Mutations in a new photoreceptor-pineal gene on 17p cause Leber congenital amaurosis.

Leber congenital amaurosis (LCA, MIM 204000) accounts for at least 5% of all inherited retinal disease and is the most severe inherited retinopathy with the earliest age of onset. Individuals affected with LCA are diagnosed at birth or in the first few months of life with severely impaired vision or blindness, nystagmus and an abnormal or flat electroretinogram (ERG). Mutations in GUCY2D (ref. 3), RPE65 (ref. 4) and CRX (ref. 5) are known to cause LCA, but one study identified disease-causing GUCY2D mutations in only 8 of 15 families whose LCA locus maps to 17p13.1 (ref. 3), suggesting another LCA locus might be located on 17p13.1. Confirming this prediction, the LCA in one Pakistani family mapped to 17p13.1, between D17S849 and D17S960-a region that excludes GUCY2D. The LCA in this family has been designated LCA4 (ref. 6). We describe here a new photoreceptor/pineal-expressed gene, AIPL1 (encoding aryl-hydrocarbon interacting protein-like 1), that maps within the LCA4 candidate region and whose protein contains three tetratricopeptide (TPR) motifs, consistent with nuclear transport or chaperone activity. A homozygous nonsense mutation at codon 278 is present in all affected members of the original LCA4 family. AIPL1 mutations may cause approximately 20% of recessive LCA, as disease-causing mutations were identified in 3 of 14 LCA families not tested previously for linkage.

Mutations in a human homologue of Drosophila crumbs cause retinitis pigmentosa (RP12).

Retinitis pigmentosa (RP) comprises a clinically and genetically heterogeneous group of diseases that afflicts approximately 1.5 million people worldwide. Affected individuals suffer from a progressive degeneration of the photoreceptors, eventually resulting in severe visual impairment. To isolate candidate genes for chorioretinal diseases, we cloned cDNAs specifically or preferentially expressed in the human retina and the retinal pigment epithelium (RPE) through a novel suppression subtractive hybridization (SSH) method. One of these cDNAs (RET3C11) mapped to chromosome 1q31-q32.1, a region harbouring a gene involved in a severe form of autosomal recessive RP characterized by a typical preservation of the para-arteriolar RPE (RP12; ref. 3). The full-length cDNA encodes an extracellular protein with 19 EGF-like domains, 3 laminin A G-like domains and a C-type lectin domain. This protein is homologous to the Drosophila melanogaster protein crumbs (CRB), and denoted CRB1 (crumbs homologue 1). In ten unrelated RP patients with preserved para-arteriolar RPE, we identified a homozygous AluY insertion disrupting the ORF, five homozygous missense mutations and four compound heterozygous mutations in CRB1. The similarity to CRB suggests a role for CRB1 in cell-cell interaction and possibly in the maintenance of cell polarity in the retina. The distinct RPE abnormalities observed in RP12 patients suggest that CRB1 mutations trigger a novel mechanism of photoreceptor degeneration.

Coccidia-induced mucogenesis promotes the onset of necrotic enteritis by supporting Clostridium perfringens growth.

This study tested the hypothesis that a host mucogenic response to an intestinal coccidial infection promotes the onset of necrotic enteritis (NE). A chick NE model was used in which birds were inoculated with Eimeria acervulina and E. maxima and subsequently with Clostridium perfringens (EAM/CP). A second group of EAM/CP-infected birds was treated with the ionophore narasin (NAR/EAM/CP). These groups were compared to birds that were either non-infected (NIF), or infected only with E. acervulina and E. maxima (EAM), or C. perfringens (CP). The impact of intestinal coccidial infection and anti-coccidial treatment on host immune responses and microbial community structure were evaluated with histochemical-, cultivation- and molecular-based techniques. Barrier function was compromised in EAM/CP-infected birds as indicated by elevated CFUs for anaerobic bacteria and C. perfringens in the spleen when compared to NIF controls at day 20, with a subsequent increase in intestinal NE lesions and mortality at day 22. These results correlate positively with a host inflammatory response as evidenced by increased ileal interleukin (IL)-4, IL-10 and IFN-gamma RNA expression. Concurrent increases in chicken intestinal mucin RNA expression, and goblet cell number and theca size indicate that EAM/CP induced an intestinal mucogenic response. Correspondingly, the growth of mucolytic bacteria and C. perfringens as well as alpha toxin production was greatest in EAM/CP-infected birds. The ionophore narasin, which directly eliminates coccidia, reduced goblet cell theca size, IL-10 and IFN-gamma expression, the growth of mucolytic bacteria including C. perfringens, coccidial and NE lesions and mortality in birds that were co-infected with coccidia and C. perfringens. Collectively the data support the hypothesis that coccidial infection induces a host mucogenic response providing a growth advantage to C. perfringens, the causative agent of NE.

