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Biomedical subjects

S A Roberts

Publications and source records attributed to S A Roberts.

At least 91 records · Page 5Linked to original sources
PubMed1999

Growth of Staphylococcus aureus in Diprivan and Intralipid: implications on the pathogenesis of infections.

BACKGROUND: The incidence and severity of infections are increased when Intralipid or Diprivan are administered to patients. Intralipid promotes infection, presumably by inhibiting the reticuloendothelial system, thereby suppressing the host's constitutive immunity, whereas Diprivan supposedly promotes infection by supporting bacterial growth and increasing the inoculating dose. This study considers whether bacterial replication alone in Intralipid and Diprivan adequately explains the increased risk of infection associated with these agents or whether other factors might also be involved. METHODS: Staphylococcus aureus was cultured in 10% Intralipid or Diprivan at clinically relevant conditions or in Intralipid containing 0.005% (w/v) sodium EDTA, a current additive, to measure growth. To determine whether Intralipid affected infection, New Zealand white rabbits were injected intravenously with S. aureus with or without Intralipid. Twenty-four hours later, bacteria in lung, liver, spleen, and kidney tissues were enumerated. RESULTS: S. aureus failed to grow in Diprivan or Intralipid containing 0.005% EDTA. Whereas S. aureus did replicate in plain Intralipid, growth was delayed until the bacteria conditioned the media. Once initiated, growth was slow at clinically relevant temperatures. The administration of Intralipid to rabbits significantly increased the recovery of staphylococci from the kidneys, P < 0.001, relative to the other tissues 24 h after an intravenous inoculation with S. aureus, compared with rabbits receiving S. aureus with no Intralipid. CONCLUSIONS: These results suggest that Diprivan, and possibly Intralipid, represent poor media for the growth of S. aureus and may promote infection through mechanisms other than increased inoculum size.

Anesthetics, Intravenous↗
PubMed1999

Nerve cell adhesion molecule expression in squamous cell carcinoma of the head and neck: a predictor of propensity toward perineural spread.

OBJECTIVE: To evaluate head and neck squamous cell carcinomas (SCCAs) for the expression of nerve cell adhesion molecule (N-CAM). We propose that expression of N-CAM by tumor cells may be associated with perineural invasion in SCCA of the head and neck. METHODS: Seventy-six archived specimens of histologically proven SCCA were analyzed by immunohistochemistry for the expression of N-CAM. Positive and negative controls were used to assess staining. Two sections of each specimen were reviewed for the presence of perineural invasion. A retrospective chart review was performed for each patient that corresponded to the above specimens. RESULTS: Perineural invasion was present in 28 (37%) of the 76 patients evaluated for the expression of N-CAM. N-CAM expression was demonstrated in 38 (50%) of the 76 specimens. The incidence of N-CAM expression was significantly associated with perineural invasion (P = .002). There was no significant association between the presence of staining or the presence of perineural invasion and the incidence of locoregional recurrence, distant metastasis, or survival status; however, the mean follow-up was only 13.6 months (range, 1-49 mo). CONCLUSION: There is a positive correlation between the presence of N-CAM expression and perineural invasion in SCCA of the head and neck. The expression of this adhesion molecule by tumor cells may facilitate both homophilic cell-to-cell and heterophilic cell-to-substrate adhesion, thereby enabling the tumor cells to use the perineural tissues or neural cells, or both as a conduit for perineural spread.

Adult↗
PubMed1999

Relationship between childhood behavioral disturbance and later schizophrenia in the New York High-Risk Project.

