Abstract P5-04-04: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Das GM, Kulkarni S, Oturkar C, Edge SB, Wilton JH, Wang J, Swetzig WM, Adjei AA, Bies R, Hutson AD, Morrison CD, Kaipparettu BA, Groman A, Kumar S, Capuccino H. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-04-04.

Does gastric bypass surgery change body weight set point?

The relatively stable body weight during adulthood is attributed to a homeostatic regulatory mechanism residing in the brain which uses feedback from the body to control energy intake and expenditure. This mechanism guarantees that if perturbed up or down by design, body weight will return to pre-perturbation levels, defined as the defended level or set point. The fact that weight re-gain is common after dieting suggests that obese subjects defend a higher level of body weight. Thus, the set point for body weight is flexible and likely determined by the complex interaction of genetic, epigenetic and environmental factors. Unlike dieting, bariatric surgery does a much better job in producing sustained suppression of food intake and body weight, and an intensive search for the underlying mechanisms has started. Although one explanation for this lasting effect of particularly Roux-en-Y gastric bypass surgery (RYGB) is simple physical restriction due to the invasive surgery, a more exciting explanation is that the surgery physiologically reprograms the body weight defense mechanism. In this non-systematic review, we present behavioral evidence from our own and other studies that defended body weight is lowered after RYGB and sleeve gastrectomy. After these surgeries, rodents return to their preferred lower body weight if over- or underfed for a period of time, and the ability to drastically increase food intake during the anabolic phase strongly argues against the physical restriction hypothesis. However, the underlying mechanisms remain obscure. Although the mechanism involves central leptin and melanocortin signaling pathways, other peripheral signals such as gut hormones and their neural effector pathways likely contribute. Future research using both targeted and non-targeted 'omics' techniques in both humans and rodents as well as modern, genetically targeted, neuronal manipulation techniques in rodents will be necessary.

Association of fatty-acid synthase polymorphisms and expression with outcomes after radical prostatectomy

BACKGROUND

Fatty-acid synthase (FASN), selectively overexpressed in prostate cancer (PCa) cells, has been described as linked to the aggressiveness of PCa. Constitutional genetic variation of the FASN gene and the expression levels of FASN protein in cancer cells could thus be expected to predict outcome after radical prostatectomy (RP). This study evaluates the associations of malignant tissue status, neoadjuvant androgen deprivation therapy (NADT) and single-nucleotide polymorphisms (SNPs) of FASN with FASN protein expression in prostate tissue. The study then examines the associations of FASN SNPs and gene expression with three measures of post-prostatectomy outcome.

METHODS

Seven tagging FASN SNPs were genotyped in 659 European American men who underwent RP at Roswell Park Cancer Institute between 1993 and 2005. FASN protein expression was assessed using immunohistochemistry. The patients were followed for an average of 6.9 years (range: 0.1-20.6 years). Outcome was assessed using three end points: biochemical failure, treatment failure and development of distant metastatic PCa. Cox proportional hazards analyses were used to evaluate the associations of the tagging SNPs and FASN expression with these end points. Bivariate associations with outcomes were considered; the associations also were controlled for known aggressiveness indicators.

RESULTS

Overall, no SNPs were associated with any known aggressiveness indicators. FASN staining intensity was stronger in malignant than in benign tissue, and NADT was associated with decreased FASN staining in both benign and malignant tissue. The relationships of FASN SNPs and staining intensity with outcome were less clear. One SNP, rs4246444, showed a weak association with outcome. FASN staining intensity also showed a weak and seemingly contradictory relationship with outcome.

CONCLUSIONS

Additional study with longer follow-up and populations that include more metastatic patients is warranted.

In vivo effects of dietary quercetin and quercetin-rich red onion extract on skeletal muscle mitochondria, metabolism, and insulin sensitivity

Red onions and low doses of the flavonoid, quercetin, increase insulin sensitivity and improve glucose tolerance. We hypothesized that dietary supplementation with red onion extract (RO) would attenuate high fat diet (HFD)-induced obesity and insulin resistance similar to quercetin supplementation by increasing energy expenditure through a mechanism involving skeletal muscle mitochondrial adaptations. To test this hypothesis, C57BL/6J mice were randomized into four groups and fed either a low fat diet (LF), HFD (HF), HFD + quercetin (HF + Q), or HFD + RO (HF + RO) for 9 weeks. Food consumption and body weight and composition were measured weekly. Insulin sensitivity was assessed by insulin and glucose tolerance tests. Energy expenditure and physical activity were measured by indirect calorimetry. Skeletal muscle incomplete beta oxidation, mitochondrial number, and mtDNA-encoded gene expression were measured. Quercetin and RO supplementation decreased HFD-induced fat mass accumulation and insulin resistance (measured by insulin tolerance test) and increased energy expenditure; however, only HF + Q showed an increase in physical activity levels. Although quercetin and RO similarly increased skeletal muscle mitochondrial number and decreased incomplete beta oxidation, establishing mitochondrial function similar to that seen in LF, only HF + Q exhibited consistently lower mRNA levels of mtDNA-encoded genes necessary for complexes IV and V compared to LF. Quercetin- and RO-induced improvements in adiposity, insulin resistance, and energy expenditure occur through differential mechanisms, with quercetin-but not RO-induced energy expenditure being related to increases in physical activity. While both treatments improved skeletal muscle mitochondrial number and function, mtDNA-encoded transcript levels suggest that the antiobesogenic, insulin-sensitizing effects of purified quercetin aglycone, and RO may occur through differential mechanisms.

PTPN14 interacts with and negatively regulates the oncogenic function of YAP

The Hippo signaling pathway regulates cellular proliferation and survival, thus exerting profound effects on normal cell fate and tumorigenesis. The pivotal effector of this pathway is YAP, a transcriptional co-activator amplified in mouse and human cancers where it promotes epithelial-to-mesenchymal transition and malignant transformation. Here, we report a novel regulatory mechanism for the YAP oncogenic function via direct interaction with non-receptor tyrosine phosphatase 14 (PTPN14) through the WW domain of YAP and the PPxY domain of PTPN14. We also found that YAP is a direct substrate of PTPN14. In addition, luciferase reporter assay showed that the inhibition of the YAP transcriptional co-activator function by PTPN14 is mediated through their protein interactions and may result from an increase in the inactive cytoplasmic form of YAP. Last, knockdown of PTPN14 induces the nuclear retention of YAP and increases the YAP-dependent cell migration. In summary, our results indicate a potential regulatory role of PTPN14 on YAP and demonstrate a novel mechanism in YAP regulation.

