Biomedical subjects

G B Martin

Publications and source records attributed to G B Martin.

At least 73 records · Page 4Linked to original sources

PubMed1998

Recognition specificity for the bacterial avirulence protein AvrPto is determined by Thr-204 in the activation loop of the tomato Pto kinase.

The Pto kinase confers resistance in tomato to P. syringae pv. tomato strains expressing the AvrPto protein. Physical interaction of the Pto kinase and AvrPto protein in the plant cell initiates host defense responses. The recognition event between these two proteins is very specific; AvrPto does not interact with other closely related kinases, including the Fen kinase, which shares 80% amino acid identity with Pto. By using Pto-Fen chimeric proteins and site-directed mutagenesis, we found that Thr-204 is required for Pto interaction with AvrPto in a yeast two-hybrid system and for recognition specificity in a tobacco leaf transient assay. Substitution of Thr-204 into the Fen kinase allowed that kinase to interact with AvrPto and to confer an AvrPto-specific defense response in tobacco leaves. Thus, simple mutations appear capable of giving rise to new resistance gene specificities.

Amino Acid Sequence↗

PubMed1998

Hypothalamic dopamine D1 receptors are involved in the stimulation of prolactin secretion by high environmental temperature in the female sheep.

Recent evidence suggests that dopamine, acting via its D1 receptors, may function as a neurotransmitter in intrahypothalamic pathways involved in the stimulation of prolactin secretion. Functional dopamine D1 receptors are present in the ventromedial hypothalamic nucleus (VMH) and we hypothesized that they might be part of a prolactin-stimulatory pathway activated by stress. We tested this hypothesis in a series of experiments on sheep involving two different forms of stressors, audiovisual (barking dog) and high environmental temperature. We attempted to block the stimulation of prolactin secretion by infusion into the VMH of an antagonist specific for the D1 receptor. Ovariectomised, oestradiol-implanted merino ewes were surgically implanted with bilateral guide tubes directed at the VMH. After a 180 min pretreatment period, the ewes either were or were not exposed to a stressor (30 min of barking dog or 120 min at 35 degrees C, 65% relative humidity). D1 receptor antagonist, SCH23390 or vehicle (0.9% saline) was infused into the VMH (1.7 microliters/h, 120 nmol/h) for 60 min prior to and during the stressor period. Blood was sampled every 15 min via jugular cannulae and the plasma was assayed for prolactin, cortisol and growth hormone (GH). Both stressors significantly increased prolactin concentrations over control levels. SCH23390 infusion significantly attenuated the prolactin response to high environmental temperature, but had no effect on the prolactin response to audiovisual stress. Cortisol concentrations were significantly increased by audiovisual stress only and were not affected by SCH23390. GH concentrations were not changed by either stressor or infusion. Drug infusion alone did not affect the concentration of the hormones. The data suggest that the VMH D1 receptors are involved in a prolactin stimulatory pathway in response to high environmental temperature. The inability of the D1 antagonist to affect the response to the barking dog indicates that this pathway is stress-specific, implying that there is more than one mechanism or pathway involved in the prolactin response to different stressors.

Acoustic Stimulation↗

PubMed1998

The myristylation motif of Pto is not required for disease resistance.

The tomato Pto kinase confers resistance to bacterial speck disease caused by strains of Pseudomonas syringae pv. tomato that express the avirulence gene avrPto. Pto contains a putative myristylation site at its amino terminus that was hypothesized to play a role in localizing Pto in the plant cell. Site-directed mutagenesis was used to change the invariant glycine residue in the myristylation motif to an alanine. Transgenes encoding the mutant Pto(G2A) and wild-type Pto were placed behind the cauliflower mosaic virus 35S promoter and transformed into tomato plants that are susceptible to bacterial speck disease. Both the mutant and wild-type forms of Pto conferred resistance to a strain of P. syringae pv. tomato expressing avrPto. These results indicate that the myristylation motif of Pto is not required for bacterial speck disease resistance.

