Cryopreservation of epididymal and ejaculated bull spermatozoa

The present study was undertaken to assess viability of frozen–thawed bull semen collected from the bull’s ejaculate and cauda epididymis. A total of 30 ejaculates were collected from three bulls twice per week for 5 weeks (Control). Caudal epididymis were collected from slaughtered beef cattle of unknown origin from the local abattoir. Caudal epididymal sperm was recovered immediately after slaughtering (EP-0 h) and after cooling at 5°C for 24 h (EP-24). The epididymal and ejaculated samples were each pooled together before being extended with Triladyl. Diluted samples per treatment were loaded into a 0.25-mL French straw and cooled to 5°C in 4 h. Cooled straws were placed 4 cm above liquid nitrogen to freeze for 10 min. Frozen straws were immersed into LN2 and kept for 7 days at −196°C. Samples were analysed immediately after dilution and post-thawing using the computer aided sperm analysis for sperm motility rate, viability and acrosome defects. The highest sperm motility rates were observed with EJ-0 h before and after cryopreservation. However, the difference in sperm motility parameters between EP-0 h and EP-24 h evaluated before and after freezing was not significant (P > 0.05). Furthermore, no significant difference in live cells mean values was observed between the three samples on freezing (P > 0.05). In relation to spermatozoa acrosome defects, there was no significant difference observed among the three samples before and on freezing (P > 0.05). In conclusion, the results from the present study revealed that cooling of epididymides at 5°C for 24 h before the recovery of sperm cells was efficient in preserving epididymal sperm viability. However, ejaculated bull spermatozoa had higher sperm motility and viability rate than epididymal sperm.

43 CORRELATIONS OF METHODS OF SPERM ANALYSIS IN FRESH SEMEN OF SOUTH AFRICAN INDIGENOUS GOAT

This study investigated the correlations between methods of assessing sperm qualities; namely, sperm total motility (TM), sperm vitality, acrosome integrity, DNA integrity, and sperm membrane integrity. A total of 60 ejaculates from 6 bucks were collected and the spermatozoa evaluated. The overall mean percentages of sperm TM, sperm vitality (eosin-nigrosin and propidium iodide stains), sperm acrosome integrity (Spermac and SpermBlue® stains), sperm DNA integrity (acridine orange and halotech), and sperm membrane integrity (hypoosmotic swelling test and water test) were 94.7 ± 0.5, 81.0 ± 0.6. 79.6 ± 3.7, 79.7 ± 1.8, 78.6 ± 5.3, 75.7 ± 5.5, 74.3 ± 5.1, 73.1 ± 3.5, and 73.4 ± 3.6, respectively. There were significant correlations (P < 0.05) between mean percentage live sperm evaluated with eosin-nigrosin stain and sperm TM (r = 0.813), between percentage intact acrosome assessed with SpermBlue® and sperm TM (r = 0.846), and between SpermBlue® and eosin-nigrosin (r = 0.965). There were highly significant correlations (P < 0.01) between sperm membrane integrity evaluated with HOS test and sperm TM (r = 0.871), between percentage of intact sperm DNA assessed with halotech and SpermBlue® (r = 0.832), and between percentage of intact spermatozoa DNA assessed with acridine orange and percentage intact acrosome evaluated with spermac stain (r = 0.862). Under the conditions of this study, the correlated methods of sperm analysis proved suitable for analysis of goat spermatozoa and can serve as useful indicator of potential fertility for sperm. They could be used for accurate assessment of the individual sperm cell rather the population as a whole. Motility, eosin-nigrosin stain, SpermBlue®, halotech and acridine orange stain still remain practical and valuable tools for predicting sperm fertilizing ability.

160 COMPARATIVE STUDY OF IN VITRO CULTURE MEDIA AND ASSISTED HATCHING TECHNIQUES ON MOUSE EMBRYOS

The in vitro culture media and assisted hatching techniques remain challenging obstacles to be utilised widely. Mechanical, chemical, enzymatic thinning, and laser-assisted techniques have been used previously but information is still lacking on its application in livestock. The aim of this study was to compare the effect of 2 in vitro culture media (Hamster F10 and TMC-199) and 4 (mechanical, chemical, enzymatic, and laser) assisted hatching techniques on blastocyst formation and hatching rate using murine embryos as a model. The C57/b and Balb/c breeds were raised until they reached maturity and bred naturally to produce F1 generation. The light in the breeding house was controlled at 14 h light and 10 h dark. Feed and water were provided ad libitum for the mice. Superovulation of females were stimulated using equine chorionic gonadotropin and human chorionic gonadotropin. The F1 generation was used for the collection of the 400 blastocysts and randomly allocated into 4 assisted hatching techniques. Blastocysts were paired into a group of 10 and replicated 4 times for each assisted hatching technique. The general linear model of SAS version 9.4 (SAS Institute Inc., Cary, NC, USA) was used to analyse the data. Assisted hatching techniques of laser, mechanical, enzymatic, and chemical yielded 46.9 ± 37.1, 51.1 ± 40.2, 39.1 ± 35.8, and 33.3 ± 4.5%, respectively, under in vitro culture of Hamster F10. The TCM-199, laser, mechanical, enzymatic, and chemical assisted hatching techniques yielded 56.3 ± 43.3, 52.6 ± 35.5, 49.2 ± 37.5, and 33.9 ± 35.5%, respectively, with a significant difference. There was no significant difference observed in assisted hatching techniques and Hamster F10 culture medium. However, the hatching rate of embryos for all techniques was higher when in vitro cultured in TCM than cultured in Hamster F10. Hatching rate of blastocysts increased from chemical, enzymatic, mechanical, and laser with response to Hamster F10 and TCM; thus, laser is a suitable assisted hatching technique with TCM-199.