OT1-03-03: Effect of Tamoxifen Therapy on Inhibition of Tumor Suppressor p53 by Estrogen Receptor

Background: A large number of patients with estrogen receptor (ER)-positive tumors are resistant to tamoxifen (TAM). Although several plausible reasons for such resistance have been suggested, the mechanisms remain unclear. ER mediates effects of estrogen by promoting proliferation of breast cancer cells. Tumor suppressor protein p53 guards against tumorigenesis by preventing proliferation of cells with genomic damage. Dr. Das's laboratory previously reported that ER binds and functionally suppresses wild type p53 in human breast cancer cells and xenograft tumor tissue, and TAM is capable of inhibiting this interaction. We hypothesize that relieving suppression of wild type p53 by ER could be an important mechanism underlying TAM action in breast cancer. To test this hypothesis, we have initiated a pilot randomized clinical trial of 50 women with newly diagnosed ERa-positive breast cancer.

Specific Aims: 1) To investigate the effect of a short pre-surgical intervention with TAM on the ER-p53 interaction in ER-positive, p53 wild type breast tumors and 2) To confirm the wild type status of p53 and analyze the functional status of the p53 pathway by monitoring expression of selected p53 target genes in tumors that have and have not been treated with TAM.

Trial design: A randomized clinical trial in the pre-surgical setting was proposed with either TAM 20mg for four weeks vs. no intervention. Patients randomized to the TAM arm will undergo multiple pharmacokinetic and phamacodynamic measurements of TAM metabolites and genotyping for common polymorphisms of TAM metabolism genes, CYP2D6 and CYP3A4/5. Fresh tumor tissue will be harvested from all patients at the time of surgery for analysis of ER-p53 protein interaction using tissue chromatin immunoprecipitation (tissue ChIP) assay. p53 gene status will be determined by sequencing. RNA and protein expression of ER, p53, and a selected group of ER and p53 target genes in the diagnostic core biopsy and surgical specimens will be analyzed by quantitative real-time PCR (qRTPCR) and immunohistochemistry (IHC). TAM metabolites will also be measured in the tumor and the surrounding benign tissue.

Eligibility criteria: Women greater or equal to eighteen years of age diagnosed with ER-positive invasive breast cancer (approximately 1cm in size) who will undergo primary surgical excision for their initial therapy are eligible. Women must not be pregnant, be on current hormonal therapy, or have a history of hypercoagulable syndrome or prior arterial or venous thrombosis.

Statistical methods: Descriptive statistics such as frequencies and relative frequencies will be computed for all categorical variables. Numeric variables will be summarized using simple descriptive statistics such as mean, standard deviation, and quartiles. Ninety-five percent confidence intervals will be computed. ChIP data will be subjected to Fisher's Exact Test. IHC date will be analyzed by Wilcoxon-Mann-Whitney test.

Present accrual and target accrual: We have accrued 17 patients to date and plan to accrue a total of 50 patients, 25 in each arm.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT1-03-03.

Correlation between patient weight and defects in DNA mismatch repair: is this the link between an increased risk of previous cancer in thinner women with endometrial cancer?

The objective is to determine the relationship between obesity and defects in DNA mismatch repair (MMR) in women with endometrial cancer and to establish whether our previous finding of a higher rate of previous malignancy in thinner women with endometrial cancer is related to these factors. Specimens from 109 patients with primary uterine cancer were used to create a tissue microarray, which was stained with antibodies against MMR genes MLH1, MSH2, MSH6, and PMS2. Genotyping of normal and tumor tissues for microsatellite instability (MSI) was performed. Patients were stratified by body mass index (BMI) and correlated with a history of previous malignancy and defects in MMR. The average BMI of the overall population was 33 kg/m(2). Defective MMR was seen in 22% of tumors. The mean BMI in patients with tumors with MSI was 30.5, compared with 33.8 in microsatellite stable (MSS) tumors (P= 0.06); MSS tumors were more commonly seen in patients with a BMI more than 40 (25% vs 5% in patients with tumors with MSI, P= 0.07). Prior to their diagnosis of endometrial cancer, 16/109 (15%) patients reported having a prior malignancy, 11 (69%) had breast cancer, and 1 had colorectal cancer. Patients with tumors with MSI had previous cancer in 17% of cases, compared with 14% of patients with MSS tumors (P= 0.75). Our previous finding of an increased rate of prior malignancy in thinner patients with endometrial cancer does not appear to be due to alterations in MMR, and hereditary nonpolyposis colorectal cancer-associated cancers are rarely the prior malignancy.

Endocrine responses in mares undergoing abrupt changes in nutritional management

Leptin, a protein hormone secreted by adipocytes, plays an important role in energy homeostasis and regulation of body composition. We previously observed that acute feed restriction resulted in a rapid decline in concentrations of leptin in obese pony mares. This acute response prompted us to characterize the temporal changes in concentrations of leptin, GH, and insulin in obese pony mares during the transition between fed and feed-restricted conditions. Nine obese pony mares of mixed breed, previously maintained on fescue pasture, were randomly allotted to 2 groups. Treatments consisted of a 48-h feed restriction, a 48-h refeeding, and a 24-h feed restriction (RFR; n = 4), or 48 h of alfalfa hay ad libitum, a 48-h feed restriction, and a 24-h refeeding (FRF; n = 5). Blood samples were taken every 15 min during restriction and feeding transitions (0600 to 1400 on d 2 and 4), and every 30 min thereafter until 0830 of the following days (d 3 and 5). In the FRF treatment, plasma concentrations of leptin declined precipitously 6 h after the removal of feed (sample by treatment interaction; P < 0.01), and remained low and unresponsive to refeeding. Similarly, in the RFR group, plasma concentrations of leptin were initially low, and did not respond to feeding during the second (refeeding) sampling period. After feed restriction in each of the 2 treatment sequences, plasma insulin decreased and GH mean concentration, pulse frequency, pulse amplitude, and area under the curve increased (P < 0.05). Refeeding reversed these effects on insulin and GH. These data provide evidence that peripheral concentrations of insulin and GH are dynamically responsive to feed removal (decrease in insulin; increase in GH) and replacement (increase in insulin; decrease in GH), whereas leptin decreases in response to feed restriction but is slow to recover from a transient nutritional insult.