Extragenic suppressors of the nimX2(cdc2) mutation of Aspergillus nidulans affect nuclear division, septation and conidiation.

The Aspergillus nidulans NIMX(CDC2) protein kinase has been shown to be required for both the G(2)/M and G(1)/S transitions, and recent evidence has implicated a role for NIMX(CDC2) in septation and conidiation. While much is understood of its G(2)/M function, little is known about the functions of NIMX(CDC2) during G(1)/S, septation, and conidiophore development. In an attempt to better understand how NIMX(CDC2) is involved in these processes, we have isolated four extragenic suppressors of the A. nidulans nimX2(cdc2) temperature-sensitive mutation. Mutation of these suppressor genes, designated snxA-snxD for suppressor of nimX, affects nuclear division, septation, and conidiation. The cold-sensitive snxA1 mutation leads to arrest of nuclear division during G(1) or early S. snxB1 causes hyperseptation in the hyphae and sensitivity to hydroxyurea, while snxC1 causes septation in the conidiophore stalk and aberrant conidiophore structure. snxD1 leads to slight septation defects and hydroxyurea sensitivity. The additional phenotypes that result from the suppressor mutations provide genetic evidence that NIMX(CDC2) affects septation and conidiation in addition to nuclear division, and cloning and biochemical analysis of these will allow a better understanding of the role of NIMX(CDC2) in these processes.

NRL S50T mutation and the importance of 'founder effects' in inherited retinal dystrophies.

The aim of this work was to identify NRL mutations in a panel of 200 autosomal dominant retinitis pigmentosa (adRP) families. All samples were subjected to heteroduplex analysis of the three exons of the NRL gene, and HphI restriction digest analysis of exon 2 (to identify the S50T mutation). Families found to have the S50T mutation, and six additional larger pedigrees (which had previously been excluded from the other nine adRP loci) underwent linkage analysis using polymorphic markers located in the region of 14q11. HphI restriction analysis followed by direct sequencing of the amplified NRL exon 2 product demonstrated the presence of the NRL S50T sequence change in three adRP families. Comparison of marker haplotypes in affected individuals from these families with those of affected members of the original 14q11 linked family revealed a common disease haplotype for markers within the adRP locus. Recombination events observed in these families define an adRP critical interval of 14.9 cM between D13S72 and D14S1041. Linkage analysis enabled all six of the larger adRP pedigrees to be excluded from the 14q11 locus. The NRL S50T mutation represents another example of a 'founder effect' in a dominantly inherited retinal dystrophy. Identification of such 'founder effects' may greatly simplify diagnostic genetic screening and lead to better prognostic counselling. The exclusion of several adRP families from all ten adRP loci indicates that at least one further adRP locus remains to be found.

Locus for autosomal recessive nonsyndromic persistent hyperplastic primary vitreous.

PURPOSE: To map the disease locus in a six-generation, consanguineous Pakistani family affected by nonsyndromic autosomal recessive persistent hyperplastic primary vitreous (arPHPV). All affected individuals had peripheral anterior synechiae and corneal opacities with variable degrees of cataract and a retrolenticular white mass behind the lens. METHODS: Genomic DNA from family members was typed for alleles at more than 400 known polymorphic genetic markers, by polymerase chain reaction. Alleles were assigned to individuals, which allowed calculation of lod scores. RESULTS: A maximum two-point lod score of 4.07 was obtained with marker D10S1225 with no recombination. Two recombinations with marker D10S208 and D10S537 localized the disease within a region of approximately 30 centimorgans (cM). However, homozygosity across the region refined the arPHPV locus to 13 cM. CONCLUSIONS: Linkage analysis shows localization of nonsyndromic arPHPV to chromosome10q11-q21.

