THE LIKELIHOOD OF SPERM COMPETITION IN MANATEES-EXPLAINING AN APPARENT PARADOX

Florida manatees ( Trichechus manatus latirostris ) are promiscuous, with multiple males mating with individual females. This suggests manatees are sperm competitors. Surprisingly, manatee testes are not relatively large. For adult males in non-winter, testicular size is approximately twice what is expected, based on allometry, for "typical" ( i. e. , non-sperm competitor) male mammals of similar size; for these manatees, combined testicular weight represents 0.19% of the body weight ( n = 27 manatees). Testicular weight was generally largest in manatees older than 7 yr in non-winter. Testicular size of some sperm competitors is as much as an order of magnitude (or more) larger than expected in a "typical" species. Perhaps in compensation for the testes not being remarkably large, the seminal vesicles of mature manatees may be larger than the testes. Production of notably large volumes of seminal fluid characterizes sperm competitor primate species and may have positive energy consequences for species such as the manatee that have extremely low metabolic rates. Another possible explanation for the observed relationship between testicular mass and body mass in manatees is that selection for a greatly expanded hindgut and extremely dense, heavy integument could make the body mass of manatees "artificially" high, and the relative testicular mass "artificially" low.     

Wide-pulse-width, high-frequency neuromuscular stimulation: implications for functional electrical stimulation.

Electrical stimulation (1-ms pulses, 100 Hz) produces more torque than expected from motor axon activation (extra contractions). This experiment investigates the most effective method of delivering this stimulation for neuromuscular electrical stimulation. Surface stimulation (1-ms pulses; 20 Hz for 2 s, 100 Hz for 2 s, 20 Hz for 3 s) was delivered to triceps surae and wrist flexors (muscle stimulation) and to median and tibial nerves (nerve stimulation) at two intensities. Contractions were evaluated for amplitude, consistency, and stability. Surface electromyograph was collected to assess how H-reflexes and M-waves contribute. In the triceps surae, muscle stimulation produced the largest absolute contractions (23% maximal voluntary contraction), evoked the largest extra contractions as torque increased by 412% after the 100-Hz stimulation, and was more consistent and stable compared with tibial nerve stimulation. Absolute and extra contraction amplitude, consistency, and stability of evoked wrist flexor torques were similar between stimulation types: torques reached 11% maximal voluntary contraction, and extra contractions increased torque by 161%. Extra contractions were 10 times larger in plantar flexors compared with wrist flexors with muscle stimulation but were similar with nerve stimulation. For triceps surae, H reflexes were 3.4 times larger than M waves during nerve stimulation, yet M waves were 15 times larger than H reflexes during muscle stimulation. M waves in the wrist flexors were larger than H reflexes during nerve (8.5 times) and muscle (18.5 times) stimulation. This is an initial step toward utilizing extra contractions for neuromuscular electrical stimulation and the first to demonstrate their presence in the wrist flexors.     

Prejunctional beta 1-adrenoceptors inhibit cholinergic transmission in canine bronchi

The aim of the present study was to determine in canine bronchi the effects produced by norepinephrine (released from adrenergic nerve terminals) on cholinergic neurotransmission. Electrical stimulation of canine bronchi activates cholinergic and adrenergic nerve fibers. The adrenergic neuronal blocker, bretylium tosylate, inhibited the increase in [3H]norepinephrine overflow evoked by electrical stimulation but did not prevent that caused by the indirect sympathomimetic tyramine. During blockade of the exocytotic release of norepinephrine with bretylium, the pharmacological displacement of the sympathetic neurotransmitter by tyramine significantly decreased the contractions evoked by electrical stimulation but did not affect contractions caused by exogenous acetylcholine. Metoprolol, a beta 1-adrenergic antagonist, abolished and propranolol significantly reduced the effect of tyramine during electrical stimulation. alpha 2-Adrenergic blockade, beta 2-adrenergic blockade, or removal of the epithelium did not significantly affect the response to tyramine. These results suggest that norepinephrine when released from sympathetic nerve endings can activate prejunctional inhibitory beta 1-adrenoceptors to depress cholinergic neurotransmission in the bronchial wall.     

