Day-blindness in three dogs: clinical and electroretinographic findings

A 6-month-old Rhodesian ridgeback-cross, a 6-year-old Chihuahua and a 12-month-old Australian cattle dog were presented to the authors with a history of colliding with obstacles in daylight. Ophthalmic examination was normal and all three dogs successfully negotiated obstacle courses in dim light. In daylight the dogs became suddenly blind and repeatedly collided with obstacles. Elecroretinography (ERG) revealed no retinal activity to high frequency (30 Hz), bright intensity blue light retinal stimulation by any dog, confirming cone dysfunction. Achromatopsia has previously been recorded in Alaskan malamutes and miniature poodles. This clinical case series illustrates the characteristic behavioral presentation and the electroretinographic findings of severe day-blindness and demonstrates that this condition may exist in other breeds of dogs.     

Results of grid keratotomy, superficial keratectomy and debridement for the management of persistent corneal erosions in 92 dogs

Ninety-two cases of persistent corneal erosions in dogs were analyzed for breed, gender, age and which eye was affected. The results of the treatment of 92 persistent corneal erosions in dogs by superficial keratectomy (SK), grid keratotomy (GK), or debridement with a sterile dry cotton swab are presented. These techniques gave better rates of healing than have been previously reported. All cases of persistent corneal erosions healed in this study. However, it must be noted that three cases treated with debridement only failed to heal after several treatments and were eventually treated with SK. After one procedure 80 out of 92 (87%) had healed. After one procedure, 63% of cases treated with debridement healed, 100% of cases treated with SK healed, and 85% of cases treated with GK healed. At the first postoperative visit, 88% (21/24 cases) of ulcers treated by SK had healed, and 75% (39/52 cases) of ulcers treated by GK had healed. Only 25% of the persistent corneal erosions had healed at the first visit after debridement. All 24 cases of persistent corneal erosions treated with SK healed after one treatment in a mean +/- SD of 9.3 +/- 3.9 days (median of 7 days). Fifty-two cases were managed with GK; 44 (83%) of these healed with one procedure and eight cases required a second GK procedure to resolve. A mean +/- SD of 13.4 +/- 5.1 days (median of 11.5 days) following GK was required for the persistent corneal erosions to heal. Nineteen cases were initially managed by debridement with a dry cotton swab under local anesthesia. Sixteen out of these 19 debridement cases healed (giving an overall healing rate of 84%) in a mean +/- SD time of 23.4 +/- 11.1 days (median 21.5). There were three cases that did not heal with debridement. These cases were debrided at 10-20 day intervals for 30-60 days, and were then treated with SK. Two of these cases healed within 7 days, the other case required 18 days to heal. Sixty-three per cent of persistent corneal erosions treated with debridement healed after one procedure; however, only four out of 19 cases (21%) were healed at the first revisit. Complications were rare: corneal edema occurred in two cases following multiple GK, and excessive granulation tissue in one case was managed with a SK. There was the occurrence of an ulcer adjacent to the surgery site in four cases, two cases following GK and two cases following SK.     

Conservation of forest biodiversity and ecosystem properties in a pastoral landscape of the Ecuadorian Andes

High Andean cloud forests are home to a diversity of unique wildlife and are important providers of ecosystem services to people in the Andean regions. The extent of these cloud forests has been widely reduced through conversion to pasture for livestock, which threatens the forests’ ability to support biodiversity and provide ecosystem services. This paper explores whether impacts on woody plant biodiversity and four ecosystem properties (woody plant species richness, juvenile timber tree abundance, soil organic matter content and soil moisture) from converting forest to pasture can be mitigated if some woody forest vegetation is maintained within pastures. Woody vegetation in pastures was found to conserve those woody plant species that are more tolerant to exposure and grazing, but conservation of the high montane cloud forest community required areas of forest from which livestock were restricted. The sampled sites clustered according to woody plant species cover; these clusters represented a gradient from pasture with patches of shrubs to mature forest. Clusters differed in both woody plant species richness and number of juvenile timber trees whereas soil organic matter and soil moisture were observed to be similar among all clusters. This suggests that the different habitats may have some equivalent ecosystem properties. We conclude that the presence of woody vegetation in pastures may reduce some of the impacts of converting forest to pasture, but should not be considered a substitute for protecting large areas of forest, which are essential for maintaining woody plant species diversity in high Andean cloud forest.     

Schirmer tear tests and intraocular pressures in conscious and anesthetized koalas (Phascolarctus cinereus)

Objective To estimate mean Schirmer tear test (STT) and intraocular pressure (IOP) values in healthy koalas both conscious and anesthetized. Methods Data were gathered from koalas in Victoria, Australia. Conscious examinations were performed on captive koalas. Free‐ranging (wild) koalas were examined under anesthesia. Anesthesia was induced using alfaxalone, and animals were maintained on oxygen and isoflurane if required. All animals were healthy and had no surface ocular pathology detectable during slit lamp biomicroscopy. STT I tests were performed using commercial STT test strips placed in the lower fornix for 1 min. IOP was measured using an applanation tonometer after topical anesthesia. The higher value of the two eyes for both STT and IOP was analyzed. STT was measured in 53 koalas (34 conscious, 19 anesthetized) and IOP was measured in 43 koalas (30 conscious, 13 anesthetized). A two‐sample t‐test was used to compare means. A P‐value <0.05 was regarded as significant. Mean ± SD is presented. Results The mean higher STT in conscious koalas was 10.3 ± 3.6 mm wetting/min and in anesthetized koalas it decreased to 3.8 ± 4.0 mm wetting/min (P < 0.0001). The mean higher IOP in conscious koalas was 15.3 ± 5.1 mmHg, and in anesthetized koalas it was 13.8 ± 3.4 mmHg (P = 0.32). There was no effect of sex on either STT or IOP. Conclusions The mean and SD of STT and IOP values for koalas both conscious and anesthetized were reported. The mean STT was significantly reduced by alfaxalone anesthesia.     

Substrate binding properties of mutant and wild-type A proteins of Escherichia coli tryptophan synthetase

Most of the mutant A proteins studied appear to be similar to the normal enzyme both in their apparent conformation about the critical cysteine residues and their ability to bind substrate. Two mutant proteins, in which a glutamic acid or arginine residue is substituted for a glycine residue, do appear abnormal suggesting that these primary structural changes radically affect the conformation in regions at or near the site or sites of substrate binding.     

A comparison of popular approaches to optimize landscape resistance surfaces

Landscape Ecology - Landscape resistance surfaces are often used to address questions related to movement, dispersal, or population connectivity. However, modeling landscape resistance is...