Novel locus for autosomal recessive cone-rod dystrophy CORD8 mapping to chromosome 1q12-Q24.

PURPOSE: To map the disease locus of a two-generation, consanguineous Pakistani family with autosomal recessive cone-rod dystrophy (arCRD). All affected individuals had night blindness, deterioration of central vision, photophobia, epiphora in bright light, and problems with color distinction. Fundoscopy revealed marked macular degeneration and attenuation of retinal vessels. Mild pigmentary changes were present in the periphery. METHODS: Genomic DNA was amplified across the polymorphic microsatellite poly-CA regions identified by markers. Alleles were assigned to individuals that allowed calculation of LOD scores using the Cyrillic (Cherwell Scientific, Oxford, UK) and MLINK (accessed from ftp://linkage. rockefeller.edu/softeware/linkage/) software programs. The cellular retinoic acid-binding protein 2 (CRABP2), cone transducin alpha-subunit (GNAT2), potassium inwardly rectifying channel, subfamily J, member 10 (KCNJ10), genes were analyzed by heteroduplex analysis and direct sequencing for mutations. RESULTS: A new locus for arCRD (CORD8) has been mapped to chromosome 1q12-q24. A maximum two-point LOD score of 4.22 was obtained with marker D1S2635 at recombination fraction of theta = 0.00. Two critical recombinations in the pedigree positioned this locus to a region flanked by markers D1S457 and D1S2681. A region of homozygosity was observed within the loci D1S442 and D1S2681, giving a probable critical disease interval of 21 cM. Mutation screening of the three candidate genes CRABP2, GNAT2, and KCNJ10 revealed no disease-associated mutations. CONCLUSIONS: The findings therefore suggest that this phenotype maps to a new locus and is due to an as yet uncharacterized gene within the 1q12-q24 chromosomal region.

A new locus for autosomal recessive RP (RP29) mapping to chromosome 4q32-q34 in a Pakistani family.

PURPOSE: To map the disease locus in a six-generation, consanguineous Pakistani family with autosomal recessive retinitis pigmentosa (arRP). All affected individuals had pigmentary retinopathy associated with symptoms of night blindness and the loss of peripheral visual fields by the age of 20 years, loss of central vision between the ages of 25 and 30 years, and complete blindness between the ages of 40 and 50 years. METHODS: Genomic DNA from family members was typed for alleles at known polymorphic genetic markers using polymerase chain reaction. Alleles were assigned to individuals, which allowed calculation of LOD scores using the programs Cyrillic (http://www.cyrillicsoftware.com) and MLINK (Cherwell Scientific Publishing LTD:, Oxford, UK). The genes for membrane glycoprotein (M6a) and chloride channel 3 (CLCN3) were analyzed by direct sequencing for mutations. RESULTS: A new locus for arRP (RP29) has been mapped to chromosome 4q32-q34. A maximum two-point LOD score of 3.76 was obtained for the marker D4S415, with no recombination. Two recombination events in the pedigree positioned this locus to a region flanked by markers D4S621 and D4S2417. A putative region of homozygosity by descent was observed between the loci D4S3035 and D4S2417, giving a probable disease interval of 4.6 cM. Mutation screening of two candidate genes, M6a and CLCN3, revealed no disease-associated mutations. CONCLUSIONS: The results suggest that the arRP phenotype maps to a new locus and is due to a mutated gene within the 4q32-q34 chromosomal region.

A novel locus for Leber congenital amaurosis (LCA4) with anterior keratoconus mapping to chromosome 17p13.

