CO<Subscript>2</Subscript>-assimilation and chlorophyll fluorescence as indirect selection criteria for host tolerance against <Emphasis Type="Italic">Striga</Emphasis>

Striga hermonthica (Del.) Benth. is a parasitic weed on tropical cereals causing serious yield losses in Africa. The use of host crop varieties with improved resistance and tolerance against this parasite is a key component of an integrated control strategy. Breeding for tolerance is however seriously hampered by the absence of reliable and yet practical selection measures. The observation that the photosynthetic rate of tolerant genotypes is less sensitive to Striga infection was used as a starting point to search for suitable selection measures. In a greenhouse pot experiment the effect of Striga infection on the photosynthesis of four sorghum (Sorghum bicolor [L.] Moench) genotypes, differing in Striga tolerance level, was measured at three moments in time (26, 48 and 75 days after sowing). Genotypes were CK60-B, E36-1, Framida and Tiémarifing. Measurements involved CO₂-assimilation (A) and three chlorophyll fluorescence characteristics (electron transport rate through photosystem II [ETR], photochemical [Pq] and non-photochemical quenching [NPq]). Striga infection negatively affected A, ETR and Pq. Based on A and Pq, genotypes with superior levels of tolerance (Tiémarifing) could be discriminated from genotypes with superior level of resistance (Framida). Both A and Pq showed high heritabilities and consequently clear and predictable differences between genotypes. Using discriminative ability, heritability and cost effectiveness as main criteria, photochemical quenching (Pq) was concluded to possess the highest potential to serve as indirect selection measure for host plant tolerance to Striga. Screening should preferably be conducted at relatively high Striga infestation levels, between Striga emergence and host plant flowering.     

Efficacy of transsphenoidal hypophysectomy in treatment of dogs with pituitary-dependent hyperadrenocorticism

The long-term survival, disease-free fractions, and the complications of hypophysectomy in 150 dogs with pituitary-dependent hyperadrenocorticism (PDH) were examined in a prospective study. Long-term survival and disease-free fractions in relation to pituitary size were analyzed by the Kaplan-Meijer estimate procedure. The 1-, 2-, 3-, and 4-year estimated survival rates were 84% (95% confidence interval [CI], 76-89%), 76% (67-83%), 72% (62-79%), and 68% (55-77%), respectively. Treatment failures included procedure-related mortalities (12 dogs) and incomplete hypophysectomies (9 dogs). The 1-, 2-, 3-, and 4-year estimated relapse-free fractions were 88% (CI: 80-93%), 75% (64-83%), 66% (54-76%), and 58% (45-70%), respectively. Postoperative reduction of tear production (58 eyes in 47 dogs) was often reversible but remained low until death in 11 eyes of 10 dogs. Central diabetes insipidus (CDI) occurred more frequently (62%) in dogs with enlarged pituitaries than in dogs with nonenlarged pituitaries (44%). Survival and disease-free fractions after hypophysectomy were markedly higher in dogs with nonenlarged pituitaries than in dogs with enlarged pituitaries. Transsphenoidal hypophysectomy is an effective treatment for PDH in dogs. The survival and disease-free fractions after hypophysectomy decrease and the incidence of CDI increases with increasing pituitary size. Therefore, early diagnosis of PDH is important and transsphenoidal hypophysectomy is expected to have the best outcome when used as primary treatment for dogs with nonenlarged or moderately enlarged pituitaries.     