Testicular measurements and reproductive characteristics in stallions.

Factors affecting testicular measurements in situ and the relationships among the measurements and various reproductive characteristics were studied using data from 48 stallions. Mean values during the breeding season are provided for scrotal width, widths and lengths of individual testes, combined weight of testicular parenchyma, daily sperm production and daily sperm output. Testicular measurements were highly repeatable from day to day and for repeated measurements on a given day; technician provided the largest source of variation in the measurements of a given stallion. Age significantly affected all testicular measurements; testicular size for 2- to 3-year-old stallions did not differ (P greater than 0.05) from that for 4- to 6-year-olds, but was smaller (P less than 0.05) than testicular size of stallions greater than or equal to 7 years old. Scrotal width was correlated (P less than 0.01) with daily sperm production (r = 0.75) and daily sperm output (r = 0.55) and was generally the most repeatable measurement.     

Testosterone secretion and semen plasma enzyme activity in rams with genital pathology stimulated with GnRH

Testosterone secretion in response to GnRH stimulation and enzymatic activity of semen plasma was evaluated comparatively in rams with or without genital abnormality. Scrota, testes and epididymides of 128 rams between 1.5 and 6 years old from various breeds were examined clinically and ultrasonographically. Bilaterally cryptorchid rams (n = 2), and rams with focal testicular degeneration (n = 3) or unilateral sperm granuloma localized in the caput (n = 3) epididymis or the cauda epididymis (n = 3), diagnosed by either clinical or ultrasonographic examination, were selected for the further investigation of spermatologic parameters, testosterone secretion in response to GnRH stimulation, and enzymatic activity of semen plasma before histopathologic confirmation of lesions. Except for the cryptorchid rams, sperm parameters determined in ejaculates were similar to intact controls (n = 3). GnRH administration increased plasma testosterone levels significantly irrespective of the type of genital pathology (P < 0.01). The testosterone response calculated based on area under the curve following GnRH administration in rams having genital abnormality was not significantly different from the controls. Aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activity in the semen plasma varied between rams, with the lowest mean values in the bilaterally cryptorchid group (P < 0.05). Spermatic granuloma localized either in the caput or cauda of the epididymis was associated with a significant reduction in the semen plasma AST activity compared to controls (P < 0.01). In conclusion, our results indicated that the ability of testicular tissue to secrete testosterone in response to GnRH stimulation in rams with bilateral cryptorchidism, focal testicular degeneration and unilateral sperm granuloma was similar to that of intact controls, and that reduced semen plasma AST activity may have a diagnostic value in the diagnosis of the epididymal obstruction in rams. Focal testicular degeneration did not influence AST, alkaline phosphatase (ALP) and LDH activity in semen plasma.     

Mouse Genital Ridges in Organ Culture: The Effects of Temperature on Maturation and Experimental Induction of Teratocarcinogenesis

Abstract. Testicular teratomas can be induced experimentally by grafting genital ridges from male mouse fetuses to the testes of adults. A high incidence of teratomas occurs in genital ridges grafted to scrotal testes, but not in genital ridges grafted to testes maintained at body temperature. Genital ridges were cultured at 32° C or 37° C prior to grafting to the testes to determine the effect of temperature on the incidence of teratomas. Genital ridges cultured at 32° C for two or three days produced a high incidence of teratomas when grafted to the testes, in contrast to genital ridges cultured at 37° C for two or three days which produced a low incidence. Histologically, genital ridges cultured at 32° C contained disorganized testicular tubules and were retarded in development. Genital ridges continued to develop in vitro at 37° C, but were histologically different from genital ridges maturing in the fetus. Genital ridges cultured at 32° C for 10 to 12 days did not develop teratomas in vitro or after grafting to the testes. Further characterization of temperature effects in vitro may lead to a better understanding of teratocarcinogenesis in vivo.     