OBJECTIVE: An association between childhood behavioral disturbance and adulthood schizophrenia has been seen previously in retrospective or follow-back studies and in prospective studies. The authors examined the relationship between childhood behavioral problems and adulthood schizophrenia-related psychoses. Because a high rate of childhood behavioral problems is known to be associated with adult substance abuse, these analyses controlled for substance abuse. METHOD: The subjects of this investigation (N = 185) were offspring of parents with schizophrenia or affective disorder and of normal parents from the New York High-Risk Project (sample A). Data on childhood behavioral problems were obtained in a parent interview at initial assessment in 1971-1972. Adulthood outcomes (schizophrenia-related psychoses, affective disorders, anxiety disorders, substance abuse) were based on lifetime axis I diagnoses according to the Research Diagnostic Criteria. RESULTS: Substance abuse had a significant interaction with the clinical outcome groups. In subjects without substance abuse, those with schizophrenia-related psychoses had exhibited significantly more behavioral problems as children than had adult offspring with affective or anxiety disorder or with substance abuse only or no disorder. CONCLUSIONS: These results support the view that schizophrenia-related psychoses can be followed back to early behavioral disturbances. The confounding effects of substance abuse should be statistically controlled in studies of longitudinal associations between childhood behavioral disturbance and axis I outcomes.

Adult↗
PubMed1999

Two-week dietary soy supplementation has an estrogenic effect on normal premenopausal breast.

An association has been reported between consumption of a high soy diet and a low incidence of breast cancer within populations of Southeast Asia. Phytoestrogens present in soy act as partial estrogen agonists or antagonists and can inhibit breast cancer cell proliferation in vitro. The effect of 14-day dietary soy supplementation with 60 g (45 mg isoflavones) on the normal breast of 84 premenopausal patients was determined. Serum concentrations of the isoflavanoids, genistein, daidzein, and equol, were raised in patients after soy supplementation (P < or = 0.025). Nipple aspirate (NA) levels of genistein and daidzein were higher than paired serum levels, both before (P < 0.001 and P = 0.001, respectively) and after soy supplementation (P < 0.001 and P = 0.049, respectively); however, there was no significant increase in NA isoflavone levels in response to soy. NA levels of apolipoprotein D were significantly lowered and pS2 levels raised in response to soy supplementation (P < or = 0.002), indicative of an estrogenic stimulus. No effect of soy supplementation on breast epithelial cell proliferation, estrogen and progesterone receptor status, apoptosis, mitosis, or Bcl-2 expression was detected. In conclusion, short term dietary soy has a weak estrogenic response on the breast, as measured by nipple aspirate apolipoprotein D and pS2 expression. No antiestrogenic effect of soy on the breast was detected.

Adult↗
PubMed1998

A realistic closed-form radiobiological model of clinical tumor-control data incorporating intertumor heterogeneity.

PURPOSE: To investigate the role of intertumor heterogeneity in clinical tumor control datasets and the relationship to in vitro measurements of tumor biopsy samples. Specifically, to develop a modified linear-quadratic (LQ) model incorporating such heterogeneity that it is practical to fit to clinical tumor-control datasets. METHODS AND MATERIALS: We developed a modified version of the linear-quadratic (LQ) model for tumor control, incorporating a (lagged) time factor to allow for tumor cell repopulation. We explicitly took into account the interpatient heterogeneity in clonogen number, radiosensitivity, and repopulation rate. Using this model, we could generate realistic TCP curves using parameter estimates consistent with those reported from in vitro studies, subject to the inclusion of a radiosensitivity (or dose)-modifying factor. We then demonstrated that the model was dominated by the heterogeneity in alpha (tumor radiosensitivity) and derived an approximate simplified model incorporating this heterogeneity. This simplified model is expressible in a compact closed form, which it is practical to fit to clinical datasets. Using two previously analysed datasets, we fit the model using direct maximum-likelihood techniques and obtained parameter estimates that were, again, consistent with the experimental data on the radiosensitivity of primary human tumor cells. This heterogeneity model includes the same number of adjustable parameters as the standard LQ model. RESULTS: The modified model provides parameter estimates that can easily be reconciled with the in vitro measurements. The simplified (approximate) form of the heterogeneity model is a compact, closed-form probit function that can readily be fitted to clinical series by conventional maximum-likelihood methodology. This heterogeneity model provides a slightly better fit to the datasets than the conventional LQ model, with the same numbers of fitted parameters. The parameter estimates of the clinically important time factors and lag periods are very similar to those obtained from the conventional LQ model, but with slightly narrower confidence intervals, reflecting the better fit to the clinical data. DISCUSSION: We have demonstrated, as have others, the importance of intertumor heterogeneity in the response of patient populations to radiotherapy. With the possible inclusion of a radiosensitivity-modifying factor (in vitro/in vivo) of around 1.7, the in vivo data can be made consistent with the in vitro SF2 and Tpot data. Fitting two previously analyzed multicenter datasets indicated that previous analyses based on conventional LQ models gave results for clinically important time factors and lags periods that were not significantly biased by the failure to include intertumor heterogeneity, with slightly narrower confidence intervals, reflecting the better fit to the clinical data. The simple closed-form model we have developed allows direct estimation of the heterogeneity in radiosensitivity within clinical series, and should prove useful in the analysis of other clinical series.

