Embryo transfer in domestic South American camelids

Intraspecific and interspecific embryo transfer in domestic South American camelids is developing into a well-established technique. Reports reveal many benefits of using reproductive biotechnologies to allow rapid propagation of alpacas and llamas of high genetic merit (e.g., high fiber quality, preserve color variation). The objective of this review is to provide up-to-date information about embryo transfer in domestic South American camelids. Specific information is provided on criteria for male selection, donor and recipient synchronization, the practice of single- vs. super-ovulation protocols, embryo recovery and transfer techniques, advances in cryopreservation of embryos, results of intra- and inter-specific transfer, and the future of the embryo transfer in domestic South American camelids.     

Blood glucose concentration in caviomorph rodents

Hystricomorph rodents are a group of species that belong to the suborder Hystricognathi. They mainly inhabit South American (caviomorph) and African (phiomorph) habitats. This group of rodents has a divergent insulin structure. For example, insulin in this group of rodents exhibits only 1-10% of biological activity in comparison to other mammals. Therefore, hystricomorph rodents may hypothetically be unable to regulate blood glucose concentration as non-hystricomorph mammals. In this work we evaluated blood glucose concentration in nine species of caviomorph rodents, with emphasis on species belonging to the families Abrocomidae, Ctenomyidae and Octodontidae. Specifically we: (1) measured glucose concentrations after a fasting period; and (2) conducted a glucose tolerance test. In the latter assay we used Octodon degus as a representative species of the genus Octodon. Results showed that blood glucose concentration values after fasting, and in the glucose tolerance test, were within the expected range for mammals. We postulate that this group of rodents has compensatory traits that may permit the maintenance of standard values of plasma glucose.     

Effects of S-nitroso-N-acetyl-penicillamine administration on glucose tolerance and plasma levels of insulin and glucagon in the dog.

It has been suggested that nitric oxide (NO, nitrogen monoxide) is a regulator of carbohydrate metabolism in skeletal muscle. The present study was undertaken to investigate the acute effects of the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP) on blood glucose levels and on the gluco-regulatory hormones insulin and glucagon in healthy dogs. The acute effects of SNAP on mean arterial pressure and heart rate were also investigated. The drug was administered intravenously and the pre- and postprandial blood glucose, plasma insulin, and glucagon concentrations were determined at half-hour time intervals postadministration after a glucose challenge. The plasma nitrate and nitrite concentrations were measured and taken as the biochemical markers of in vivo NO formation. The oral glucose tolerance test revealed an impaired glucose tolerance in SNAP-treated dogs as reflected by the area under the glucose curve, 1150.50 +/- 63.00 mmol x 150 min and 1355.25 +/- 102.01 mmol/L x 150 min in dogs treated with 10 and 20 mg/kg of SNAP, respectively, compared with 860.25 +/- 60.68 mmol/L x 150 min in captopril-treated controls (P < 0.05). The 2-h blood glucose concentration in dogs treated with 20 mg/kg body wt of SNAP was 9.17 +/- 1.10 mmol/L compared with 5.59 +/- 0.26 mmol/L for captopril-treated controls (P = 0.015). The oral glucose tolerance test also confirmed an impaired insulin secretion in the SNAP-treated dogs. While the plasma insulin concentration increased gradually in the captopril-treated controls to a peak value of 39.50 +/- 2.55 microIU/ml, 1.5 h after a glucose challenge there was a decrease in the plasma insulin concentration in SNAP-treated dogs to a low value of 20.67 +/- 0.88 microIU/ml (P = 0.006). In contrast, there were no significant differences in plasma glucagon concentration in SNAP-treated dogs and captopril-treated dogs at any time points. Using the Griess reaction, we found that there was a 27-95% increase in plasma nitrate/nitrite concentration on administration of SNAP. The sustained hyperglycemic effect observed in SNAP-treated dogs was accompanied by a marginal decrease in the mean arterial blood pressure and a significant increase in heart rate (P < 0.05). We conclude that acute administration of SNAP in the oral glucose tolerance test releases NO that modulates the parameters of carbohydrate metabolism.     