PURPOSE: A two-generation consanguineous Pakistani family with autosomal recessive Leber congenital amaurosis (LCA, MIM 204,000) and keratoconus was identified. All affected individuals have bilateral keratoconus and congenital pigmentary retinopathy. The goal of this study was to link the disease phenotype in this family. METHODS: Genomic DNA was amplified across the polymorphic microsatellite poly-CA regions identified by markers. Polymerase chain reaction (PCR) products were separated by nondenaturing polyacrylamide gel electrophoresis. Alleles were assigned to individuals, which allowed calculation of LOD scores using the Cyrillic and MLINK software program. The retinal guanylate cyclase (RETGC-1, GDB symbol GUC2D) and pigment epithelium-derived factor (PEDF) genes were analyzed by heteroduplex analysis and direct sequencing for mutations in diseased individuals. RESULTS: Based on a whole genome linkage analysis the first locus for this combined phenotype has been mapped to chromosome 17p13. Linkage analysis gave a two point LOD score of 3.21 for marker D17S829. Surrounding this marker is a region of homozygosity of 15.77 cM, between the markers D17S1866 and D17S960; however, the crossover for the marker D17S1529 refines the region to 10.77 cM within which the disease gene is predicted to lie. Mutation screening of the nearby RETGC-1 gene, which has been shown to be associated with LCA1, revealed no mutations in the affected individuals of this family. Similarly, another prime candidate in the region PEDF was also screened for mutations. The factor has been shown to be involved in the photoreceptor differentiation and neuronal survival. No mutations were found in this gene either. Furthermore, RETGC-1 was physically excluded from the critical disease region based on the existing physical map. CONCLUSIONS: It is therefore suggested that this combined phenotype maps to a new locus and is due to an as yet uncharacterized gene within the 17p13 chromosomal region.

Autosomal dominant cone and cone-rod dystrophy with mutations in the guanylate cyclase activator 1A gene-encoding guanylate cyclase activating protein-1.

OBJECTIVE: To describe the phenotype in 3 families with dominantly inherited cone and cone-rod dystrophy with mutations in guanylate cyclase activator 1A (GUCA1A), the gene-encoding guanylate cyclase activator protein-1 (GCAP-1). METHODS: Phenotypic characterization with psychophysical and electrophysiological evaluation and confocal laser scanning ophthalmoscopy was performed in 2 families with a Tyr99Cys mutation and 1 family with a Pro50Leu mutation. Haplotype analysis was performed in the families with Tyr99Cys mutation. RESULTS: The families with a Y99C mutation were shown to be ancestrally related. Decreased visual acuity and loss of color vision occurred after the age of 20 years, followed by progressive atrophy of the central 5 degrees to 10 degrees. Electrophysiological testing revealed generalized loss of cone function, with preservation of rod function. Abnormal rod and cone sensitivities were confined to the central 5 degrees to 10 degrees. Confocal laser scanning ophthalmoscopy imaging showed abnormalities of autofluorescence in early disease. Subjects with a Pro50Leu mutation demonstrated marked variability in expressivity from minimal abnormalities of macular function to cone-rod dystrophy. CONCLUSIONS: The phenotype associated with the Y99C mutation in GUCA1A is distinctive, with little variation in expression. By contrast, that associated with the P50L mutation demonstrates variable expressivity. CLINICAL RELEVANCE: Phenotype-genotype correlation in these 2 mutations demonstrates 2 different phenotypes.

Familial cavernous hemangioma: An expanding ocular spectrum.

OBJECTIVE: To describe the clinical and genetic findings in a family with multiple cases of cavernous hemangiomas. DESIGN: Investigational clinical and genetic study in which 3 generations of a family consisting of 12 members were screened with magnetic resonance brain imaging, dilated ophthalmoscopic examination, and cutaneous survey coupled with linkage analysis to determine affected individuals and to better define manifestations of this neuro-oculo-cutaneous syndrome. RESULTS: The proband had multiple cerebral cavernous hemangiomas and a choroidal hemangioma. Her son was found to harbor a retinal cavernous hemangioma. The proband's sister manifested a cerebral cavernous hemangioma, cutaneous hemangiomas, and a presumed choroidal hemangioma; her daughter demonstrated radiological findings suggestive of a cerebral cavernous hemangioma. The father of the proband demonstrated multiple, cutaneous hemangiomas. The remaining family members were free of lesions. The 7q locus could not be excluded as harboring the causative gene. CONCLUSIONS: This family may have a dominantly inherited neuro-oculo-cutaneous condition of cavernous hemangiomas with variable expressivity. The presence of choroidal hemangiomas in this phacomatosis has not been described previously to our knowledge. CLINICAL RELEVANCE: The presence of either retinal cavernous or choroidal hemangioma should alert the physician to search for features suggestive of systemic and familial involvement; either lesion may constitute the ocular component of the neuro-oculo-cutaneous phacomatosis, sometimes referred to as cavernoma multiplex. Arch Ophthalmol. 2000;118:969-973

