Proliferation of functional hair cells in vivo in the absence of the retinoblastoma protein

In mammals, hair cell loss causes irreversible hearing and balance impairment because hair cells are terminally differentiated and do not regenerate spontaneously. By profiling gene expression in developing mouse vestibular organs, we identified the retinoblastoma protein (pRb) as a candidate regulator of cell cycle exit in hair cells. Differentiated and functional mouse hair cells with a targeted deletion of Rb1 undergo mitosis, divide, and cycle, yet continue to become highly differentiated and functional. Moreover, acute loss of Rb1 in postnatal hair cells caused cell cycle reentry. Manipulation of the pRb pathway may ultimately lead to mammalian hair cell regeneration.     

Short-term anaesthesia in piglets using a liquid injection, rebreathing, inhaler device

An economical anaesthetic technique of short duration that can be administered to piglets in the field is desirable for humanitarian reasons, for castration, tail docking or other brief procedures. Using the principles of anaesthetic uptake and distribution, an inhaler was developed to vaporize and administer isoflurane to piglets. The inhaler design consisted of a mask, vaporization chamber and a rebreathing bag. A stopcock provided access for injection of liquid isoflurane onto a wick contained in the vaporization chamber. Inspiratory and expiratory flow of air over the wick enhanced anaesthetic vaporization. The amount of liquid isoflurane required for induction and 2–3 minutes of surgical anaesthesia was calculated using the square root of time model proposed by Lowe & Ernst (1981) for liquid injection, closed circuit anaesthesia in people. Calculations were based on an assumed MAC of 1.4% and the achievement of a target alveolar concentration of 1.3 MAC to provide a surgical plane of anaesthesia. The appropriate isoflurane concentrations in the mask, inhaler, rebreathing bag and the piglet's FRC and tissues were calculated. Original calculations were based on metabolic size (BW^0.75) and then converted to weight (kg). Based on the piglet's scale weight, the total microliters of liquid isoflurane required were formulated into a table for field use. Isoflurane was injected into the inhaler stopcock followed by oxygen to fill the rebreathing bag and initiate vaporization. After the mask was placed over the piglet's nose a slide switch was activated to allow gases to move in and out of the inhaler and rebreathing bag. Fifty‐seven male piglets weighing (mean ± SD 3.0 ± 0.7 kg) and aged 7.7 ± 1.0 days were randomly selected to receive anaesthesia prior to castration. Remaining littermates served as controls for assessing morbidity or mortality. The time to induction, recovery and total anaesthetic time were measured. The Pe ′CO₂ was measured at the piglet's nostril immediately after the mask was removed at the end of the surgical procedure. Data were analysed in SAS using the Proc Mixed procedure. Inductions were rapid, 47 ± 9 seconds, generally with minimal or no resistance. The duration of surgery was 1–2 minutes. Anaesthesia was adequate and recovery was rapid, 122 ± 44 seconds. Total time from start to standing was 260 ± 51 seconds. The Pe ′CO₂ was 5.2 ± 1.1 kPa (39.4 ± 8.4 mm Hg). There was no morbidity or mortality associated with either group of piglets. After piglets were standing and mobile, they were returned to the sow and other littermates, where they immediately started nursing and were indistinguishable from littermates except by determination of ear notch number. This technique provides safe, rapid anaesthesia and recovery that is appropriate for use by veterinarians for brief field procedures.     

Homogeneous Linewidths in the Optical Spectrum of a Single Gallium Arsenide Quantum Dot

The homogeneous linewidths in the photoluminescence excitation spectrum of a single, naturally formed gallium arsenide (GaAs) quantum dot have been measured with high spatial and spectral resolution. The energies and linewidths of the homogeneous spectrum provide a new perspective on the dephasing dynamics of the exciton in a quantum-confined, solid-state system. The origins of the linewidths are discussed in terms of the dynamics of the exciton in zero dimensions, in particular, in terms of lifetime broadening through the emission or absorption of phonons and photons.     

Evidence that moxidectin is a greater risk factor than ivermectin in the development of resistance to macrocyclic lactones by Ostertagia spp in sheep in south eastern Australia

AIM: To determine associations between resistance of Ostertagia (= Teladorsagia) spp to macrocyclic lactone (ML) anthelmintics and history of use of anthelmintics, by type, on commercial sheep farms in temperate regions of southern South Australia and Victoria, Australia.

METHODS: Faecal egg count reduction tests (FECRTs) were conducted during a 2.5-year period (from August 2001 to January 2004) and records of the type of anthelmintic used in the 5 years preceding the FECRTs were collected from commercial sheep farms (n=103) in southern South Australia and Victoria, and data analysed retrospectively. ML resistance was defined as <95% reduction of Ostertagia spp 10–14 days after treatment with ivermectin (IVM), orally, at half the manufacturer's recommended dose rate. Use of anthelmintics in the preceding 5 and 10 years on each property was classified according to the nett number of years each of the following classes of drug had been used: IVM oral liquid (IVO), IVM controlled-release capsules (CRCs), abamectin (ABA), moxidectin (MOX) or a non-ML an- thelmintic. The prevalence of ML resistance, by property, was analysed for associations with prior use of anthelmintics.

