Characterization of parasympatholytic chronotropic responses following intravenous administration of atropine to clinically normal dogs.

OBJECTIVE: To determine heart rate (HR) and heart rate variability (HRV) after IV administration of 3 doses of atropine to clinically normal, large-breed adult dogs. ANIMALS: 6 mixed-breed dogs, weighing between 23 and 50 kg. PROCEDURE: Continuous ECG were recorded prior to and following IV administration of saline (0.9% NaCl) solution and 0.02, 0.04, and 0.06 mg of atropine/kg of body weight. Heart rate and HRV within sympathetic and parasympathetic domains were determined, using customized software, and responses to treatments were compared. Each dog received all treatments with > or = 2 days between treatments. RESULTS: HR increased and HRV within the parasympathetic domain decreased after all atropine treatments, compared with pretreatment values. Heart rate was significantly higher after administration of 0.06 mg of atropine/kg than after 0.02 mg/kg but was not different from HR after administration of 0.04 mg/kg. Five of 6 dogs given the 0.04 or 0.06 mg/kg dose attained HR > 135 beats/min, but only 1 of 6 dogs given the 0.02 mg/kg dose attained a HR > 135 beats/min. Heart rate variability within the parasympathetic domain decreased significantly from pretreatment values after all atropine treatments. Atropine doses of 0.04 and 0.06 mg/kg induced significantly lower HRV than did the 0.02 mg/kg dose, but HRV after the higher doses were not different from each other. HRV within the sympathetic domain after any treatment did not change from pretreatment values. CONCLUSIONS AND CLINICAL RELEVANCE: IV administration of 0.04 or 0.06 mg of atropine/kg increased HR and induced complete parasympathetic blockade in clinically normal, large-breed adult dogs.     

Economic characteristics of extensive shrimp farms in the Mekong delta

Abstract

Extensive forms of shrimp aquaculture have become an important source of income for farm households in the brackish water region of the Mekong Delta, Vietnam. The economic and production characteristics of farms are discussed in this paper, based on a 1997 farm survey, with particular emphasis on shrimp farming practices. Two types of shrimp fanning practice were observed, one based on natural recruitment of seedstock with few supplementary inputs, and the other based on relatively high cash investments in Penaeus monodon seedstock and other inputs. Households practising monodon culture made significantly more income, but faced high risk associated with shrimp mortality. An investigation of the factors affecting monodon yields indicated that investment in higher quality inputs had a positive effect on yield and income. However, further research is needed on the extent to which management can reduce risk of shrimp mortality by investing in such premium quality inputs.     

An experimental evaluation of castellated laryngofissure and bilateral arytenoid literalisation for the relief of laryngeal paralysis in dogs

The aim of this study was to compare the efficacy of 2 surgical procedures for providing an adequate laryngeal airway in dogs after surgically induced laryngeal paralysis. The laryngeal function of 10 healthy, adult experimental dogs was assessed by clinical examination, laryngoscopy, arterial blood gas measurement and analysis of tidal breathing flow-volume loops before, and after, bilateral recurrent laryngeal neurectomy. A castellated laryngofissure with vocal fold resection was done on 5 dogs and bilateral arytenoid cartilage lateralisation performed on the remaining 5 dogs. Six weeks later, the laryngeal function of the 10 dogs was reassessed, before the dogs were killed and a necropsy performed. The visible changes in laryngeal structure were recorded. Both surgical procedures alleviated some of the airway obstruction caused by the bilateral recurrent laryngeal neurectomy, but bilateral arytenoid cartilage lateralisation produced more consistent clinical improvement, a wider rima glottidis, increased inspiratory air flow and a significant increase in post-operative arterial oxygen tension.     

Observations by the international tsunami survey team in Sri Lanka

In response to the 26 December 2004 tsunami, a survey team of scientists was dispatched to Sri Lanka. Measurements made by the team show that the tsunami elevation and runup ranged from 5 to 12 meters. Eyewitnesses report that up to three separate waves attacked the coast, with the second or third generally the largest. Our conclusion stresses the importance of education: Residents with a basic knowledge of tsunamis, as well as an understanding of how environmental modifications will affect overland flow, are paramount to saving lives and minimizing tsunami destruction.     

Immunohistochemical and clinical evaluation of p53 in canine cutaneous mast cell tumors

One hundred twenty-six cutaneous mast cell tumors obtained by excisional biopsy from 106 dogs were evaluated using immunohistochemical staining for the presence of p53 protein. A standard avidin-biotin immunohistochemical protocol was used incorporating a polyclonal antibody of rabbit origin (CM-1) as the primary antibody. Histopathologic grading of tumors was performed on hemotoxylin and eosin-stained samples. There was a significant difference in the percentage of cells staining positive for p53 for the histopathologic grades (P = 0.0005). Grade III tumors had a significantly greater p53 content than did grade I or II tumors (P < 0.05). Clinical data obtained retrospectively was available for 54 dogs. Tumor recurred in 19 of 54 (35.2%) dogs. Twenty-nine dogs died by the end of the study; 9 of 29 (31.0%) died of mast cell tumor disease. Histopathologic grade showed a significant negative association with survival time. Both clinical stage and histopathologic grade showed a significant negative association with time to recurrence. The percentage of cells staining positive for p53 did not significantly improve the forward analysis. Immunohistochemical detection of p53 did not appear useful in characterizing the clinical association between cutaneous mast cell tumor cellular features and survival time or time to tumor recurrence in dogs.     