Alanine↗

PubMed1998

A nitrilase-like protein interacts with GCC box DNA-binding proteins involved in ethylene and defense responses.

Ethylene-responsive element-binding proteins (EREBPs) of tobacco (Nicotiana tabacum L.) bind to the GCC box of many pathogenesis-related (PR) gene promoters, including osmotin (PR-5). The two GCC boxes on the osmotin promoter are known to be required, but not sufficient, for maximal ethylene responsiveness. EREBPs participate in the signal transduction pathway leading from exogenous ethylene application and pathogen infection to PR gene induction. In this study EREBP3 was used as bait in a yeast two-hybrid interaction trap with a tobacco cDNA library as prey to isolate signal transduction pathway intermediates that interact with EREBPs. One of the strongest interactors was found to encode a nitrilase-like protein (NLP). Nitrilase is an enzyme involved in auxin biosynthesis. NLP interacted with other EREBP family members, namely tobacco EREBP2 and tomato (Lycopersicon esculentum L.) Pti4/5/6. The EREBP2-EREBP3 interaction with NLP required part of the DNA-binding domain. The specificity of interaction was further confirmed by protein-binding studies in solution. We propose that the EREBP-NLP interaction serves to regulate PR gene expression by sequestration of EREBPs in the cytoplasm.

Amino Acid Sequence↗

PubMed1998

Emergency department cardiopulmonary bypass in the treatment of human cardiac arrest.

OBJECTIVE: To study the use of emergency department (ED) femoro-femoral cardiopulmonary bypass (CPB) in the resuscitation of medical cardiac arrest patients. DESIGN: Prospective, uncontrolled trial. SETTING: Urban academic ED staffed with board-certified emergency physicians (EPs). PARTICIPANTS: Ten patients with medical cardiac arrest unresponsive to standard therapy. INTERVENTIONS: Femoro-femoral CPB instituted by EPs. RESULTS: The time of cardiac arrest prior to CPB (mean+/-SD) was 32.0+/-13.6 min. The cardiac output while on CPB was 4.09+/-1.03 L/min with an average of 229+/-111 min on bypass. All 10 patients had resumption of spontaneous cardiac activity while on CPB. Seven of these were weaned from CPB with intrinsic spontaneous circulation. Of these, six patients were transferred from the ED to the operating room for cannula removal and vessel repair while the other patient died in the ED soon after discontinuing CPB. Mean survival was 47.8+/-44.7 h in the six patients leaving the ED. Although these patients had successful hemodynamic resuscitation, there were no long-term survivors. CONCLUSION: CPB instituted by EPs is feasible and effective for the hemodynamic resuscitation of cardiac arrest patients unresponsive to advanced cardiac life support therapy. Future efforts need to focus on improving long-term outcome.

Adolescent↗

PubMed1998

Central metabolic messengers and the effects of nutrition on gonadotrophin secretion in sheep.