Growth hormone excess and the effect of octreotide in cats with diabetes mellitus

In this prospective study 16 cats with diabetes mellitus were examined for concurrent acromegaly by measuring plasma growth hormone (GH) and insulin-like growth factor-I concentrations, and magnetic resonance imaging (MRI) of the pituitary fossa. Additionally, the effects of octreotide administration on the plasma concentrations of glucose, GH, α-melanocyte-stimulating hormone (α-MSH), adrenocorticotrophic hormone (ACTH), and cortisol were measured.Five cats were diagnosed with hypersomatotropism. The pituitary was enlarged in these 5 cats and in 2 other cats. Six cats that required a maximum lente insulin dosage ≥1.5 IU/kg body weight per injection had pituitary enlargement and 5 of these cats had acromegaly. Plasma concentrations of GH, ACTH, and cortisol decreased significantly after single intravenous administration of the somatostatin analogue octreotide in the acromegalic cats. The effect on GH concentrations was more pronounced in some of the acromegalic cats than in others. In the non-acromegalic cats only ACTH concentrations decreased significantly. In both groups plasma glucose concentrations increased slightly but significantly, whereas α-MSH concentrations were not significantly affected.In conclusion, the incidence of hypersomatotropism with concomitant pituitary enlargement appears to be high among diabetic cats with severe insulin resistance. Some of these cats responded to octreotide administration with a pronounced decrease in the plasma GH concentration, which suggests that octreotide administration could be used as a pre-entry test for treatment with somatostatin analogues.     

Lightmicroscope and submicroscope observations of salts in marine alluvium (India)

In samples from a salt-affected Indian soil series, a curly stem-like salt efflorescence occurred. Unimpregnated soil material and thin sections from these samples, prepared in two different ways, were studied with lightmicroscopy and submicroscopy. The samples came from the Dandi soil series, classified as Halaquepts (Soil Survey Staff U.S.D.A., 1975), which occur extensively on marine alluvium in the semi-arid parts of Gujarat (India). In the unimpregnated samples, several habits of halite (massive crusts, cubical forms, thin threads and curly stem-like forms) were determined with SEM—EDXRA. In large thin sections (8 × 15 cm) covered with a thin glass slide, which could only be studied under a lightmicroscope, no halite was observed. However, another salt of unknown composition, not observed in unimpregnated soil material, was detected. In addition, in small thin sections (2 × 3 cm) with highly polished surfaces, remnants of halite could be observed under the lightmicroscope. With submicroscopy the presence of halite was confirmed and the unknown salt was proved to be a habit of gypsum. This gypsum forms roughly circular shapes, that have diameters varying between 80–200 μm, cracked surfaces and diffuse extinction patterns under crossed polarizers. It occurs along void walls, often in association with halite and in the fine-grained groundmass near voids. Halite occurs along void walls and as angular grains in coarse-grained laminae. The habit of the gypsum observed and the curly stem-like halite on the unimpregnated soil material, have not previously been reported in the literature. The habits of halite need not all be pedogenetic; though the gypsum, a much less soluble salt, probably is pedogenetic. Techniques of preparing thin sections must be improved for the further study of easily soluble salts in soils.     

Influence of Veterinary Care on the Urinary Corticoid: Creatinine Ratio in Dogs

Physical and emotional stresses are known to increase the production and secretion of glucocorticoids by the adrenal cortex in both humans and experimental animals. The urinary corticoid: creatinine (C:C) ratio is increasingly used as a measure of adrenocortical function. In this study we investigated whether a visit to a veterinary practice for vaccination, a visit to a referral clinic for orthopedic examination, or hospitalization in a referral clinic for 1.5 days resulted in increases of the urinary C: C ratio in pet dogs. In experiment 1, owners collected voided urine samples from 19 healthy pet dogs at specified times before and after taking the dogs to a veterinary practice for yearly vaccination. In experiment 2, 12 pet dogs were evaluated in a similar way before and after an orthopedic examination at a referral clinic. In experiment 3, 9 healthy pet dogs were hospitalized for 1.5 days and urine samples were collected before, during, and after this stay. Basal urinary C:C ratios in all experiments ranged from 0.8 to 8.3 × 10^-6. In experiment 1, the urinary C:C ratio after the visit to the veterinary practice ranged from 0.9 to 22.0 × 10^-6. Six dogs had a significantly increased urinary C:C ratio (responders), but in 5 of these dogs the ratio was ≤10 × 10^-6 In experiment 2. 8 of 12 dogs responded significantly with urinary C:C ratios ranging from 3.1 to 27.0 × 10^-6. In experiment 3, 8 of 9 dogs had significantly increased urinary C:C ratios, ranging from 2.4 to 24.0 × 10^-6, in some or all urine samples collected during hospitalization. In 4 dogs urinary C:C ratios 12 hours after hospitalization were still significantly higher than the initial values. Thus, a visit to a veterinary practice, an orthopedic examination in a referral clinic, and hospitalization can be considered stressful conditions for dogs. A large variation occurs in response, and in individual dogs the increases in urinary C:C ratios can exceed the cutoff level for the diagnosis of hyperadrenocorticism. Therefore, urine samples for measurement of the C: C ratio in the diagnosis of hyperadrenocorticism should be collected in the dog's home environment, to avoid the influence of stress on glucocorticoid secretion.     