Autosomal dominant cone-rod dystrophy with mutations in the guanylate cyclase 2D gene encoding retinal guanylate cyclase-1.

OBJECTIVE: To describe the phenotype in 4 families with dominantly inherited cone-rod dystrophy, 1 with an R838C mutation and 1 with an R838H mutation in the guanylate cyclase 2D (GUCY2D) gene encoding retinal guanylate cyclase-1. METHODS: Psychophysical and electrophysiological evaluation and confocal laser scanning ophthalmoscopic imaging was performed on 10 affected members of 4 British families. RESULTS: Although subjects had lifelong poor vision in bright light, a major reduction in visual acuity did not occur in most of them until after their late teens. Fundus abnormalities were confined to the central macula, and increasing central atrophy was noted with age. Increased background autofluorescence was observed surrounding the central atrophic area. Electrophysiological testing revealed a marked loss of cone function with only minimal rod involvement, even in older subjects. Photopic and scotopic static perimetry demonstrated central and peripheral cone-mediated threshold elevations with midperipheral sparing. CONCLUSION: The phenotype associated with autosomal dominant cone-rod dystrophy with either an R838C or R838H mutation in GUCY2D is distinctive, with predominantly cone system involvement. There is some variation in severity within the 3 families with the R838C mutation. CLINICAL RELEVANCE: Families with the R838C or R838H mutation have a much milder phenotype than the family previously described that had 2 sequence changes, E837D and R838S, in GUCY2D.

Clinical features of codon 172 RDS macular dystrophy: similar phenotype in 12 families.

OBJECTIVE: To report the phenotype associated with the codon 172 RDS (gene for retinal degeneration slow) mutation in 11 separate families with an arginine-to-tryptophan substitution with common ancestry, and 1 family with an arginine-to-glutamine transition. PATIENTS: Screening for RDS gene mutations was performed in 400 subjects with autosomal dominant retinal degeneration. Twelve families were identified with a mutation in codon 172. Haplotype analysis was performed. Full ophthalmic evaluation was performed, including electrophysiologic and psychophysical investigation and imaging of autofluorescence using confocal laser scanning ophthalmoscopy. RESULTS: Haplotype analysis demonstrated that the 11 families were ancestrally related. All 12 families showed a common phenotype of macular dysfunction, with the deficit increasing with age. Abnormally high autofluorescence predated loss of visual acuity or visual field changes. Pattern electroretinographic (PERG) findings were affected early in disease. There was high intrafamilial and interfamilial consistency of phenotype. CONCLUSION: These families demonstrate a striking conformity of symptoms and signs. CLINICAL RELEVANCE: In the codon 172 RDS mutation, unlike disease resulting from other RDS mutations, prediction of approximate age of onset and progression of visual deficit is possible. This should assist diagnosis and counseling.

Insulin-like growth factor 1, but not growth hormone, has in vitro proliferative effects on neonatal foreskin fibroblasts without affecting 5-alpha-reductase or androgen receptor activity.