Long-term effect on the equine eye of an intravitreal device used for sustained release of cyclosporine A

OBJECTIVE: To determine the long-term toxicity of an intravitreal device releasing continuous cyclosporinee A (CsA) in normal eyes of horses by evaluating clinical signs, electroretinography, and histopathology. Animals Studied Ten adult horses with normal ophthalmic examinations were used in this study Procedure(s) Four horses had one eye implanted with a CsA device, and six horses had the right eye implanted with a CsA-containing device (10 eyes with CsA in total) and the left eye (six eyes in total) with the device without drug (control). The implants were placed in the vitreous of the eyes through a sclerotomy 1 cm posterior to the limbus in the dorso-temporal quadrant of the eye. Scotopic electroretinograms were performed prior to implantation and at 1 week, and at 1, 3, 6, 9, and 12 months postimplantation. Two of the unilaterally implanted horses were euthanized at 1 weeks postimplantation, and two at 6 weeks postimplantation. Two of the bilaterally implanted horses were euthanized at 6 months, two at 9 months, and two at 12 months postimplantation. At euthanasia, the eyes were removed, aqueous and vitreous humor aspirated, and tissues fixed in 10% buffered formalin and processed for histopathology. CsA concentrations were measured by high pressure liquid chromatography in the aqueous and vitreous humors, and in peripheral blood. RESULTS: The devices were tolerated well in 14 of 16 eyes. There was minimal postoperative inflammation in most eyes, with a normal appearance within 7 days. In two eyes implanted with the CsA device, severe inflammation resulted in phthisis bulbi by 28 days. One of these eyes exhibited suspected bacterial endophthalmitis, and one had a sterile endophthalmitis and cataract presumably from trauma to the lens during implantation. In the other 14 eyes, no change was observed in the scotopic electroretinograms (ERG) from preoperative results, and no significant differences between the right (CsA) and left (control device) eyes were observed. CsA levels in the aqueous and vitreous humor, and peripheral blood were below the detection limit of the HPLC. Histologic findings revealed only a mild lymphoplasmacytic cellular infiltrate in the ciliary body and pars plana near the implantation site. CONCLUSIONS: The CsA devices were well tolerated with no long-term complications from the implants themselves. However, complications may occur from inadvertent implantation trauma or contamination during surgery. The long-term safety of the device may make it useful for delivery of CsA in the control of equine recurrent uveitis.     

Lunar surface strength: implications of luna 9 landing

The ability of the lunar surface to support statically the Luna 9 copsule indicates that the surface can bear at least 5 x 10(3) dyne per square centimeter (10(-1) lb/in.(2)). Analysis of the landing dynamics, using available data, gives a lower bound of about 1 to 2 x 10(5) dyne/cm(2), but this estimate may not be conservative because of uncertainties regarding the shock-absorbing system used and the direction of the velocity vector at impact.     

Phytochrome-mediated bioelectric potentials in mung bean seedlings

Excised root tips from dark-grown mung bean seedlings (Phaseolus aureus) that adhere to a negatively charged glass surface when irradiated with red light and release when irradiated by far-red light develop a positive bioelectric potential (about 1.0 millivolt) at the tip in red light and a negative bioelectric potential in far-red light. The sign of the bioelectric potential was repeatedly photo-reversible, and the adhesion and release kinetics were similar to those of the development of the bioelectric potentials. Photoconversion of the phytochrome holochrome perhaps changes permeability characteristics of the cell membrane, resulting in an induced localized electrochemical gradient manifested as a bioelectric potential. This supports the view that phytochrome in situ is membrane bound.     

Swimming against the flow: a mechanism of zooplankton aggregation

Zooplankton reside in a constantly flowing environment. However, information about their response to ambient flow has remained elusive, because of the difficulties of following the individual motions of these minute, nearly transparent animals in the ocean. Using a three-dimensional acoustic imaging system, we tracked >375,000 zooplankters at two coastal sites in the Red Sea. Resolution of their motion from that of the water showed that the animals effectively maintained their depth by swimming against upwelling and downwelling currents moving at rates of up to tens of body lengths per second, causing their accumulation at frontal zones. This mechanism explains how oceanic fronts become major feeding grounds for predators and targets for fishermen.