163 EVALUATION OF VIABILITY OF BULL SEMEN COLLECTED BY ELECTRO-EJACULATION USING COMMERCIAL SEMEN EXTENDER AND 2 CULTURE MEDIA AT CONTROLLED ROOM TEMPERATURE

Preservation of semen is an important process to ensure that semen quality is sufficient for assisted reproductive technologies. The aim of this study was to evaluate the viability of bull semen collected by electro-ejaculation using commercial semen extender and 2 modified culture media stored at controlled RT (24°C) for 72 h. Two Nguni bulls were used for semen collection; after collection, the semen was evaluated macroscopically for volume, pH, and colour, and microscopically for sperm motility, viability, and morphology. Uncontaminated semen samples with progressive motility >70% and morphological defects <20% were pooled after collection before being aliquoted into 3 extenders, namely Triladyl, modified Ham’s F10, and TCM-199 culture media, at a dilution ratio of 1:4 and then stored at controlled RT (24°C). Sperm motility rate was analysed using the computer-aided sperm analyser after 0, 24, 48, and 72 h of storage. Sperm morphology and viability was performed after staining the sperm cells with spermac and nigrosine-eosin stain, respectively. The study was replicated 4 times and data were analysed using ANOVA. Triladyl had a higher sperm viability rate (41.3%) and total motility rate (96.3%) for 72 h (P < 0.01) compared with the 2 modified culture media, Ham’s F10 (26.5 and 86.8%) and TCM-199 (25.0 and 86.7%), respectively. However, Ham’s F10 had higher progressive motility rate (37.8%) as compared with the other extenders, TCM-199 (31.7%) and Triladyl (23.4). There was no significant difference (P > 0.05), in viability rate between Ham’s F10 (26.5%) and TCM-199 (25.0%). No significant difference (P > 0.05) in straight line velocity was observed for the three extenders. Furthermore, no significant difference was observed in total sperm abnormalities, except for reacted acrosomes and absent tails (P > 0.05), between the 2 Nguni bulls. Nguni semen can be preserved in Triladyl or modified Ham’s F10 and TCM-199 culture media stored at 24°C and stay viable for 72 h. Triladyl proved to be the best suitable extender of the 3 extenders, showing higher sperm viability and total motility rate as compared with Ham’s F10 and TCM-199 modified culture media.

154 COMPARISON OF DIFFERENT CULTURE MEDIA AND INCUBATION METHODS ON CULTURING MURINE EMBRYOS IN VITRO USING STRAW AS A RECEPTACLE

In vitro fertilization in the straw system might increase the efficiency of fertilization and the quality of blastocyst formation as compared with micro-drops-IVF systems. The aim of the study was to in vitro fertilize mouse oocytes and culture the resulting zygotes in bi-gas incubator and in a goat vagina and compare the in vitro embryo developmental stages in TCM-199 and Ham’s F10 culture media until the blastocyst-stage of development. F1 generations (Balb C × C57) were used to harvest oocytes and spermatozoa. The fresh sperm were capacitated in different incubation methods (bi-gas incubator and in the vagina of a goat). A volume of 2–4 µL of Ham’s F10 containing capacitated sperm (~8 × 106 per mL) were placed into Ham’s F10 fertilization drops under the oil, containing 10 oocytes and penicillamine, hypotaurine, and epinephrine for enhancing sperm motility and penetration of oocytes. The same procedure was used with the TCM-199 medium and IVF drops without oil (both TCM-199 and Ham’s F10) for straw filling. The presumptive embryos in Ham’s F10 and TCM-199 were divided into different groups: first group were cultured in micro-drops, second group the embryos were aspirated in semen straws and placed in the incubator (incubator straws) for culture, and other straws were covered with a sponge and inserted in the vagina of a goat (vaginal straws) for culture. The resulted blastocysts were stained using Hoechst 33528 solution and blastomeres were counted on a fluorescent UV light inverted microscope at 400× magnification (Nikon Eclipse TI, Narishige Co., Ltd., Amityville, NY, USA). The results were analysed by 2 × 2 factorial designs and Student’s t-test was used to separate the mean. There was no statistical difference (P > 0.05) between the media and incubators on the stage of murine embryo development. The overall fertilization rate was 94 to 99%. The incubator straws with Ham’s F10 (80.5%) had the highest rate of embryos that reached the blastocyst stage, followed by incubator straws with TCM-199 (77.0%), and vaginal straws with Ham’s F10 (60.0%) had the lowest rate of embryos that reached the blastocyst stage. The overall mean number of blastomeres in the blastocyst stage of the embryos ranged from 85 ± 9 to 90 ± 9 cells in all receptacles and incubators. It was concluded that the fertilization and culturing of murine embryos are possible in straws incubated in a bi-gas incubator and in the goat vagina as an alternative method of fertilizing oocytes and culturing murine embryos. In addition, Ham’s F10 and TCM-199 can both be used to fertilize oocytes and culture murine embryos until blastocyst formation embryo in vitro, incubated in a bi-gas incubator or in the vagina.

57 EFFECT OF SEMINAL PLASMA REMOVAL ON SPERM CHARACTERISTICS AND MITOCHONDRIAL MEMBRANE FOLLOWING CRYOPRESERVATION OF SOUTH AFRICAN INDIGENOUS BUCK SEMEN

