Biomedical subjects

C Brownie

Publications and source records attributed to C Brownie.

At least 19 recordsLinked to original sources

PubMed2006

Genetics of sex pheromone blend differences between Heliothis virescens and Heliothis subflexa: a chromosome mapping approach.

Males of the noctuid moths, Heliothis virescens and H. subflexa locate mates based on species-specific responses to female-emitted pheromones that are composed of distinct blends of volatile compounds. We conducted genetic crosses between these two species and used AFLP marker-based mapping of backcross families (H. subflexa direction) to determine which of the 30 autosomes in these moths contained quantitative trait loci (QTL) controlling the proportion of specific chemical components in the pheromone blends. Presence/absence of single H. virescens chromosomes accounted for 7-34% of the phenotypic variation among backcross females in seven pheromone components. For a set of three similar 16-carbon acetates, two H. virescens chromosomes interacted in determining their relative amounts within the pheromone gland and together accounted for 53% of the phenotypic variance. Our results are discussed relative to theories about population genetic processes and biochemical mechanisms involved in the evolution of new sexual communication systems.

Animals↗

PubMed2005

Technical note: technique for dissection and analysis of the rumen in young calves.

This paper discusses a technique used to evaluate rumen development in young calves, including removal, dissection, and analysis of tissue. The method allowed for examination of the different sacs of the rumen (dorsal, ventral, cranial, and caudal) using scanning electron microscopy to measure papillae denseness and histology slides to measure papillae length and width. Computer software was used to produce accurate measurements of papillae. The rumens of young calves were dissected, and samples were taken from the cranial, caudal, ventral, and dorsal sections. Calves were part of a nutrition research study, and dietary treatments did have an effect on development measurements such as length, width, and papillae denseness.

Animal Nutritional Physiological Phenomena↗

PubMed2003

Effects of amounts and degradability of dietary protein on lactation, nitrogen utilization, and excretion in early lactation Holstein cows.

Five treatment diets varying in crude protein (CP) and rumen undegradable protein (RUP) were calculated to supply a postruminal lysine to methionine ratio of about 3:1. Diets were fed as a total mixed ration to 65 Holstein cows that were either primiparous (n = 28) or multiparous (n = 37) from 21 to 120 d in milk to determine effects on lactation and nitrogen utilization. Crude protein % and calculated RUP (% of CP) of diets [on a dry matter (DM) basis] were: 1) 19.4, 40 (HPMU), 2) 16.5, 34 (LPLU), 3) 16.8, 40 (LPMU), 4) 16.8, 46 (LPHU), 5) 17.2, 43 (LPHU + UREA), which is the result of adding 0.4% of the diet DM as urea to LPHU. The corn silage-based treatment diets contained an average of 24% acid detergent fiber and 1.6 Mcal/kg net energy of lactation. Milk urea nitrogen (MUN) concentrations and body weights (BW) were used to calculate predicted amounts of urinary nitrogen (N) using the relationship: urinary N (g/d) = 0.0259 x BW (kg) x MUN (mg/dl). Cows fed HPMU had greater CP and RUP intakes, which resulted in higher concentrations of plasma urea nitrogen, rumen ammonia, MUN, and predicted urinary N. Milk yield, fat yield, fat percent, protein yield, and protein percent were not significantly different among treatments. Parity primarily affected parameters that were related to body size and not measurements of N utilization. The interaction of treatment and parity was not significant for any measurements taken. In this study, cows fed LPHU had significantly lower MUN and predicted urinary N without limiting production. These results demonstrate the potential to optimize milk production while minimizing N excretion in lactating dairy cattle.

Ammonia↗

PubMed2001

Inhibition of cholinesterase enzymes following a single dermal dose of chlorpyrifos and methyl parathion, alone and in combination, in pregnant rats.

