric gastroesophageal reflux is common and its complications may be serious. The diagnosis is being suspected and confirmed with increasing frequency in children because of heightened awareness of the symptoms peculiar to pediatric patients. Thirty-one children who underwent Nissen fundoplication for gastroesophageal reflux are reviewed. Diagnosis was obtained by barium meal, isotope scanning, esophagoscopy and pH monitoring. Failure to thrive, recurrent pneumonia, apnea, feeding difficulty and esophageal stricture unresponsive to medical management were the indications for operation. Children with brain damage or previous repair of esophageal atresia are at high risk for gastroesophageal reflux and its complications. A protective fundoplication is a desirable adjunct to feeding gastrostomy in brain-damaged children. Fundoplication eliminated reflux in 30 of 31 patients, relieved symptoms in 28 and improved symptoms in 2. Nissen fundoplication is a safe and effective surgical procedure for correction of gastroesophageal reflux in children.

Elective surgery without transfusion: influence of preoperative hemoglobin level and blood loss on mortality.

To clarify the widespread practice of preoperative transfusion to attain a 10 g/dL level of hemoglobin, the relationship between preoperative hemoglobin level, operative blood loss, and mortality was studied by analyzing the results of 113 operations in 107 consecutive Jehovah's Witness patients who underwent major elective surgery. Ninety-three patients had preoperative hemoglobin values greater than 10 g/dL; 20 had preoperative hemoglobin levels between 6 to 10 g/dL. Mortality for preoperative hemoglobin levels greater than 10 g/dL was 3 of 93 (3.2%); for preoperative hemoglobin levels between 6 to 10 g/dL, mortality was 1 of 20 (5%). Mortality was significantly increased with an estimated blood loss of greater than 500 mL, regardless of the preoperative hemoglobin level (p less than 0.025). More importantly, there was no mortality if estimated blood loss was less than 500 mL, regardless of the preoperative hemoglobin level. From these data, we conclude that: (1) Mortality in elective surgery appears to depend more on estimated blood loss than on preoperative hemoglobin levels; and (2) Elective surgery can be done safely in patients with a preoperative hemoglobin level as low as 6 g/dL if estimated blood loss is kept below 500 mL.

Taste acuity and food attitudes of selected patients with cancer.

Patients with cancer may display taste abnormalities. In this study, abnormalities observed before treatment involved decreased salt and sweet sensitivity. For some thresholds, greater abnormalities were observed among men and women, among patients with colon cancer than among those with breast cancer, and among those with a greater extent of disease. Observations of slight increases in thresholds for sour detection and bitter recognition during the early treatment period and normalization of high sweet recognition thresholds after two weeks of treatment suggest that additional changes in taste acuity may accompany short-term treatment with 5'fluorouracil. However, absence of a correlation of taste changes with changes in food preferences points to the role of other factors in determining patients' food preferences during such treatment. Consideration of the incidence of taste abnormalities in these groups of patients with cancer and observation of altered food attitudes among patients receiving 5-fluorouracil does provide a basis for general recommendations for serving foods which will appeal to these patients.

The neprilysin family in health and disease.

The mammalian neprilysin (NEP) family comprises at least seven members: NEP itself, Kell blood group antigen (KELL), the endothelin-converting enzymes (ECE-1 and ECE-2), the enzyme PEX, associated with X-linked hypophosphataemia, "X-converting enzyme" (XCE) a CNS-expressed orphan peptidase and a soluble, secreted endopeptidase (SEP). These zinc metallopeptidases are all type II integral membrane proteins. Where identified, these enzymes have roles in the processing or metabolism of regulatory peptides and therefore represent potential therapeutic targets. A distinct feature of ECE-1 species is their existence as distinct isoforms differing in their N-terminal cytoplasmic tails. These tails play a role in enzyme targeting and turnover with di-leucine and tyrosine-based motifs affecting localization. Additional anchorage of these enzymes can also occur through palmitoylation. Bacterial homologues of the neprilysin family exist, for example the products of the pepO genes from L. lactis and S. parasanguis, and a recently described gene product of P. gingivalis which is an ECE-1 homologue that can catalyse the conversion of big endothelin to endothelin. A genomics based approach to understanding the functions of this proteinase family is aided by the completion of the C. elegans and Drosophila genomes, both of which encode multiple copies of NEP-like enzymes.

Hepatoportal sclerosis in childhood: a mimic of extrahepatic portal vein obstruction.