Effects of short-term feed deprivation and melatonin implants on circadian patterns of leptin in the horse1

Leptin is a protein hormone produced by adipose tissue that influences hypothalamic mechanisms regulating appetite and energy balance. In species tested thus far, including horses, concentrations of leptin increase as animal fat mass increases. The variables and mechanisms that influence the secretion of leptin are not well known, nor is it known in equine species how the secretion of leptin is influenced by acute alterations in energy balance, circadian patterns, and/or reproductive competence. Our objectives were to determine in horses: 1) whether plasma concentrations of leptin are secreted in a circadian and/or a pulsatile pattern; 2) whether a 48-h period of feed restriction would alter plasma concentrations of leptin, growth hormone, or insulin; and 3) whether ovariectomy and/or a melatonin implant would affect leptin. In Exp. 1, mares exposed to ambient photoperiod of visible light (11 h, 33 min to 11 h, 38 min), received treatments consisting of a 48-h feed restriction (RES) or 48 h of alfalfa hay fed ad libitum (FED). Mares were maintained in a dry lot before sampling and were tethered to a rail during sampling. Analyses revealed that leptin was not secreted in a pulsatile manner, and that mean leptin concentrations were greater (P < 0.001) in FED vs. RES mares (17.20 +/- 0.41 vs. 7.29 +/- 0.41 ng/mL). Plasma growth hormone was pulsatile, and mean concentrations were greater in RES than FED mares (2.15 +/- 0.31 vs. 1.08 +/- 0.31 ng/mL; P = 0.05). Circadian patterns of leptin secretion were observed, but only in FED mares (15.39 +/- 0.58 ng/mL for morning vs. 19.00 +/- 0.58 ng/mL for evening; P < 0.001). In Exp. 2, mares that were ovariectomized or intact received either a s.c. melatonin implant or a sham implant. Thereafter, blood was sampled at weekly intervals at 1000 and 1700. Concentrations of leptin in samples collected at 1700 were greater (P < 0.001) than in those collected at 1000 (28.24 +/- 1.7 vs. 22.07 +/- 1.7 ng/mL). Neither ovariectomy nor chronic treatment with melatonin affected plasma concentrations of leptin or the circadian pattern of secretion. These data provide evidence that plasma leptin concentrations in the equine are sensitive to acute changes in nutritional status and vary in a circadian pattern that is sensitive to fasting but not to melatonin treatment or ovariectomy.

Leptin, tumor necrosis factor-α (TNF), and CD14 in ovine adipose tissue and changes in circulating TNF in lean and fat sheep2

Four studies were designed to determine whether 1) tumor necrosis factor-alpha (TNF) and the Lipopolysaccharide (LPS) binding ligand, CD14, are produced by sheep adipose tissue; 2) nutritional reserves and/or short-term fasting affect circulating concentrations of TNF; 3) there is a relationship between TNF and metabolic factors in sheep; and 4) inflammation alters circulating concentrations of leptin. In Exp. 1 and 2, ewes were assigned, based on ultrasonic assessments of last-rib subcutaneous fat measurements to fat (fat thickness > 1 cm; mean = 1.52 +/- 0.03 cm) or thin (fat thickness < 1 cm; mean = 0.25 +/- 0.03 cm) groups. Fat and thin ewes were assigned to fed or fasted groups for a total of four groups (fed-fat; fasted-fat; fed-thin; fasted-thin). Fed-ewes had ad libitum access to feed, and fasted-ewes were prohibited feed 48 h before initiation of sample collection. In Exp. 1, subcutaneous fat samples were collected from just above the last rib for detection of TNF and CD14 mRNA, and immunoreactivity. Tumor necrosis factor-alpha-like immunoreactivity in adipocytes was sparse, more pronounced in cells in fed-ewes than fasted-ewes, and localized to membranes between adjacent cells in nucleated regions. Immunoreactivity for CD14 was minimally observed but present in adipocytes and widely expressed in infiltrating monocytes and epithelial vascular cells. Leptin was detected in adipocytes. In Exp. 2, plasma samples collected every 6 h for 24 h were analyzed for plasma concentrations of TNF. Fat ewes had greater plasma concentrations of TNF than thin ewes (P = 0.039). In Exp. 3, wethers were injected i.v. with interleukin-1beta or TNF. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not affected by treatment (P > 0.39). In Exp. 4, wethers were injected with LPS. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not altered by LPS (P > 0.20). These results provide evidence: 1) of TNF-like immunoreactivity within fat tissue; 2) that elements within fatty tissues have CD14 that may allow adipocyte function to be directly affected by LPS; 3) that plasma concentrations of leptin are not altered by LPS treatment; and 4) that circulating concentrations of TNF are elevated with obesity in sheep.

Luteinizing hormone and growth hormone secretion in ewes infused intracerebroventricularly with neuropeptide Y

Neuropeptide Y (NPY) provides an important hypothalamic link between nutritional status and neuroendocrine mechanisms regulating growth and reproduction. The objective of the following series of experiments was to determine the effects of single or continuous administration of NPY on secretion of luteinizing hormone (LH) and (or) growth hormone (GH). In experiment 1, four ovariectomized (OVX) ewes and four OVX + estrogen-treated ewes each received, in a 4 x 4 Latin Square arrangement of treatments, a single injection of 0, 0.5, 5, or 50 microg NPY via an intracerebroventricular (i.c.v.) cannulae to determine the effects on secretion of GH. NPY significantly elevated serum GH at the 50 microg dose regardless of estrogen exposure (P = 0.003). In experiment 2, eight OVX ewes were infused i.c.v. with NPY or saline (n = 4/trmt) continuously for 20 h in a linearly increasing dose, ending at 50 microg/h NPY. Blood samples were collected via jugular cannulae every 10 min during hour -4-0 (interval 1, pre-treatment), hour 6-10 (interval 2) and hour 16-20 (interval 3) relative to the initiation of infusion (0 h). Mean LH and LH pulse frequency were lower in NPY- versus saline-infused ewes during intervals 2 and 3 (P < 0.01), but NPY had no discernable effect on serum GH (P > 0.10). In experiment 3, four OVX ewes were continuously infused with NPY as in experiment 2, except that the maximum 50 microg/h dose was achieved after only 10 h of infusion. Blood samples were collected every 10 min, beginning 4 h before and continuing until 4h after the NPY infusion. Mean serum LH changed significantly over time (P = 0.0001), decreasing below pre-treatment levels by hour 3 of NPY infusion (P < 0.01), and returning to pre-treatment concentrations following the end of infusion (P > 0.15). Serum GH also changed significantly over time (P < 0.001). Mean GH levels tended to be greater than pre-treatment levels by hour 2 of infusion (P < 0.08), but thereafter returned to basal levels. Serum GH also increased following the end of NPY infusion (P < 0.03). From these data we conclude that NPY exerts a persistent inhibitory effect on secretion of LH, and may stimulate the secretion of GH during the initiation and cessation of infusion of NPY. These observations support a role for NPY in mediating the effects of undernutrition on both LH and GH, and also provide evidence for potential mechanisms by which leptin, acting through NPY, may stimulate the secretion of GH.

