Assessment of the accuracy of quantitative urine collection in mink (Mustela vison) using osmotic pumps for continuous release of p-amino-hippuric acid and inulin

A method is described to assess the accuracy of quantitative collection of urine in small experimental animals using implanted Alzet osmotic pumps for continuous release of specific urinary markers. The nominal pumping rate (10.00 +/- 0.15 microliters/h; mean +/- SEM) of 10 osmotic pumps was verified (9.96 +/- 0.12 microliters/h) in a 10-day in vitro assay in isotonic saline at 39.0 degrees C. Ten adult female mink (1100 +/- 34 g) had a 2-ml osmotic pump implanted intraperitoneally for 7 days while maintained in metabolic cages on a conventional mink diet. In 5 mink the pumps contained [3H]-labelled p-aminohippuric acid (PAH) only. The remaining 5 animals received a pump containing [3H]-PAH and [14C]-labelled inulin. The experiment was well tolerated by all animals. In fed animals, the amount of urine collected per day was not influenced by the osmotic pumps, whereas 24 h of fasting (water allowed) caused a dramatic fall in urinary volume. In 4 consecutive 24-h collections of urine (n = 10 animals) the recovery of [3H]-PAH was 70.8 +/- 3.6% (range: 52.0-87.2%), and urinary plus faecal water (= total) recovery of [3H]-PAH averaged 77.0 +/- 3.7% (range: 60.3%-94.3%). For [14C]-inulin (n = 5 animals) the urinary and total recoveries were 68.4 +/- 2.2% and 77.2 +/- 2.4%, respectively. In urine the 14C to 3H counts-ratio was almost identical to that of the infusion solution, indicating that metabolic decomposition of the markers was negligible. The results indicate that the daily recovery of suitable urinary markers, released by implanted osmotic pumps, provides a reproducible and valid measure of the accuracy achieved in quantitative collection of urine in mink and probably also in other animal species. Hence, this technique may be useful in future studies on animal nutrition and/or drug disposition.

Effect of protein and fat content in feed on plasma alanine-aminotransferase and hepatic fatty infiltration in mink

The effect of the content of protein and fat in the feed on the development of fatty infiltration of the liver in the period from weaning until pelting was measured in two groups of male scanblack mink (Mustela vision) fed 20% and 45%, respectively, of metabolizable energy (ME) from protein. Furthermore, plasma activity of alanine-aminotransferase and the content of specifically chosen clinical-chemical variables in the blood were measured. At pelting time in December, the liver weights were absolutely and relatively heavier to body weight and had a considerably higher fat content at 20% of ME from protein than at 45% of ME from protein. From August to pelting time, the activity of alanine-aminotransferase in plasma was higher at a low protein level than at a higher protein level in the feed. It is concluded that the content of protein and fat in the feed affects the incidence of hepatic fatty infiltration in mink. In the growth period, it is possible, based on plasma activity of alanine-aminotransferase, to select animals with histological fatty infiltration of the liver.

Chronic oral exposure to bunker C fuel oil causes adrenal insufficiency in ranch mink (Mustela vison)

Animals living in the near-shore marine environment are predisposed to contact with chemical contaminants through land- and ocean-based activities. The release of petroleum hydrocarbons into the marine environment is a stressor to this environment and its resident wildlife. The stress response to chemical threats is dependent on an intact hypothalamic-pituitary-adrenal axis, which also may be a target to the effects of these chemicals. Ranch mink (Mustela vison) were used as surrogates for sea otters (Enhydra lutris) to examine the development of adrenal hypertrophy after chronic, oral exposure to low concentrations of bunker C fuel oil. Animals were fed three different concentrations of fuel oil (48, 520, and 908 ppm) or mineral oil (control) for 60-62 days. At the end of the exposure, blood and fecal samples were collected and organs were weighed and examined microscopically. In all fuel oil groups, exposure resulted in adrenal hypertrophy, an adaptation suggestive of adrenal activation. However, concentrations of serum and fecal glucocorticoids and serum progesterone were not elevated over control values. Hematologic parameters and serum chemistries showed no changes consistent with increased adrenal activity. In addition, adrenal glands from animals fed the higher concentrations of fuel oil contained large numbers of heavily vacuolated cells. We conclude that petroleum hydrocarbons are inducing an adrenal insufficiency that leads to the adaptive enlargement of the gland. This would increase the susceptibility of fuel oil-exposed animals to the deleterious effects of other environmental stressors.