The removal of seminal plasma has a significant effect on semen characteristics. The aim of the study was to evaluate the effect of seminal plasma removal on sperm characteristics following semen dilution with Triladyl® or Bioxcell® extenders during cryopreservation. Semen samples were collected from 6 matured South African indigenous bucks for a period of 8 weeks by means of electro-ejaculation. Semen samples were pooled and then divided into 4 aliquots (Triladyl® -washed and non-washed or Bioxcell® -washed and non-washed) and diluted (1:4 vol/vol). Assessment of sperm motility characteristics was done by computer-aided sperm analysis (CASA) technology. Evaluation of mitochondria membrane integrity was done using JC-1 staining solution. Triladyl® and Bioxcell® washed semen sample groups were centrifuged at 1500 × g for 10 min, and seminal plasma was separated from sperm pellet using 1-mL plastic pipettes. After dilution of all semen sample groups, they were cooled by placing tubes into water (25°C) and then immediately placed in a 5°C fridge for equilibration for 2 h. At the end of equilibration period, all aliquot semen sample (final dilution concentration of 150 × 106 sperm/mL) groups were loaded into straws (0.25 mL) per treatment groups and placed horizontally 5 cm above the liquid nitrogen vapour for 10 min. At the end of freezing process, all semen straws per group were plunged directly into liquid nitrogen (−196°C) and stored until thawed. Frozen-thawed semen samples per treatment were analysed for sperm motility characteristics by CASA. JC-1 staining solution was also used during evaluation of mitochondria membrane integrity of frozen-thawed semen samples per treatment. Significant differences (P < 0.05) among mean values of semen parameters were determined by Tukey’s method. Sperm total motility rate of non-washed semen in Bioxcell® (85.0 ± 3.4) and Triladyl® (73.9 ± 13.8) was significantly reduced (P < 0.05) by cryopreservation compared with fresh (98.9 ± 1.2) semen sample. There was greater (P < 0.05) sperm mitochondrial membrane damage due to cryopreservation in non-washed semen group extended with Bioxcell® (50.2 ± 20.1) compared with semen extended with Triladyl® (31.3 ± 26.8) and fresh (16.6 ± 14.2) semen sample. Sperm total motility rate in Bioxcell® (68.2 ± 13.5) and Triladyl® (63.1 ± 15.1) groups on the non-washed semen were significantly reduced (P < 0.05) following cryopreservation, compared with fresh (98.3 ± 2.7) semen sample. The percentage of sperm with damaged mitochondria membrane in washed semen was significantly reduced (P < 0.05) in Triladyl® (21.6 ± 16.8) group compared with Bioxcell® (34.7 ± 14.9) group and fresh (35.0 ± 20.8) semen sample. In conclusion, seminal plasma removal reduced sperm motility rate in both extenders (Bioxcell® and Triladyl®) following post-thaw. In addition, sperm mitochondria membrane damage was higher in non-washed semen samples extended with Bioxcell® extender.

Expressing hNF-LE397K results in abnormal gaiting in a transgenic model of CMT2E

Charcot-Marie-Tooth disease (CMT) is the most commonly inherited peripheral neuropathy. CMT disease signs include distal limb neuropathy, abnormal gaiting, exacerbation of neuropathy, sensory defects and deafness. We generated a novel line of CMT2E mice expressing an hNF-L(E397K) transgene, which displayed muscle atrophy of the lower limbs without denervation, proximal reduction in large caliber axons and decreased nerve conduction velocity. In this study, we showed that hNF-L(E397K) mice developed abnormal gait of the hind limbs. The identification of severe gaiting defects in combination with previously observed muscle atrophy, reduced axon caliber and decreased nerve conduction velocity suggests that hNF-L(E397K) mice recapitulate many of clinical signs associated with CMT2E. Therefore, hNF-L(E397K) mice provide a context for potential therapeutic intervention.

Distal to proximal development of peripheral nerves requires the expression of neurofilament heavy

At the initiation of radial growth, neurofilaments are likely to consist primarily of neurofilament light and medium as neurofilament heavy expression is developmentally delayed. To better understand the role of neurofilament heavy in structuring axons, axonal diameter and neurofilament organization were measured in proximal and distal segments of the sciatic nerve and along the entire length of the phrenic nerve. Deletion of neurofilament heavy reduced axonal diameters and neurofilament number in proximal nerve segments. However, neurofilament spacing was greater in proximal versus distal phrenic nerve segments. Taken together, these results suggest that loss of neurofilament heavy reduces radial growth in proximal axonal segments by reducing the accumulation of neurofilaments. As neurofilament heavy expression is developmentally delayed, these results suggest that without neurofilament heavy, the neurofilament network is established in a distal to proximal gradient perhaps to allow distal axonal segments to develop prior to proximal segments.

Variation of the neurofilament medium KSP repeat sub-domain across mammalian species: implications for altering axonal structure

The evolution of larger mammals resulted in a corresponding increase in peripheral nerve length. To ensure optimal nervous system functionality and survival, nerve conduction velocities were likely to have increased to maintain the rate of signal propagation. Increases of conduction velocities may have required alterations in one of the two predominant properties that affect the speed of neuronal transmission: myelination or axonal diameter. A plausible mechanism to explain faster conduction velocities was a concomitant increase in axonal diameter with evolving axonal length. The carboxy terminal tail domain of the neurofilament medium subunit is a determinant of axonal diameter in large caliber myelinated axons. Sequence analysis of mammalian orthologs indicates that the neurofilament medium carboxy terminal tail contains a variable lysine-serine-proline (KSP) repeat sub-domain flanked by two highly conserved sub-domains. The number of KSP repeats within this region of neurofilament medium varies among species. Interestingly, the number of repeats does not change within a species, suggesting that selective pressure conserved the number of repeats within a species. Mapping KSP repeat numbers onto consensus phylogenetic trees reveals independent KSP expansion events across several mammalian clades. Linear regression analyses identified three subsets of mammals, one of which shows a positive correlation in the number of repeats with head-body length. For this subset of mammals, we hypothesize that variations in the number of KSP repeats within neurofilament medium carboxy terminal tail may have contributed to an increase in axonal caliber, increasing nerve conduction velocity as larger mammals evolved.