Nutrition influences the reproductive axis via alteration of gonadotrophin secretion. However, a link between nutrition and the secretion of GnRH, which drives the axis, has yet to be established. The aim of the present study was to measure the change in the concentrations of metabolic substances in the cerebrospinal fluid of adult male sheep offered a diet designed to maintain constant gonadotrophin secretion (Group M; n = 6), or a diet known to increase gonadotrophin secretion (Group M + L; n = 6). On days 1, 3 and 10 of the dietary treatments, cerebrospinal fluid and jugular blood were sampled and analysed for metabolic fuels (glucose, amino acids and free fatty acids) and metabolic hormones (insulin, insulin-like growth factor I, GH, prolactin, cortisol and the thyroid hormones). On day 11 of the dietary treatment, LH pulse frequency and mean FSH concentrations in Group M + L had increased relative to Group M and to day 0. Plasma concentrations of prolactin and insulin on days 3 and 10, and glucose and insulin-like growth factor I on day 10, were higher in Group M + L than in Group M, but only cerebrospinal fluid concentrations of insulin, glucose and certain amino acids were affected by the dietary treatments on days 3 and 10. Cerebrospinal fluid, but not plasma, concentrations of aspartate, tyrosine, cystine, phenylalanine and arginine on day 3, and glutamine, gamma-aminobutyric acid, threonine, alanine on days 3 and 10, were higher in Group M + L relative to Group M. On day 10, plasma and cerebrospinal fluid concentrations of arginine, phenylalaine, proline, tyrosine, methionine and phosphoserine, but only the plasma concentrations of linoleic acid, aspartate and serine, were higher in Group M + L than in Group M. Concentrations of triiodothyronine, thyroxine, and cortisol in plasma and cerebrospinal fluid were not affected. These results show that the nutritional stimulation of gonadotrophin secretion is accompanied primarily by fluctuations in plasma and cerebrospinal fluid concentrations of insulin and certain amino acids, which suggests that, when nutritional status is improved, insulin, amino acids and possibly glucose interact to modulate GnRH secretion.

Amino Acids↗

PubMed1998

Morphometric and endocrine analyses of the effects of nutrition on the testis of mature Merino rams.

The effects of nutrition on the testis were investigated in groups of five mature Merino rams that were fed either a sub-maintenance (low) diet or a supra-maintenance (high) diet for 69 days. Testosterone, oestradiol and inhibin were measured in blood plasma sampled simultaneously from jugular and testicular veins after an i.v. injection of 200 ng ovine LH kg-1. Plasma concentrations of testosterone, inhibin and oestradiol were higher in testicular than in jugular vein plasma for both diets (P < 0.01). After the LH injection, jugular plasma testosterone increased more rapidly (P < 0.01) in rams fed the high diet than in rams fed the low diet. This was not seen in the testicular vein. Oestradiol concentrations were higher in rams on the high diet than in those on the low diet, in both the testicular (P < 0.0001) and the jugular vein (P < 0.02). Diet did not affect inhibin concentrations. Testes were surgically removed and processed for light microscopy. Testicular mass and seminiferous tubule length and diameter were higher with the high diet than the low diet (P < 0.01). The number of Sertoli cell nuclei per testis was also affected (high diet: 120 +/- 6 x 10(8); low diet: 77 +/- 7 x 10(8); P < 0.001), whereas the proportion of testis occupied by Sertoli cell nuclei was not affected. The number of Leydig cells per testis was not affected by diet, but Leydig cells occupied a greater volume of testis in rams on the high diet than in those on the low diet (P < 0.001). The effects of nutrition on Leydig and Sertoli cells are consistent with changes in the endocrine and exocrine functions of the testis. The finding that Sertoli cell population was altered in adult rams may be explained by the GnRH-independent effects of nutrition.

Analysis of Variance↗

PubMed1997

Administration of fatty acids and gonadotrophin secretion in the mature ram.