Primary hyperaldosteronism, a mediator of progressive renal disease in cats

In recent years, there has been renewed interest in primary hyperaldosteronism, particularly because of its possible role in the progression of kidney disease. While most studies have concerned humans and experimental animal models, we here report on the occurrence of a spontaneous form of (non-tumorous) primary hyperaldosteronism in cats. At presentation, the main physical features of 11 elderly cats were hypokalemic paroxysmal flaccid paresis and loss of vision due to retinal detachment with hemorrhages. Primary hyperaldosteronism was diagnosed on the basis of plasma concentrations of aldosterone (PAC) and plasma renin activity (PRA), and the calculation of the PAC:PRA ratio. In all animals, PACs were at the upper end or higher than the reference range. The PRAs were at the lower end of the reference range, and the PAC:PRA ratios exceeded the reference range. Diagnostic imaging by ultrasonography and computed tomography revealed no or only very minor changes in the adrenals compatible with nodular hyperplasia. Adrenal gland histopathology revealed extensive micronodular hyperplasia extending from zona glomerulosa into the zona fasciculata and reticularis. In three cats, plasma urea and creatinine concentrations were normal when hyperaldosteronism was diagnosed but thereafter increased to above the upper limit of the respective reference range. In the other eight cats, urea and creatinine concentrations were raised at first examination and gradually further increased. Even in end-stage renal insufficiency, there was a tendency to hypophosphatemia rather than to hyperphosphatemia. The histopathological changes in the kidneys mimicked those of humans with hyperaldosteronism: hyaline arteriolar sclerosis, glomerular sclerosis, tubular atrophy and interstitial fibrosis. The non-tumorous form of primary hyperaldosteronism in cats has many similarities with "idiopathic" primary hyperaldosteronism in humans. The condition is associated with progressive renal disease, which may in part be due to the often incompletely suppressed plasma renin activity.     

Vasopressin secretion in response to osmotic stimulation and effects of desmopressin on urinary concentrating capacity in dogs with pyometra

OBJECTIVE: To determine vasopressin (VP) secretory capacity during osmotic stimulation and the response to desmopressin treatment in dogs with pyometra and control dogs. ANIMALS: 6 dogs with pyometra before and after ovariohysterectomy and 6 control dogs. PROCEDURE: Urine osmolality (Uosm) was measured during 12 hours. Values measured on the first day defined the basal Uosm pattern. On the second day, dogs were given desmopressin to induce a desmopressin-stimulated Uosm pattern. On day 3, the VP response to osmotic stimulation was examined. RESULTS: Median Uosm on day 1 was 340 mOsm/kg (range, 104 to 1,273 mOsm/kg) and 807 mOsm/kg (range, 362 to 1,688 mOsm/kg) in dogs with pyometra before and after surgery, respectively, and 1,511 mOsm/kg (range, 830 to 1,674 mOsm/kg) in control dogs. Median Uosm during desmopressin treatment was 431 mOsm/kg (range, 168 to 1,491 mOsm/kg) and 1,051 mOsm/kg (range, 489 to 1,051 mOsm/kg) in dogs with pyometra before and after surgery, respectively, and 1,563 mOsm/kg (range, 1,390 to 2,351) in control dogs. In dogs with pyometra, threshold for VP secretion was lower before surgery (median, 340 mOsm/kg; range, 331 to 366 mOsm/kg) than after surgery (median, 358 mOsm/kg; range, 343 to 439 mOsm/kg) or in control dogs (median, 347 mOsm/kg; range, 334 to 360 mOsm/kg). Highest maximum plasma VP values were found in dogs with pyometra. CONCLUSIONS AND CLINICAL RELEVANCE: Dogs with pyometra had increased urine concentration in response to desmopressin but not to the degree of control dogs, whereas VP secretory ability was not reduced.     