248 IN VITRO PRODUCTION OF CATTLE × BUFFALO HYBRID EMBRYOS USING BOVINE OOCYTES AND AFRICAN BUFFALO (SYNCERUS CAFFER CAFFER) EPIDIDYMAL SPERM

Interspecies hybridization of bovids occurs between domestic cattle and at least 3 other species: the American bison (Bison bison), yak (Bos grunniens), and banteng (Bos banteng). Birth of a cattle � buffalo hybrid was reported in Russia, but the report was never authenticated. Such hybrids could be important in improving livestock production and managing diseases that impede production in tropical Africa. We investigated hybridization between cattle and their closest African wild relative, the African buffalo (Syncerus caffer caffer). In an attempt to produce pre-implantation cattle � buffalo hybrid embryos in vitro, matured bovine oocytes were subjected to a standard IVF procedure with either homologous (n = 1166 oocytes) or heterologous (n = 1202 oocytes) buffalo epididymal sperm. After IVF, 67.2% of the oocytes inseminated with homologous sperm cleaved. In contrast, insemination with buffalo sperm resulted in a 4.6% cleavage rate. Cleavage was also slower in hybrids than in cattle embryos. Up to 52.2% of cleaved homologous embryos progressed to the morula stage compared with 12.7% for hybrids. No hybrid embryos developed beyond the 16-cell stage, whereas 40.1% of the cleaved bovine embryos developed to the blastocyst stage. Developmental anomalies such as polyspermy, uneven cleavage, vacuolization, and absence of nuclei in some blastomeres were common in the hybrid embryos. We conclude that interspecies fertilization of cattle oocytes with African buffalo sperm occurs in vitro and that the barrier to hybridization is in the early stages of embryonic development. Also, chromosomal disparity is the likely cause of fertilization abnormalities, abnormal development, and subsequent arrest, impairing the formation of pre-implantation hybrid embryos. Investigation into developmental abnormalities, including reciprocal hybridization and genetic studies of the hybrid embryos, are recommended.

Nuclear transport: never-ending cycles of signals and receptors

Proteins transported into and out of the nucleus require amino acid motifs called NLSs and NESs, respectively. The amino acid sequences of these signals vary considerably. A superfamily of transport receptors has been identified and each member contains three transport-related domains. Transport receptors bind to the signal sequences, either directly or through adapter proteins, to promote nucleocytoplasmic transport. The diversity of signals, receptors and adapter proteins suggests that there are many pathways for nuclear entry or exit. The direction of transport (into or out of the nucleus) is regulated in part by the small GTPase Ran as well as by intrinsic substrate motifs.

Out-of-season breeding of milk goats--the effect of light treatment, melatonin and breed

The purpose of this study was to evaluate the effectivity of melatonin in addition to light treatment (exposure to 2 hours of light during the night = a long-day photoperiod) to modify the breeding season of Saanen and cross-bred milk goats and to compare the difference between the breeds. Twenty-two Saanen and 22 cross-bred does were randomly divided into 3 treatment groups. Group 1 (controls) received no treatment, Group 2 received light treatment for 37 days and Group 3 received light treatment plus melatonin implants after the light treatment. After a further 35 days the 3 groups were brought together and a billy goat that had also been exposed to the extra light at night, had received a melatonin implant and had been isolated from the does during the treatment period, was introduced to the does for natural mating. Ultrasound scanning was used to diagnose pregnancy and all the pregnant goats kidded. Significantly more Saanen does compared to cross-bred does (P = 0.018) became pregnant and kidded after natural mating, when the group that received melatonin as well as light treatment was compared to the group that received light treatment only. Compared to light treatment only, the addition of melatonin to light treatment improved (P = 0.0028) conception after natural mating, in both the Saanen and the cross-bred does.

Attenuation of the slow component of delayed rectification, action potential prolongation, and triggered activity in mice expressing a dominant-negative Kv2 alpha subunit

An in vivo experimental strategy, involving cardiac-specific expression of a mutant Kv 2.1 subunit that functions as a dominant negative, was exploited in studies focused on exploring the role of members of the Kv2 subfamily of pore-forming (alpha) subunits in the generation of functional voltage-gated K(+) channels in the mammalian heart. A mutant Kv2.1 alpha subunit (Kv2.1N216) was designed to produce a truncated protein containing the intracellular N terminus, the S1 membrane-spanning domain, and a portion of the S1/S2 loop. The truncated Kv2.1N216 was epitope tagged at the C terminus with the 8-amino acid FLAG peptide to generate Kv2. 1N216FLAG. No ionic currents are detected on expression of Kv2. 1N216FLAG in HEK-293 cells, although coexpression of this construct with wild-type Kv2.1 markedly reduced the amplitudes of Kv2. 1-induced currents. Using the alpha-myosin heavy chain promoter to direct cardiac specific expression of the transgene, 2 lines of Kv2. 1N216FLAG-expressing transgenic mice were generated. Electrophysiological recordings from ventricular myocytes isolated from these animals revealed that I(K, slow) is selectively reduced. The attenuation of I(K, slow) is accompanied by marked action potential prolongation, and, occasionally, spontaneous triggered activity (apparently induced by early afterdepolarizations) is observed. The time constant of inactivation of I(K, slow) in Kv2. 1N216FLAG-expressing cells (mean+/-SEM=830+/-103 ms; n=17) is accelerated compared with the time constant of I(K, slow) inactivation (mean+/-SEM=1147+/-57 ms; n=25) in nontransgenic cells. In addition, unlike I(K, slow) in wild-type cells, the component of I(K, slow) remaining in the Kv2.1N216FLAG-expressing cells is insensitive to 25 mmol/L tetraethylammonium. Taken together, these observations suggest that there are 2 distinct components of I(K, slow) in mouse ventricular myocytes and that Kv2 alpha subunits underlie the more slowly inactivating, tetraethylammonium-sensitive component of I(K, slow). In vivo telemetric recordings also reveal marked QT prolongation, consistent with a defect in ventricular repolarization, in Kv2.1N216FLAG-expressing transgenic mice.

Water fluoridation and the sudden infant death syndrome

AIMS

To determine whether exposure to fluoridated water supplies prenatally or postnatally at the time of death increases the risk of sudden infant death syndrome (SIDS).

METHODS

A nationwide, case-control study, with infant's water fluoridation status determined from census area unit information for mother's usual address at the time of the infant's birth, infant's usual address at the time of death / nominated sleep and address where infant died / was at nominated sleep. SIDS risk associated with fluoride exposure postnatally was assessed according to method of infant feeding (breast or reconstituted formula), for the two days prior to infant's death / nominated sleep.