Age at puberty, total fat and conjugated linoleic acid content of carcass, and circulating metabolic hormones in beef heifers fed a diet high in linoleic acid beginning at four months of age

In the current study, we hypothesized that diets high in linoleic acid would increase conjugated linoleic acid (CLA) tissue content, reduce adiposity and leptin production, and result in an increase in the age at puberty in heifers. Heifers were weaned and blocked by body weight (heavy, n = 10, and light, n = 10) and allocated randomly within block to receive isocaloric and isonitrogenous diets with either added fat (HF, n = 10) or no added fat (C, n = 10) from 4 mo of age until post-pubertal slaughter. Whole sunflower seed (55% oil; 70% linoleic acid) was used as the fat source in HF diets and provided 5% added fat from the start of the study until heifers weighed 250 +/- 8 kg, at which time added fat was increased to 7% of dry matter until slaughter. Body weights were recorded weekly, and blood samples were collected weekly for total cholesterol and hormone analyses. Puberty was confirmed based on serum concentrations of progesterone and ultrasonographic confirmation of corpora lutea. Heifers were slaughtered at 325 +/- 10 d of age, and longissimus muscle between the 9th and 11th rib was collected and analyzed to estimate carcass composition. Subcutaneous and kidney, pelvic, and heart fat were collected at slaughter for fatty acid analyses. The HF heavy group tended (P < 0.10) to reach puberty later than all other groups, and one HF light heifer did not reach puberty during the study. Linoleic acid and cis-9, trans-11 CLA tissue contents were higher (P < 0.03) in HF heifers than controls, but neither total carcass fat nor percentage of dry matter differed by dietary group, although the percentage of protein tended (P < 0.10) to be lower in HF heifers. Mean serum concentrations of leptin did not differ due to diet; however, leptin increased (P < 0.01) linearly as puberty approached. Circulating concentrations of growth hormone and insulin-like growth factor I increased or remained relatively constant between wk 2 to 10 of feeding, and then declined (P < 0.01) until the onset of puberty. Serum IGF-I was lower (P < 0.01) in heifers receiving the HF diet. Mean serum concentrations of insulin and total cholesterol increased (P < 0.01) with time in both groups, but only total cholesterol was increased by the HF diet (P < 0.05). Results indicate that diets high in linoleic acid fed to growing beef heifers beginning early in life have little or no effect on total carcass fat, circulating leptin, or age at puberty despite measurable increases in CLA accumulation.

Leptin in horses: tissue localization and relationship between peripheral concentrations of leptin and body condition

Obesity has been a major concern in the horse industry for many years, and the recent discovery of leptin and leptin receptors in numerous nonequine species has provided a basis for new approaches to study this problem in equine. The objectives were to: 1) clone a partial sequence ofthe equine leptin and leptin receptor genes so as to enable the design of primers for RT-PCR determination of leptin and leptin receptor gene presence and distribution in tissues, 2) develop a radioimmunoassay to quantify peripheral concentrations of leptin in equine, 3) determine if peripheral concentrations of leptin correlate with body condition scores in equine, and 4) determine if changing body condition scores would influence peripheral concentrations of leptin in equine. In Experiment 1, equine leptin (GenBank accession number AF179275) and the long-form of the equine leptin receptor (GenBank accession number AF139663) genes were partially sequenced. Equine leptin receptor mRNA was detected in liver, lung, testis, ovary, choroid plexus, hypothalamus, and subcutaneous adipose tissues using RT-PCR. In Experiment 2, 71 horses were categorized by gender, age, and body condition score and blood samples were collected. Sera were assayed for leptin using a heterologous leptin radioimmunoassay developed for equine sera. Serum concentrations of leptin increased in horses with body condition score (1 = thin to 9 = fat; r = 0.64; P = 0.0001). Furthermore, serum concentrations of leptin were greater in geldings and stallions than in mares (P = 0.0002), and tended to increase with age of the animal (P = 0.08). In Experiment 3, blood samples, body weights, and body condition scores were collected every 14 d from 18 pony mares assigned to gain or lose weight over a 14-wk interval based on initial body condition score. Although statistical changes (P = 0.001) in body condition scores were achieved, congruent statistical changes in peripheral concentrations of leptin were not observed, likely due to the small range of change that occurred. Nonetheless, serum concentrations of leptin tended to be greater in fat-restricted mares than in thin-supplemented mares (P = 0.09). We conclude that leptin and leptin receptors are present in equine tissues and that peripheral concentrations of leptin reflect a significant influence of fat mass in equine.

Serum leptin and its adipose gene expression during pubertal development, the estrous cycle, and different seasons in cattle

Circulating concentrations of leptin and IGF-I, leptin gene expression, and serum binding of [126I]ovine leptin in cattle during pubertal development, as well as leptin gene expression and circulating concentrations of leptin during the estrous cycle and different calendar seasons, were investigated. Multivariate regression analysis was utilized to evaluate temporal changes in BW, leptin mRNA, and serum concentrations of IGF-I and leptin normalized to the week of puberty (Exp. 1). Body weight accounted for most of the variation associated with the onset of puberty in the full regression model (R2 = 0.99; P < 0.01). However, serum leptin was closely related to changes in BW (r = 0.85; P < 0.02) and in the absence of BW was most predictive of pubertal onset (r2 = 0.73; P < 0.01). Mean concentrations of leptin increased (P < 0.0001) linearly from 16 wk before until the wk of pubertal ovulation in yearling heifers reaching sexual maturation from early spring to midsummer. Leptin mRNA transformed to a percent of the value at puberty increased (P < 0.02) as puberty approached, but serum leptin and leptin mRNA values were not well correlated. We found no evidence of leptin-binding proteins in serum of developing heifers. Combined mean serum concentrations of IGF-I (ng/mL) during periods III and IV (-9 wk to wk of puberty; 216.6 +/- 9) were 21% higher (P < 0.0001) than combined mean concentrations of IGF-I during periods I and II (-19 to wk of puberty; 193 +/- 10). In mature heifers and cows (Exp. 2), serum leptin tended to decrease (P = 0.10) during the late luteal/early follicular phase of the estrous cycle, which corresponded to a reduction (P < 0.03) in adipocyte leptin gene expression. In mature ovariectomized cows, serum concentrations of leptin increased (P < 0.001) by 34% from early winter to the summer solstice and remained unchanged throughout the remainder of the year (Exp. 3). Results from these studies indicate that marked increases in both circulating leptin and leptin gene expression occur in developing heifers during pubertal development and are associated with increases in serum IGF-I and BW. Seasonal effects on circulating leptin observed in mature cows from winter to summer could also plausibly account for a portion of the prepubertal rise in serum leptin observed in heifers.