Effect of dietary glycine and benzoate level on benzoate metabolism in mink (Mustela vision), blue fox (Alopex lagopus), and raccoon dog (Nyctereutes procyonoides)

Three 2 x 4 factorial experiments were carried out from August to September with 30 juvenile male mink, 24 raccoon dogs, and 24 blue foxes to investigate the effect of dietary glycine supply (low or high) on the efficiency of these species to excrete hippuric acid with incremental benzoate intake (0, 1, 2, or 4 mmol/kg BW). For mink, two additional treatments with 1 or 2 mmol/kg BW of ethyl benzoate were included. A basal low-glycine diet was formulated to meet the minimum protein requirements of fur animals (30% of ME). This diet was supplemented with 0 or 3 g/kg of glycine, or with 0, 1.0, 2.07, or 4.15 g/kg of sodium benzoate for mink and blue foxes, and with 0 or 4.5 g/kg of glycine and 0, 1.58, 3.17, or 6.34 g/kg of sodium benzoate for raccoon dogs, respectively. Two additional diets with .76 or 1.53 g/kg of ethyl benzoate were made for mink. Fecal and urinary benzoic and hippuric acid excretion were measured for 3 d. The 24-h recovery of [14C]benzoic acid injected intraperitoneally was measured from urine, the liver, and the kidneys. All animals appeared healthy and no clinical signs of benzoate overdose were observed. Dietary benzoate level did not affect ADFI or ADG in any species. Glycine supplementation lowered ADFI in mink. The majority of ingested benzoates were absorbed from the gut (over 95%), except in blue foxes, which excreted 6 to 15% of ingested benzoates in feces with incremental increases in benzoate intake. Urinary free benzoic acid excretion accounted for 10% of the ingested benzoates in blue foxes but less than 5% in mink and raccoon dogs. When benzoate intake was 1 mmol/kg BW, mink, blue foxes, and raccoon dogs excreted 71, 77, and 34% of ingested benzoates as hippuric acid in urine, respectively. With higher benzoate intakes, urinary hippuric acid excretion decreased quadratically with mink to 20%, and linearly with blue foxes and raccoon dogs to 45 and 16%, respectively. The hippuric acid pathway appears to be the principal route of benzoate elimination in the mink and blue fox, whereas, in the raccoon dog, other pathways appear to be more important. In mink, the elimination of ethyl benzoate did not differ from that of sodium benzoate. Because glycine conjugation is the primary route of benzoate elimination, it is recommended that benzoate content in fur animal feeds should not exceed 1 g/kg feed on an as-fed basis.

A first estimate of the amino acid requirement for milk production of the high-producing female mink (Mustela vison)

Thirty mink dams nursing litters of six kits were assigned to one of three dietary treatments [high protein (HP), medium protein (MP) and low protein (LP)], fed ad libitum for 4 week from parturition, to investigate the effects of protein supply on milk yield and milk composition in order to estimate the amino acid requirement of the lactating mink. Twelve dams were held in an intensive care unit and subjected to balance experiments and the kits were injected with deuterium oxide to determine water kinetics and milk yield. Eighteen dams were kept under normal farm conditions but with feed intake of dams and live weight gain of kits being determined and milk samples collected. The ME intake was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet, whereas the amino acid intake (g/day) was lowest (p < 0.05) in dams fed the LP diet. In the third and fourth weeks of lactation milk yield was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet. Chemical composition of milk was not affected (p > 0.05) by dietary treatment. However, protein content tended (p = 0.06) to be lower in dams fed the LP diet. Amino acid content (g/16 g N) of milk was higher (p < 0.05) in dams fed the LP and MP diets than in dams fed the HP diet. This resulted in the highest (p < 0.05) amino acid intake and highest (p < 0.001) live weights of kits nursed by dams fed the LP and MP diets, which may be explained by a combined effect of higher ME intake and reduced energetic costs for glucose production through less amino acids being used in gluconeogenesis. In conclusion, the improved performance of dams fed the LP diet suggested that their requirement of essential amino acids and non-specific N were covered, and the requirement of digestible amino acids of lactating mink (kg(0.75)) was, thereby, estimated by use of a factorial approach including the amino acid excretion in milk of LP dams.