Mechanisms of reflex bladder activation by pudendal afferents

Activation of pudendal afferents can evoke bladder contraction or relaxation dependent on the frequency of stimulation, but the mechanisms of reflex bladder excitation evoked by pudendal afferent stimulation are unknown. The objective of this study was to determine the contributions of sympathetic and parasympathetic mechanisms to bladder contractions evoked by stimulation of the dorsal nerve of the penis (DNP) in α-chloralose anesthetized adult male cats. Bladder contractions were evoked by DNP stimulation only above a bladder volume threshold equal to 73 ± 12% of the distension-evoked reflex contraction volume threshold. Bilateral hypogastric nerve transection (to eliminate sympathetic innervation of the bladder) or administration of propranolol (a β-adrenergic antagonist) decreased the stimulation-evoked and distension-evoked volume thresholds by -25% to -39%. Neither hypogastric nerve transection nor propranolol affected contraction magnitude, and robust bladder contractions were still evoked by stimulation at volume thresholds below the distension-evoked volume threshold. As well, inhibition of distention-evoked reflex bladder contractions by 10 Hz stimulation of the DNP was preserved following bilateral hypogastric nerve transection. Administration of phentolamine (an α-adrenergic antagonist) increased stimulation-evoked and distension-evoked volume thresholds by 18%, but again, robust contractions were still evoked by stimulation at volumes below the distension-evoked threshold. These results indicate that sympathetic mechanisms contribute to establishing the volume dependence of reflex contractions but are not critical to the excitatory pudendal to bladder reflex. A strong correlation between the magnitude of stimulation-evoked bladder contractions and bladder volume supports that convergence of pelvic afferents and pudendal afferents is responsible for bladder excitation evoked by pudendal afferents. Further, abolition of stimulation-evoked bladder contractions following administration of hexamethonium bromide confirmed that contractions were generated by pelvic efferent activation via the pelvic ganglion. These findings indicate that pudendal afferent stimulation evokes bladder contractions through convergence with pelvic afferents to increase pelvic efferent activity.     

Activation and inhibition of the micturition reflex by penile afferents in the cat

Coordination of the urinary bladder and the external urethral sphincter is controlled by descending projections from the pons and is also subject to modulation by segmental afferents. We quantified the effects on the micturition reflex of sensory inputs from genital afferents traveling in the penile component of the somatic pudendal nerve by electrical stimulation of the dorsal nerve of the penis (DNP) in alpha-chloralose anesthetized male cats. Depending on the frequency of stimulation (range, 1-40 Hz), activation of penile afferents either inhibited contractions of the bladder and promoted urine storage or activated the bladder and produced micturition. Stimulation of the DNP at 5-10 Hz inhibited distension-evoked contractions and increased the maximum bladder capacity before incontinence. Conversely, stimulation at 33 and 40 Hz augmented distension-evoked contractions. When the bladder was filled above a threshold volume (70% of the volume necessary for distension-evoked contractions), stimulation at 20-40 Hz activated de novo the micturition reflex and elicited detrusor contractions that increased voiding efficiency compared with distension-evoked voiding. Electrical stimulation of the DNP with a cuff electrode or percutaneous wire electrode produced similar results. The ability to evoke detrusor contractions by activation of the DNP was preserved following acute spinal cord transection. These results demonstrate a clear role of genital afferents in modulating the micturition reflex and suggest the DNP as a potential target for functional restoration of bladder control using electrical stimulation.     

Effects of cold storage on plasma membrane, DNA integrity and fertilizing ability of feline testicular spermatozoa

This study examined the effects of cold storage on plasma membrane, DNA integrity, and fertilizing ability of domestic cat spermatozoa. Intact cat testes were stored at 4°C in Dulbecco's phosphate buffered saline (DPBS) for 7 days. Membrane integrity (experiment 1) and DNA integrity (experiment 2) of extracted spermatozoa were assessed over time during storage. Testicular spermatozoa were also tested for their fertilizing ability via intracytoplasmic sperm injection (ICSI) in term of gamete activation and early embryonic development at 18 h (experiment 3). The membrane integrity of testicular spermatozoa was well preserved in DPBS for 4 days compared to non-preserved control (Day 0) (P<0.05). The incidence of testicular sperm DNA fragmentation was <1% after 7 days of cold storage and was not significantly affected by the duration of cold storage (P>0.05). Finally, testicular spermatozoa could form pronuclei and sustain embryo development following ICSI regardless of the storage time (P>0.05). In conclusion, cat testicular spermatozoa can be preserved at 4°C for up to 7 days without severely compromising of plasma membrane and DNA integrity while retaining a normal fertilizing ability.     