Analysis of mitochondrial DNA in Bolivian llama,alpaca and vicuna populations: a contribution to the phylogeny of the South American camelids

The objectives of this work were to assess the mtDNA diversity of Bolivian South American camelid (SAC) populations and to shed light on the evolutionary relationships between the Bolivian camelids and other populations of SACs. We have analysed two different mtDNA regions: the complete coding region of the MT‐CYB gene and 513 bp of the D‐loop region. The populations sampled included Bolivian llamas, alpacas and vicunas, and Chilean guanacos. High levels of genetic diversity were observed in the studied populations. In general, MT‐CYB was more variable than D‐loop. On a species level, the vicunas showed the lowest genetic variability, followed by the guanacos, alpacas and llamas. Phylogenetic analyses performed by including additional available mtDNA sequences from the studied species confirmed the existence of the two monophyletic clades previously described by other authors for guanacos (G) and vicunas (V). Significant levels of mtDNA hybridization were found in the domestic species. Our sequence analyses revealed significant sequence divergence within clade G, and some of the Bolivian llamas grouped with the majority of the southern guanacos. This finding supports the existence of more than the one llama domestication centre in South America previously suggested on the basis of archaeozoological evidence. Additionally, analysis of D‐loop sequences revealed two new matrilineal lineages that are distinct from the previously reported G and V clades. The results presented here represent the first report on the population structure and genetic variability of Bolivian camelids and may help to elucidate the complex and dynamic domestication process of SAC populations.     

Semen preservation and artificial insemination in domesticated South American camelids

Semen preservation and artificial insemination in South American camelids are reviewed giving emphasis to work done in Peru and by the authors. Reports on semen evaluation and the preservation process indicate that semen of alpacas and llamas can be manipulated by making it liquid first. Collagenase appears to be the best enzyme to eliminate viscosity. Tris buffer solution maintains a higher motility than egg-yolk citrate, phosphate buffered saline (PBS), Triladyl, and Merck-I extenders. Cooling of semen took 1 h after collected, and equilibrated with 7% glycerol presented a better motility and spermatozoa survival at 1, 7, 15 and 30 days after being slowly frozen in 0.25 mL plastic straws. Trials of artificial insemination with freshly diluted semen and frozen–thawed semen are encouraging and needs to be tested extensively under field conditions. Recently, fertility rates varied from 3 to 67%. Semen preservation and most important, artificial insemination appear to be a reality, and could be used to improve the genetic quality of alpacas and llamas.     

Prediction of gestational age by ultrasonic fetometry in llamas (Lama glama) and alpacas (Lama pacos)

Fetal biparietal diameter (BPD) and thorax height (TH) were measured by ultrasound during intrauterine growth in pregnant llamas (Lama glama) and alpacas (Lama pacos). The goal was to establish representative curves that allows estimation of gestational age (GA) from real-time ultrasonic measurements of these fetal structures at any stage of gestation. Llamas and alpacas were mated under controlled conditions. Ultrasound exams were conducted to determine pregnancy status 1 month later. Measurements of fetal BPD and TH were conducted from the second month of pregnancy until term. Observation and assessment of fetal TH was difficult during the last 3 months of pregnancy, specially in llamas. Regression curves were calculated from the data as a function of GA, with the best fit represented by the following equations: llama GA=(BPD-0.002399)43.02293,r=0.98,P<0.001; llama GA=(TH-0.07137)46.94485, r=0.95,P<0.001; alpaca GA=(BPD-0.11376)47.23287, r=0.98,P<0.001; alpaca GA=(TH-0.36436)52.87663, r=0.96,P<0.001, where GA was measured in days and BPD and TH in centimeters. Results indicate that ultrasonic measurement of these fetal biometric variables constitute a valuable tool to estimate GA at any stage of pregnancy in these domestic South American camelids.     

Induction of superovulation in South American camelids

The development of assisted reproductive technologies such as embryo transfer (ET), artificial insemination (AI) and in vitro fertilization (IVF) in South American camelids is considerably behind that of other livestock species. Poor success of the embryo transfer technique has been related to a lack of an effective superstimulatory treatment, low embryo recovery rate, and the recovery of hatched blastocysts that are not conducive to the cryopreservation process. Superstimulation has been attempted using equine chorionic gonadotropin (eCG) and follicle stimulating hormone (FSH) during the luteal, or the sexually receptive phase, sometimes given at follicular wave emergence. The rationale for inducing a luteal phase prior to or during superstimulation in camelids is not clearly understood, but it may simply reflect an empirical bias to conventional methods used in other ruminants. The number of ovulations or CL varies widely among studies, ranging from 2 to more than 15 per animal, with the number of transferable embryos ranging from 0 to 4 per animal. The control of follicular growth combined with superstimulatory protocols has resulted in a more consistent ovarian response and a greater number of follicles available for aspiration and oocyte collection. Recent studies in llamas have demonstrated that the use of ovulation inducing treatments or follicle ablation can synchronize follicular wave emergence allowing the initiation of gonadotropin treatment in the absence of a dominant follicle resulting in a more consistent ovulatory response. Few studies in alpacas have been reported, but it appears from recent field studies that the ovarian response is more variable and that there is a greater number of poor responders than in llamas. A review of superstimulation protocols that have been used in llamas and alpacas in the last 15 years is provided, including a discussion of the potential of protocols designed to initiate treatment at specific stages of follicular growth.     