Pregnant Sprague-Dawley rats (14-18 d of gestation) were treated with either a single dermal subclinical dose of 30 mg/kg (15% of dermal LD50) chlorpyrifos (O,O-diethyl-O-[3,5,6-trichloro-2-pyridinyl] phosphorothioate) or a single dermal subclinical dose of 10 mg/kg (15% of dermal LD50) methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate) or the two in combination. Chlorpyrifos inhibited maternal and fetal brain acetylcholinesterase (AChE) activity within 24 h of dosing, (48% and 67% of control activity, respectively). Following application of methyl parathion, peak inhibition of maternal and fetal brain AChE activity occurred at 48 h and 24 h after dosing (17% and 48% of control activity, respectively). A combination of chlorpyrifos and methyl parathion produced peak inhibition of maternal and fetal brain AChE activity at 24 h postdosing (35% and 73% of control activity, respectively). Maternal and fetal brain AChE activity recovered to various degrees of percentage of control 96 h after dosing. Application of methyl parathion or chlorpyrifos alone or in combination significantly inhibited maternal plasma butyrylcholinesterase (BuChE) activity. No significant inhibition of fetal plasma BuChE activity was detected. Peak inhibition of maternal liver BuChE occurred 24 h after application of methyl parathion or chlorpyrifos alone or in combination (64%, 80%, and 61% of control activity, respectively). Significant inhibition of placental AChE occurred within 24 h after application of methyl parathion or chlorpyrifos alone or in combination. The results suggest that methyl parathion and chlorpyrifos, alone or in combination, were rapidly distributed in maternal and fetal tissues, resulting in rapid inhibition of cholinesterase enzyme activities. The lower inhibitory effect of the combination could be due to competition between chlorpyrifos and methyl parathion for cytochrome P-450 enzymes, resulting in inhibition of the formation of the potent cholinesterase inhibitor oxon forms. The faster recovery of fetal plasma BuChE is attributed to the de novo synthesis of cholinesterase by fetal tissues compared to maternal tissues.

Acetylcholinesterase↗

PubMed2001

Species diagnosis and Bacillus thuringiensis resistance monitoring of Heliothis virescens and Helicoverpa zea (Lepidoptera: Noctuidae) field strains from the southern United States using feeding disruption bioassays.

Validation of a feeding disruption bioassay for the detection of resistance to Bacillus thuringiensis toxin and species identification is reported using field strains of Heliothis virescens and Helicoverpa zea collected from the southern United States in 1998. Feeding disruption is measured by a lack of fecal production from larvae exposed to a diagnostic concentration of CryIAc in a blue indicator diet. The bioassay provided rapid (24 h) diagnosis of the species composition of larvae tested and also monitored for the presence of resistance in H. virescens. An additional diagnostic concentration was established for monitoring resistance in H. zea. A probit model was used to compare the fecal production responses of insect strains over a range of CryIAc doses. Probability calculations, derived from our assay results, are also presented to aid in the interpretation of future results from field trials. Integration of the feeding disruption bioassay into integrated pest management programs is discussed.

Animals↗

PubMed2000

Effect of whole and expanded-expelled cottonseed on milk yield and blood gossypol.

Thirty-two primiparous and 12 multiparous Holstein cows were randomly assigned at calving to treatments to determine the effects of type and amount of cottonseed product on plasma gossypol, milk production, and composition, and conjugated linoleic acid concentration in milk fat. Rations consisted of corn silage, corn grain, soybean meal, and cottonseed hulls, and contained on average 16.8% crude protein and 25.3% acid detergent fiber on a dry matter basis. On a dry matter basis, diets contained one of the following: 1) 14% whole cottonseed; 2) 14% expanded-expelled cottonseed; 3) 21% expanded-expelled cottonseed; or 4) 28% expanded-expelled cottonseed. Cows remained on treatment from 30 through 120 d in milk. Dry matter intakes were not significantly different, but intakes of crude protein, acid detergent fiber, and fat were higher for multiparous cows fed whole cottonseed. Multiparous cows fed whole cottonseed had higher yields of milk, fat-corrected milk, crude protein, fat and solids-not-fat than those fed any level of expanded-expelled cottonseed. Concentrations of milk fat, protein, and SNF were not affected by treatment. Although there were treatment differences in fat intake, there were no production differences in primiparous cows. Milk production efficiency (fat-corrected milk/dry matter intake) was not affected by treatment for either multiparous or primiparous cows. Cows fed 14% whole or 14% expanded-expelled cottonseed had similar levels of total plasma gossypol and plasma levels of the negative isomer of gossypol. Increasing the level of expanded-expelled cottonseed in the diet increased both total plasma gossypol and the negative isomer. In this experiment, multiparous but not primiparous cows fed whole cottonseed produced more milk than those fed expanded-expelled cottonseed at 14 to 28% of the diet dry matter, however, feed efficiencies were similar for all treatments.