A systematic method to quantify the presence of cross-talk in stimulus-evoked EMG responses: implications for TMS studies

Surface electromyography (EMG) responses to noninvasive nerve and brain stimulation are routinely used to provide insight into neural function in humans. However, this could lead to erroneous conclusions if evoked EMG responses contain significant contributions from neighboring muscles (i.e., due to "cross-talk"). We addressed this issue with a simple nerve stimulation method to provide quantitative information regarding the size of EMG cross-talk between muscles of the forearm and hand. Peak to peak amplitude of EMG responses to electrical stimulation of the radial, median, and ulnar nerves (i.e., M-waves) were plotted against stimulation intensity for four wrist muscles and two hand muscles (n = 12). Since electrical stimulation can selectively activate specific groups of muscles, the method can differentiate between evoked EMG arising from target muscles and EMG cross-talk arising from nontarget muscles. Intramuscular EMG responses to nerve stimulation and root mean square EMG produced during maximal voluntary contractions (MVC) of the wrist were recorded for comparison. Cross-talk was present in evoked surface EMG responses recorded from all nontarget wrist (5.05-39.38% Mmax) and hand muscles (1.50-24.25% Mmax) and to a lesser degree in intramuscular EMG signals (～3.7% Mmax). The degree of cross-talk was comparable for stimulus-evoked responses and voluntary activity recorded during MVC. Since cross-talk can make a considerable contribution to EMG responses in forearm and hand muscles, care is required to avoid misinterpretation of EMG data. The multiple nerve stimulation method described here can be used to quantify the potential contribution of EMG cross-talk in transcranial magnetic stimulation and reflex studies.     

Spermatogenic activities of the left and right testes of hemicastrated and intact cockerels

One hundred cockerels of the Hacco strain were reared in deep litter. At 5 weeks of age the left testes of 30 cockerels and right testes of another 30 cockerels were surgically removed. The remaining cockerels were sham operated. At 10, 15, 20 and 25 weeks of age equal numbers from each group were killed. The rate of testis growth, the spermatid/spermatozoa reserve for each genital tract, and the relative spermatogenic activity (i.e., spermatid/sperm per g of testicular tissue) were determined for the left and right testes at the different ages.At 10 weeks of age only spermatids were found in all the testes, with concomitant very low relative spermatogenic activities. The weights of the testes increased with age and compensatory hypertrophy occurred in the testes of the hemicastrates from 15 weeks of age. The mean of the sperm reserve of the left (7.391 × 10⁹ sperm) and right (8.66 × 10⁹ sperm) genital tracts of hemicastrates contained significantly more (P < 0.05) sperm than the sum of the means of the sperm reserves in the left and right genital tracts (5.19 × 10⁹sperm) of the intact cockerels at 25 weeks of age.The relative spermatogenic activities varied with age but the pattern was similar for all cockerels, with the activities of the testes of the hemicastrates being significantly higher (P < 0.5). In all cases the values for the right testes were higher than those for the corresponding left testes.At 15 weeks of age both spermatids and spermatozoa were found in 71.4% and 100% of the right and left testes of the hemicastrates, respectively, and in 25% of the left testes of the intact cockerels. Only spermatids were found in the right testes of the intact cockerels.Hemicastration caused the right testes of the hemicastrates to produce sperm earlier than those of intact cockerels. The left testes in all cases produced sperm earlier than the corresponding right testes. Hemicastration enhanced sperm numbers per g testes (i.e., relative spermatogenic activity).     