RESULTS

Infants exposed to fluoridated water supplies during pregnancy were not at increased risk for SIDS, adjusted odds ratio (OR) 1.19 (95% confidence interval (CI) 0.82, 1.74). For breast-fed infants at the time of death / nominated sleep, fluoridated water exposure was not associated with an increased risk for SIDS, adjusted OR 1.09 (95% CI 0.66, 1.79). Similarly, 'fluoridated' formula feeding, when compared with 'unfluoridated' formula feeding, showed no increased risk of SIDS, adjusted OR 1.25 (95% CI 0.73, 2.13). There was no evidence of an interaction between fluoridation and infant feeding for the last two days (chi2 = 0.171, df = 1, p = 0.68).

CONCLUSION

Exposure to a fluoridated water supply prenatally or postnatally at the time of death did not affect the relative risk for SIDS.

Functional knockout of the transient outward current, long-QT syndrome, and cardiac remodeling in mice expressing a dominant-negative Kv4 alpha subunit

A novel in vivo experimental strategy, involving cell type-specific expression of a dominant-negative K+ channel pore-forming alpha subunit, was developed and exploited to probe the molecular identity of the cardiac transient outward K+ current (I(to)). A point mutation (W to F) was introduced at position 362 in the pore region of Kv4.2 to produce a nonconducting mutant (Kv4.2W362F) subunit. Coexpression of Kv4.2W362F with Kv4.2 (or Kv4.3) attenuates the wild-type currents, and the effect is subfamily specific; ie, Kv4.2W362F does not affect heterologously expressed Kv1.4 currents. With the use of the alpha-myosin heavy chain promoter to direct cardiac-specific expression, several lines of Kv4.2W362F transgenic mice were generated. Electrophysiological recordings reveal that I(to) is selectively eliminated in ventricular myocytes isolated from transgenic mice expressing Kv4.2W362F, thereby demonstrating directly that the Kv 4 subfamily underlies I(to) in the mammalian heart. Functional knockout of I(to) leads to marked increases in action potential durations in ventricular myocytes and to prolongation of the QT interval in surface ECG recordings. In addition, a novel rapidly activating and inactivating K+ current, which is not detectable in myocytes from nontransgenic littermates, is evident in Kv4.2W362F-expressing ventricular cells. Importantly, these results demonstrate that electrical remodeling occurs in the heart when the expression of endogenous K- channels is altered.

In vitro maturation and fertilization of oocytes recovered from free-ranging Burchell's zebra (Equus burchelli) and Hartmann's zebra (Equus zebra hartmannae)

A noninvasive repeatable method to harvest oocytes for in vitro fertilization (IVF) could potentially be used to assist reproduction in endangered equid species. The objectives of this study were to evaluate a specific transvaginal ultrasound-guided oocyte recovery procedure for use in zebra mares and the general applicability of IVF procedures in zebra. Ovaries were collected from Burchell's zebra (Equus burchelli) and Hartmann's zebra (Equus zebra hartmannae) mares at routine culling for Expt. I. Of the 144 oocytes recovered from these ovaries, 70% were of excellent quality. No significant difference in oocyte quality was found between the two zebra species. Zona drilling was performed on in vitro-matured oocytes prior to IVF. Epididymal sperm from culled Burchell's zebra stallions were used for IVF. The sperm either were exposed to calcium ionophore or were not treated and served as a control. In vitro fertilized oocytes were then co-cultured with zebra granulosa cells (ZGC) or with bovine oviduct cells (BOC) for up to 8 days. Overall, a 38% cleavage rate was obtained with 16% of sperm-exposed oocytes developing to the morula or blastocyst stage. All of the embryos that developed to at least the morula stage were cultured on BOC; whereas, none of those cultured on ZGC reached the morula stage during the same interval. Cleavage rates of oocytes inseminated with ionophore-treated or with control sperm were not significantly different, suggesting that ionophore treatment of epididymal sperm for IVF in these zebra species may be redundant. In Expt. II, 10 transvaginal ultrasound-guided oocyte aspiration procedures on five captive Burchell's zebra mares recovered a total of 33 oocytes (6.6 oocytes/female) of which 94% were considered viable. This approach may be an attractive means of producing gametes for assisted reproduction in endangered species. Furthermore, results from this study indicate that IVF may become a means of producing offspring from zebra and other equid species in the future.

Developmental analysis reveals mismatches in the expression of K+ channel alpha subunits and voltage-gated K+ channel currents in rat ventricular myocytes

In the experiments here, the developmental expression of the functional Ca(2+)-independent, depolarization-activated K+ channel currents, Ito and IK, and of the voltage-gated K+ channel (Kv) alpha subunits, Kv1.2, Kv1.4, Kv1.5, Kv2.1, and Kv4.2 in rat ventricular myocytes were examined quantitatively. Using the whole-cell patch clamp recording method, the properties and the densities of Ito and IK in ventricular myocytes isolated from postnatal day 5 (P5), 10 (P10), 15 (P15), 20 (P20), 25 (P25), 30 (P30), and adult (8-12 wk) rats were characterized and compared. These experiments revealed that mean Ito densities increase fourfold between birth and P30, whereas IK densities vary only slightly. Neither the time- nor the voltage-dependent properties of the currents vary measurably, suggesting that the subunits underlying functional Ito and IK channels are the same throughout postnatal development. In parallel experiments, the developmental expression of each of the voltage-gated K+ channel alpha subunits, Kv1.2, Kv1.4, Kv1.5, Kv2.1, and Kv4.2, was examined quantitatively at the mRNA and protein levels using subunit-specific probes. RNase protection assays revealed that Kv1.4 message levels are high at birth, increase between P0 and P10, and subsequently decrease to very low levels in adult rat ventricles. The decrease in message is accompanied by a marked reduction in Kv1.4 protein, consistent with our previous suggestion that Kv1.4 does not contribute to the formation of functional K+ channels in adult rat ventricular myocytes. In contrast to Kv1.4, the mRNA levels of Kv1.2, Kv1.5, Kv2.1, and Kv4.2 increase (three- to five-fold) between birth and adult. Western analyses, however, revealed that the expression patterns of these subunits proteins vary in distinct ways: Kv1.2 and Kv4.2, for example, increase between P5 and adult, whereas Kv1.5 remains constant and Kv2.1 decreases. Throughout development, therefore, there is a mismatch between the numbers of Kv alpha subunits expressed and the functional voltage-gated K+ channel currents distinguished electrophysiologically in rat ventricular myocytes. Alternative experimental approaches will be required to define directly the Kv alpha subunits that underlie functional voltage-gated K+ channels in these (and other) cells. In addition, the finding that Kv alpha subunit protein expression levels do not necessarily mirror mRNA levels suggests that caution should be exercised in attempting functional interpretations of observed changes in mRNA levels alone.