Animal Feed↗

PubMed1999

5-AZA-2'-deoxycytidine-induced dysmorphogenesis in the rat.

5-aza-2'-deoxycytidine (d-AZA) causes temporally related defects in the developing mouse. Treatment of 1.0 mg/kg on gestation day (GD) 8 results in axial skeletal defects; on GD9, cleft palate and vertebral defects; on GD10, hindlimb phocomelia; and on GD11, digital defects. An unusual aspect of d-AZA teratogenicity in mice is that the phocomelia appears to be specific to the hindlimb, and the forelimb is not similarly affected regardless of treatment day. The current study was initiated to evaluate the embryonic response of another species, the rat, to this unique teratogen. Pregnant Sprague Dawley (CD) rats were treated with d-AZA or vehicle control. The compound was administered i.p. on GD9, 10, 11, or 12 to parallel developmental staging of the mouse. The highest dose (1.0 mg/kg) elicited effects indicating increased sensitivity to the compound in the rat as compared to the mouse. GD9 treatment was characterized by massive resorptions; GD10, by a predominance of axial skeletal defects and cleft palate; GD11, by a predominance of forelimb phocomelia and missing ribs; and GD12 by hindlimb phocomelia and forelimb digit defects. These data indicate significant differences in the developmental responses to d-AZA of the mouse and the rat. This may reflect interspecies differences in the temporal expression of genes involved in morphogenesis and/or the methylation patterns of such genes. Molecular data generated in the mouse will be compared to that of the rat to further characterize the developmental dynamics responsible for the interspecies differences. Teratogenesis Carcinog. Mutagen. 19:329-338, 1999.

Abnormalities, Drug-Induced↗

PubMed1998

Milk production and plasma gossypol of cows fed cottonseed and oilseed meals with or without rumen-undegradable protein.

Twenty-four multiparous Holstein cows were randomly assigned at calving to treatment diets using a modified split-plot design to determine the effects of protein source on milk production and composition. The treatment diets consisted of an 80:20 combination of corn and alfalfa silages and whole cottonseed at 12% of the dietary dry matter (DM). The treatment diets were formulated to contain 17% crude protein (CP) and 20% acid detergent fiber on a DM basis. One of the following sources of supplemental CP was included in each treatment diet: 1) cottonseed meal, 2) cottonseed meal plus a rumen-undegradable protein (RUP) supplement, 3) soybean meal, and 4) soybean meal plus an RUP supplement. Cows were fed the initial treatment diet for 6 wk and then were switched to the other oilseed meal source but continued to receive the same amount of RUP during the second period of the study. Milk production and composition were not affected by treatment diet. Cows fed treatment diets without RUP supplementation consumed more DM and thus more CP. Supplementation with RUP resulted in greater milk production efficiency per unit of DM consumed. Cows fed treatment diets containing cottonseed meal had higher plasma gossypol concentrations than did cows fed treatment diets containing soybean meal. Plasma gossypol concentrations for all cows in each group were below the recommended upper limit that is considered to be safe. Data suggest that cottonseed meal in the diet can be substituted for soybean meal, resulting in similar milk production and composition.

Acetates↗

PubMed1998

Anatomic site and interanimal variability in morphologic characteristics of bottlenose dolphin (Tursiops truncatus) skin likely to affect dermal absorption studies.