Dose-Response Relationship, Radiation↗
PubMed1998

Resolution of peanut allergy: case-control study.

OBJECTIVES: To determine whether there are any differences between children who remain mildly or moderately allergic to peanut and children with similar histories but a negative reaction on challenge with peanut. DESIGN: Case-controls matched for age and sex. SETTING: Children's day wards in two teaching hospitals. INTERVENTION: Open food challenge with peanut. SUBJECTS: 15 children with resolved peanut allergy (resolvers) and 15 with persistent allergy (persisters). MAIN OUTCOME MEASURE: Reaction on challenge with peanut, serum total and peanut specific IgE concentrations. RESULTS: The groups had a similar median age at first reaction to peanut (11 months, range 5-38) and similar symptoms. Allergy to other foods was less common in resolvers (2/15) than persisters (9/15) (P=0.02). On skin prick testing with peanut all 13 resolvers tested but only 3/14 persisters had a weal of <6 mm (P<0.0001). Total and peanut specific IgE concentrations did not differ much between the groups. CONCLUSION: Appropriately trained clinicians must be prepared to challenge preschool children with peanut as some will be tolerant despite a history of reactions to peanut and a positive skin prick test with peanut. Preschool children whose apparent peanut allergy is refuted by food challenge show allergy to other foods less often than those in whom peanut allergy persists. The size of weal on skin prick testing to peanut predicts reactivity but not severity on peanut challenge.

Arachis↗
PubMed1998

The New York High-Risk Project: attention, anhedonia and social outcome.

In the New York High-Risk Project we have followed two samples of subjects (Sample A and Sample B) at risk for schizophrenic or affective disorders and low-risk controls from childhood to adulthood, in an attempt to identify early predictors of later psychopathology. We administered a large number of cognitive, psychometric and other types of measures to both samples as possible psychopathology predictors, including an index of attentional deviance assessed in childhood, the Physical Anhedonia Scale in adolescence, and three measures of social outcome in adulthood ('Suspicious Solitude', 'Social Insecurity', and 'Lack of Empathy'), derived from the Personality Disorders Examination. In the analysis of the combined samples, parental diagnostic group, gender, attentional deviance in childhood, and physical anhedonia in adolescence were used to predict three measures of social outcome in adulthood. While only physical anhedonia was directly related to all three social outcome measures, with the strongest relationship to Suspicious Solitude, attention deviance successfully predicted two of the three outcomes. Subjects at risk for affective disorder did not show increased levels of attention deviance, physical anhedonia, or social dysfunction, relative to the normal control subjects. Attention deviance appears to be a key neurobiological indicator and physical anhedonia appears to be a potentiating factor mediating the relationship between risk for schizophrenia and later social dysfunction.

Adolescent↗
PubMed1998

Similar decreases in local tumor control are calculated for treatment protraction and for interruptions in the radiotherapy of carcinoma of the larynx in four centers.