Leptin and its role in the central regulation of reproduction in cattle

Leptin, a 16kDa product of the adipose obese (ob) gene, has been shown to contribute to the regulation of energy metabolism, feeding behavior, and reproduction in several monogastric species, including humans. Recent reports have provided evidence that the leptin gene is functionally relevant in cattle and sheep, and may contribute to an array of important reproductive events, including puberty. Leptin gene expression and circulating leptin increase markedly during sexual maturation in heifers reaching puberty during late spring or early summer. In addition, serum leptin concentrations increased by over 30% from early winter to the summer solstice in mature cows, and also increased with significant changes in adiposity. However, only limited changes in circulating leptin have been observed during the estrous cycle. Short-term fasting of growing peripubertal heifers causes marked reductions in leptin gene expression and circulating leptin, concomitant with declines in LH pulse frequency, and serum concentrations of insulin and IGF-1. Although short-term fasting of mature cows in excellent body condition is without effects on LH pulse frequency, it has remarkably similar metabolic effects to those observed in heifers. Moreover, ICV administration of recombinant oleptin resulted in a marked hypersecretion of LH in fasted cows, and in vitro studies using both hypothalamic and anterior pituitary explants have provided evidence that this effect is at the pituitary level. Paradoxically, ICV administration of oleptin normalized circulating insulin in fasted cows but hleptin was without effect on insulin in estradiol-implanted wethers. Collectively, work in cattle and sheep indicates that leptin can modulate both the hypothalamic-pituitary axis and endocrine pancreas under defined nutritional conditions. Additional work to more fully characterize these roles is clearly warranted and could lead to the development of novel strategies for modifying reproductive potential in food-producing species.

Central infusion of recombinant ovine leptin normalizes plasma insulin and stimulates a novel hypersecretion of luteinizing hormone after short-term fasting in mature beef cows

The present studies tested the hypotheses that short-term fasting would reduce leptin gene expression and circulating concentrations of leptin and insulin in mature, ovariectomized, estradiol-implanted cows and that intracerebroventricular infusions of recombinant ovine leptin (oleptin) would attenuate reductions in insulin concentration and stimulate LH secretion. Ovariectomized cows were assigned to either control (normal fed; n = 6) or fasted (60 h of fasting; n = 7) groups and infused with 200 microg recombinant oleptin three times at hourly intervals on Day 2 (n = 6 per group). Fasting decreased plasma concentrations of insulin (P < 0.01) and leptin (P < 0.04) but, as expected, did not reduce plasma concentrations of glucose or any LH secretion variable. Central infusion of leptin on Day 2 increased (P < 0.01) plasma concentrations of leptin in both control and fasted groups. Concomitantly, leptin treatment increased plasma insulin (P < 0.01) and LH (P < 0.03) concentrations in fasted but not in control cows. Increases in overall mean and baseline concentrations of LH after leptin treatment were the result of an augmentation of the size of LH pulses. The effects of fasting on leptin gene expression and the potential diurnal effects on circulating leptin were examined in a group of cows (n = 12) not treated with leptin. Fasting for 60 h reduced (P < 0.001) leptin gene expression by 30%, and no diurnal effects on circulating leptin were observed. These results indicate that although short-term fasting does not reduce the frequency or amplitude of LH pulses or the concentration of LH in mature cows, this nutritional perturbation clearly sensitizes both the hypothalamic-pituitary axis and endocrine pancreas to exogenous leptin, which in these experiments resulted in heightened secretion of both LH and insulin.

Effect of intravenous infusion of recombinant ovine leptin on feed intake and serum concentrations of GH, LH, insulin, IGF-1, cortisol, and thyroxine in growing prepubertal ewe lambs

In sheep, serum concentrations of leptin change congruently with increases or decreases in nutritional status, while intracerebroventricular infusions of leptin dramatically suppress feed intake in well-fed lambs, and may also increase growth hormone (GH), and/or luteinizing hormone (LH) in undernourished lambs. The objective of the present study was to determine the effects of peripherally delivered ovine leptin, via intravenous infusions, on feed intake and serum concentrations of GH, LH, insulin, IGF-1, cortisol, and thyroxine. Twelve ewe lambs weighing 29.4 +/- 0.7 kg were infused intravenously with a linearly increasing dose of leptin or saline (n = 6 per group) for 10 days, reaching a maximum dose delivered of 0.5mg/h on day 10. Feed intake was assessed twice daily, and blood samples were collected every 10 min for 6 h on days 0, 2, 5, 8, and 10. Serum concentrations of leptin increased in leptin-treated lambs by day 2 (P = 0.05), and continued to increase to concentrations 9-fold greater than saline-infused lambs by day 10 (P < 0.001). Despite the substantial increase in serum leptin, feed intake did not differ between leptin and saline-infused lambs except on day 3.5 (P = 0.01). Furthermore, intravenous infusions of leptin did not significantly influence serum concentrations of insulin, cortisol, IGF-1, thyroxine, LH, or GH. Collectively, these observations contrast with the potent hypophagic effects of leptin when delivered intracerebroventricularly into well-fed lambs. The reasons for the disparate response of lambs treated intravenously with leptin, versus that reported for lambs treated intracerebroventricularly with leptin are not known, but may provide insight into the mechanism(s) of leptin resistance.