OBJECTIVE: To investigate anatomic site and interanimal variability in dolphin skin for use in development of models for cutaneous absorption studies. SAMPLE POPULATION: Skin from 30 healthy free-ranging bottlenose dolphins (17 males and 13 females grouped by age) and 10 captive males between 13 and 19 years old. PROCEDURE: Biopsy specimens were collected from the 10 male dolphins at 3 anatomic sites and from the 30 dolphins at 1 site; specimens were evaluated by light microscopy. Stratum externum thickness, minimal depth to the vasculature, and maximal epidermal depth were measured at 4 locations on 4 sequential sections. Comparisons of replicate measurements for 3 skin characteristics were made within and among anatomic sites, between dolphins of the same sex and approximate age, and across males and females of various ages. RESULTS: The stratum externum in male dolphins was thicker. Differences attributable to age and anatomic site were not significant. Variation attributable to differences in stratum externum thickness between dolphins was significant. Differences among body sites within the same dolphin were significant but were not consistent from dolphin to dolphin. Mean stratum externum thickness was not different between males of the 2 cohorts, but mean maximal epidermal depth and mean minimal depth to the vasculature were different. Variances within the 2 male cohorts were not significantly different. CONCLUSIONS: Studies affected by stratum externum thickness should eliminate the effect attributable to sex difference by using dolphins of the same sex or grouping analytical data by sex. Precision could be improved without increasing the total number of dolphins by collecting more than 1 sample/dolphin.

Animals↗

PubMed1996

In vitro percutaneous absorption of benzidine in complex mechanistically defined chemical mixtures.

Little work has been done on the topical absorption of the bladder carcinogen benzidine. Since humans are more likely to be exposed to chemical mixtures than to a single chemical, a program was developed in these laboratories to examine the cumulative effect of complex mixtures on percutaneous absorption of important toxicants such as benzidine. In this investigation, a mixture is defined as a physical combination consisting of a marker chemical and several other chemicals, each of which can have independent and/or synergistic effects on dermal penetration and absorption of the marker chemical. Ten mixtures, consisting of a marker chemical (benzidine, B), a solvent (acetone, A or DMSO, D), a surfactant (0 or 10% sodium lauryl sulfate, SL), a vasodilator (0 or 180 microg methyl nicotinate, M), and a reducing agent (0 or 2% SnCl2, s) were employed in this study. Isolated perfused porcine skin flaps (IPPSFs), which have proven to be a suitable in vitro model for assessing dermal absorption and toxicity, and flow-through diffusion cell systems were utilized. The extent of benzidine absorption in skin sections dosed with either B + A (0.94% dose) or B + D (1.01% dose) was similar to that when IPPSFs were dosed with either B + A (0.54% dose) or B + D (1.31% dose). However, flux vs time profiles were different when the two in vitro methods were compared. For mixtures containing (1) DMSO only or acetone only or (2) solvents containing SL + M, benzidine absorption was enhanced when compared with other mixtures. Compared to acetone, DMSO appears to enhance dermal penetration of benzidine in most of the mixtures. Compared to other mixtures evaluated, SnCl2 inhibited benzidine absorption irrespective of solvent present. SnCl2 also appears to inhibit benzidine penetration in DMSO mixtures containing SL only, but not in acetone mixtures. It is proposed that chemical-chemical interactions between benzidine and SnCl2 may be inhibiting benzidine absorption and chemical-biological interactions between M + SL and skin may be enhancing benzidine absorption. Across all mixtures, maximum observed benzidine absorption was almost 3% of the topical dose over 8 hr, but maximum penetration was 22% over the same time period which would suggest a potential for greater systemic exposure over longer time frames. This work underscores the need to study potentially toxic chemicals in mixture exposure scenarios since the interactions observed would confound risk assessment based on single chemical data.

Animals↗

PubMed1995

A likelihood-based approach to capture-recapture estimation of demographic parameters under the robust design.