Effect of folic acid supplementation on folate status and formate oxidation rate in mink (Mustela vision)

We investigated the folate-dependent toxicity of formate to mink to better understand the use of formic acid in fur animal feeds. Folic acid supplementation (0, 1, 5, 10, and 20 mg/kg of DM) in the feed of weanling mink for 4 wk resulted in hepatic tetrahydrofolate (H4folate) concentrations of 3.94, 8.51, 9.15, 10.4, and 15.0 nmol/g, respectively (SE 1.03). Oxidation tests in metabolic chambers, preceeding a single injection of sodium [14C]formate (500 mg/kg BW), showed that the nonsupplemented mink oxidized formate into CO2 at a rate 37% less than that of the supplemented mink. The oxidation rate increased with supplementation level and was maximal, 54.2 mEq.kg1.h1 (SE 3.0), at 10 mg of folate/kg; at the highest level of supplementation (20 mg/kg), CO2 production tended to be lower. Concentration of hepatic 14C increased with the hepatic H4folate, and its accumulation continued after the highest point of oxidation. These observations indicate that mink oxidize formate readily but at a slightly lower rate than do rats. However, if extra folate is not supplemented in the feed during the period of early intensive growth, hepatic H4folate level may decline to the levels found in humans and monkeys, which are susceptible to formate accumulation. Average daily weight gain improved with each increase in supplementation of folic acid; however, only the differences between the nonsupplemented diet and the two highest levels of the vitamin reached statistical significance (P < .05).

Organochlorine and heavy metal contaminants in wild mink in western Northwest Territories, Canada

The mink (Mustela vision) is a top trophic level species that readily bioaccumulates environmental pollutants and is considered to be a sensitive indicator of ecosystem health. Spatial trends in levels of organochlorine and heavy metal contaminant burdens were determined from 1991 to 1995 for wild mink from western Northwest Territories (NWT), Canada. Tissue samples from 207 mink from seven communities were analyzed for residues of 63 organochlorines and 10 heavy metals. All groups of organochlorines were detected in mink livers at relatively low levels; maximum community means were 9.52 ng/g sigma DDT and 73.07 ng/g sigma PCB (sum of 43 congeners). There was a general trend of decreasing organochlorine burdens along a northerly or westerly gradient for some groups of compounds, primarily sigma DDT, sigma PCB, sigma chlordane and dieldrin. Toxic equivalents (TEQs) of mink liver tissue were low, with the maximum community mean of 0.28 pg/g wet weight (5.5 pg/g lipid weight). Levels of heavy metal burdens in liver and kidney tissues were found to be relatively low, with the exception of Hg, which was found at moderate levels. There was no obvious geographic trend to the pattern of heavy metal burdens. The available evidence suggests that long-range atmospheric transport is the main source of the organochlorine contaminants observed. Local conditions (geology, water and soil chemistry, diet, etc.) may determine heavy metal burdens. Levels of contaminants in NWT mink appear to be one to two orders of magnitude lower than levels observed to cause reproductive impairment, reduced survival of kits, or lethality in adult mink. In the western NWT mink may be the best indicator to assess trends in environmental contaminants and ecosystem health; periodic monitoring is recommended.

Growth and reproductive effects from dietary exposure to Aroclor 1268 in mink (Neovison vison), a surrogate model for marine mammals