PURPOSE: Data on patients with cancer of the larynx are analyzed using statistical models to estimate the effect of gaps in the treatment time on the local control of the tumor. METHODS AND MATERIALS: Patients from four centers, Edinburgh, Glasgow, Manchester, and Toronto, with carcinoma of the larynx and treated by radiotherapy were followed up and the disease-free period recorded. In all centers the end point was control of the primary tumor after irradiation alone. The local control rates at > or = 2 years, Pc, were analyzed by log linear models, and Cox proportional hazard models were used to model the disease-free period. RESULTS: T stage, nodal involvement, and site of the tumor were important determinants of the disease-free interval, as was the radiation schedule used. Elongation of the treatment time by 1 day, or a gap of 1 day, was associated with a decrease in Pc of 0.68% per day for Pc = 0.80, with a 95% confidence interval of (0.28, 1.08)%. An increase of 5 days was associated with a 3.5% reduction in Pc from 0.80 to 0.77. At Pc = 0.60 an increase of 5 days was associated with an 7.9% decrease in Pc. The time factor in the Linear Quadratic model, gamma/alpha, was estimated as 0.89 Gy/day, 95% confidence interval (0.35, 1.43) Gy/day. CONCLUSIONS: Any gaps (public holidays are the majority) in the treatment schedule have the same deleterious effect on the disease free period as an increase in the prescribed treatment time. For a schedule, where dose and fraction number are specified, any gap in treatment is potentially damaging.

Carcinoma↗
PubMed1998

A quantitative histometric murine in vivo model of radiation-induced oral mucositis.

Gastrointestinal toxicity is a limiting factor in the effectiveness of cancer therapy. This toxicity is most visible in the mouth. There is considerable interest in developing strategies involving growth-factor manipulation of the epithelial stem cells to afford protection to these cells during treatment and/or to speed up the regenerative process following treatment. In order for this to be achieved, studies have to be undertaken in animal systems to demonstrate the proof of principle and determine optimal protocols. Here, a murine model for oral mucositis based on measurements of tissue cellularity at various times after exposure to radiation was used to investigate cytotoxicity. Several sites in the mouth were analysed and the pronounced circadian rhythm in these various epithelial sites determined. The circadian rhythm is important in that it would determine the timing of administration of growth factors. A microscope with an interactive computer was used to define areas of epithelium and lengths of basal layer, within which, and along which, the total number of cell nuclei was determined over a range of times following exposure to 10, 20 and 30 Gy of X-rays. For various practical reasons, the ventral surface of the tongue was identified as the most appropriate tissue to analyse. Here, measurements of cellularity reached minimum values between 6 and 8 days following 20 Gy. Labelling of S-phase cells demonstrated foci of regeneration and a burst of proliferative regeneration that commenced at about 5 days and reached peak values at 8 days after irradiation. This burst of regenerative proliferation was coincident with the minimum in tissue cellularity on about day 8. The lower dose of radiation (10 Gy) had minimal effects on cellularity: after the higher dose (30 Gy), there was clearly a more severe level of cellular depletion. This quantitative model of oral mucositis could be used to study the effects of other cytotoxics, including combinations of agents, and the potential role of growth factors to reduce the severity of the cellular depletion and to speed up the kinetics of regeneration.

Animals↗
PubMed1998

Chromosome instability is a predominant trait of fibroblasts from Li-Fraumeni families.