In the absence of cirrhosis, most children with portal hypertension and bleeding esophageal varices have extrahepatic portal vein occlusion. In the past 2 yr this clinical picture has been mimicked by two children with hepatoportal sclerosis causing their variceal hemorrhage. Hepatoportal sclerosis has been well described in adults. It is manifested by splenomegaly, portal hypertension, and variable ascites and hepatomegaly. Liver histology is initially normal but subsequently shows periportal fibrosis without cirrhosis. Hepatic manometrics indicate a presinusoidal block, but angiography demonstrates a patient portal vein. Typically there is abrupt narrowing of the intrahepatic portal branches, giving a "withered tree" appearance. These findings are illustrated by two children who presented with esophageal variceal bleeding at 21 and 20 mo of age, respectively. They are the youngest reported cases of hepatoportal sclerosis. The etiology of hepatoportal sclerosis is uncertain, but the disease appears to be only slowly progressive. Control of variceal bleeding by central portosystemic shunts in this condition is associated with a 50% incidence of hepatic encephalopathy. Therefore alternate methods of therapy need be considered. Endoscopic injection sclerotherapy successfully controlled variceal bleeding in one child reported here. Hepatoportal sclerosis is a distinct entity and must be considered in the differential diagnosis of portal hypertension in infants and children.

Familial congenital diaphragmatic hernia is an autosomal recessive variant.

Forty families that have had more than one sibling with a congenital diaphragmatic hernia have been identified. The 85 children among the 40 families describe a subset of congenital diaphragmatic hernia displaying an autosomal recessive inheritance mode. The chance of a diaphragmatic hernia among siblings within this subset is 25%.

Imperforate anus: the neurologic implication of sacral abnormalities.

The association of imperforate anus with bony sacral abnormalities and neurologic deficits is well recognized. These neurologic deficits have been considered static rather than progressive. However, recent experience indicates that some patients may develop progressive neurologic problems due to spinal cord lesions that are amenable to neurosurgical correction. To investigate the frequency of such lesions, routine myelography of imperforate anus patients with sacral anomalies was undertaken. The extraordinarily high incidence of unsuspected lesions known to cause progressive bowel, bladder, and musculoskeletal dysfunction is the basis of this interim report. Thirty percent of patients with anorectal abnormalities had sacral dysplasia. Of the nine patients undergoing myelography to date, eight have been abnormal. Six children had a tethered spinal cord, one had narrowing of the bony spinal canal and dural sac stenosis, and one an anterior meningocele. Spinal cord conditions that may cause deterioration of bowel, bladder, and extremity function should be defined and corrected before irreversible damage occurs. Because of the high incidence of spinal cord lesions detected in these patients with coexisting anorectal and sacral anomalies, routine screening for spinal cord lesions is recommended.

The accuracy of abbreviated esophageal pH monitoring in children.

Extended (18 to 24 hour) esophageal pH monitoring establishes the diagnosis of gastroesophageal reflux (GER) utilizing a pH score, and relates respiratory symptoms to GER when the mean duration of sleep reflux (ZMD) is prolonged. A disadvantage of this method is the expense of overnight hospitalization. We performed extended esophageal pH recordings in 66 consecutive children (1 week to 15 years old) being evaluated for GER. Six portions of the 18- to 24-hour esophageal pH recording were compared to the complete record in an attempt to define the relative accuracy of abbreviated monitoring periods. The abbreviated monitoring periods included the 30 minutes after apple juice feedings (30 minutes AJ), the 2 hours after apple juice feedings (2 hours PC AJ), the 2 hours after milk-formula feedings (2 hours PC MF), the 8 hours with two feedings of apple juice (8 hours AJ), the 8 hours with two feedings of milk formula (8 hours MF), and the first 12 hours of recording (1st 12 hours). The accuracy relative to the 18- to 24-hour recording was poor for 30 minutes AJ, 2 hours PC AJ, and 2 hours PC MF periods (30% to 58%). An improved accuracy occurred during 8-hour AJ periods (29/31, 94%) in children without respiratory symptoms. Although the accuracy in patients with respiratory symptoms was best during 8-hour MF (31/35, 89%) and 1st 12-hour (33/35, 94%) periods, a high false-negative rate for the ZMD (31% to 41%) during abbreviated pH monitoring indicates that many patients with reflux-induced respiratory symptoms will be unrecognized.(ABSTRACT TRUNCATED AT 250 WORDS)