Plasma clearance of exogenous creatinine, exo-iohexol, and endo-iohexol in hyperthyroid cats before and after treatment with radioiodine

BACKGROUND: Glomerular filtration rate (GFR) can be measured by clearance methods of different markers showing discrepancies and different reproducibility in healthy cats. Studies comparing different methods of GFR measurement in hyperthyroid cats have not yet been performed. HYPOTHESIS: Plasma clearance of exogenous creatinine (PECCT), exo-iohexol (PexICT), and endo-iohexol (PenICT) could lead to differences in GFR measurement and the need to use the same clearance method when comparing GFR before and after radioiodine treatment in hyperthyroid cats. ANIMALS: Fifteen client-owned hyperthyroid cats. METHODS: GFR was measured 1 day before and 1, 4, 12, and 24 weeks after treatment. Intravenous injection of iohexol was followed immediately by IV injection of creatinine. Plasma creatinine was measured by an enzymatic method. Plasma endo- and exo-iohexol were measured by high-performance liquid chromatography coupled to ultraviolet detection. RESULTS: Globally, the 3 GFR methods resulted in significantly different (P < .001) GFR results. GFR results among the different methods were the same (P= .999) at all time points. All 3 techniques indicated decreasing GFR after (131)I treatment. For each GFR technique, a significant decrease in GFR was observed between time point 0 and all other time points. This decrease stabilized 4 weeks after treatment, with very little decline afterward. CONCLUSION AND CLINICAL IMPORTANCE: It is mandatory to use the same GFR technique in follow-up studies. GFR testing at 4 weeks posttreatment could allow assessment of the final renal functional loss after treatment in hyperthyroid cats.     

Melanocortin 2 receptor antagonists in canine pituitary-dependent hypercortisolism: in vitro studies

Canine hypercortisolism is most often caused by an ACTH-secreting pituitary adenoma (pituitary-dependent hypercortisolism; PDH). An interesting target for a selective medical treatment of PDH would be the receptor for ACTH: the melanocortin 2 receptor (MC2R). In this study we investigated whether two peptide compounds, BIM-22776 (#776) and BIM-22A299 (#299), are effective MC2R antagonists in vitro. Their effects on cortisol production and mRNA expression of steroidogenic enzymes, MC2R and melanocortin 2 receptor accessory protein (MRAP) were evaluated in primary adrenocortical cell cultures (n?=?8) of normal canine adrenal glands. Cortisol production stimulated by 50 nM ACTH was dose-dependently inhibited by #299 (inhibition 90.7?±?2.3% at 5 μM) and by #776 (inhibition 38.0?±?5.2% at 5 μM). The ACTH-stimulated mRNA expression of steroidogenic enzymes, MC2R and MRAP was significantly inhibited by both compounds, but most potently by #299. These results indicate that canine primary cell culture is a valuable in vitro system to test MC2R antagonists, and that these compounds, but especially #299, are effective MC2R antagonists in vitro. To determine its efficacy in vivo, further studies are warranted. Antagonism of the MC2R is a promising potential treatment approach in canine PDH.