The Jolly-Seber method has been the traditional approach to the estimation of demographic parameters in long-term capture-recapture studies of wildlife and fish species. This method involves restrictive assumptions about capture probabilities that can lead to biased estimates, especially of population size and recruitment. Pollock (1982, Journal of Wildlife Management 46, 752-757) proposed a sampling scheme in which a series of closely spaced samples were separated by longer intervals such as a year. For this "robust design," Pollock suggested a flexible ad hoc approach that combines the Jolly-Seber estimators with closed population estimators, to reduce bias caused by unequal catchability, and to provide estimates for parameters that are unidentifiable by the Jolly-Seber method alone. In this paper we provide a formal modelling framework for analysis of data obtained using the robust design. We develop likelihood functions for the complete data structure under a variety of models and examine the relationship among the models. We compute maximum likelihood estimates for the parameters by applying a conditional argument, and compare their performance against those of ad hoc and Jolly-Seber approaches using simulation.

Animals↗

PubMed1994

Percutaneous absorption of topical parathion through porcine skin: in vitro studies on the effect of environmental perturbations.

Topical use of pesticides in domestic animals such as swine is a common practice; however, the effect of environmental factors on the extent of absorption has not received attention. Since no single factor can exert its effects alone in the natural environment, the interaction of environmental factors on the percutaneous absorption of pesticides must be understood before potential toxicity of dermal absorption of pesticides can be effectively estimated. In the present studies, the effects of air temperature (Ta), perfusate temperature (Tp), perfusate flow (F) and relative humidity (%RH) on absorption of parathion were studied in vitro in porcine skin. Parathion absorption was determined by measuring radiolabel appearing in the perfusate over time. Three main environmental parameters were found to have a significant effect on parathion penetration. Increasing Ta from 37 degrees C to 42 degrees C, %RH from 60% to 90% or F from 4 ml/h to 8 ml/h each produced a significant increase in penetration. The following significantly positive two-way interactions among test parameters were seen: Ta x F and %RH x F at the 4 micrograms dose, %RH x F at the 40 micrograms dose and Ta x %RH, Ta x F and %RH x F at the 400 micrograms dose. There were no three-way interactions at any of the three doses tested. These results suggest that the factors tested are not independent variables and must be considered interactive when used in assessing pesticide percutaneous absorption.

Animals↗

PubMed1992

Fractional excretion of electrolytes in lactating dairy cows.

Samples of serum and urine were obtained simultaneously from 56 healthy lactating cows to determine ranges of fractional excretion (FE) of calcium (Ca), phosphate (PO4), magnesium (Mg), sodium (Na), potassium (K), and chloride (Cl). Samples were obtained at 3 stages of lactation: period 1 = 1 to 7 days, 2 = 83 to 112 days, and 3 = 175 to 197 days. The FE of electrolytes were significantly different among periods 1, 2, and 3 for Ca (P less than 0.001), PO4 (P less than 0.025) and Mg (P less than 0.025), but were not significantly different for Na, K, and Cl. Least squares mean FE of Ca was lowest in period 1 and not significantly different for periods 2 and 3, whereas mean FE values for PO4 and Mg were highest in period 2 and not significantly different for periods 1 and 3. The mean FE values of Na, K, and Cl did not change with stage of lactation. Age and category of milk production (high, medium, and low) did not influence the FE values of the electrolytes.

Animals↗

PubMed1992

A rank-based mixed model approach to multisite clinical trials.

New rank-based methods for analyzing data from multisite clinical trials are presented in the context of "mixed" linear models. In contrast to current rank methods, the new procedures test for a drug main effect in the presence of a random drug by site interaction (or drug by investigator interaction when there is only one investigator per site). Analogous procedures are also provided for the "fixed-effects" situation, and comparisons are made with current methods. The rationale for an analysis that assumes random investigator effects is described.

Analysis of Variance↗

PubMed1992

Clinical and metabolic findings in dogs with chronic renal failure fed two diets.