Effect of body fat mass and nutritional status on 24-hour leptin profiles in ewes

This study was designed to determine the effect of feeding or fasting of fat or thin ewes on 24-h leptin profiles. Ewes were assigned, based on ultrasonic assessments of last-rib subcutaneous fat measurements, into fat (fat thickness > 1 cm; mean = 1.52 +/- 0.03 cm; range 1.14 to 2.18 cm) or thin (fat thickness < 1 cm; mean = 0.25 +/- 0.03 cm; range 0.03 to 0.84 cm) groups. Fat and thin ewes were then assigned to either fed or fasted (deprived of feed) groups consisting of five ewes per group. Thus, four groups existed and were designated as fat-fed, fat-fasted, thin-fed, and thin-fasted. Fed ewes had ad libitum access to feed throughout the study. Fasted ewes were prohibited access to feed beginning 48 h preceding the experiment. Plasma samples were collected for leptin analysis from ewes every 15 min for 24 h beginning 48 h after the initiation of feed restriction or the congruent interval in fed ewes. Data were subjected to CLUSTER pulse analysis procedures. Profiles of plasma concentrations of leptin were episodic in nature and did not differ in a diurnal manner. Fed ewes had greater mean concentrations of leptin, area under the curve, number of peaks, peak height, peak nadir, and a shorter interval between peaks than fasted ewes (P < or = 0.05). Fat ewes had greater mean concentrations of leptin, area under the curve, number of peaks, peak height, peak nadir, and a shorter interval between peaks than thin ewes (P < 0.02). There also was a tendency for a body condition x treatment interaction for number of peaks (P = 0.073) and interval between peaks (P = 0.056). These results provide evidence that plasma concentrations of leptin are episodic in nature and are influenced by nutritive state and fat thickness over the ribs, but display no circadian variation.

Relationships of metabolic hormones and serum glucose to growth and reproductive development in performance-tested Angus, Brangus, and Brahman bulls

Understanding mechanisms that regulate growth and reproduction are important for improving selection strategies in cattle. In this study, Angus, Brangus, and Brahman bulls (n = 7 per breed) of similar age were selected from a group of 65 weanlings. Bulls were evaluated after weaning (i.e., approximately 6 mo of age) for 112 d for serum concentrations of metabolic hormones and glucose, growth, and reproductive traits. Performance data and blood sera were collected on d 0, 28, 56, 84, and 112. Sera were also collected in periods from d 50 to 59 (56D) and 103 to 112 (112D). Angus bulls were heavier (P < 0.05) throughout the study than Brahman bulls and were heavier than Brangus bulls on d 56, 84, and 112. Initial and final BW for Angus, Brangus, and Brahman bulls were 292.7, 260.6, and 230.4 and 468.3, 435.6, and 350.7 +/- 12 kg, respectively. Conversely, Brahman bulls had greater hip height (P < 0.05) than Brangus, and Brangus were taller (P < 0.05) than Angus. Angus bulls had the greatest (P < 0.05) scrotal circumference (SC) and Brahman bulls the least. Mean SC across days was 31.5, 29.7, and 25.0 +/- 0.6 cm for the three respective breeds. Serum testosterone was greater (P < 0.01) in Angus and Brangus bulls (10.0 and 8.9 +/- 1.4 ng/mL) than in Brahman bulls (4.0 +/- 1.4 ng/mL) throughout the study. After d 112, 100, 86, and 57% of the Angus, Brangus, and Brahman bulls passed a breeding soundness exam (P = 0.51). Serum concentrations of IGF-I and leptin were greater (P < or = 0.06) in Angus bulls on d 56, 84, and 112 than in Brangus and Brahman bulls. Serum concentrations of GH (P < 0.08) and glucose (P < 0.03) were greater in Brangus bulls than in Angus or Brahman bulls throughout the study. Prediction analyses suggested that serum concentrations of leptin could be used to predict (P < or = 0.08) BW and SC (R2 > 0.82) in the 56D and 112D periods among these breeds. Leptin was also useful in predicting (P < or = 0.09) serum concentrations of GH and testosterone in the 112D period (R2 > 0.32). Residual correlation analyses with the effect of breed removed suggested that leptin was correlated (r > or => 0.53, P < 0.05) with both SC and serum testosterone. Angus and Brahman cattle differ in phenotype, level of adiposity, and rate of sexual development. Data herein suggest that these characteristics could be due to varying mechanisms by which metabolic hormones such as leptin, GH, and(or) IGF-I are regulated.

Leptin concentrations in periparturient ewes and their subsequent offspring

Leptin is an adipocyte-derived hormone that suppresses feed intake and increases energy expenditure. Leptin is also involved in regulating body temperature. Thus, the presence of leptin in milk, which can be absorbed through the gut of neonates immediately after birth, may aid in the survival of neonates born in cold weather. Our objectives were to determine the temporal relationship between concentrations of leptin in postpartum ewe blood serum and ewe milk serum, and to determine whether ewe blood and milk serum leptin concentrations were correlated with concentrations of leptin in lamb blood serum in their off-spring. Approximately 1 wk before the expected date of lambing, blood samples, weights, and body condition scores (BCS; 0 to 5 scale) were collected from 27 mixed-parity ewes. Following parturition, ewe blood and milk samples were collected within 2 h of parturition (d 0), 12 h (d 0.5) and 24 h (d 1) after parturition, again on d 5, and weekly thereafter until d 47. Lambs were blood-sampled and weighed within 2 h of parturition (d 0), bled daily until d 5, and bled and weighed weekly thereafter to d 47. Prior to lambing, ewe blood serum leptin was positively correlated with congruent BCS (r2 = 0, 10, P = 0.06), but not weight (P = 0.14). Following parturition, ewe blood serum leptin was positively correlated with BCS, weight, and milk serum leptin (r2 = 0.14, P < 0.0001, r2 = 0.12, P < 0.0001, and r2 = 0.028, P = 0.04). Leptin in milk serum was correlated with ewe weight (r2=0.05, P = 0.007) but not ewe BCS (P = 0.7); however, concentrations of leptin in both ewe blood and milk serum varied with day of lactation (P = 0.0001), being maximal within 24 h of parturition and declining to nadir concentrations by d 5. Leptin in lamb serum was correlated with milk serum leptin, (r2 = -0.05; P = 0.001), but not ewe blood serum leptin (P = 0.5). Concentrations of leptin in lamb serum increased from birth to d 5 and declined thereafter to nadir concentrations by d 19. Elevated concentrations of leptin in milk during the early stages of lactation may provide a mechanism for thermoregulation, satiation, and homeostatic endocrine control in the neonate.