Myocardial potassium channels: electrophysiological and molecular diversity

Myocardial K+ currents function to control resting membrane potentials, the heights and durations of action potentials, and refractoriness and automaticity. They are important targets for the actions of transmitters and hormones or drugs known, or postulated, to modulate cardiac functioning. A variety of K+ currents that subserve these functions have now been identified in myocardial cells isolated from different species, as well as in cells isolated from different regions of the heart in the same species. These currents include the voltage-gated K+ types, such as the transient outward (Ito) and delayed rectifier (IK) currents, as well as the inwardly rectifying currents, IK1, IK(ACh), and IK(ATP). The physiological and functional properties of the various K+ currents/channels expressed in different myocardial cell types are the focus of this review. Advances made in cloning K+ channel subunits of the Kv, eag, Kir, and IsK families are discussed, and progress made in identifying the K+ channel subunits expressed in the mammalian myocardium is summarized. The relationships between the various cloned K+ channel subunits and the functional K+ channels characterized electrophysiologically in myocardial cells are explored.

Differential expression of voltage-gated K+ channel subunits in adult rat heart. Relation to functional K+ channels?

Polyclonal antibodies against each of the K+ channel subunits (Kv1.2, Kv1.4, Kv1.5, Kv2.1, and Kv4.2) shown previously to be expressed in adult rat heart at the mRNA level were used to examine the distributions of these K+ channel subunits in adult rat atrial and ventricular membranes. Immunohistochemistry on isolated adult rat ventricular myocytes revealed strong labeling with the anti-Kv4.2 and anti-Kv1.2 antibodies. Although somewhat weaker (than with anti-Kv1.2 or anti-Kv4.2), positive staining was also observed with the anti-Kv1.5 and anti-Kv2.1 antibodies. Ventricular myocytes exposed to the anti-Kv1.4 antibody, in contrast, did not appear significantly different from background. Qualitatively similar results were obtained on isolated adult rat atrial myocytes. Western blots of atrial and ventricular membrane proteins confirmed the presence of Kv1.2, Kv1.5, Kv2.1, and Kv4.2 and revealed differences in the relative abundances of these subunits in the two membrane preparations. Kv4.2, for example, is more abundant in ventricular than in atrial membranes, whereas Kv1.2 and Kv2.1 are higher in atrial membranes; Kv1.5 levels are comparable in the two preparations. In contrast to these results, nothing was detected in Western blots of atrial or ventricular membrane proteins with the anti-Kv1.4 antibody at concentrations that revealed intense labeling of a 97-kD protein in adult rat brain membranes. A very faint band was detected at 97 kD in the atrial and ventricular preparations when the anti-Kv1.4 antibody was used at a 5- to 10-fold higher concentration. The simplest interpretation of these results is that Kv1.4 is not an abundant protein in adult rat atrial or ventricular myocytes. Therefore, it seems unlikely that Kv1.4 plays an important role in the formation of functional depolarization-activated K+ channels in these cells. The relation(s) between the (other four) K+ channel subunits and the depolarization-activated K+ channels identified electrophysiologically in adult rat atrial and ventricular myocytes is discussed in the present study.

Childhood asthma in four countries: a comparative survey

BACKGROUND

Asthma mortality among young people varies widely between different countries. Geographical differences in asthma prevalence are also believed to exist, but evidence is sparse owing to the lack of multicentre surveys using common protocols. A survey was conducted of 12-year-old children living in defined areas of New Zealand, Wales, South Africa and Sweden, in order to see whether asthma prevalence and mortality rates in children show parallel differences.

METHODS

Questionnaires enquiring about a history of asthma and respiratory symptoms were issued to the parent. The children performed a simple exercise challenge test.

RESULTS

Information was obtained for 4353 children. A history of asthma at any time was reported for 16.8% of children in New Zealand, 12.0% in Wales, 11.5% in South Africa and 4.0% of Sweden, and a similar pattern was shown by several other indices of asthma (various relevant symptoms, inhaler use, response to exercise challenge, and asthma mortality at ages 5-19 years). In Sweden wheezing was negatively associated with pet ownership; elsewhere there was a positive (though non-significant) association. Cat ownership was highest in New Zealand and lowest in Sweden.

CONCLUSIONS

The prevalence of asthma in children shows geographical variation which is parallel to that of asthma mortality, being high in New Zealand and low in Sweden. Differential exposure to animal allergens is a possible factor in this variation.

Breastfeeding and the risk of sudden infant death syndrome

The New Zealand Cot Death Study, a multicentre case-control study, was set up to identify risk factors associated with sudden infant death syndrome (SIDS). In the 3 years of the study there were 485 infant deaths classified as SIDS in the study areas and 1800 infants who were randomly selected as controls. Data were collected by parent interviews and from obstetric notes. A full set of data for this analysis was available from 356 cases and 1529 control infants. The relationship between length of any breastfeeding and SIDS was examined: 92% of the controls were initially breastfed compared to 86% of the cases. As time went by, cases stopped breastfeeding sooner than controls: by 13 weeks, 67% controls were breastfed versus 49% cases. A reduced risk for SIDS in breastfed infants persisted during the first 6 months after controlling for confounding demographic, maternal and infant factors. Infants exclusively breastfed 'at discharge from the obstetric hospital' (odds ratio [OR] = 0.52, 95% confidence interval (CI): 0.35-0.71) and during the last 2 days (OR = 0.65, 95% CI: 0.46-0.91) had a significantly lower risk of SIDS than infants not breastfed after controlling for potential confounders. We have shown a substantial association of breastfeeding with a lowered risk for SIDS. This supports the need for more positive promotion and active community support to further enhance the level and length of exclusive breastfeeding.