Infectious causes of reproductive loss in camelids

Reproductive losses in camelids are due to infertility, pregnancy loss, udder diseases and neonatal mortality caused by a variety of infectious diseases. Uterine infection and abortion represent the major complaint in camelid veterinary practice. The major infectious organisms in endometritis and metritis are E. coli and Streptococcus equi subspecies zooepidemicus. Abortion rates due to infectious diseases vary from 10% to more than 70% in some areas. Leptospirosis, toxoplasmosis and chlamydiosis have been diagnosed as the major causes of abortion in llamas and alpacas. In camels, brucellosis and trypanosomiasis represent the major causes of infectious abortion in the Middle East and Africa. Mastitis is rare in South American camelids. The prevalence of subclinical udder infection in camels can reach very high proportions in dairy camels. Udder infections are primarily due to Streptococcus agalactiae and Staphylococcus aureus. Neonatal mortality is primarily due to diarrhea following failure of passive transfer and exposure to E. coli, rotavirus, coronavirus, Coccidia and Salmonella. This paper reviews the etio-pathogenesis of these causes of reproductive losses, as well as the major risk factors and strategies to prevent their occurrence.     

Ovulation-inducing factor in the seminal plasma of alpacas and llamas

Studies were conducted to document the existence of an ovulation-inducing factor in the seminal plasma of alpacas (experiment 1) and llamas (experiment 2) and to determine if the effect is mediated via the pituitary (experiment 3). In experiment 1, female alpacas (n = 14 per group) were given alpaca seminal plasma or saline intramuscularly or by intrauterine infusion. Only alpacas that were given seminal plasma i.m. ovulated (13/ 14, 93%; P < 0.01). In experiment 2, ovulation was detected in 9/10 (90%) llamas at a mean of 29.3 +/- 0.7 h after seminal plasma treatment. Plasma progesterone concentrations were maximal by Day 9 and were at nadir by Day 12 posttreatment. In experiment 3, female llamas were given llama seminal plasma, GnRH, or saline i.m., and ovulation was detected in 6/6, 5/ 6, and 0/6 llamas, respectively (P < 0.001). Treatment was followed by a surge (P < 0.01) in plasma LH concentration beginning 15 min and 75 min after treatment with GnRH and seminal plasma, respectively. Plasma LH remained elevated longer in the seminal plasma group (P < 0.05) and had not yet declined to pretreatment levels after 8 h. Compared with the GnRH group, corpus luteum tended to grow longer and to a greater diameter (P = 0.1) and plasma progesterone concentration was twice as high in the seminal plasma group (P < 0.01). Results document the existence of a potent factor in the seminal plasma of alpacas and llamas that elicited a surge in circulating concentrations of LH and induced an ovulatory and luteotropic response.     

Prevalence of Eimeria macusaniensis (Apicomplexa: Eimeriidae) in midwestern Lama spp

To compare the prevalence of Eimeria macusaniensis among midwestern llamas (Lama glama), alpacas (Lama pacos), and guanacos (Lama guanicoe), feces were obtained from Lama spp. in 10 states between October 1989 and February 1996. Feces were examined by centrifugal flotation in sugar solution (specific gravity--1.28-1.30), and oocysts were quantified by a modified McMaster method. Data were compared by host species and age classifications. Typical oocysts occurred in samples from 28% of 76 herds and 10.4% of 443 animals including 12% of 301 llamas, 7% of 115 alpacas, and 7.4% of 27 guanacos. Prevalence was significantly greater (P = 0.009) in animals < 1 yr of age in comparison to older animals for llams (22.1 v.s. 8.5%) and for all Lama spp. combined (17.1 vs. 8.4%). Fecal oocyst abundance was significantly greater (P = 0.001) in llamas < 1 yr of age in comparison to older llamas (30 vs. 16 oocysts per g of feces). Fecal oocyst intensities did not differ significantly. Prevalence in both age groups of midwestern llamas was greater than previously reported for llamas in the western United States. Prevalence in midwestern alpacas < 1 yr of age was lower than reported for alpacas of similar age in South America, but oocyst intensities were similar. These results indicate that infection with E. macusaniensis is more common in Lama spp. in North America than previously recognized.     