Clinical observation of patients with congenital growth hormone (GH) deficiency and Laron-type dwarfism suggests that factors such as GH or insulin-like growth factor 1 (IGF-1) might in addition to androgens, be needed for normal phallic growth. We speculated GH or IGF-1 might have direct actions on genital tissues and performed the present study to evaluate the in vitro effects of GH and IGF-1 on cultured neonatal foreskin fibroblasts. Cells derived from foreskins of normal newborns were studied between cell passages 6 and 15. Serum-free media with and without 100 ng/ml GH, IGF-1, or both were added 24 hours prior to and at the time of study. To determine the activity of 5-alpha-reductase (5-alpha-R), 3H-testosterone (T: 2 nM) was added, and 5-alpha-R activity was calculated as femtomoles 3H-dihydrotestosterone and 3H-androstanediol produced/microgram DNA/hour. Androgen receptor (AR) binding was determined by the addition of 3H-dihydrotestosterone (dHT; 0.03125-0.5 nM) in the presence and absence of a 200-fold excess of unlabeled dHT. Specific binding was used in Scatchard analysis for determination of AR number (Bmax) and binding affinity (Kd). The rate of DNA synthesis was determined by incorporation of 3H-thymidine (3H-Thy) into trichloroacetic acid-insoluble material. DNA and protein content were determined on cell lysates. IGF-1, but not GH, had proliferative effects (significant increases in the rate of 3H-Thy incorporation, DNA, and protein content) but no effect on 5-alpha-R activity, Bmax or Kd.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenotype of autosomal recessive congenital microphthalmia mapping to chromosome 14q32.

BACKGROUND: Congenital microphthalmia (OMIM: 309700) may occur in isolation or in association with a variety of systemic malformations. Isolated microphthalmia may be inherited as an autosomal dominant, an autosomal recessive, or an X linked trait. METHODS: Based on a whole genome linkage analysis, in a six generation consanguineous family with autosomal recessive inheritance, the first locus for isolated microphthalmia was mapped to chromosome 14q32. Eight members of this family underwent clinical examination to determine the nature of the microphthalmia phenotype associated with this locus. RESULTS: All affected individuals in this family suffered from bilateral microphthalmia in association with anterior segment abnormalities, and the best visual acuity achieved was "perception of light". Corneal changes included partial or complete congenital sclerocornea, and the later development of corneal vascularisation and anterior staphyloma. Intraocular pressure, as measured by Schiotz tonometry, was greatly elevated in many cases. CONCLUSIONS: This combination of ocular defects suggests an embryological disorder involving tissues derived from both the neuroectoderm and neural crest. Other families with defects in the microphthalmia gene located on 14q32 may have a similar ocular phenotype aiding their identification.

Macrophage conditioned media affects steroid hormone production by placental cultures.

Placental steroid hormone production appears to be critical in maintaining pregnancy and possibly initiating parturition. Cytokines, produced by activated macrophages and decidua, are present during delivery, but their role in this process is not yet clear. To our knowledge, only one recent study, which used JEG-3 choriocarcinoma cells as an in vitro model, has evaluated the possibility that cytokines might affect placental steroidogenesis. Our current study reports observations on the effect of macrophage conditioned media (MCM, known to contain several cytokines) on the synthesis of progesterone and estradiol by term, normal, human placenta. Macrophage conditioned media significantly decreased progesterone (36 percent) and increased estradiol (76 percent) production by short-term placental organ cultures. These results suggest that macrophage secretory products might significantly alter placental steroidogenesis which could make them important factors in the physiology of parturition.

The effect of macrophage conditioned media on Leydig cell function.

Primary gonadal failure frequently occurs in male patients with serious illness. This has suggested that activation of the immune system may affect the endocrine function of the testis. Most previous studies have evaluated the effects of individual cytokines on testosterone (T) production but with conflicting results. The present study was performed to compare the effects on Leydig cell function of a mixture of cytokines found in macrophage conditioned media (MCM), with that of individual recombinant cytokines. The MCM was found to contain an acid stable, heat labile, 16.5 kD factor(s) which significantly decreased the production of testosterone (T), dihydrotestosterone (dHT), adenosine 3':5'-cyclic monophosphate (cAMP), and guanosine 3':5'-cyclic monophosphate (cGMP). The MCM had no effect on the specific binding of human chorionic gonadotropin (hCG) but decreased the activity of 3-beta-hydroxysteroid dehydrogenase (3-beta-HSD) (a regulated Leydig cell enzyme). Neither tumor necrosis factor alpha (TNF alpha) interleukin 1 alpha (IL1 alpha), interleukin 1 beta (IL1 beta), interleukin 2 (IL2), interleukin 6 (IL6), or human interferon alpha,beta (IFN alpha,beta) had a similar effect. These results show that the cytokines or other factor(s) contained in MCM are potent regulators of T production, which could be important in understanding the low serum T levels associated with serious illness.