The addition of lupin grain to a maintenance diet increases circulating concentrations of volatile fatty acids and gonadotrophin secretion in mature rams. The experiments reported in this paper tested whether these responses were linked causally. The first experiment used 24 rams, of which 16 had two intra-ruminal cannulae inserted each, one for infusion of buffer and the other for infusion of volatile fatty acids. The treated rams (n = 8) were infused for 10 h each day with 1 litre of a solution of volatile fatty acids containing 1.93 moles acetate, 1.89 moles propionate and 0.68 moles butyrate, and 2 litres of a buffer solution containing 14.78 moles sodium bicarbonate, 6.39 moles potassium bicarbonate and 2.06 moles sodium chloride. The eight negative control rams were fed to maintenance and four of them were infused intra-ruminally each day with 3 litres of buffer containing the same mass of salts as the treated rams were given. The eight positive control rams were fed the maintenance diet plus a daily supplement of 900 g lupin grain and four of them were also infused with buffer salts. Blood was sampled before treatment, on Day 3 and at the end of the treatment period (Day 10) for measurement of the plasma concentrations of gonadotrophins (LH and FSH), glucose, insulin and cortisol. In the second experiment, another 24 mature rams were fed to maintain constant live weight and, for 12 of them, sodium acetate (127 g), sodium propionate (64 g) and vegetable oil (60 g) were added to the diet every day for 11 days. Blood was sampled before, and at the end of the treatment period for measurement of the plasma concentrations of gonadotrophins, inhibin, glucose and insulin. In Experiment 1, intraruminal infusion of buffer alone did not affect any of the endocrine variables measured. The infusion of fatty acids and buffer did not alter gonadotrophin secretion, but depressed food intake and increased the plasma concentrations of glucose, insulin and cortisol. When the fatty acids were added to the diet (Experiment 2), the pulsatile secretion of LH was stimulated and FSH and inhibin concentrations were increased. Lupin feeding increased LH pulse frequency on Days 5 and 10, but did not affect FSH concentrations. There were no changes in the circulating concentrations of glucose or insulin. The effects of intra-ruminal infusion of fatty acids on cortisol concentrations and appetite, which were completely absent when similar amounts of fatty acids were fed, suggest that such infusions have undesirable, perhaps stressful, side-effects that prevent expression of the reproductive endocrine responses. On the other hand, the stimulation of gonadotrophin secretion following addition of fatty acids to the diet possibly suggests that changes in the plane of nutrition or rams, for example with lupin supplements, stimulates the reproductive centres of the brain via pathways associated with the synthesis or utilisation of fatty acids. These pathways do not seem to involve changes in glucose homeostasis.

Animals↗

PubMed1997

The Pto kinase conferring resistance to tomato bacterial speck disease interacts with proteins that bind a cis-element of pathogenesis-related genes.

In tomato, the Pto kinase confers resistance to bacterial speck disease by recognizing the expression of a corresponding avirulence gene, avrPto, in the pathogen Pseudomonas syringae pv. tomato. Using the yeast two-hybrid system, we have identified three genes, Pti4, Pti5 and Pti6, that encode proteins that physically interact with the Pto kinase. Pti4/5/6 each encode a protein with characteristics that are typical of transcription factors and are similar to the tobacco ethylene-responsive element-binding proteins (EREBPs). Using a gel mobility-shift assay, we demonstrate that, similarly to EREBPs, Pti4/5/6 specifically recognize and bind to a DNA sequence that is present in the promoter region of a large number of genes encoding 'pathogenesis-related' (PR) proteins. Expression of several PR genes and a tobacco EREBP gene is specifically enhanced upon Pto-avrPto recognition in tobacco. These observations establish a direct connection between a disease resistance gene and the specific activation of plant defense genes.

Amino Acid Sequence↗

PubMed1997

Gonadotrophin and prolactin secretion in castrated male sheep following subcutaneous or intracranial treatment with testicular hormones.

Interactions between testosterone, estradiol, and inhibin in the control of gonadotrophin secretion in males are poorly understood. Castrated rams were treated with steroid-free bovine follicular fluid (bFF), testosterone, or estradiol and for 7 d (2 x 2 x 2 factorial design). Given independently, none of the exogenous hormones affected follicle-stimulating hormone (FSH) concentrations, but the combination of one or both steroids with bFF reduced FSH secretion. Testosterone and estradiol reduced luteinizing hormone (LH) pulse frequency (there was no synergism), and bFF had no effect. Plasma prolactin concentrations were not affected by any treatment. To locate the central sites of steroid action, castrated rams were bilaterally implanted in the preoptic area (POA), ventromedial nucleus (VMH), or arcuate nucleus (ARC). These implants did not affect FSH or prolactin concentrations, or LH pulse amplitude. The frequency of the LH pulses was not affected by testosterone in any site. Estradiol located in the ARC, but not the POA or VMH, decreased LH pulse frequency. In summary, FSH secretion is controlled by synergistic interactions between inhibin and estradiol or testosterone, whereas GnRH/LH pulse frequency is controlled by testicular steroids. Estradiol acts partly, at least, in the ARC, but the central site of action, testosterone remains unknown.

