Isolation,partial purification and characterization of a potato peel ∞-solanine cleaving glycosidase

An enzyme which hydrolyzes the rhamnose from ∞-solanine was isolated and partially purified by ammonium sulfate precipitation from the peels of Kennebec and Wauseon potatoes. Enzyme activity was found to be present in the 60 to 80% ammonium sulfate fraction. Enzyme activity was increased by the use of non-ionic detergents with a mixture of Triton X-100:Triton CF-54 (2:1, w/w) providing the greatest increase in activity. The pH optimum for the rhamnosidase for both varieties was found to be 6.0 while of the temperatures evaluated 42 °C was the optimum temperature. The effect of substrate concentration on enzyme activity was determined for both varieties and the Vmax and Km were calculated from Lineweaver-Burke double reciprocal plots. The Vmax and Km for the Kennebec and Wauseon rhamnosidases were found to be 0.27 mg/ml and 5.4 x 10^-4 M and 0.48 mg/ml and 8.2 x 10^-4 M, respectively.     

Regulation of adrenocorticotropin secretion from cultured canine anterior pituitary cells.

Pituitary cells, collected from five healthy dogs, were cultured and treated with various doses of ovine corticotropin-releasing hormone (CRH), arginine vasopressin (AVP), oxytocin (OT), or angiotensin II (AII) to determine which of these hypothalamic peptides affected adrenocorticotropin (ACTH) secretion. Of the 4 peptides, only CRH significantly increased ACTH secretion from cultured canine anterior pituitary cells. The lowest dose of CRH tested, 0.01 nM, significantly stimulated ACTH release. Co-addition of AVP, OT, or AII with CRH did not increase ACTH secretion beyond that caused by addition of CRH alone. Similarly, neither co-addition of AVP with OT, AVP with AII, or OT with AII significantly stimulated ACTH secretion. These results support a role for CRH in the physiologic regulation of ACTH secretion from the canine anterior pituitary, but do not support regulatory roles for AVP, OT, or AII.     

Effects of synthetic ovine corticotropin-releasing hormone on plasma concentrations of immunoreactive adrenocorticotropin, alpha-melanocyte-stimulating hormone, and cortisol in dogs with naturally acquired adrenocortical insufficiency.

We evaluated the effect of ovine corticotropin-releasing hormone (CRH) on plasma immunoreactive (IR) concentrations of ACTH, alpha-melanocyte-stimulating hormone, and cortisol in 8 dogs with naturally acquired adrenocortical insufficiency. Of the 7 dogs with primary adrenal insufficiency, 6 had markedly high basal plasma IR-ACTH concentrations and exaggerated ACTH responses to CRH administration, whereas 1 dog that was receiving replacement doses of prednisone at the time of testing had normal basal IR-ACTH concentrations and a nearly normal response to CRH. In contrast, the 1 dog with secondary adrenocortical insufficiency had undetectable basal plasma IR-ACTH concentrations, which failed to increase after administration of CRH. Basal plasma alpha-melanocyte-stimulating hormone concentrations in the dogs with adrenal insufficiency were within normal range and were unaffected by CRH administration. In all 8 dogs with adrenal insufficiency, plasma cortisol concentrations were low and did not increase after administration of CRH. Therefore, stimulation with CRH produced 2 patterns of plasma IR-ACTH response when administered to dogs with naturally acquired adrenal insufficiency. Dogs with primary adrenal insufficiency had high basal plasma IR-ACTH concentrations and exaggerated responses to CRH, whereas the dog with secondary adrenal insufficiency had undetectable basal plasma concentrations of IR-ACTH that did not increase after stimulation with CRH.     

Binding characteristics of swine erythrocyte insulin receptors

Crossbred gilts (controls; n = 7) had 8.8 +/- 1.1% (mean +/- SEM) maximum binding of [125I]insulin to insulin receptors on erythrocytes. The number of insulin-binding sites per cell was 137 +/- 19, with a binding affinity ranging from 7.4 X 10(7)M-1 to 11.2 X 10(7)M-1 and mean of 8.8 X 10(7)M-1. Pregnant sows (n = 5) had a significant increase (P less than 0.01) in maximum binding due to an increase in number of receptor sites per cell. Lactating sows fed a high-fiber diet (n = 3) and a low-fiber diet (n = 4) did not develop a significant difference in maximum binding of insulin. Sows fed the low-fiber diet had a significantly higher number of binding sites and a significantly lower binding affinity than did sows fed a high-fiber diet. Receptor-binding affinity was lower in the low-fiber diet group than in cycling gilts, whereas data from sows fed the high-fiber diet did not differ from data for cycling gilts. Data from this study indicated that insulin receptors of swine erythrocytes have binding characteristics similar to those in other species. Pregnancy and diet will alter insulin receptor binding in swine.     

Fertility of sows mated on different days of the week

The farrowing rates resulting from matings on different days of the week were determined for a 2800-sow intensive piggery in both 1983 and 1984. The results showed that sows mated early in the week achieved a significantly higher farrowing rate than sows mated late in the week (P less than 0.0001). During the seasonal (summer to autumn) infertility period, Wednesday matings resulted in a poor farrowing rate whereas for the rest of the year farrowing rates following Wednesday matings were similar to those for Sunday Monday and Tuesday matings. Consistent results were obtained for data from both years. It is proposed that the stress of regrouping unmated sows on Wednesday to accommodate newly weaned sows is responsible for this decrease in fertility. This study illustrates how detailed analysis of farrowing rates on a day of mating basis can identify a problem which is otherwise masked by weekly data.     