急性神经损伤引起脊髓背角C-纤维诱发电位长时程增强

神经损伤引起神经病性疼痛,表现为持续性痛超敏和痛觉过敏。目前对神经病性疼痛的机制尚缺乏了解。我们以往的工作表明强直电刺激坐骨神经可引起脊髓背角C-纤维诱发电位的长时程增强(long-term potentiation,LTP),该LTP被认为是病理性疼痛的突触模型。本研究的目的在于探讨急性神经损伤是否能在完整动物的脊髓背角诱发出C-纤维诱发电位LTP。在以测试刺激(10～20V,0．5ms)电刺激坐骨神经的同时在脊髓背角用微电极记录C一纤维诱发电位。分别用强直刺激、剪断或夹捏坐骨神经诱导LTP。结果发现：(1)剪断或夹捏坐骨神经都可以诱导脊髓背角C-纤维诱发电位的LTP,该LTP可持续到实验结束(3～9h),在剪断神经前10min用利多卡因局部阻滞坐骨神经则可完全阻断LTP的产生;(2)神经损伤诱导的LTP可被NMDA受体阻断剂AP5所阻断;(3)用单次强直刺激引起LTP后,切断坐骨神经可使LTP的幅度进一步增大,而用多次强直电刺激使LTP饱和后,损伤神经则不能使LTP进一步增大。切断神经引起LTP后,强直电刺激也不能使LTP进一步增大。这些结果表明,急性神经损伤可以诱导脊髓背角C纤维诱发电位LTP,且切断神经能更有效地诱导LTP。该试验进一步支持我们的设想,即脊髓背角C-纤维诱发电位LTP可能在病理性疼痛的形成中起重要作用。     

Low aromatase activity and gene expression in human fetal testes

Because of previous indications that estradiol (E2) plays a role in the regulation of testicular testosterone (T) production in some species, the production of E2 and aromatase gene expression in human fetal testes were investigated. Testicular minces from 14 fetuses (fetal age 15-23 weeks) were incubated with and without 200 ng/ml highly purified hCG, and the production of E2 and T was measured by RIA. Basal T production was high at 15-18 weeks of gestation and decreased thereafter. Estradiol production was low in all testes. Aromatase mRNA (P-450 arom messenger ribonucleic acid) was not detectable in fetal testicular tissues when studied by Northern and dot blot techniques. Placenta and fetal liver expressed aromatase mRNA, but fetal ovary contained only miniscule amounts. HCG significantly stimulated the production of both T and E2 in the testes of older fetuses (19-23 weeks), but the testicular E2 production of the youngest fetuses (15-18 weeks) did not increase significantly after hCG stimulation. These results indicate that aromatase activity and gene expression are very low in human fetal testes. These findings suggest that E2 may not play a major role in testicular T production in the human fetus.     

Growth,testicular and endocrine function of boars exposed to 8, 16 or 24 hours of light daily before puberty

Sixty Yorkshire boars were used in two replicates to evaluate the influence of duration of photoperiod on growth, testicular and reproductive endocrine function. Boars born in May and July were exposed to either 8, 16 or 24 h of fluorescent light (200 1x) daily between 2 and 8 months of age. Body weights were obtained at 2-week intervals. At 4, 6 and 8 months of age, venous cannulae were placed in five boars from each treatment and samples of serum were collected to evaluate concentrations of luteinizing hormone (LH) and testosterone. Samples of boars from each treatment were castrated at 6 and 8 months of age, and weights and sperm content of the testes and epididymides were determined. Body weights of boars were similar for all treatments throughout the experiment. Duration of photoperiod did not affect weights of the testes or epididymides or total numbers of sperm within these tissues at either 6 or 8 months of age. Testicular and epididymidal weights and epididymidal sperm numbers increased between 6 and 8 months of age. Concentrations of luteinizing hormone (LH) and testosterone in serum at 4, 6 or 8 months of age were not affected by duration of photoperiod. These results indicate that growth rate and testicular development of prepubertal Yorkshire boars born in May and July are not influenced by duration of photoperiod.     