Halothane genotype, pre-slaughter handling and stunning method all influence pork quality.

Seventy-six Landrace and four Large White × Landrace pigs (n=80) of 90-134 kg liveweight were randomly allocated to a 2×2×2 factorial experiment to determine the effect of halothane genotype [heterozygous for the halothane gene (Nn) and homozygous dominant (NN)], pre-slaughter handling (minimal and negative) and stunning method (CO(2) stunning and electrical) on pork quality. The rate of muscle pH decline post-slaughter of the m. longissimus thoracis et lumborum (LTL) muscle was faster in Nn pigs compared with NN pigs (0.86 and 0.30 pH units/h, respectively). Pork from Nn pigs was also paler in colour, had higher percentage drip loss and purge and lower sarcoplasmic and myofibrillar protein solubility compared with NN pigs. Pork from CO(2) stunned pigs had a lower drip loss compared to pork from electrically stunned pigs (5.80 and 7.28%, respectively - means of both genotypes combined). Tenderness of pork assessed at 24 h post-slaughter was not influenced by genotype, pre-slaughter handling or stunning method. However, pork from Nn pigs aged for 5 days post-slaughter was less tender than NN pigs (5.84 and 4.84 kg, respectively). Pale, soft and exudative pork was produced in all negatively handled Nn pigs, regardless of stunning method. The average amount of ecchymosis-affected muscle trimmed from carcasses of electrically stunned pigs was higher compared to pigs stunned with CO(2) (65 and 0.7 g, respectively). These data indicate that although halothane status was the most important factor influencing pork quality, pre-slaughter handling and stunning method also influenced meat and carcass quality.

Comparison of CO(2) stunning with manual electrical stunning (50 Hz) of pigs on carcass and meat quality.

The effects of carbon dioxide stunning on carcass and pork quality attributes were compared with the effects of manual electrical stunning using either head-only or head-to-brisket electrodes. A total of 30 Large White×Landrace boars (homozygous dominant for the halothane gene) were randomly allocated immediately prior to slaughter to one of three stunning treatments: carbon dioxide (90% CO(2)), head only (HO; 1.3 A for 4 s at a frequency of 50 Hz) or head to brisket (HBR; 1.3 A for 4 s at a frequency of 50 Hz) electrical stunning. The pH of the M. longissimus thoracis (LT) muscle measured at two sites [between the fifth and sixth thoracic vertebrae (Site 1) and the last thoracic rib (Site 2)] at 40 min post-slaughter was lower (P<0.001) in HBR stunned pigs compared with both CO(2) and HO stunned pigs. No differences in ultimate pH of the LT at either measurement site were found due to stunning method. However, a faster (P<0.05) relative rate of pH decline was found in the LT at Site 1 from HBR stunned pigs compared with CO(2) stunned pigs. No difference in the relative rate of muscle pH decline (P>0.05) between stunning methods was found in the LT muscle at Site 2. Pork from HBR stunned pigs was paler (P<0.05) and had a higher (P<0.001) percentage drip loss compared with pork from HO and CO(2) stunned pigs. LT muscles from HBR stunned pigs had lower (P<0.001) WB shear force values compared with pork from HO stunned pigs (6.57 vs. 8.12 kg, S.E.D. 0.49). Carcass quality was improved by CO(2) stunning, with less (P<0.05) ecchymosis-affected pork trimmed from shoulder primals compared with electrically stunned pigs. These results indicate that manual electrical stunning of pigs using HO tongs and CO(2) stunning reduced percentage drip loss, reduced muscle lightness and reduced the rate of muscle pH decline compared with pigs manually electrically stunned using HBR tongs.