The effect of ovarian follicle size on pituitary and ovarian responses to copulation in domesticated South American camelids.

The relation of ovarian follicle size to pituitary and ovarian responses to copulation was studied in domesticated South American camelids (llamas and alpacas). Females from each species were divided into four groups according to follicle size: small (4-5 mm), growing (6-7 mm), mature (8-12 mm), and regressing (10-7 mm). The pituitary response to copulation was determined by analysis of LH and FSH concentrations in plasma. The ovarian response to copulation was determined by ultrasonography and by analysis of estrone sulfate (follicular status) and pregnanediol glucuronide (luteal status) concentrations in urine. Females with small follicles (4-5 mm) released less LH after copulation than did those with larger follicles, and ovulation was not induced. Females with growing and mature follicles (7-12 mm) released LH in response to copulation that was adequate to induce ovulation and to initiate normal luteal activity. While copulation-induced LH release in females with regressing follicles was similar to that released in animals with growing and mature follicles, regressing follicles were luteinized instead of being ovulated. The luteal structure formed as a result of luteinization of follicles had a short life span, i.e., 5.1 days. Copulation-induced LH release was significantly higher in llamas vs. alpacas in animals with mature or regressing follicles, but not in those with small or growing follicles. Urinary estrone sulfate and pregnanediol glucuronide concentrations correlated positively with the presence of follicles and corpora lutea, respectively.     

Acute caffeine ingestion does not impair glucose tolerance in persons with tetraplegia.

Acute caffeine (Caf) ingestion impairs glucose tolerance in able-bodied humans during an oral glucose tolerance test (OGTT). The mechanism responsible for this effect remains unclear, however, it is suggested to be due to the accompanying increase in epinephrine concentration. We examined whether or not Caf would elicit a glucose intolerance in persons with tetraplegia (TP) who do not exhibit an increased epinephrine response following Caf ingestion. All TP [n = 14; 9 incomplete (Inc) lesion, 5 complete (Com) lesion] completed two OGTT 1 h after consuming either gelatin (Pl) or Caf capsules (dose = 4 mg/kg). Blood samples were collected at baseline (time = 0 min), 1 h after capsule ingestion (time = 60 min), and every 30 min during the OGTT (time = 90-180 min). Glucose, insulin, proinsulin, and C-peptide responses were similar (P > 0.05) between treatments, demonstrating no effect of Caf on glucose tolerance. This lack of a Caf effect may be due to the low epinephrine concentration that remained unchanged (P > 0.05) throughout all experiments. Interestingly, the Com exhibited a 50% higher glucose response (P 0.05) lower insulin response (vs. Inc), suggesting a more pronounced glucose intolerance within this subgroup. Furthermore, nine TP (5 Com, 4 Inc) had glucose levels of >or= 7.8 mM at the end of the OGTT (time = 180 min), classifying them as glucose intolerant. In summary, acute Caf ingestion does not increase epinephrine concentration or impair glucose tolerance in TP.     

Concordant induction of rapid in vivo pulsatile insulin secretion by recurrent punctuated glucose infusions