Effects of dietary cobalt on testicular structure

Adult male rats were maintained on a diet containing 265 ppm cobalt for up to 98 days. Three rats were sacrificed weekly and assayed for testicular damage by light and electron microscopy. Testicular damage was first apparent after 70 days of treatment, followed by a progressive deterioration of cell architecture and decrease in testicular volume. The degenerative changes were of a very general nature; e.g., thickening of basal lamina and basement membranes, increased packing of red blood cells in veins and arteries, formation of "giant" cells, loss of sperm tail filaments, and degeneration of sperm mitochondria. No cobalt residues could be detected by energy dispersive x-ray microanalysis. These data indicate that testicular degeneration was not a primary response to cobalt and suggest that the testes become hypoxic due both to blockage of veins and arteries by red blood cells and to changes in permeability caused by thickening of basal lamina and basement membranes.     

Transcriptomic and biochemical effects of pycnogenol in ameliorating heat stress-related oxidative alterations in rats

BackgroundHeat stress is a condition that is due to extreme heat exposure. It occurs when the body cannot keep its temperature healthy in response to a hot climate and associated with oxidative stress. Testicular hyperthermia can induce apoptosis of sperm cells, affect sperm production and decrease sperm concentration, leading to sperm disorder, for this reason, we examined the protective impact of pycnogenol that it has a wide range of biological benefits, including antioxidant, anti-inflammatory and anti-cancer activities against the oxidative alterations that happen in testicular and brain tissues due to heat stress in rats.Study designForty-eight Wistar male rats, approximately around 6 weeks age were allocated randomly into four groups (12 in each) of control, HS (subjected to heat stress and supplemented orally with 50 mg of pycnogenol/kg b. w./day dissolved in saline for 21 days), and pycnogenol (rats supplemented orally with 50 mg of pycnogenol/kg b. w./day dissolved in saline for 21 days).ResultsData revealed a promising role of pycnogenol as an antioxidant, natural product to successfully reverse the heat-induced oxidative alterations in testicular and brain tissues of rats through significant upregulation of superoxide dismutase-2, catalase, reduced glutathione, and anti-apoptotic gene, while downregulating pro-apoptotic, and heat shock protein70. Pycnogenol treatment also reversed the reproductive hormone level and spermatogenesis to their normal values.ConclusionPycnogenol as a natural protective supplement could recover these heat stress-induced oxidative changes in testes and hypothalamus.     

Motor unit recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly: triceps surae

Neuromuscular electrical stimulation (NMES) can be delivered over a nerve trunk or muscle belly and can generate contractions by activating motor (peripheral pathway) and sensory (central pathway) axons. In the present experiments, we compared the peripheral and central contributions to plantar flexion contractions evoked by stimulation over the tibial nerve vs. the triceps surae muscles. Generating contractions through central pathways follows Henneman's size principle, whereby low-threshold motor units are activated first, and this may have advantages for rehabilitation. Statistical analyses were performed on data from trials in which NMES was delivered to evoke 10-30% maximum voluntary torque 2-3 s into the stimulation (Time(1)). Two patterns of stimulation were delivered: 1) 20 Hz for 8 s; and 2) 20-100-20 Hz for 3-2-3 s. Torque and soleus electromyography were quantified at the beginning (Time(1)) and end (Time(2); 6-7 s into the stimulation) of each stimulation train. H reflexes (central pathway) and M waves (peripheral pathway) were quantified. Motor unit activity that was not time-locked to each stimulation pulse as an M wave or H reflex ("asynchronous" activity) was also quantified as a second measure of central recruitment. Torque was not different for stimulation over the nerve or the muscle. In contrast, M waves were approximately five to six times smaller, and H reflexes were approximately two to three times larger during NMES over the nerve vs. the muscle. Asynchronous activity increased by 50% over time, regardless of the stimulation location or pattern, and was largest during NMES over the muscle belly. Compared with NMES over the triceps surae muscles, NMES over the tibial nerve produced contractions with a relatively greater central contribution, and this may help reduce muscle atrophy and fatigue when NMES is used for rehabilitation.     