Previous work has indicated a role for p53 in cell cycle control, genomic stability and cellular responses to DNA-damaging agents. However, few data are available for human fibroblasts heterozygous for defined germline mutations in TP53. We report studies on 25 strains derived from 12 families with Li-Fraumeni syndrome (LFS) and 18 strains from normal volunteers. The families include three that are classical LFS families, but in whom no TP53 mutation has been found. In the families with mutations, increased longevity and resistance to low-dose-rate ionizing radiation showed a statistically significant association with the presence of TP53 mutations. However, not all heterozygotes had increased longevity or were radioresistant, and fibroblasts from cancer-affected members of LFS families without TP53 mutations showed no significant increase in either of these end points. In contrast, all mutation-carrying strains showed evidence of genomic instability, expressed as aneuploidy, and accumulated structural chromosome aberrations in up to 100% of cells, usually accompanied by loss of the wild-type TP53 allele, immediately before senescence. Levels of aneuploidy higher than in normal cells were also observed in fibroblasts from families without TP53 mutations, suggesting that chromosome instability is a major factor in determining the cancer proneness of these families.

Adolescent↗
PubMed1998

Radiation-induced micronucleus induction in lymphocytes identifies a high frequency of radiosensitive cases among breast cancer patients: a test for predisposition?

Enhanced sensitivity to the chromosome-damaging effects of ionizing radiation is a feature of many cancer-predisposing conditions. We previously showed that 42% of an unselected series of breast cancer patients and 9% of healthy control subjects showed elevated chromosomal radiosensitivity of lymphocytes irradiated in the G2 phase of the cell cycle. We suggested that, in addition to the highly penetrant genes BRCA1 and BRCA2, which confer a very high risk of breast cancer and are carried by about 5% of all breast cancer patients, there are also low-penetrance predisposing genes carried by a much higher proportion of breast cancer patients, a view supported by recent epidemiological studies. Ideally, testing for the presence of these putative genes should involve the use of simpler methods than the G2 assay, which requires metaphase analysis of chromosome damage. Here we report on the use of a simple, rapid micronucleus assay in G0 lymphocytes exposed to high dose rate (HDR) or low dose rate gamma-irradiation, with delayed mitogenic stimulation. Good assay reproducibility was obtained, particularly with the HDR protocol, which identified 31% (12 out of 39) of breast cancer patients compared with 5% (2 out of 42) of healthy controls as having elevated radiation sensitivity. In the long term, such cytogenetic assays may have the potential for selecting women for intensive screening for breast cancer.

Adult↗
PubMed1998

The intrinsic radiosensitivity of normal and tumour cells.

PURPOSE: To examine whether in vitro measurements of normal and tumour cell radiosensitivity can be used as prognostic factors in clinical oncology. MATERIALS AND METHODS: Stage I-III cervix carcinoma patients were treated with radical radiotherapy with a minimum of 3 years' follow-up. Lymphocyte and tumour radiosensitivities were assayed using, respectively, a limiting dilution and soft agar clonogenic assay to obtain surviving fraction at 2 Gy (SF2). The results were related, in an actuarial analysis, to late morbidity assessed using the Franco Italian glossary. RESULTS: Patients with radiosensitive lymphocytes had a significantly increased risk of developing late complications (n = 93, p = 0.002). Increasing tumour radiosensitivity was associated with an increased risk of morbidity (n= 113, p=0.032). A significant correlation was found between fibroblast and tumour cell radiosensitivity (r=0.57, p=0.03), but a weak inverse association was found between lymphocyte and tumour cell radiosensitivity (r= -0.32, p=0.03). Patients with radiosensitive lymphocytes and tumour cells had higher levels of late complications than those whose cells were radioresistant. CONCLUSION: The work described highlights the importance of cellular radiosensitivity as a parameter determining the clinical response to radiotherapy.

Carcinoma↗
PubMed1998

Effects of soy-protein supplementation on epithelial proliferation in the histologically normal human breast.