Smoking and the sudden infant death syndrome

OBJECTIVE

Maternal smoking has been shown to be a risk factor for sudden infant death syndrome (SIDS). The effect of smoking by the father and other household members has not previously been examined.

METHODS

A large nationwide case-control study. Four hundred eighty-five SIDS deaths in the postneonatal age group were compared with 1800 control infants.

RESULTS

Infants of mothers who smoked during pregnancy had a 4.09 (95% confidence interval [CI] = 3.28, 5.11) greater risk of death than infants of mothers who did not smoke. Infants of mothers who smoked postnatally also had an increased risk of SIDS compared with infants of nonsmokers and, furthermore, the risk increased with increasing levels of maternal smoking. Smoking by the father and other household members increased the risk (odds ratio [OR] = 2.41, 95% CI = 1.92, 3.02 and OR = 1.54, 95% CI = 1.20, 1.99, respectively). Smoking by the father increased the risk of SIDS if the mother smoked, but had no effect if she did not smoke. In analyses controlled for a wide range of potential confounders, smoking by the mother and father was still significantly associated with an increased risk of SIDS.

CONCLUSION

Passive tobacco smoking is causally related to SIDS.

Dummies and the sudden infant death syndrome

The association between dummy use and sudden infant death syndrome (SIDS) was investigated in 485 deaths due to SIDS in the postneonatal age group and compared with 1800 control infants. Parental interviews were completed in 87% of subjects. The prevalence of dummy use in New Zealand is low and varies within New Zealand. Dummy use in the two week period before death was less in cases of SIDS than in the last two weeks for controls (odds ratio (OR) 0.76, 95% confidence interval (CI) 0.57 to 1.02). Use of a dummy in the last sleep for cases of SIDS or in the nominated sleep for controls was significantly less in cases than controls (OR 0.44, 95% CI 0.26 to 0.73). The OR changed very little after controlling for a wide range of potential confounders. It is concluded that dummy use may protect against SIDS, but this observation needs to be repeated before dummies can be recommended for this purpose. If dummy sucking is protective then it is one of several factors that may explain the higher mortality from SIDS in New Zealand than in other countries, and may also explain in part the regional variation within New Zealand.

Birth of live calves after transfer of frozen-thawed bovine embryos fertilised in vitro

Follicular oocytes were aspirated from bovine ovaries collected at a local abattoir. The cumulus-intact oocytes were matured, fertilised and subsequently cultured in vitro. Of 2297 oocytes exposed to in vitro procedures during a 30-day experimental period, 92 per cent matured, 83 per cent were fertilised, 73 per cent cleaved, 48 per cent developed to the morulae and 14 per cent developed to the expanded blastocyst stage. During this experimental period, 300 similar embryos fertilised in vitro were frozen at different post in vitro block developmental stages. After approximately one year of storage in liquid nitrogen, 98 of these embryos were thawed and cultured either for up to four hours or for two days in tissue culture medium-199. Culturing the embryos for up to four hours was not as successful for in vitro development as culturing for two days. Of the 40 embryos cultured for two days, 67 per cent of early blastocyst stage embryos developed to expanded blastocysts in vitro and 46 per cent of morula stage embryos developed to expanded blastocysts, whereas only 8 per cent of 16-cell stage embryos developed to expanded blastocysts. A 50 per cent pregnancy rate resulted when frozen-thawed embryos were co-cultured for two days before transfer compared with 20 per cent for frozen-thawed embryos cultured for up to four hours before transfer. Five calves were born after a normal gestation period with birthweights ranging from 37.3 to 54.5 kg.

Ethnic differences in mortality from sudden infant death syndrome in New Zealand

OBJECTIVES

To examine the factors which might explain the higher mortality from sudden infant death syndrome in Maori infants (7.4/1000 live births in 1986 compared with 3.6 in non-Maori children).

DESIGN

A large nationwide case control study.

SETTING

New Zealand. 485 infants who died of sudden infant death syndrome were compared with 1800 control infants. There were 229 Maori and 240 non-Maori cases of sudden infant death syndrome (16 cases unassigned) and 353 Maori and 1410 non-Maori controls (37 unassigned).

RESULTS

Maori infants had 3.81 times the risk (95% confidence interval 3.06 to 4.76) of sudden infant death syndrome compared with non-Maori infants. The risk factors for sudden infant death syndrome within groups were remarkably similar. When Maori and non-Maori controls were compared the prevalence of many of the known risk factors was higher in Maori infants. In particular, mothers were socioeconomically disadvantaged, younger, and more likely to smoke and their infants were of lower birth weight and more likely to share a bed with another person. Multivariate analysis controlling for potential confounders found that simply being Maori increased the risk of sudden infant death syndrome by only 1.37 (95% CI = 0.95 to 2.01), not statistically significantly different from 1. Population attributable risk was calculated for prone sleeping position, maternal smoking, not breast feeding, and infants sharing a bed with another person. In total these four risk factors accounted for 89% of deaths from sudden infant death syndrome in Maori infants and 79% in non-Maori infants.

CONCLUSION

The high rate of sudden infant death syndrome among Maori infants is based largely on the high prevalence in the Maori population of the major risk factors. Other risk factors, not related to ethnicity, probably explain remaining differences between Maori and non-Maori children.