Endocrine responses of ovariectomized ewes to i.c.v. infusion of urocortin

Urocortin is a novel corticotropin-releasing factor-like peptide, first isolated from the rat midbrain, which has anorexigenic properties, possibly associated with its involvement in the stress axis. Urocortin has been implicated in blood pressure regulation, ACTH release and feed intake, but its role as an integral component of the reproduction-nutrition axis has not been examined. The present experiment was designed to determine the effects of i.c.v. infusion of urocortin on feed intake and endocrine profiles of LH, GH, IGF-I, cortisol and leptin in ovariectomized ewes. Ewes were fitted with two laterocerebroventricular cannulae and urocortin was continuously infused in a linearly increasing manner from 0.001 microg/h on day 0, to a maximum of 31.6 microg/h on day 5. Blood samples were collected via jugular catheters at 10 min intervals for 4 h on day 1, 3 and 5, and assayed by RIA for LH, GH, IGF-I, cortisol and leptin. All ewes were allowed free access to feed and water, and feed intake was recorded daily. Urocortin-infused ewes responded with a significant decrease in feed intake beginning on day 1 (P<0.02) and were aphagic for the remainder of the experiment. Serum concentrations of LH were elevated in individual samples from urocortin-treated compared with saline-treated ewes on day 3 (treatment x day x sample, P=0.05), but were not different on day 1 or 5. Mean serum concentrations of GH increased (P<0.04) over days with urocortin treatment, although concentrations of IGF-I were not influenced by treatment (P>0.5). Serum concentrations of cortisol were markedly increased by urocortin treatment (P<0.001). Leptin tended to be influenced by treatment and day (P=0.08), with leptin levels tending to be elevated in urocortin-treated vs saline-treated ewes on day 5 (P=0.08). The ability of urocortin to decrease feed intake while increasing LH, GH, cortisol and leptin provides evidence that urocortin is not only an integral component of the stress axis, but possibly of the nutrition-reproduction axis in sheep.

Increased D allele frequency of the angiotensin-converting enzyme gene in pulmonary fibrosis

An insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme has previously been studied extensively in relationship to cardiovascular and renal disease. The deletion/deletion (D/D) genotype is associated with a poor outcome in immunoglobulin (Ig) A nephropathy. However, the association of this genetic marker in cardiovascular and renal disease has generated controversy, with the exception of the rate of progression and therapeutic responsiveness in IgA nephropathy. Many of the same cytokines and polypeptide mediators involved in fibrosis of the cardiovascular and renal systems have been shown to be involved in pulmonary fibrosis. We examined the I/D polymorphism of the angiotensin-converting enzyme in a group of 24 patents with interstitial pneumonia and moderate to severe pulmonary fibrosis defined by radiographic studies, pulmonary function tests, and histologic findings. The incidence of the D allele in this study population was 69.0%, which is approximately 15.0% higher than the incidence in the general population of 54.0%. The incidence of the D/D genotype was 42.0%, which is approximately 11.0% greater than that in the general population (31.0%). The distribution of the D/D, I/D, and insertion/insertion genotypes of these 24 patients was not significantly different from that of historical controls (P =.1; chi(2) test); there were marginally significantly more D alleles among the 48 observed alleles than would be expected (P =.04).

Central infusion of leptin into well-fed and undernourished ewe lambs: effects on feed intake and serum concentrations of growth hormone and luteinizing hormone

Leptin has been implicated in the regulation of feed intake, growth, and reproduction. The objective of this study was to determine if centrally administered leptin would affect feed intake and the secretion of growth hormone (GH) and luteinizing hormone (LH) in ewe lambs. Eighteen ewe lambs were ovariectomized and fitted with intracerebroventricular (i.c.v.) cannulae. Lambs were randomly assigned to receive either a maintenance diet (fed), or a diet that provided 38% of maintenance requirements (diet-restricted) for 14 weeks. Subsequently, recombinant ovine leptin or vehicle was continuously infused, via i.c.v. cannulae, in a linearly increasing dose for 8 days, reaching a maximum of 1.25 microg/kg per h. Feed intake was recorded on days -1 to 7. Blood was collected via jugular cannulae every 10 min for 4 h on days 0, 2, 4, 6 and 8 for the determination of serum leptin, insulin, LH and GH. Leptin suppressed feed intake in fed lambs on days 4 to 7 (P<0.001), but had no effect on feed intake in diet-restricted lambs (P>0.25). Fed lambs had greater serum concentrations of leptin than diet-restricted lambs (P=0.007). Also, although not different on day 0 (pretreatment), on day 8 serum leptin concentrations were greater in leptin-treated lambs than in saline-treated lambs (P=0.003). Insulin was lower in diet-restricted than in fed lambs (P=0.003), but was not affected by leptin treatment (P=0.82). LH pulse frequencies were lower in diet-restricted lambs than in fed lambs (P=0.038), but were not affected by leptin treatment (P=0.85). Mean serum GH was greater in diet-restricted than in fed lambs (P<0.01). In diet-restricted lambs treated with leptin or saline, mean GH did not differ on day 0, but increased in response to leptin treatment (P<0.006). Treatment of fed lambs with leptin did not affect serum GH (P>0.32). From this work, we propose that leptin represents an important functional link between adipose stores and hypothalamic function in ruminants. We demonstrate that leptin concentrations change in response to reduced nutritional status, and that leptin has the ability to regulate multiple physiological processes in lambs, including both feed intake and secretion of GH.

Immunohistochemistry in the diagnosis of neoplasms of the central nervous system

The diagnosis and evaluation of neoplasms of the central nervous system frequently involves the use of immunohistochemical stains. This article reviews some of the more commonly used markers including glial fibrillary acidic protein, synaptophysin, neurofilament protein, S-100 protein, epithelial membrane antigen, and cytokeratin markers. The focus of the discussion is on the use of these markers including their utility in resolving differential diagnostic issues. We also review the use of p53 and a variety of cell proliferation markers including proliferating cell nuclear antigen, Ki-67, MIB-1 and their potential role as adjuncts in the grading of tumors and their potential role in predicting tumor behavior.