A high dietary intake of soy products (eg, as in Japan and Singapore) has been associated with a reduction in the incidence of breast cancer in premenopausal women. Phytoestrogens present in soybeans inhibit human breast cancer cell proliferation in vitro and breast cancer development in animal models, but no data exist on the effects of phytoestrogens on histologically normal human breasts. This study examines the effects of dietary soy supplementation on the proliferation rate of premenopausal, histologically normal breast epithelium and the expression of progesterone receptor. Women (n = 48) with benign or malignant breast disease were randomly assigned to receive their normal diet either alone or with a 60-g soy supplement (containing 45 mg isoflavones) taken daily for 14 d. Biopsy samples of normal breasts were labeled with [3H]thymidine to detect the number of cells in S phase and were immunocytochemically stained for the proliferation antigen Ki67. The phytoestrogens genistein, daidzein, equol, enterolactone, and enterodiol were measured in serum samples obtained before and after supplementation. Serum concentrations of the isoflavones genistein and daidzein increased in the soy group at 14 d. Results showed a strong correlation between Ki67 and the thymidine labeling index (r = 0.868, P < or = 0.001). The proliferation rate of breast lobular epithelium significantly increased after 14 d of soy supplementation when both the day of menstrual cycle and the age of patient were accounted for. Progesterone receptor expression increased significantly in the soy group. Short-term dietary soy stimulates breast proliferation; further studies are required to determine whether this is due to estrogen agonist activity and to examine the long-term effects of soy supplementation on the pituitary gland and breast.

Adult↗
PubMed1998

5T4 oncofetal antigen in gastric carcinoma and its clinical significance.

OBJECTIVE: To evaluate the role of 5T4 antigen in gastric cancer progression and prognosis. DESIGN: A prospective study of 5T4 antigen expression in primary, secondary and recurrent gastric carcinoma, the relationship to selected prognostic parameters and the course of disease. PATIENTS: Eighty six patients operated on for gastric cancer. TISSUE: One hundred and twenty two gastric tumours were studied, including 86 primary carcinomas, 32 coexisting lymph node metastases and four recurrent carcinomas. METHODS: Immunohistochemistry using 5T4 monoclonal antibody on frozen sections. RESULTS: The 5T4 antigen was detected in 41% of primary gastric tumours including early gastric cancer. A strong relationship was found between 5T4 positivity and tumour histology. Thus, 52% of gastric carcinomas of intestinal type expressed 5T4 antigen compared with 28% of the diffuse type (P = 0.028). Among 16 sets of primary gastric carcinomas and regional lymph node metastases, coordinate 5T4 expression was seen in 14 cases; the other two showed acquisition of positivity on metastatic tumour cells (carcinomas of diffuse type). 5T4 antigen was detected more frequently in carcinomas with p53 accumulation compared with those with undetectable p53 levels (P = 0.015). The presence of 5T4 in cancer cells was correlated with poor short-term prognosis (24% vs 49% of 2 year survival for 5T4 positive and negative tumours respectively, P = 0.024). The effect on survival was evident in the p53 negative group, with patients 5T4 positive showing worse survival (28% vs 60% in 2 years). CONCLUSIONS: Our results suggest that the assessment of 5T4 expression in gastric carcinoma can be helpful in identifying patients with poor short-term prognosis.

Adult↗
PubMed1998

Phenylalanine and tyrosine metabolism in neonates receiving parenteral nutrition differing in pattern of amino acids.

Tyrosine is considered to be an indispensable dietary amino acid in the neonate, yet achieving adequate parenteral tyrosine intake is difficult due to its poor solubility. Increasing the supply of phenylalanine is the most common means of compensating for low tyrosine levels. Unfortunately, plasma phenylalanine concentrations are sometimes elevated in infants receiving high phenylalanine intake. This led us to study the phenylalanine and tyrosine metabolism in 16 neonates randomized to receive total parenteral nutrition with either a high or a moderate phenylalanine-containing amino acid solution. A primed, 24-h continuous stable isotope infusion of L-[1-13C]phenylalanine and L-[3,3-2H2]tyrosine was given to enable the measurement of phenylalanine and tyrosine kinetics. Results demonstrated that 1) phenylalanine hydroxylation was significantly greater in infants receiving high phenylalanine, 2) phenylalanine oxidation and percent dose oxidized was also significantly greater in infants receiving high phenylalanine, 3) apparent phenylalanine retention was greater in neonates receiving high phenylalanine, and 4) alternate catabolites of phenylalanine and tyrosine metabolism were significantly greater in infants receiving high phenylalanine compared with moderate phenylalanine. We conclude that neonates respond to increased parenteral phenylalanine intake by increasing their hydroxylation and oxidation rates. The greater oxidation of phenylalanine in infants receiving high phenylalanine in conjunction with the urinary excretion of alternate catabolites of phenylalanine and tyrosine suggests that the high phenylalanine intake may be in excess of needs. However, the lower apparent phenylalanine retention observed in infants receiving moderate phenylalanine suggests that the total aromatic amino acid level of moderate phenylalanine may be deficient for neonatal needs.