Inverse relationship between testicular proliferation and apoptosis in mammalian seasonal breeders

Seasonal cycles of testicular activity occur in many mammals and can include transitions between total arrest and recrudescence of spermatogenesis. We hypothesize that involution and reactivation of testis result from two antagonistic processes, proliferation and programmed cell death (apoptosis), which are activated at different times. To test this hypothesis, quantitative measurements of both proliferation-specific marker and apoptotic produced nucleosomes have been compared with sperm and testosterone production in testes from adult roe deer during breeding and non-breeding seasons (May to September). Testes of brown hare were included from periods of testes regression (June to August) and recrudescence (November to December). The highest testicular weights in roe deer were found in the rutting period from late July to early August (27.25 +/- 8.56 g), corresponding with the highest number of testicular sperm/g parenchyma. The peak of sperm production coincided with a peak in testosterone concentration (1.19 +/- 0.53 microg/g testis). The maximum level of proliferation-specific marker was also found during the breeding season (98.6 +/- 58.2 U/g testis in comparison to 20.1 +/- 22.0 U/g in the prerutting period). In contrast, the most significant apoptosis was observed in the nonbreeding season than the breeding period (71.11 +/- 5.79 U/mg testis and 18.88 +/- 6.79 U/mg, respectively). Testicular proliferation was low in the brown hare (0.061 +/- 0.062 U/g) during involution of the testes. It was newly activated in November and December (0.85 +/- 0.33 U/g), preceding the increase in testicular volume. Testosterone production increased in conjunction with testicular proliferation. At this time, testicular apoptosis was significantly lower (14.16 +/- 2.12 U/mg testis) than during the period of pronounced testicular regression (30.16 +/- 19.95 U/g). These results suggest that regulation of seasonal testicular activity is characterized by an inverse relationship of proliferation and apoptosis.     

Testicular and spermatozoan parameters in the pukeko (Porphyrio porphyrio melanotus)

The pukeko (Porphyrio porphyrio melanotus) is widespread in New Zealand, and is the closest living relative to the endangered takahe (Porphyrio mantelli), which has a relatively high rate of infertility. In this study, sperm collected from a number of pukeko was analysed in order to model the reproductive physiology of the male takahe. In addition, testicular parameters were measured. To ascertain the best method of sperm collection five techniques for harvesting sperm were used on two occasions during the breeding season. All five techniques resulted in the successful recovery of sperm. However, the float-out technique produced the best quality samples. Following collection, the morphometry of unstained sperm was assessed. Our findings suggest that pukeko sperm is non-motile in the male reproductive tract. We found the mean sperm head length in the pukeko is 16.9mum, but sperm head length varied significantly between birds. Testicular weight and length was significantly correlated with bird weight (P<0.05). Within each bird, testes weights were asymmetric. However, testes length was significantly correlated (P<0.05). There was a significant difference (P<0.05) in testes length between birds. The methodologies presented for obtaining and analysing pukeko sperm morphometry can be used to assist opportunistic studies of the reproductive biology of other New Zealand native birds.     

Restoration of spermatogenesis and male fertility by transplantation of dispersed testicular cells in the chicken

Transplantation of male germ cells into sterilized recipients has been widely used in mammals for conventional breeding and transgenesis purposes. This study presents a workable approach for germ cell transplantation between male chickens. Testicular cells from adult and prepubertal donors were dispersed and transplanted by injection directly into the testes of recipient males sterilized by repeated gamma irradiation. We describe the repopulation of the recipient seminiferous epithelium up to the production of heterologous sperm in about 50% of transplanted males. In comparison to males transplanted with testicular cell preparations from adult donors, in which the first ejaculates with sperm were recovered about 5 wk after transfer, a substantial interval (about 10 wk) was necessary to obtain ejaculates after the transfer of testicular cells from prepubertal donors. However, in both cases, recipient males produced ejaculates capable of fertilizing ova and producing progeny expressing donor genes.