Historical, clinical and laboratory features of 126 hyperthyroid cats.

The historical and clinical features and the haematological and biochemical changes in 126 cats with hyperthyroidism are described; 125 of the cats were domestic short- or longhaired, and one was a chinchilla. There were 62 males and 64 females with a mean age of 13.0 years. The duration of signs ranged from two days to two years with a mean of 5.4 months. The historical and clinical features were weight loss, polyphagia, polyuria/polydipsia, tachycardia, hyperactivity, diarrhoea, respiratory abnormalities, other cardiac abnormalities, skin lesions, vomiting, moderately raised temperature, decreased activity, decreased appetite, congestive cardiac failure, haematuria and intermittently decreased appetite. Goitre was palpable in 123 cats. The serum total thyroxine concentrations of the cats were more than three standard deviations above the mean of the reference range. Serum total tri-iodothyronine concentrations ranged from 0.78 to 14.96 nmol/litre and were within the reference range in 11 of the cats. Mild hyperthyroidism was a much commoner cause of high normal or marginally above normal thyroid hormone concentrations than severe, concurrent, non-thyroidal illness. Other common biochemical changes were increased of serum alanine aminotransferase, urea, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase. There were minimal changes in the red cell parameters. Leucocyte changes showed two trends: a mature neutrophilia, either with or without an accompanying leucocytosis often in association with a lymphopenia, or an eosinophilia, either with or without a lymphocytosis.     

Dynamic adrenal function testing in eight dogs with hyperadrenocorticism associated with adrenocortical neoplasia.

The results of adrenocorticotropin (ACTH) stimulation and low-dose dexamethasone suppression tests (LDDST) were evaluated retrospectively in eight dogs with clinical signs of hyperadrenocorticism arising from functional adrenocortical tumours, and compared with the results from 12 dogs with confirmed pituitary-dependent hyperadrenocorticism (PDH). The post-ACTH cortisol concentration in the dogs with adrenocortical tumours ranged from 61 to 345-6 nmol/litre (median 251.5 nmol/litre) and they were within the reference range (150 to 450 nmol/litre) in five and unexpectedly low (< 150 nmol/litre) in three dogs. Both the basal and post-ACTH cortisol concentrations were significantly lower in the dogs with adrenocortical neoplasia than in the dogs with PDH. Eight hours after the LDDST, only two of six dogs with adrenocortical tumours had a cortisol concentration above 30 nmol/litre, and the median resting, three, and eight-hour cortisol concentrations were 31.5, 23.0, and 22.7 nmol/litre respectively. There was no significant cortisol suppression during the LDDST, although interpretation was complicated by the low cortisol concentrations, but two dogs showed a pattern of apparent suppression. Two dogs with adrenal tumours showed a diagnostically significant increase in 17-OH-progesterone concentration in response to ACTH although their cortisol concentrations did not increase greatly. These results differ from previous reports of the response of functional adrenal tumours to dynamic endocrine tests.     

Clinical Evaluation of a Novel Liquid Formulation of L-Thyroxine for Once Daily Treatment of Dogs with Hypothyroidism

Background: A liquid solution of levothyroxine (L-T4) is available for treatment of canine hypothyroidism.
Hypothesis: Once daily oral administration of a liquid L-T4 solution is effective and safe for controlling hypothyroidism in dogs.
Animals: Thirty-five dogs with naturally occurring hypothyroidism.
Methods: Dogs received L-T4 solution PO once daily at a starting dosage of 20 μg/kg body weight (BW). The dose was adjusted every 4 weeks, based on clinical signs and peak serum total T4 (tT4) concentrations. Target peak serum tT4 and thyroid stimulating hormone (TSH) concentrations, 4–6 hours posttreatment, were 35–95 nmol/L and < 0.68 ng/mL, respectively. Dogs were followed for up to 22 weeks after establishment of the maintenance dose.
Results: Clinical signs of hypothyroidism improved or resolved in 91% of dogs after 4 weeks of L-T4 treatment at 20 μg/kg once daily. The maintenance dose was established in 76, 94, and 100% of dogs after 4, 8, and 12 weeks of treatment, respectively. This was 20 μg L-T4/kg BW for 79% of the dogs, 30 μg/kg BW for 15%, and 10–15 μg/kg BW in the remaining 6%, once daily. Thereafter, median peak tT4 and TSH concentrations were 51 nmol/L and 0.18 ng/mL, respectively, and remained stable during the 22-week follow-up; clinical signs did not recur.
Conclusions and Clinical Importance: All of the hypothyroid dogs had rapid clinical and hormonal responses to supplementation with the PO-administered L-T4 solution. The starting dosage of 20 μg L-T4/kg BW once daily was suitable for 79% of dogs.     

Epidemiological, clinical, haematological and biochemical characteristics of canine hypothyroidism