Four modifiable and other major risk factors for cot death: the New Zealand study

New Zealand's high mortality rate from sudden infant death syndrome (SIDS) prompted the development of the New Zealand Cot Death Study. A report of the analysis of the data from the first year has been published. This report now gives the major identified risk factors from the full 3 year data set. In this case-control study there were 485 infants who died from SIDS in the post-neonatal age group, and 1800 control infants, who were a representative sample of all hospital births in the study region. Obstetric records were examined and parental interviews were completed in 97.5% and 86.9% of subjects, respectively. As expected many risk factors for SIDS were confirmed including: lower socio-economic status, unmarried mother, young mother, younger school-leaving age of mother, younger age of mother at first pregnancy, late attendance at antenatal clinic, non-attendance at antenatal classes, Maori, greater number of previous pregnancies, the further south the domicile, winter, low birthweight, short gestation, male infant and admission to a special care baby unit. In addition, however, we identified four risk factors that are potentially amenable to modification.(ABSTRACT TRUNCATED AT 250 WORDS)

Further evidence supporting a causal relationship between prone sleeping position and SIDS

A 3 year case-control study identifying the risk factors for SIDS was undertaken. Preliminary analysis of the data from the first year suggested that SIDS mortality could fall by 50% if the prevalence of the prone sleeping position changed from 40 to 0%. During the 3 year study the prevalence of the prone sleeping position among infants has fallen from 43% in the first year to 20% in the third year. SIDS mortality has fallen to 3.1/1000 live births, which is very close to that predicted. When considered with other available evidence this strongly supports a causal relationship between the prone sleeping position and SIDS.

Prevalence of asthma among 12 year old children in New Zealand and South Wales: a comparative survey

A survey of 12 year old schoolchildren was carried out in New Zealand and South Wales, the same questionnaire and exercise provocation test being used. The prevalence of a history of asthma at any time was higher in New Zealand (147/873, 17%) than in South Wales (116/965, 12%). The New Zealand children were also more likely than the Welsh children to have a history of "wheeze ever" (27% versus 22%), and wheeze brought on by running (15% versus 10.5%). The sex ratio of asthmatic and wheezy children was very similar in the two countries. A history of hospital admission for chest trouble was twice as common in New Zealand as in South Wales. An exercise test produced a fall in peak expiratory flow rate of 15% or more in more New Zealand children (12.2%) than Welsh children (7.7%). These results suggest that the prevalence of childhood asthma is higher in New Zealand than in South Wales.

Results from the first year of the New Zealand cot death study

New Zealand's high mortality rate from the sudden infant death syndrome (SIDS) prompted the development of the New Zealand cot death study. This report of the preliminary analysis of the first year of the data gives the major identified risk factors. One hundred and sixty-two infants who died from SIDS were compared with 589 control infants, who were a representative sample of all hospital births in the study region. Obstetric records were examined and parental interviews were completed in 96% and 89% of subjects respectively. Data were available for all the variables in this study in 95% of those interviewed, thus 128 cases and 503 controls make up the subjects of this report. As expected we confirmed many risk factors for SIDS including: lower socioeconomic status, unmarried mother, young mother, younger school leaving age of mother, younger age of mother at first pregnancy, late attendance at antenatal clinic, nonattendant at antenatal classes, Maori, greater number of previous pregnancies, lower birth weight, shorter gestation, male infant, admission to neonatal intensive care unit. In addition, however, we identified three risk factors which are potentially amenable to modification. These were the prone sleeping position of baby (odds ratio = 3.53, 95% confidence interval 2.26, 5.54), maternal smoking (1-9 cigarettes/day OR = 1.87, 95% CI = 0.98, 3.54; 10-19/day OR = 2.64, 95% CI = 1.47, 4.74; 20+/day OR = 5.06, 95% CI = 2.86, 8.95) and breast feeding (OR = 2.93, 95% CI = 1.84, 4.67).(ABSTRACT TRUNCATED AT 250 WORDS)

Medical staff bylaws: protecting hospitals' financial viability

The failure of physicians to comply with Medicare's new standards or the hospital's existing standards may cause the hospital to suffer financial losses. Medical staff bylaws are a way physicians can be made to work with the hospital to ensure its viability. Therefore, financial managers must become familiar with these bylaws and ensure that financial and quality issues are addressed.

Independent laboratory or hospital laboratory: what difference does it make?

Performing referral work in a hospital laboratory is not always less desirable--for reimbursement reasons--than performing such work in an independent laboratory. Here, the author explains why.

Failure of protein loading tests to identify heterozygosity for ornithine carbamoyltransferase deficiency

Protein loading tests for the diagnosis of heterozygous ornithine carbamoyltransferase deficiency were performed on two occasions on an asymptomatic woman whose daughter and two infant sons died of the disease. Neither loading test produced the expected increases in urinary orotic acid excretion and studies of other pyrimidine and purine metabolites in urine and plasma did not suggest that these would provide better discrimination from non-carriers. The results probably reflect an extensive inactivation of the mutant X chromosome in liver cells and reinforce the need for caution in interpreting negative test results.

Pyrimidine and purine metabolites in ornithine carbamoyl transferase deficiency

Detailed biochemical studies have been carried out in a female heterozygote for ornithine carbamoyl-transferase (OCT) deficiency. Increased levels of the pyrimidines, orotic acid, uridine and uracil, were observed in plasma as well as urine by utilizing an adaptation of high performance liquid chromatography (HPLC). Urinary clearances of these compounds were high, that of orotic acid indicating net secretion. Urinary uric acid clearance was also elevated, a finding attributed to the uricosuric effect of the orotic acid excreted concomitantly. The results in this child and her family are typical of OCT deficiency. They confirm considerable genetic heterogeneity in the biochemical as well as clinical expression in this defect.

Increased incidence of gram-negative neonatal sepsis with intramuscula iron administration

During a five-year period the incidence of neonatal sepsis was 20 times higher in Polynesian newborns compared with European newborns (11 per 1,000 vs. 0.6 per 1,000 total births). This high incidence in Polynesians was confined to a period when the infants were being given intramuscular iron dextran. When the iron administration was stopped the incidence of disease in Polynesians decreased from 17 per 1,000 to 2.7 per 1,000 total births. An analysis of the Polynesian iron-treated and non-iron-treated groups showed a statistically significant difference in the incidence of sepsis, the type of causative organism, and mortality. The data suggest that the iron dextran injections have impaired the immunity of the treated infants, making them more susceptible to Escherichia coli sepsis.