Polychlorinated biphenyls (PCBs) from the commercial mixture Aroclor 1268 were historically released into the Turtle-Brunswick River estuary (southeastern Georgia, USA) from industrial operations. Sum PCBs (ΣPCBs) in blubber samples from Turtle-Brunswick River estuary bottlenose dolphins (Tursiops truncatus) have been reported at concentrations more than 10-fold higher than those observed in dolphins from adjacent regional estuaries. Given that toxicity data specific to Aroclor 1268 and applicable to marine mammals are limited, predicting the toxic effects of Aroclor 1268 in dolphins is uncertain, particularly because of its unique congener profile and associated physiochemical characteristics compared with other PCB mixtures. American mink (Neovison vison) were chosen as a surrogate model for cetaceans to develop marine mammalian PCB toxicity benchmarks. Mink are a suitable surrogate species for cetaceans in toxicity studies because of similarities in diet and taxonomic class, and a characteristic sensitivity to PCBs provides a potential safety factor when using mink toxicology data for cross-species extrapolations. Effects of dietary exposure to Aroclor 1268 on reproduction, growth, and mortality in mink were compared with both a negative control and a positive control (3,3',4,4',5-pentachlorobiphenyl, PCB 126). Aroclor 1268 dietary ΣPCB concentrations ranged from 1.8 µg/g feed wet weight to 29 µg/g feed wet weight. Whelp success was unaffected by Aroclor 1268 exposure at any level. Treatment mean litter size, kit growth, and kit survival were adversely affected relative to the negative control at dietary ΣPCB concentrations of 10.6 µg/g feed wet weight and greater.

Accumulation of mercury and selenium in the brain of river otters (Lontra canadensis) and wild mink (Mustela vison) from Nova Scotia, Canada

Total Hg, methyl-Hg (MeHg) and Se levels were measured in the brain of river otters (Lontra canadensis) and wild mink (Mustela vison) carcasses collected from Nova Scotia, Canada. Total Hg concentrations in the otters' brain were highly variable, ranging from 0.3 to 18.0 microg/g dw and were significantly higher in animals caught from inland areas of the province versus coastal animals. Similarly, inland otters contained significantly more MeHg in the brain than did coastal otters. MeHg was highly correlated with total Hg in both inland and coastal otters and represented on average approximately 82% of the total Hg. Selenium concentrations in the otter brain ranged from 1.0 to 7.8 microg/g dw but unlike Hg, there was no significant difference in Se levels between inland and coastal otters. There was a significant positive relationship between Se and total Hg concentrations in the otters with the molar ratio of Se:Hg approximately 1:1 for animals having an Hg concentration>18 nmol/g dw. The non-random sampling protocol for the mink precluded extensive statistical analysis of the data. However, unlike otters, virtually all (i.e. 98%) of the total Hg in mink brain was present as MeHg in both inland and coastal mink. Also unlike the otter results, Se concentrations showed no relationship with either total or MeHg in both inland and coastal mink. The data suggest that mink and otters may have different mechanisms for managing high levels of Hg in the brain.

Influence of age, season, body condition and geographical area on concentrations of chlorinated and brominated contaminants in wild mink (Neovison vison) in Sweden

The wild mink has gained acceptance as a sentinel species in environmental monitoring. However, only limited data are available in the literature on factors driving variability in concentrations of organic pollutants in this species. This study characterizes the differences in contaminant concentrations in subcutaneous fat of male mink from four different areas in Sweden and demonstrates how age, season and body condition influence concentrations of polychlorinated biphenyl (PCB) congeners, polybrominated diphenyl ether (PBDE) congeners (including methoxylated forms, MeO-PBDEs), as well as the pesticides dichlorodiphenyldichloroethylene (DDE), chlordane and hexachlorobenzene (HCB). The data were statistically treated using multiple regression and principal component analysis. The ∑PCB concentration and concentrations of PCB congeners 138, 156, 157, 180, 170/190, 189, 194, 206, 209 as well as PBDE 153/154 varied with age. Season had an influence on ∑PCB, PBDE 47 and PBDE 153/154 concentrations, as well as concentrations of most PCB congeners, with the exception of PCB 101, 110, 141 and 182/187. Lean mink had higher concentrations of most PCBs and PBDEs than mink with larger fat depots. The analyzed pesticides (DDE, oxychlordane, HCB) showed no systematic variation with season, age or body condition. The concentrations of MeO-PBDEs were generally low and 6MeO-PBDE 47 was the most commonly detected MeO-PBDE in mink from marine, brackish and freshwater areas. The results indicate that age, season and body condition are factors that may influence the concentrations of PCBs and PBDEs, and it is thus recommended to take these factors into account when analyzing mink exposure data.