Animals↗

PubMed1997

Level of nutrition modulates the dynamics of oestradiol feedback on plasma FSH in ovariectomized ewes.

The frequency of multiple ovulations in mature, cyclic ewes is strongly influenced by the level of nutrition, but it is difficult to demonstrate concurrent changes in plasma concentrations of gonadotropins. The failure to do so might be a consequence of rapid compensation by the homeostatic feedback mechanism linking secretion by the hypothalamus/pituitary gland and ovarian hormones. Most experimental models have examined the components of the homeostatic feedback system after steady state relationships had been established. We hypothesised that the effects of nutrition might be observed more readily if the system were disrupted and then examined while equilibrium was being re-established. This hypothesis was tested in three experiments in Merino ewes by allowing gonadotropin secretion to escape feedback for 5 days after ovariectomy and then replacing ovarian hormones and examining effects of feeding regimen on the return of plasma concentrations of FSH to baseline values. In all three experiments, oestrogen replacement caused plasma concentrations of FSH to decline more rapidly (P < 0.05) in ewes fed at 0.5x maintenance, than in ewes fed at 1.4x maintenance, with groups fed at maintenance being intermediate. No effect of diet was observed on plasma FSH concentrations in the absence of oestradiol, and neither progesterone nor charcoal-treated bovine follicular fluid influenced the effect of nutrition. Plasma concentrations of oestradiol were 9.8% lower on average (NS) in ewes fed above maintenance than in the sheep fed below maintenance over the three experiments, suggesting that there may have been a reduced clearance of oestradiol which contributed to the result. We conclude that feeding regimen affects the secretion or clearance of gonadotropins in mature ewes, as in the mature ram, and that this is one mechanism by which ovulation rate may be affected.

Analysis of Variance↗

PubMed1997

GnRH secretion into CSF in rams treated with a GnRH antagonist.

The equilibrium of the brain-pituitary-testicular axis is controlled by negative feedback exerted primarily through changes in the circulating concentrations of gonadal steroids. This is usually studied in gonadectomised animals treated with single large doses or constant low levels of exogenous steroid. However, the feedback system probably also contains dynamic components, perhaps expressed as delays to changes in GnRH secretion following a change in steroid concentration. These delays must be measured without interference from surgical procedures, including anaesthesia, bias associated with changes in pituitary responsiveness (which affect the efficiency of pulse detection), and chronic side-effects of gonadectomy. We used a GnRH antagonist ['Antarelix': Ac-D-Nal, D-Cpa, D-Pal, Ser, Tyr, D-Hci, Leu, Lys-(iPr), Pro, D-Ala-NH2] to transiently block LH and steroid secretion (in effect, inducing and reversing castration) in mature male sheep, and measured GnRH secretion into cerebrospinal fluid (CSF) in the third cerebral ventricle. The CSF was withdrawn with a peristaltic pump at a rate of 2 ml/h and pooled every 20 min. Jugular plasma was sampled every 20 min and analysed for testosterone and LH pulses. The antagonist (500 microg i.v.) was injected after 6 h of baseline sampling and the study continued for a further 24 h. The pulses of LH and testosterone disappeared shortly after antagonist injection, with delays of 20 +/- 12 min for LH and 80 +/- 29 min for testosterone. This led to an increase in GnRH pulse frequency, starting 300 +/- 54 min after antagonist injection. Secretion of LH and testosterone pulses resumed at 553 +/- 38 and 530 +/- 30 min (after antagonist injection), and GnRH pulse frequency returned to baseline values after 170 +/- 42 min (relative to LH) and 117 +/- 35 min (relative to testosterone). The consistent nature of these responses across the group of animals suggests that this can be used to test the effects of exteroceptive factors on the dynamics of negative feedback.