Insulin is largely secreted as serial secretory bursts superimposed on basal release, insulin secretion is regulated through changes of pulse mass and frequency, and the insulin release pattern affects insulin action. Coordinate insulin release is preserved in the isolated perfused pancreas, suggesting intrapancreatic coordination. However, occurrence of glucose concentration oscillations may influence the process in vivo, as it does for ultradian oscillations. To determine if rapid pulsatile insulin release may be induced by minimal glucose infusions and to define the necessary glucose quantity, we studied six healthy individuals during brief repetitive glucose infusions of 6 and 2 mg x kg(-1) x min(-1) for 1 min every 10 min. The higher dose completely synchronized pulsatile insulin release at modest plasma glucose changes ( approximately 0.3 mM = approximately 5%), with large ( approximately 100%) amplitude insulin pulses at every single glucose induction (n = 54) at a lag time of 2 min (P < 0.05), compared with small (10%) and rare (n = 3) uninduced insulin excursions. The smaller glucose dose induced insulin pulses at lower significance levels and with considerable breakthrough insulin release. Periodicity shift from either 7- to 12-min or from 12- to 7-min intervals between consecutive glucose (6 mg x kg(-1) x min(-1)) infusions in six volunteers revealed rapid frequency changes. The orderliness of insulin release as estimated by approximate entropy (1.459 +/- 0.009 vs. 1.549 +/- 0.027, P = 0.016) was significantly improved by glucose pulse induction (n = 6; 6 mg x kg(-1) x min(-1)) compared with unstimulated insulin profiles (n = 7). We conclude that rapid in vivo oscillations in glucose may be an important regulator of pulsatile insulin secretion in humans and that the use of an intermittent pulsed glucose induction to evoke defined and recurrent insulin secretory signals may be a useful tool to unveil more subtle defects in beta-cell glucose sensitivity.     

Measuring the energy expenditure and water flux in free-ranging alpacas (Lama pacos) in the peruvian andes using the doubly labelled water technique

Energy expenditure and water flux were measured in free-ranging alpacas Lama pacos, a South American camelid, on natural pastures of the Peruvian Andes (altitude: 4,400 m above sea level). Water influx rate (WIR) was estimated in 16 males (age 2 years, weight 48.5+/-8.6 kg) labelled with 2H. In addition, the field metabolic rate (FMR) was measured in four of these animals labelled with both an oxygen (18O) and a hydrogen (2H) isotope. The WIR averaged 3.62 L H2O/day and the mean total body water 33.1 kg, equal to 68.2% of body weight (BW). The FMR of the four doubly labelled animals was 14.05 MJ/day. New allometric equations were calculated describing the relationships between WIR or FMR and BW, respectively, including published data on ruminants and the present alpaca results. The regression equation indicates that daily WIR scales to a similar metabolic size (kilograms of BW(0.94)) in alpacas than in wild or domesticated ruminants and camelids originating from arid and semiarid habitats. The resulting regression equation for FMR explained over 99% of the variation and corresponded to the function FMR (kilojoules per day)=1079 (kilograms of BW0.668) (n=5, r2=0.995, P<0.001). The FMR measured in this study, the first reported for a South American camelid species, suggests that free-ranging alpacas have similar energy expenditures on a metabolic weight basis as other wild ruminants living under harsh climatic conditions.     

Digestibility,nitrogen balance,and blood metabolites in llama (Lama glama) and alpaca (lama pacos) fed barley or barley alfalfa diets

To determine the effect of barley diets on digestibility, nitrogen balance, and blood metabolites, mature gelded llamas and alpacas (n = 8; 4 llamas, 36 ± 4 months, 90 ± 10.7 kg; 4 alpacas, 24–36 months, 50 ± 4 kg) were randomly fed 100% barley (B) and 20% alfalfa/80% barley (BA) hay. Animals were housed in metabolism crates and diets were fed for a 7 days adjustment period followed by a 5 days collection period. Feed, feed refusal, feces and urine were collected, dried and N content determined by combustion analysis. Blood samples were collected on day 12 at 30 min intervals over a 6 h period. Plasma was harvested and analyzed for electrolytes (Na, K, Cl, Ca, Ca²⁺, P, Mg), metabolites glucose, non-esterified fatty acids (NEFAs), urea N, creatinine, albumin, total protein (TPP), osmolality (Osm). Plasma glucose, urea N, albumin, osmolality, electrolyte and metabolite levels were similar between species, and were unaffected by diet. On a metabolic weight basis, only diet was significant for N intake, urinary and fecal N, and total N excreted. Dry matter intake was not significantly different; however, BA consumption was greater than B, (B) 1272 g N/day and (BA) 1636 g N/day for llamas, and for alpacas (B) 835 g N/day and (BA) 1034 g N/day, respectively. Nitrogen intake followed the same pattern, (B) 21.4 g N/day and (BA) 33.9 g N/day, respectively for llamas, and (B) 13.6 g N/day and (BA) 20.6 g N/day, respectively for alpacas (diet, P < 0.002). Diet affects were significant for urine N excretion (P < 0.02), (B) 11.2 g/day and (BA) 18.2 g/day for llamas, and (B) 6.8 and (BA) 10.8 g N/day for alpacas. Fecal N excretion was different for diet (P < 0.03), with fecal excreted N of 9.0 g N/day and 11.9 g N/day for B and BA in llamas, and 5.9 g N/day and 9.1 g N/day for B and BA respectively in for alpacas, respectively. Nitrogen retention, DM digestibility and N digestibility were unaffected by diet or species. However, the llamas in this study displayed an increase in nitrogen intake of 64.6% between the B and BA diets with a 381% increase in N retention. Alpacas increased their N intake by 57.4% when they consumed the BA forage, which only increased N retention by 22.2%. These species differences indicate that alpacas have a lower N requirement to meet metabolic needs than llamas, which are likely related to the smaller body size of the alpaca. When examining the biological value of N from the respective diets, alpacas and llamas had a value of 56.2% when consuming barley. The BA diet had a higher biological value of 65.0% in llamas compared to 57.4% in alpacas. Therefore, on the basis of this study, extrapolations between llamas and alpacas with respect to nitrogen requirement and balance are not valid.     