Immunohistochemical demonstration and radioimmunoassay of melatonin in the mink pineal gland

An antiserum raised against N-amino-3-propyl melatonin bound to a protein carrier was used to visualize melatonin by immunohistochemistry and to measure melatonin concentration by radioimmunoassay in the pineal gland of intact mink females killed throughout the 24 h cycle and females killed after a bilateral ablation of the cervical superior ganglion. Melatonin immunoreactivity revealed by immunofluorescence or by the peroxidase-antiperoxidase complex was observed in the cytoplasm of presumed pinealocytes of all the females. Circadian changes in pineal melatonin content were not visualized by immunohistochemistry; furthermore, immunoreactivity was also present in the pineal gland of the ganglionectomized females. However, the melatonin content measured by radioimmunoassay was significantly higher in the pineal gland from intact females killed during the night compared with that of intact females killed during the day or of ganglionectomized females. The discrepancy between the results obtained using the two methods may arise because immunohistochemistry can detect very small amounts of melatonin.

Toleration of high concentrations of dietary zinc by mink

Adult and kit male and female natural dark ranch mink (Mustela vison) were fed a conventional diet supplemented with 0, 500, 1,000, or 1,500 ppm zinc, as ZnSO4.7H2O, for 144 days. No marked adverse effects were observed in feed consumption, body weight gains, hematologic parameters, fur quality, or survival. Zinc concentrations in liver, kidney, and pancreas of the mink increased in direct proportion to the zinc content of the diet. Histopathologic examination of the livers, kidneys, and pancreata revealed no lesions indicative of zinc toxicosis. The results indicate that mink can tolerate at least 1,500 ppm dietary zinc, as ZnSO4.7H2O, for several months without apparent adverse effects.

Fatty acid alterations caused by PCBs (Aroclor 1242) and copper in adipose tissue around lymph nodes of mink

Fatty acid composition was determined in adipose tissue surrounding the mesenteric lymph nodes of mink (Mustela vison) exposed to polychlorinated biphenyls (PCBs: 1 mg Aroclor 1242 in food day-1 for 28 days) and/or copper (62 mg kg-1 food). These specific adipose tissues are known to have functional relationships with lymphocytes, and proliferation of cultured lymphocytes is influenced by the quality of fatty acids available in media. In six experimental groups the diet was based on freshwater fish, and in two groups it was based on marine fish. These basal diets differed in terms of fatty acid composition and content of fat-soluble vitamins A1 and E. The fatty acid composition of membrane phospholipids (PL) responded to PCBs more than that of triacylglycerols (TG). The effects of copper were small. In female minks fed a diet of freshwater fish, the proportion of highly unsaturated fatty acids in PL decreased by 5 wt.% due to PCBs, and the acids seemed to be replaced by monounsaturated fatty acids (9 wt.% increase of total). This decrease of highly unsaturated fatty acids in PL was milder in minks on the marine fish diet rich in fat-soluble vitamins. In TG of minks on the marine diet, however, PCBs decreased the proportion of docosahexaenoic acid (22:6n-3). The possibility that these alterations in the fatty acid metabolism of adipose tissue supporting the lymph nodes affect immune function during PCB exposure should be studied further. Interestingly, the quality of the fish diet affected the magnitude of the alterations. The fatty acid responses may also differ between males and females.

Mucopolysaccharide histochemistry of the mink uterus during gestation

Histochemical localization of polysaccharide and protein-polysaccharide complexes (mucopolysaccharides or MPS) was studied in the uteri of female mink in three phases of gestation. These phases were the period of delay which precedes nidation, days 2 to 7 postimplantation, and days 13 to 16 postimplantation. Glycogen was found in uterine epithelial cells during delay, but appears to be depleted at nidation. This depletion may reflect the postnidation increases in progesterone observed in mink plasma. There is a general increase in MPS concentration in postimplantation uteri when compared with delay uteri. In addition, sulfated MPS are found in the uterine glands of postimplantation specimens, but not in the glands of delay specimens. The observed increase and shift in site of MPS production may reflect a perinidational increase in uterine protein.An acidic MPS layer is present between fetal and maternal placental components during postimplantation pregnancy. This coat appears to be synthesized by the trophoblast and may represent an immunoisolatory mechanism.