Animals↗

PubMed1997

Role of glucose, fatty acids and protein in regulation of testicular growth and secretion of gonadotrophin, prolactin, somatotrophin and insulin in the mature ram.

This study tested whether the effects of nutrition on gonadotrophin secretion and testicular growth in mature rams are due to increases in the supply of glucose, fatty acids (FA) or amino acids. Responses to protein (casein) and glucose, alone or in combination, were compared with responses to lupin grain and responses to a combination of protein, glucose and FA (acetate, propionate and vegetable oil). Glucose and casein were infused intra-abomasally whereas lupins and FA were added to the diet. Lupin feeding decreased blood growth hormone (GH) concentrations, but increased pulsatile luteinizing hormone (LH) secretion and increased the concentrations of follicle-stimulating hormone (FSH), prolactin, glucose and insulin. These effects were associated with testicular growth. Glucose or casein increased insulin concentrations and decreased GH concentrations, but did not affect gonadotrophins or testicular growth. There was no synergism between casein and glucose. Responses elicited by adding FA to the glucose+casein treatment were similar to those observed with lupins. In conclusion, the reproductive axis does not seem to be closely linked with dietary intakes of amino acids or with circulating concentrations of glucose, insulin or GH. However, the energetic components of the diet, particularly the fatty acids, appear to play a key role in the reproductive responses to changes in nutrition.

Analysis of Variance↗

PubMed1997

Physiological limits to further improvement in the efficiency of oestrous synchronization in goats.

The variability between animals in the timing of oestrus after administration of a synchronization treatment seems to explain the low rate of fertility in goats inseminated at a predetermined time after progesterone withdrawal. Two experiments were performed during the breeding season to test whether the variation was due to the exogenous hormone regime or to the endogenous physiology of the animals. Twenty-one goats were given a synchronization treatment consisting of a vaginal sponge impregnated with 45 mg of fluorogestone acetate (FGA) for 11 days associated with intramuscular injection of 400 I.U. of equine chorionic gonadotrophin (eCG) and 50 microg of cloprostenol 48 h before sponge removal. Progesterone concentrations were measured during the subsequent cycle and the patterns were modelled to allow precise determination of the onset of luteolysis. Oestrus and the luteinizing hormone (LH) surge began 33.0+/-6.8 h and 76.0+/-33.0 h after sponge withdrawal, v. 43.4+/-5.7 h and 90.0+/-36.0 h after natural luteolysis. For both observations, the between-goat variability was larger during the natural than during the synchronized oestrus (P < 0.05). The duration of the oestrous cycle was independent of the number of corpora lutea (CL), whereas the duration of luteal phase was shorter in goats with 2-3 CL (16.4+/-0.9 day than in those with 1 CL: 17.7+/-1.3 day; P < 0.05). In the second experiment, 20 goats were ovariectomized and given a vaginal sponge as described above. Sixteen h after sponge removal, they were injected with 50 microg of oestradiol benzoate (ODB). This treatment was repeated with the second sponge being inserted 1-2 days after observation of oestrus. Oestrus and LH surge were observed: 32.8+/-6 8 h v. 27.8+/-7.8 h after the first ODB injection, and 36.6+/-7.3 h v. 34.3+/-4.8 h after the second ODB injection. No relationship was observed between data of the two experiments. In both cases, the variability in the occurrence of oestrus and LH surge was of the same order as observed in the first experiment. This study shows that the timing of oestrus and LH surge is less variable after progestagen treatment than during a natural oestrous cycle. Moreover, a significant proportion of variability is inherent in the delays following the oestradiol peak, suggesting that further improvement in the synchronizing capacity of treatment based on progestagen administration is unlikely.

Animals↗

PubMed1997

Involvement of insulin-like growth factors in the interactions between nutrition and reproduction in female mammals.