Amino Acids↗
PubMed1998

Altered stem cell regeneration in irradiated intestinal crypts of senescent mice.

Ageing is associated with a progressive deterioration in the functions of many organs within the body. In tissue with high cell turnover, the maintenance of the stem cells is of particular importance. Any accumulation of damage in stem cells may affect their function and hence threaten the homeostasis and regenerative capacity of the tissue. The small intestine represents a good model for the study of stem cells because of its spatial and hierarchical organisation. We have examined the effect of age on stem cell regenerative capacity after irradiation, using the microcolony assay. Crypt survival levels, the growth rate of surviving crypts, and the number of cells able to repopulate a crypt have been investigated by irradiating groups of 6-7 month old and 28-30 month old ICRFa male mice. After high doses of irradiation, the surviving crypts in old mice were both smaller and fewer in number than in young mice. The growth rate of surviving crypts was determined by measuring the crypt area and the number of cells/crypt at various times after 14 Gy irradiation. There was a growth delay of between about one half and one day in the older mice. Surprisingly, the number of clonogenic cells per crypt was estimated to be greater in the older mice. These studies indicate important age-related alterations in the capacity to regenerate the crypts after radiation damage.

Aging↗
PubMed1998

Fall and winter hormone concentrations related to stress in pigs identified as normal and carrier for stress susceptibility.

Stress is associated with significant losses in the swine industry. Seasonal changes have been shown to affect stress resistance in several species of animals. In the present study, we examined the effect of two seasons (fall or winter) on plasma insulin, cortisol, and adrenocorticotrophin hormone (ACTH) levels from fasted normal and carrier pigs for stress susceptibility when submitted to a blood-sampling stressor between 10:00 and 11:00. Comparisons were made of 10 diurnally active normal (NN) and 8 carrier (Nn) pigs reared in the fall to 9 NN and 10 Nn pigs reared in the winter. The light-dark cycle throughout the period of the experiment was 10 h light/14 h dark, with lights on from 07:00 to 17:00. Feed consisted of the traditional western Canadian swine ration consumed ad libitum. Results revealed significant season-by-genotype interactions for plasma insulin and ACTH concentrations in response to the blood-sampling stressor. The normal pigs displayed a significantly lower plasma insulin level during winter compared to the fall season. Plasma ACTH of normal pigs was 18% lower in the winter compared to the fall season, although this difference was not statistically significant. The carrier genotype, on the other hand, demonstrated higher plasma insulin concentration and lower plasma ACTH concentration in the winter compared to the fall season. Furthermore, there was a main genotype effect in plasma cortisol concentration such that the carrier pigs experienced a greater level compared to the normal genotype. Similarly, the carrier pigs had a more acute ACTH response to the blood-sampling stressor compared to the normal pigs during the fall season. Results have demonstrated that these two seasons of the year affect the response of both genotypes to a blood-sampling stressor, with the carrier genotype experiencing a more intense stress reaction in the fall season. These results further contribute to the recent research indicating that carrier pigs for stress susceptibility have a unique stress response.

Adrenocorticotropic Hormone↗