High versus low protein diets to mink--postprandial plasma urea and creatinine response, osmotic load and pattern of nitrogen and electrolyte excretion

Nitrogen balance, pattern of excretion of nitrogenous end-products, endogenous urinary N excretion, postprandial plasma urea and creatinine, osmotic load, urinary electrolyte excretion and water intake/output relationships were studied in 12 adult female mink fed a high protein diet (HP; n = 6) providing about 155 g protein/kg or a low protein diet (LP; n = 6) providing about 95 g protein/kg. Two balance periods of each 3 d were used and diets were fed raw or cooked. After the last balance period followed a 48 h fasting period. Postprandial plasma urea and creatinine were studied for 48 h following a test meal given after an overnight fast. Osmotic load was determined based on collection of non-acidified urine carried out during 48 h. Level of protein supply did not affect N balance, being close to zero, whereas slightly negative balances were achieved for fasting animals. Protein supply was clearly reflected in excretion of urinary urea and allantoin but not in creatinine and uric acid. Endogenous urinary N excretion was estimated by a second order regression equation giving an intercept of 280 mg/kg0.75. Post-prandial plasma urea concentrations were strongly influenced by protein supply, HP animals having substantially higher peaks than LP animals, but values returned to fasting values within 24 h after the test meal. Plasma creatinine followed a biphasic pattern with a peak about 2 h after feeding and a nadir approximately 6 h after feeding. Physical form of diet influenced postprandial urea, animals fed raw diets having a higher peak, but not creatinine. The HP diet provided almost the double osmotic load of the LP diet and a corresponding increase in urine volume. The resulting water balances were identical irrespective of diet, showing that water intake/output relationships are very accurately regulated.

Fifty Years of Research on European Mink Mustela lutreola L., 1761 Genetics: Where Are We Now in Studies on One of the Most Endangered Mammals?

The purpose of this review is to present the current state of knowledge about the genetics of European mink Mustela lutreola L., 1761, which is one of the most endangered mammalian species in the world. This article provides a comprehensive description of the studies undertaken over the last 50 years in terms of cytogenetics, molecular genetics, genomics (including mitogenomics), population genetics of wild populations and captive stocks, phylogenetics, phylogeography, and applied genetics (including identification by genetic methods, molecular ecology, and conservation genetics). An extensive and up-to-date review and critical analysis of the available specialist literature on the topic is provided, with special reference to conservation genetics. Unresolved issues are also described, such as the standard karyotype, systematic position, and whole-genome sequencing, and hotly debated issues are addressed, like the origin of the Southwestern population of the European mink and management approaches of the most distinct populations of the species. Finally, the most urgent directions of future research, based on the research questions arising from completed studies and the implementation of conservation measures to save and restore M. lutreola populations, are outlined. The importance of the popularization of research topics related to European mink genetics among scientists is highlighted.

Reproductive performance of two generations of female semidomesticated mink fed diets containing organic mercury contaminated freshwater fish

Semidomesticated female mink (Mustela vison) were fed daily diets containing 0.1 ppm, 0.5 ppm, and 1.0 ppm of total mercury. Piscivorous and nonpiscivorous fish naturally contaminated with organic mercury were used to prepare the diets. Twenty-month-old females (G1 generation) that were exposed to the experimental diets for approximately 400 days in 1994 and 1995 and their 10-month-old female offspring (G2 generation) that were exposed to mercury for approximately 300 days in 1995, were all mated to 10-month-old males. Males were fed the diet containing 0.1 ppm mercury 60 days prior to the mating season. Diets containing 0.1 ppm and 0.5 ppm were not lethal to G1 and G2 females for an exposure period of up to 704 days. At the age of 11 months, mortalities occurred in 1994 for G1 females (30/50) and in 1995 for G2 females (6/7) fed the 1.0 ppm mercury diet after 90 days and 330 days of exposure, respectively. The length of the gestation periods and the number of kits born per female were not different among dietary groups for the two generations of females. The proportion of females giving birth was low for all groups, except for the G1 females fed the 0.1 ppm diet. There was an inverse relationship between whelping proportion and exposure group, but was not statistically significant. There was evidence that kits were exposed to mercury both in utero and/or during lactation as indicated by the presence of mercury in their livers. Mercury exposure did not influence the survival and growth of neonatal kits.