The comparative pathogenicity of four serovars of Actinobacillus (Haemophilus) pleuropneumoniae

The pathogenicity of 2 isolates of each of serovars 7, 3, 1 and 2 of Actinobacillus pleuropneumoniae was tested by intranasal inoculation into 60, 6-week-old large white pigs. Four dose rates varying from 0.27 to 560 x 10(6) organisms per pig with 10-fold serial dilutions were used. Surviving pigs were necropsied 7 days after inoculation. The proportion of pigs dying and developing gross lesions following infection was significantly greater for pigs given serotype 1 than for each of the other 3 serotypes, which did not differ significantly from each other. Twelve of 16 pigs given either of the 2 isolates of serovar 1 died after acute illness and 1 of 44 pigs given either of the 2 isolates each of serovars 7, 3 and 2 died. Pigs given serovar 1 showed high temperatures, severe respiratory distress, frothy haemorrhagic nasal discharge and weight loss. Lung lesions were produced in all 16 pigs given serovar 1, in 7 of 14 pigs given serovar 7, 7 of 14 pigs receiving serovar 3 and in 5 of 16 pigs given serovar 2. The lethal infections were characterised by a severe acute fibrinohaemorrhagic necrotising pleuropneumonia, whereas non-lethal cases had lung lesions ranging from necrotising purulent pleuropneumonia to abscessation. Significant differences between isolates in proportions of tissues culture positive for A. pleuropneumoniae for serovars 7 and 2, but not for serovars 3 and 1 suggested that isolates may vary in virulence within serovars, but more detailed studies are needed to clarify this point.     

Experimental evidence that tryptamine alkaloids do not cause Phalaris aquatica sudden death syndrome in sheep

The acute toxicity for sheep of 3 alkaloids that occur in Phalaris acquatica was examined by intravenous and oral administration. The lowest tested dose rates that produced clinically observed signs were, for 5-methoxy dimethyltryptamine, 0.1 mg/kg body weight intravenously and 40 mg/kg orally; for gramine, 10 mg/kg intravenously and 500 mg/kg orally; and for hordenine, 20 mg/kg intravenously and 800 mg/kg orally. All induced the clinical signs observed in the nervous form of phalaris toxicity, but none induced the cardiac, sudden death, syndrome.     

Abnormal canine triiodothyronine-binding factor characterized as a possible triiodothyronine autoantibody

Of more than 6,000 canine serum samples submitted to the Endocrine Diagnostic Laboratory of the School of Veterinary Medicine, Auburn University, Ala, for thyroid evaluation in 1983, 18 contained an abnormal triiodothyronine (T3)-binding factor (T3BF). These samples were easily distinguished from non-T3BF containing samples because the factor interfered with the radioimmunoassay for total T3 resulting in a profound increase in apparent values for T3 concentration. Most of the T3BF-containing samples did not have unusual thyroxine binding or inappropriate thyroxine concentrations. Triiodothyronine binding in samples containing T3BF was inhibited by addition of exogenous T3 and was, with one exception, not affected by the addition of 8-anilino-1-naphthalene sulfonic acid (ANS). Apparent affinity constants determined by Scatchard analysis were considerably greater than those of circulating T3-binding proteins found in human beings, but were similar to values obtained for human T3 autoantibodies. After the addition and incubation of [125I] T3 with T3BF-containing samples, a large fraction of the radioactivity bound by T3BF could be precipitated by the addition of goat antibody to dog immunoglobulin G. Additional observations that the binding was insensitive to inhibition by ANS, was resistant to heat inactivation, and had a high apparent affinity constant for T3 were consistent with the idea that the factor was an autoantibody to T3.     

Insulin and growth hormone responses to glucose infusion in mature and first-lactation dairy cows

Five mature Holstein cows and 6 first-lactation Holstein cows were administered 100 mg of glucose/kg of body weight, IV, over a 20-minute period on postpartum day 30. A series (preinfusion, glucose infusion, and postinfusion) of blood samples was collected at -15, -10, -5, 5, 10, 15, 20, 30, 45, 60, 75, 90, 105, and 120 minutes from the start of the infusion. Serum was obtained and was assayed for glucose, immunoreactive insulin (IRI), growth hormone (GH), and free fatty acid concentrations. Baseline glucose and free fatty acid concentrations were similar in cattle of both groups throughout the sample collection period. Both groups of cattle disposed of the infused glucose in a similar manner. The first-lactation cows secreted significantly (P less than 0.0001) more IRI to utilize the glucose load than did the mature cows, 71 +/- 13 microU/ml vs 38 +/- 7 microU/ml, respectively (mean +/- SEM). Preinfusion and glucose infusion GH concentrations were similar in cattle of both groups. In the postinfusion period, GH values were significantly (P less than 0.0002) higher in the first-lactation cows (8.7 +/- 1.8 ng/ml) than in the mature cows (5.8 +/- 1.6 ng/ml). Compared with that in the mature cows, the higher IRI concentration required by the first-lactation cows to utilize approximately the same glucose load suggested that first-lactation cows were insulin resistant. The increased insulin response to increased glucose concentration may be one reason first-lactation cows produce less milk than do mature cows. Other factors, such as variation in the ability of the mammary gland to synthesize milk cannot be excluded.