The effects of nutrition on the reproductive system of female mammals are discussed in an attempt to determine the importance of the role of the insulin-like growth factor (IGF) system of proteins in the physiological mechanisms. The IGF system comprises IGF-I, IGF-II, their receptors and binding proteins. For this review, insulin and its receptors have been included in this system. The reproductive responses have been separated into two classes, based on fundamental differences in the reproductive biology and physiological mechanisms underlying them. The first involves the effects of nutrition on the induction of ovulation, at puberty or postpartum. In this case, the question is whether or not the animal will reproduce. The second class of response, changes in ovulation rate, involves consideration of reproductive efficiency in animals in which ovulation is inevitable.

Animals↗

PubMed1997

Phytoestrogens reduce bone loss and bone resorption in oophorectomized rats.

To examine a potential role for phytoestrogens in postmenopausal bone loss, the oophorectomized (OOX) rat model has been used in three studies to investigate the effects of the phytoestrogens coumestrol, zearalanol and a mixture of isoflavones on estrogen-dependent bone loss. In the studies of coumestrol and zearalanol, the rats were allocated to a control group, a phytoestrogen-treated group (1.5 micromol coumestrol or 3.1 mmol zearalanol twice per week, intramuscular) or, in the coumestrol study, an estrogen-treated group (28.1 nmol, intramuscular). In the isoflavone study, the rats were allocated to a control group, an estrogen treated group or a treatment group that received 131.25 mg of phytoestrogens per week incorporated into the nonpurified rat diet. Bone mineral density was measured globally and at the spine and femur at base line and 6 wk post-oophorectomy. In the coumestrol study, blood and urine samples were collected. Compared with the control group, rats receiving coumestrol and zearalanol had significantly reduced bone loss at all sites measured. The estrogen-treated group had significantly greater bone density than the control and the coumestrol-treated groups in the spine and global measurements. Coumestrol reduced urine calcium excretion and the bone resorption markers pyridinoline and deoxypyridinoline after 1 wk of treatment. Oral isoflavone phytoestrogens had no effect on oophorectomized rats including bone loss at the dose used. Thus, for the first time, the bioactivity of coumestrol and zearalanol in preventing bone loss has been demonstrated in a well-recognized model of postmenopausal bone loss.

Animals↗

PubMed1997

Semen production by the emu (Dromaius novaehollandiae). 1. Methods for collection of semen.

Two methods for collecting semen from male emus using an artificial cloaca (AC) have been developed. In the first method, the male mounts the female teaser and the collector effects erection and subsequent ejaculation using the AC. The second method takes advantage of the development of sexual behaviour directed towards the semen collector and semen is collected when the male mounts the collector's back. Eight of 11 males were successfully trained with teasers and 5 of the 7 males trained without teasers ejaculated successfully. The ease of training varied between birds. The use of a teaser was very valuable, as the crouching behavior of the teaser elicited mating attempts in every male. The training and collection of semen was done by one person. Both methods can be used for routine collection of semen, as they take advantage of natural stimulation and the voluntary ejaculation reflex to which the birds adapted readily.

Animals↗

PubMed1997

Semen production by the emu (Dromaius novaehollandiae). 2. Effect of collection frequency on the production of semen and spermatozoa.

This experiment tested the hypothesis that frequent collection of semen from emus would increase the total output of semen and spermatozoa over less frequent collection. Semen was collected from trained male emus using an artificial cloaca. In Experiment 1, semen was collected from males every 4th d (96-h interval), every 2nd d (48-h interval), and every day (24-h interval) for 16 d. In Experiment 2, semen was collected daily (24-h interval), twice daily (6-h interval), and three times per day (3-h interval) over 6 d. Twice-daily collections yielded twice as much volume and number of spermatozoa than daily collections. Collecting semen three times per day did not yield extra semen, as it adversely affected the libido of males. Twice-daily collections appears to yield the optimum output over the 6 d of this experiment, but longer periods of collection need to be studied.

Animals↗