Leptin gene expression, circulating leptin, and luteinizing hormone pulsatility are acutely responsive to short-term fasting in prepubertal heifers: relationships to circulating insulin and insulin-like growth factor I(1)

In the present study, we tested the hypothesis that short-term fasting would reduce leptin gene expression, circulating leptin, and LH pulsatility in prepubertal heifers in association with a decrease in circulating concentrations of insulin and insulin-like growth factor I (IGF-I). Twelve prepubertal crossbred heifers (mean +/- SD = 315 +/- 5 kg body weight) were assigned randomly to one of two treatments in two replicates: 1) control; normal feed consumption (n = 6) and 2) fasted; 48 h of total feed restriction (n = 6). Blood samples were collected at 15-min intervals for 8 h on Days 0 and 2 of the experiment and twice on Day 1. Subcutaneous fat samples were collected before treatment onset (Day -1) and at the end of the intensive blood sampling on Day 2. Acute feed restriction markedly reduced leptin mRNA in adipose tissue (P < 0.01) and circulating concentrations of leptin (P < 0.05), IGF-I (P < 0.01), and insulin (P = 0.05) as compared with controls on Day 2. Moreover, the treatment x day interaction (P < 0.076) and within-day contrasts (expressed as a percentage of Day 0 values) revealed that the mean frequency of LH pulses in the fasted group was lower (P < 0.06) than in controls on Day 2. Neither mean concentrations of growth hormone (GH) nor GH secretory dynamics were affected by acute feed restriction. Fasting-mediated decreases in leptin gene expression and circulating leptin, in association with reductions in secretion of IGF-I, insulin, and LH, provide a basis for investigating leptin as a hormone signaling energy status to the central reproductive axis in cattle.

Laparoscopic postmortem examination: a minimally invasive approach to the autopsy

Laparoscopic and thoracoscopic autopsies have previously only been performed on an experimental basis to determine their potential usefulness as a substitute for a conventional postmortem examination. We present the case of a patient with an unusual variant of malignant melanoma (diffuse melanosis) in whom the immediate cause of death clinically was thought to be fulminant hepatic failure, the etiology of which was unknown. The family was unwilling to consent to a conventional autopsy, but would permit a postmortem examination limited to a 2-cm abdominal incision and removal of a sample of liver. In view of the unanswered clinical questions regarding the cause of the acute hepatic failure and its possible relationship to the diagnosis of diffuse melanosis, we decided that more extensive examination of the abdominal cavity, specifically the liver, was required and that the only way that this could be accomplished was by laparoscopic techniques. Laparoscopic examination of the abdominal cavity revealed multiple melanotic nodules on the surface of the liver and studding the omentum. Multiple liver samples were easily obtained; these revealed massive diffuse necrosis of the liver parenchyma with scattered nodular deposits of dark pigment consistent with melanin. We report the first known case in which a laparoscopic autopsy was used to obtain valuable information that answered clinically relevant questions. Laparoscopic autopsy can offer the a family that is unwilling to consent to a conventional postmortem examination an alternative that can potentially provide answers to clinical questions that otherwise would have been unresolved.

The role of leptin in nutritional status and reproductive function

Infertility associated with suboptimal nutrition is a major concern among livestock producers. Undernourished prepubertal animals will not enter puberty until they are well fed; similarly, adult, normally cyclic females will stop cycling when faced with extreme undernutrition. Work in our laboratory has focused on how body fat (or adiposity) of an animal can communicate to the brain and regulate reproductive competence. In 1994, the discovery in rodents of the obese (ob) gene product leptin, secreted as a hormone from adipocytes, provided a unique opportunity to understand and hence regulate whole body compositional changes. There is now evidence that similar mechanisms are functioning in livestock species in which food intake, body composition, and reproductive performance are of considerable economic importance. Leptin has been reported to be a potent regulator of food intake and reproduction in rodents. There is evidence indicating that at least some of the effects of leptin occur through receptor-mediated regulation of the hypothalamic protein neuropeptide Y (NPY). NPY is a potent stimulator of food intake, is present at high concentrations in feed-restricted cattle and ewes, and is an inhibitor of LH secretion in these livestock species. In our investigations in sheep, we have cloned a partial cDNA corresponding to the ovine long-form leptin receptor, presumably the only fully active form, and have localized the long-form leptin receptor in the ventromedial and arcuate nuclei of the hypothalamus. Leptin receptor mRNA expression was colocalized with NPY mRNA-containing cell bodies in those regions. We have also determined that hypothalamic leptin receptor expression is greater in feed-restricted ewes than in well-fed ewes. These observations provide a foundation for future investigations into the nutritional modulators of reproduction in livestock.

Infant walker injuries persist in Canada after sales have ceased

OBJECTIVE

To identify the source of acquisition of infant walkers and attitudes regarding the continuing use of walkers following an injury to an infant in order to design preventive strategies.

DESIGN

Descriptive and retrospective.

SETTING

Emergency department of a children's hospital involved in primary, secondary and tertiary care.

PATIENTS

All patients presenting with injuries associated with infant walkers over a 42-month period.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Source of acquisition of infant walker and actions taken after the injury.

RESULTS

The demographic and outcome data of the 36 patients were similar to previous reports. The caretakers of 26 patients were reached by telephone. Eight walkers were purchased in the United States and 18 were second-hand acquisitions (new walkers are not available for sale in Canada). Only two families continued using their walkers in the same fashion as prior to the injury.

CONCLUSIONS

Although new infant walkers are not sold in Canada, injuries associated with their use continue. An aggressive public education campaign discouraging infant walker use and an incentive driven recall campaign to retrieve circulating walkers are seen as complimentary preventive strategies. A similar approach should be considered in other countries that choose to regulate infant walkers.

The contribution of motor skills and playfulness to the play performance of preschoolers

Consideration of a child's motor proficiency, intrinsic motivation, internal locus of control, and freedom to suspend many of the constraints of objective reality were proposed to provide a more comprehensive assessment of play than would an assessment of play performance alone. For empirical validation of this conceptual model of play, 29 subjects (15 nondisabled children and 14 children with juvenile rheumatoid arthritis) between the ages of 4 years 6 months and 6 years 6 months were given four assessments: (a) the Preschool Play Scale (Bledsoe & Shepherd, 1982, Knox, 1974); (b) the Bruininks-Oseretsky Test of Motor Proficiency (Bruininks, 1978); (c) the Preschool and Primary Internal-External Locus of Control Scale (Nowicki & Duke, 1974); and (d) tests of associative fluency (Wallach & Koogan, 1965; Ward, 1968). Multiple regression procedures revealed that, when considered together, scores on the Bruininks-Oseretsky Test of Motor Proficiency, tests of associative fluency, and the Preschool and Primary Internal-External Locus of Control Scale predicted scores on the Preschool Play Scale, thereby supporting the usefulness of the proposed theoretical model. Further, there was no significant difference in the mean scores of the two groups on the Preschool Play Scale. Although this finding may be an artifact of the small sample size, it also may support the authors' belief that children with motor impairments are able to compensate for their limitations by developing areas of relative strength that allow them to play normally. When this belief was further tested with Pearson product-moment correlations and Fisher's Z transformations, it was found that correlations between the test scores of the nondisabled children were not significantly different from those of the children with juvenile rheumatoid arthritis. Clearly, further research is needed.