RESULTS: Resistance by Ostertagia spp to ML anthelmintics was evident on 51/103 (49.5%) properties. The prevalence of resistance was lowest (23%) on properties on which MOX had not been used, and was significantly higher (64–77%) on properties on which MOX had been used for ≥2 of the preceding 5 years (p<0.001). In contrast, the prevalence of resistance was highest (70–74%) on the properties on which IVM, or IVM and/ or ABA, had not been used in the previous 5 years (on which the use of MOX was predominant), and was markedly lower (20– 42%) on properties that had used IVM or IVM and/or ABA for at least one of the preceding 5 years. Prevalence of resistance was higher for properties on which the only ML anthelmintic used was MOX (19/29=66%) than for those on which the only ML used was IVO (2/19=11%; p<0.001). Properties on which the only ML used was MOX were 2.72 times more likely to have resistance than properties on which the only ML used was IVO (95% confidence interval (CI) = 1.01–5.08).

CONCLUSION: Use of MOX for ≥2 of the preceding 5 years was associated with a higher prevalence of resistance to ML by Ostertagia spp on sheep farms in south eastern Australia than the use of IVO.     

Ultrastructural mucosal injury after experimental ischemia of the ascending colon in horses.

The ultrastructural injury that develops sequentially in the ascending colon during experimentally induced ischemia was examined in 6 halothane-anesthetized horses. Colonic ischemia was created by 2 types of vascular occlusion 24 cm proximal and distal to the pelvic flexure. In all horses, transmural vascular compression was created. The colonic venous circulation was obstructed in 3 horses, whereas in the other 3 horses, arterial and venous circulation was obstructed. Two additional horses were anesthetized as controls for determination of any morphologic alterations associated with the experimental protocol. Full-thickness colonic biopsy specimens were obtained from the antimesenteric border of the pelvic flexure at 0, 0.25, 0.5, 1, 1.5, 1.75, 2, 2.25, 2.5, 3, 3.5, 4, 4.5, and 5 hours during occlusion, and were studied by light and transmission electron microscopy. Morphologic alterations did not develop in the colon of control horses. Mucosal congestion was observed by light microscopy in the colon of horses with experimentally induced ischemia, but congestion developed early in those with obstructed colonic venous circulation, compared with those having arterial and venous obstruction. Inter- and intracellular vacuolation and loss of staining initially resulted in groups of 3 to 5 superficial luminal epithelial cells. Alterations in the glandular epithelium lagged behind those in the superficial epithelium, but were observed in both groups by 2 hours of obstruction. These changes progressed to 100% sloughing of all epithelium by 4.5 to 5 hours. The initial cellular alterations, which were observed by transmission electron microscopy, developed at 0.25 hour in horses with colonic venous obstruction and was characterized by inter- and intracellular edema.(ABSTRACT TRUNCATED AT 250 WORDS)     

Addition of Recombinant Human Growth Hormone to In Vitro Maturation Medium of Bovine Oocytes

The aim of this study was to increase the bovine embryonic development rate, adding recombinant human growth hormone (rhGH) to maturation medium of bovine oocytes. Oocytes were matured for 24 h in TCM 199 Earle's salts and five treatments were developed: T1, 0.01 IU/ml of recombinant human follicle stimulating hormone (rhFSH); T2, 0.01 IU/ml of rhFSH + 100 ng/ml of rhGH; T3, 0.01 IU/ml of rhFSH + 1000 ng/ml of rhGH; T4, 100 ng/ml of rhGH; and T5, 1000 ng/ml of rhGH at 39 degrees C and 5% of CO(2) in air and saturated humidity. In vitro fertilization from cumulus-oocyte complexes was conducted in TALP-Fert medium (18-22 h) and spermatozoa were selected by Percoll gradient. Zygotes were incubated in SOFaaci medium in 5% of CO(2) in air, 5% of O(2) at 39 degrees C and saturated humidity for 11 days. There was no statistical difference in cleavage rate and embryo production on day 7 and day 9 among treatments. However, the hatching rate increased significantly in the T4 and T5 treatments (11.0 and 12.8%, respectively), compared with the T1 treatment (4.6%) (p < 0.05). Therefore, the rhGH addition to the oocyte maturation medium showed beneficial effects on the hatching rate of in vitro-produced bovine embryos.     

Microvascular circulation of the cecum in horses

The microvascular circulation of the cecum was studied in 15 adult horses, using microangiography and light microscopy combined with gross studies and scanning electron microscopy of vascular replicas. After heparinization, the horses were euthanatized and the cecum was transected at the cecocolic junction. Blood was flushed free of the circulation with isotonic NaCl and the cecal lumen was slightly distended. In 6 horses, the vascular system was injected with a modified radiopaque medium and evaluated radiographically. Sections evaluated radiographically were also prepared for histologic examination by standard methods. Eight horses were injected with 1 of 2 types of plastics and studied grossly or by scanning electron microscopy. In 1 additional horse, the lateral and medial arteries were injected with different colored plastic for gross studies. The lateral and medial cecal arteries appear to supply the respective areas of the cecum with minimal mixing of the 2 circulations. The major vascular supply to the cecal apex appeared to be through the medial cecal artery. Both the lateral and medial cecal arteries gave rise to cecal retia, which formed a mesh-like network around the respective veins. Vessels from these retia supplied the cecal tissue and the cecal lymph nodes. The continuation of the retia was through long terminal arteries that coursed around the circumference in the submucosa, forming an extensive submucosal plexus. This plexus supplied both the mucosa, and the tunica muscularis and serosa. Vessels within the longitudinal and circular muscle layers of the muscularis externa ran parallel to the muscle fibers, and consequently, perpendicular to each other.(ABSTRACT TRUNCATED AT 250 WORDS)