阿司匹林增加胰岛素抵抗大鼠胰岛素敏感性的实验研究

目的　观察阿司匹林对高脂饮食大鼠胰岛素敏感性的影响。方法　灌服阿司匹林前后采用腹腔注射胰岛素耐量试验 (IITT)观察大鼠胰岛素的敏感性 ,并测定空服胰岛素、血糖和血脂等。结果　高脂饮食 4月、阿司匹林治疗 4周后 ,IITT发现高脂组腹腔注射胰岛素后 1h、1 5h和 2h的血糖及空腹胰岛素和甘油三酯水平显著高于正常对照组 (P <0 0 5或P <0 0 1 ) ;而阿司匹林治疗组腹腔注射胰岛素后 1h、1 5h和 2h的血糖及空腹胰岛素和甘油三酯水平显著低于高脂组 (P <0 0 5或P <0 0 1 ) ,与正常对照组差异无显著性。结论　大剂量阿司匹林有增加胰岛素敏感性和改善脂代谢紊乱的作用     

Five batches representative of Ontario-grown American ginseng root produce comparable reductions of postprandial glycemia in healthy individuals

Evidence indicates that the glycemia-lowering effect of American ginseng root may be batch dependent. We therefore evaluated the effect of 5 root batches, representative of Ontario-grown American ginseng, on postprandial glucose and insulin indices. Twelve healthy subjects (5 male, 7 female), mean +/- SE age 26.5 +/- 2 years, body mass index 23.96 +/- 3.41 kg/m2, fasting blood glucose 4.77 +/- 0.04 mmol/L, were assigned to consume 9 g of American ginseng from 5 farms (A-E), administered in randomized sequence on 5 separate visits, and a water-control during the 6th and last visit. Treatments were consumed 40 min before a 2-hour 75-gram oral glucose tolerance test. Plasma glucose and insulin were measured at baseline, before, and during the test. Compared with control, batches A and C reduced glucose incremental area under the curve (IAUC) by 35.2% (156 vs. 240 mmol.min/L) and 32.6% (162 vs. 240 mmol.min/L), respectively. Batches A, C, and E reduced incremental peak glucose by 1.3, 1.2, and 1.1 mmol/L, respectively. Batch C reduced the insulin IAUC by 27.7% (15.8 vs. 21.8 nmol.min/L). Effects on glucose and insulin parameters were not different across ginseng treatments. The mean of the 5 ginseng treatments reduced peak postprandial glucose by 1.0 mmol/L, glucose IAUC by 27.7% (173 vs. 240 mmol.min/L), and insulin IAUC by 23.8% (16.6 vs. 21.8 nmol.min/L) relative to control. (All results statistically significant at p < 0.05.) American ginseng decreased postprandial glycemia and insulinemia; however, 40% of the batches did not reduce glycemia with the anticipated magnitude, irrespective of their saponin composition.     