Exogenous creatinine clearance, urinary electrolyte excretions, calcium and phosphorus balance, serum cholesterol concentration, arterial blood pressure, and body weight were evaluated in dogs with chronic renal failure that were fed 2 commercial diets. Nine dogs ranging in age from 1 to 15 years were identified as having mild to moderate chronic renal failure (CRF, exogenous creatinine clearance = 0.5 to 2.13 ml/kg of body weight/min). These dogs and a group of 10 clinically normal controls were fed a diet containing 31% protein for 8 weeks at which time hematologic and biochemical evaluations and clearance studies were performed. All dogs then were fed a phosphorus-restricted diet containing 16% protein and then reevaluated after 8 weeks. The dogs in this study had hematologic and biochemical abnormalities typical of CRF. Urine absolute and fractional excretion of electrolytes was higher in dogs with CRF than in controls and was affected by diet. Serum cholesterol concentration was higher in dogs with CRF and increased in those dogs after feeding the low protein diet. Changes in dietary sodium intake did not affect arterial blood pressure. The phosphorus-restricted diet did not affect serum amino terminal parathyroid hormone concentration in either group. Control dogs lost body weight, whereas dogs with CRF gained weight when fed the low protein diet. We concluded that dogs with mild to moderately severe CRF have the same biochemical abnormalities and response to dietary restriction of protein and phosphorus as has been previously reported in dogs with experimentally induced CRF. Restriction of dietary sodium may not decrease arterial blood pressure in some dogs with CRF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1992

Amino acid profiles in dogs with chronic renal failure fed two diets.

Amino acid profiles and serum albumin and serum total protein concentrations were evaluated in dogs with renal disease. Nine dogs ranging in age from 1 to 15 years were identified as having mild to moderate chronic renal failure (CRF; exogenous creatinine clearance, 0.5 to 2.13 ml/kg of body weight/min). These dogs and a group of 10 clinically normal control dogs were fed a diet containing 31% protein for 8 weeks, at which time serum and urine amino acid assays and clearance studies were performed. All dogs then were fed a diet containing 16% protein for 8 weeks and then reevaluated. Chronic renal failure was associated with mild abnormalities in serum concentrations of amino acids. When fed the higher protein diet, dogs with CRF had lower serum concentrations of glutamine, leucine, proline, and serine and higher serum concentrations of cystathionine and 3-methylhistidine than clinically normal control dogs. When fed the low protein diet, dogs with CRF had lower serum serine concentrations and higher serum concentrations of cystathionine, phenylalanine, and 3-methylhistidine. Urine excretion of amino acids in all dogs on both diets was low, and dogs with CRF had lower renal clearances of 3-methylhistidine than control dogs. There were no significant differences in concentrations of serum albumin and total solids between either group, regardless of diet. We concluded that dogs with mild to moderately severe CRF have mild abnormalities of serum free amino acid concentrations, but renal conservation of essential amino acids is not impaired.

Amino Acids↗

PubMed1991

Impact of menstrual periodicity on serum lipid levels and estimates of dietary intakes.

Nine eumenorrheic women were studied at five separate times each month for a minimum of 2 months. Fasting bloods and 1-day food records were obtained from all women at these times to describe the pattern and magnitude of within-person variation in selected nutrient and lipid indicators attributable to menstrual cyclicity. Serum cholesterol, beta-carotene, 17 beta-estradiol (E2), and dietary selenium intakes exhibited significant periodic regressions against time. For the group as a whole, however, only serum cholesterol and E2 measures exhibited significantly strong consistent periodicities. Future studies with a larger sample of women are warranted to confirm these findings. Unless strict blood sampling protocols are followed, variation attributable to menstrual cyclicity may mitigate the reliability of the serum cholesterol screenings advocated in the past few years.

Adult↗

PubMed1991

Mixture models for continuous data in dose-response studies when some animals are unaffected by treatment.

A mixture model is described for dose-response studies where measurements on a continuous variable suggest that some animals are not affected by treatment. The model combines a logistic regression on dose for the probability an animal will "respond" to treatment with a linear regression on dose for the mean of the responders. Maximum likelihood estimation via the EM algorithm is described and likelihood ratio tests are used to distinguish between the full model and meaningful reduced-parameter versions. Use of the model is illustrated with three real-data examples.

Algorithms↗