Hypothyroidism was diagnosed in 50 dogs and excluded in 86 dogs suspected of hypothyroidism, on the basis of the results of bovine thyrotropin response tests. Breed, pedigree, sex or neutering status did not significantly influence the likelihood of the dogs being hypothyroid. The hypothyroid dogs were significantly older than the non-hypothyroid dogs referred to the University of Glasgow during the same period. However, when dogs under two years of age were excluded from the statistical analyses there was no significant difference in age between the two groups. The most common clinical characteristics associated with hypothyroidism were metabolic signs (84 per cent of cases), particularly lethargy (76 per cent), obesity or weight gain (44 per cent), and exercise intolerance (24 per cent); and dermatological abnormalities (80 per cent), including alopecia (56 per cent), poor coat quality (30 per cent) and hyperpigmentation (20 per cent). When compared with the laboratory reference limits the most common biochemical and haematological abnormalities were increased concentrations of triglycerides (88 per cent), cholesterol (78 per cent), glucose (49 per cent), and fructosamine (43 per cent), and increased activities of creatine kinase (35 per cent), and decreased concentrations of inorganic phosphate (63 per cent), and a low red blood cell count (40 per cent). When compared with reference limits derived from the euthyroid dogs the most common abnormalities were increased concentrations of gamma-glutamyltransferase (21 per cent), cholesterol (18 per cent), and aspartate aminotransferase (15 per cent) and a decreased red blood cell count (29 per cent), and decreased neutrophils (18 per cent) and decreased activity of creatine kinase (15 per cent). Assessment of cholesterol, creatine kinase, aspartate aminotransferase, gamma-glutamyltransferase, and red blood cell and neutrophil counts may be particularly useful in distinguishing hypothyroid dogs from euthyroid animals with similar clinical signs.     

Photosynthetic Mechanisms and Paleoecology from Carbon Isotope Ratios in Ancient Specimens of C4 and CAM Plants

Carbon istotope ratios of modern, 10,000-year-old, and more than 40,000-year-old Atriplex confertifolia (C(4)) material from Nevada caves indicate that the C(4) photosynthetic pathway was operating in these plants over that period. Samples of a plant with crassulacean acid metabolism, Opuntia polyacantha, were also measured, and a shift in the 8(13)C value from -21.9 per mil (more than 40,000 years ago) to -13.9 per mil (10,000 years ago) was observed. This provides unique physiological evidence to support the hypothesis that the late Pleistocene pluvial climate in the region already had become drier about 10,000 years ago.     

Using micromorphology to understand the rewetting mechanisms in milled peat

Milled peat, an important energy resource in Ireland, is produced by scarifying the surface of a peat bog and allowing the resultant particulate material to air dry prior to storage in large stockpiles on the peat bogs. The storage period can vary from 6 months to several years, during which time the stockpiles are subject to atmospheric precipitation which causes rewetting and a subsequent reduction in calorific and monetary value. A study was undertaken to characterise the pore structure of stockpiles and identify relationships between structure and propensity to rewet. Recent research examining rewetting mechanisms in milled peat stockpiles has focused mainly on macroscale physical data. With respect to the importance of the structure of a porous medium for water movement and storage, a characterisation of the pore and particulate structure of milled peat in stockpile was conducted using micromorphological techniques. Samples with water contents up to 0.6 g g⁻¹ were impregnated in the field. Thin sections produced in days as opposed to months (no period of chemical dehydration was required) were used to quantify macroporous structures using image analysis. Results illustrated that a significant hydraulic discontinuity existed between the surface and subsurface layers of stockpiles, a factor not identified by laboratory physical analysis. This endorsed the current hypothesis in that the milled peats of different genetic origin had different pore architectures which had a significant effect on the active rewetting mechanisms. The visualisation of water flow pathways using dye tracers suggested that in addition to the wetting front water movement, by-pass flow was an active rewetting mechanism.     

Seismic-wave attenuation associated with crustal faults in the new madrid seismic zone

The attenuation of upper crustal seismic waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid seismic zone in the central Mississippi Valley. The waves that have the strongest attenuation pass through the seismic trend along the axis of the Reelfoot rift in the area of the Blytheville arch. Defocusing of the waves in a low-velocity zone and/or seismic scattering and absorption could cause the attenuation; these effects are most likely associated with the highly deformed rocks along the arch. Consequently, strong seismic-wave attenuation may be a useful criterion for identifying seismogenic fault zones.     

Radioactive iodine therapy for feline hyperthyroidism: Efficacy and administration routes

The efficacy of radioactive iodine (¹³¹I) administration was studied in a series of 50 hyperthy-roid cats. The dose administered to each cat was based on the clinical severity of the thyrotoxicosis, the serum total thyroxine (TJ concentration and the size of the goitre estimated by palpation. The activity ranged from 80 to 200 MBq (mean ± SD, 143 ± 24 MBq}. The ¹³¹I was injected intravenously in 27 cases and subcutaneously in 23 cases. Each cat was hospitalised for 30 days after the injection. Regardless of the route of injection, none of the cats exhibited any side effects after therapy and all tolerated the hospitalisation period well. There was a significant (P<0.001) decrease in the serum total T₄ concentration (reference range, 10.4 to 42.0 nmol/litre) from a mean ± SD of 181.3 ± 111.4 nmol/litre (range, 43.8 to 575.6 nmol/litre) to a mean ± SD of 19.0 ± 29.6 nmol/litre (range, 2.0 to 175.7 nmol/litre) 30 days following the injection of the radioisotope. Five cats remained hyperthyroid, although in each case the serum total T₄ concentrations had decreased from pre-treatment values. Two of the cats subsequently became euthyroid within three and five months of therapy, respectively, two were lost to adequate follow-up and the remaining cat was successfully retreated four months later. Before treatment, four of these cases had high scores based on the three criteria used for dose estimation. Serum total T₄ concentrations below the reference range developed after treatment in many cases, but were often transient. Clinical evidence of hypothyroidism was not apparent in any cat. Recurrence of hyperthyroidism has not occurred in follow-up periods of up to 32 months. There was no difference in the outcome between the cats injected intravenously or subcutaneously and the latter was considered to be safer and simpler. The administration of an approximated dose of ¹³¹I proved to be an effective treatment for hyperthyroidism in 47 (94.0 per cent) of the cats and obviated the need for sophisticated nuclear computer facilities. There may be a lag period in some cases before euthy-roidism is achieved and this should be considered before the administration of a second dose. ¹³¹I can be administered subcutaneously without untoward effects.