Whole body insulin responsiveness is higher in beef steers selected for increased muscling

The aim of this experiment was to evaluate the impact of selection for greater muscling on whole body insulin responsiveness in cattle, as reflected by greater uptake of glucose in response to constant insulin infusion and greater glucose disappearance following an intravenous glucose tolerance test. This study used 18-month-old steers from an Angus herd visually assessed and selected for divergence in muscling over 15 years. Eleven high-muscled (High), 10 low-muscled (Low) and 3 high-muscled steers, which were heterozygous for a myostatin polymorphism (HighHet), were infused with insulin using the hyperinsulineamic-euglyceamic clamp technique. Insulin was constantly infused at two levels, 0.6 μIU/kg per min and 6.0 μIU/kg per min. Glucose was concurrently infused to maintain euglyceamia and the steady state glucose infusion rate (SSGIR) indicated insulin responsiveness. An intravenous glucose tolerance test was also administered at 200 mg/kg live weight. Sixteen blood samples were collected from each animal between -30 and 130 min relative to the administration of intravenous glucose, plasma glucose and insulin concentration was determined in order to analyse insulin secretion and glucose disappearance. Insulin-like growth factor-1 (IGF-1) was also measured in basal plasma samples. At the low insulin infusion rate of 0.6 mU/kg per min, the SSGIR was 73% higher for the High muscling genotype animals when compared to the Low (P<0.05). At the high insulin infusion rate of 6.0 mU/kg per min, these differences were proportionately less with the High and the HighHet genotypes having only 27% and 34% higher SSGIR (P<0.05) than the Low-muscled genotype. The High-muscled cattle also had 30% higher plasma IGF-1 concentrations compared to the Low-muscled cattle. There was no effect of muscling genotype on basal insulin or basal glucose concentrations, glucose disappearance or insulin secretion following an intravenous glucose tolerance test. The increased whole body insulin responsiveness in combination with higher IGF-1 concentrations in the High-muscled steers is likely to initiate a greater level of protein synthesis, which may partially explain the increased muscle accretion in these animals.     

Digitalis-like factor response to hyperinsulinemia accompanying a euglycemic hyperinsulinemic clamp or oral glucose tolerance test

Many studies of essential hypertension find evidence of insulin resistance in the same individuals, leading some to postulate a hypertensive role for insulin. However, the mechanisms by which insulin might exert a hypertensive effect are not fully resolved. An endogenous sodium pump inhibitor or digitalis-like factor (DLF) has been proposed as a hypertensive agent and its plasma concentrations are elevated in hypertension and in Type II diabetes, where insulin levels are elevated. Hence, we studied the effect of insulin on DLF using two approaches to achieve hyperinsulinemia. Normotensive men and women underwent a hyperinsulinemic, euglycemic clamp (40 mU/m2/min insulin, 40 mU = 1.6 x 10(-6) g) in which plasma insulin concentration was kept at high, but physiologic levels. Serum DLF (measured as inhibition of [Na,K]ATPase activity) and insulin levels were measured at baseline and every 30 min throughout the 2 hr clamp. Additionally, other subjects underwent an oral glucose tolerance test (OGTT) as a second means of increasing insulin levels. Insulin and DLF levels were measured prior to and hourly for 3 hours after receiving 100 gm of oral glucose. Serum DLF increased significantly during the clamp from a baseline of 4.6 +/- 0.81 to a peak of 8.7 +/- 1.2% inhibition (p=0.001). Comparison of the baseline and peak DLF levels with concomitant plasma insulin levels revealed a significant correlation (R=0.60, p=0.003). During the OGTT, DLF levels rose from a baseline of 2.4 +/- 1.0 to a peak level of 5.0 +/- 0.4%, p = 0.04. These results suggest that DLF, a factor that can cause vascular smooth muscle contraction and potentially influence blood pressure, is increased by hyperinsulinemia and provides a mechanism by which insulin may increase blood pressure.     

Genetic variation in the blood of llamas, Llama glama, and alpacas, Llama pacos

Blood samples of llamas and alpacas were typed using haemolytic, electrophoretic and isoelectric focusing procedures to assay polymorphism at 13 loci. Blood group variation was assessed using six antibody specificities produced by allo- and heteroimmunizations. Two red cell factors (A and B) behave as autosomal, codominant alleles at a closed A locus. The other four factors (C, D, E and F) behave as autosomal, dominant traits. Biochemical variation was found for red cell enzymes catalase, phosphogluconate dehydrogenase, glucose phosphate isomerase and for plasma proteins transferrin and post-albumin. No variants were found for haemoglobin, phosphoglucomutase and albumin. Estimates of probability of exclusion were 0.883 for llamas and 0.681 for alpacas, which are adequate initial levels of efficacy for purposes of parentage verification. Preliminary estimate of Nei's genetic distance measure (D) suggests that llamas and alpacas are more likely related as subspecies than as separate species.