Cortisol increases the activities of intestinal apical membrane hydrolases and nutrient transporters before weaning in mink (Mustela vison)

Glucocorticoids from endogenous and exogenous sources accelerate maturation of brush-border membrane (BBM) hydrolases in omnivorous laboratory rodents and pigs. Less is known for carnivores, and whether the route of administration (oral or systemic) has an influence. The present study examined the influence of administering cortisol (hydrocortisone succinate, 5 mg/kg-day) to mink during postnatal week 4, just prior to weaning, on small intestine glucose and amino acid (aspartate, leucine, lysine, methionine, proline) absorption and on the activities of BBM disaccharidases and peptidases. Kits treated with cortisol were smaller (P<0.05), but had small intestines that were proportionally larger (P<0.05 for length and mass per kg body weight, but not for mucosal mass) than control kits with higher rates of absorption for most nutrients, except leucine, and increased activities of most BBM hydrolases, except lactase. As a consequence, cortisol increased hydrolytic and absorptive capacities of the entire small intestine, with the responses more pronounced when the cortisol was given orally. These findings indicate administration of cortisol stimulates growth of the developing mink small intestine, but does not accelerate the postnatal declines in nutrient transport, and may be a dam-to-kit signal that prepares suckling mink to digest and absorb the adult diet.

Radioactivity in urine and feces of mink (Mustela vison) treated with [14C] aflatoxin B1

Excretion of radioactivity by mink (Mustela vison) during 7 days after intraperitoneal injection of two different amounts of aflatoxin B1 was studied. Male mink that received a single dose of 25 mug aflatoxin B1/kg body weight excreted an average of 89.5% of administered radioactivity (56.8% via feces, 32.7% via urine); whereas female mink excreted an average of 85% (63.6% via feces, 21.4% via urine) of administered radioactivity during the 7-day period. Male and female mink given 150 mug aflatoxin B1/kg body weight excreted an average of 76.9-80.1% of administered radioactivity during the 7 days that followed treatment with toxin. These mink excreted somewhat more of the administered radioactivity in their urine than did the mink that received the lower dose of aflatoxin (37.2 vs. 32.7% for males and 32.7 vs. 21.4% for females). Regardless of sex and dosage of toxin, most of the radioactivity ultimately excreted either through feces or urine appeared in the first 24 h after toxin was administered to mink.

Genetic variation and population structure of American mink Neovison vison from PCB-contaminated and non-contaminated locales in eastern North America

American mink Neovison vison may be particularly vulnerable to toxicities of persistent contaminants such as PCBs because of their aquatic-based diet, position near the top of the food web, and small deme sizes. Furthermore, ranched mink are sensitive to reproductive toxicities of fish diets from PCB-polluted sites. The upper Hudson River is highly contaminated with PCBs and previous studies have shown elevated hepatic burdens of total and coplanar PCBs in mink collected near the river compared with those from more distant locales in New York and elsewhere. We hypothesized that bioaccumulation of PCBs in Hudson River mink has reduced their levels of genetic diversity or altered their genetic population structure. To address this, we conducted microsatellite DNA analysis on collections made in proximity to and from more distant locales in the Hudson River watershed, elsewhere in New York State, and at other sites in eastern North America including New Brunswick, four locales in Ontario, multiple drainages in Maine, and two ecoregions in Rhode Island. We did not find reduced genetic diversity at the individual or population levels in mink collected near (<6 km) to PCB hotspots in the Hudson River nor evidence of altered population structure. Consistent with their distribution in small localized and isolated demes, we did find significant genetic population structure among many mink collections in New York State and elsewhere. Depending on the analytical approach used, genetically distinct populations numbered between 16 when using STRUCTURE to 19-20 when using Exact G tests, F ST, or AMOVA analyses. Genetically distinct population units were found among major ecoregions and minor ecoregions in New York State, among different hydrologic subunits within the Hudson River watershed, among spatially separate locales in Ontario, and among most watersheds in Maine. However, despite this localization and potential heightened impact of stressors, genetic diversity and genetic population structure in mink does not seem to be affected by their bioaccumulation of high levels of PCBs of Hudson River origin.

Total PCBs, dioxin-furan TEQs, and total mercury concentrations in mink in and out of the Rochester Embayment area of concern near and inland from the shore of Lake Ontario

In terms of reproductive and other adverse outcomes after exposure to polychlorinated biphenyls (PCBs), dioxins, and furans, the mink (Mustela vison) is one of the most sensitive mammals. Our objective was to determine if there are differences in the concentrations of total mercury (Hg), total PCBs, and dioxin-furan toxic equivalents (TEQs) between mink living in and out of the Rochester Embayment of Lake Ontario (RELO) Area of Concern (AOC) and between mink living near the shore of Lake Ontario and inland. Concentrations of total Hg in the brain, total PCBs and dioxin-furan TEQs in adipose, and total PCBs in liver were significantly higher for mink living near the shore of Lake Ontario than inland. For mink living in and out of the AOC, differences in total PCBs and dioxin-furan TEQs in adipose and the liver were substantial but not significant. Correlations among concentrations of total Hg, total PCBs, and dioxin-furan TEQs in mink were high. Our results suggest that contamination of mink living near the southern shore of Lake Ontario primarily comes from contact with the Lake Ontario food web, not from sources in the RELO AOC.

Effects of diets containing sodium fluoride on mink

Mink (Mustela vison) kits still nursing, and adult male mink were fed diets containing various levels of fluorine (as NaF) to determine the effects on health, growth and pelt quality. Different groups were fed diets containing 25.5 (control), 46.0, 111.5 or 287.0 ppm fluorine (on a wet basis) for 7-8 mo. Gross, radiographic and microscopic changes were seen in bones from some animals ingesting the higher levels of fluorine. Chemical analyses for fluorine generally reflected levels ingested. Fluorine caused no detectable differences in pelt quality. After data were evaluated, tolerance levels in the feed of not more than 50 ppm fluorine for breeding stock and 100 ppm fluorine for animals being raised only for pelts are recommended.

Liver fatty acid composition and peroxisomal fatty acid oxidase activity in blue foxes (Alopex lagopus) and mink (Mustela vison) fed diets containing different levels of fish oil

At the time of pelting (Nov.), blue foxes had a lower liver lipid content (4-5%) than mink (7-10%), whereas the phospholipid (PL) content was 0.5-1% in both species. Dietary fat content had little influence on total liver fat content but affected the liver fatty acid composition. Levels of n3 fatty acids were higher in the PL fraction than in the remaining fraction of liver lipids in both species. Because PL accounted for a larger part of the total liver lipids in blue foxes than in mink, the proportion of the total liver lipids accounted for by n3 fatty acids was highest in blue foxes. On the other hand, the mink and foxes had about the same quantity of n3 per gram liver owing to higher fat content of mink liver. Analyses of liver lipid fatty acid composition did not reveal any differences between the species in their ability to metabolize n3 fatty acids originating from fish oil. Peroxisomal beta-oxidation activity in the liver was significantly higher in blue foxes than in mink. For both species the total activity rose as the level of dietary fish oil increased.

Expression of the insulin-like growth factor II gene in polychlorinated biphenyl exposed female mink (Mustela vison) and their fetuses

AIM

To study how polychlorinated biphenyls (PCBs) affect fetal growth and the expression of the insulin-like growth factor (IGF II) gene in the mink (Mustela vision).

METHODS

Ten female mink were each exposed to 0.65 or 1.3 mg Clophen A50/day, respectively, during the reproductive season. The numbers and sizes of viable fetuses were recorded. The expression of the IGF II gene was studied by northern blotting using a mink specific IGF II cDNA probe.

RESULTS

The number of viable fetuses decreased after PCB exposure in a dose dependent fashion. Expression of the IGF II gene in adult livers from PCB exposed animals was decreased, compared with control animals, in a dose dependent fashion. In contrast, IGF II expression in placentas and fetuses was unaltered. Furthermore, the maternal excretion of urinary cortisol increased in both exposed groups during the implantation period.

CONCLUSIONS

Expression of the IGF II gene is downregulated by PCB exposure in the adult liver. There is also an indication that the regulation of the expression of this gene differs between adult and fetal life.