Plasma digoxin concentration in dogs with mitral regurgitation.

Fifteen and eight mature beagles, without (normal group) and with experimental mitral regurgitation (MR group), respectively, were given 0.02 mg/kg/day digoxin powder for 10 days orally. The optimum time for sample collection after administration of digoxin was observed to be 8-18 hr and 10-22 hr in the normal and MR groups, respectively. In both groups, a stable concentration was reached after 3-5 days of treatment. No differences in plasma level were observed between sexes. The optimum concentration of digoxin was attained at an earlier stage than has been previously reported for both dogs and humans.     

Influence of Body Weight and Food Density on Kinetics of Ammonia Excretion by the Brine Shrimp Artemia franciscana

This study was undertaken to quantify the relationships between the rate of ammonia excretion by brine shrimp and dry weight (body size) and food density. Measurements of the rate of ammonia excretion of the brine shrimp were made at 25 C in darkness. Under these conditions, the excretion rate of ammonium-nitrogen can be generalized as a function of body weight and food (Nannochloropsis sp.) density. The relationship between the body weight (W) and excretion rate of ammonium nitrogen (E_N) is expressed as E_N=α W^γ, where α is the metabolic level. The parameter α is dependent on ration, such that α=α_o±α_r where α_o= metabolic level in starvation and α_r= the metabolic level which increased with feeding or changed with the food density. In experiments in which the animal starved, the equation above becomes E_N=α_oW^γ, and the values of α and γ were 0.22 and 0.93, respectively. The rate of ammonium excretion rose from 5.42 × 10^?4 to 2.28 × 10^?1μg N/animal/h as dry weight measured from 1.57 × 10^?3? 1.04 mg dry weight per animal. Next, it is convenient to express α_r as α_r=α_fmax= (1 ? 10^?kc), where α_fmax is the maximum rate of α_f at saturated level of food density, C is the mean cell density, and k is a constant defining the rate of change of the metabolic rate with cell density. Therefore, the rate of ammonia excretion by brine shrimp could be expressed as E_N=α_o [1 ? a(l ? 10^?kC)]W^γ, and a =α_fmax/α_o. The values of the kinetics parameters obtained from experiments where shrimp were fed were a = 2.3 and k = 0.15×10^?7. Consequently, the maximum rate of ammonia excretion at a saturated food density is equivalent to 3.3 times the rate of animals that are not fed.     

Effect of progesterone on ovulation in the hypophysectomised hen

1. One hundred and seven laying hens were hypophysec‐tomised to clarify the relationship between hypophysectomy and the effect of progesterone (P4) on ovulation.

2. Hens were hypophysectomised at 6 intervals from 4.5 to 11.0 h before the expected time of ovulation. Ovulation occurred in the hens operated on from 4.5 to 7.3 h, but did not take place in birds operated on from 9.2 to 9.8 h before the expected time of ovulation.

3. When a single dose of P4 (2 mg/hen) was injected iv immediately after the removal of the anterior pituitary from 7.5 to 9.8 h before the expected time of ovulation, ovulation was induced. However, the percentage of hens responding decreased in proportion to the lapse of time between the hypophysectomy and the expected time of ovulation. No ovulation was induced in hens which were hypophysectomized and given P4 10.2 to 11.0 h before the expected time of ovulation.

4. It is suggested that ovulation is induced by P4 alone possibly in the absence of preovulatory gonadotrophins and that P4 acts directly on the ovary to induce follicle rupture.     

Catalog of Micro-Tom tomato responses to common fungal, bacterial, and viral pathogens

Lycopersicon esculentum cultivar Micro-Tom is a miniature tomato with many advantages for studies of the molecular biology and physiology of plants. To evaluate the suitability of Micro-Tom as a host plant for the study of pathogenesis, Micro-Tom plants were inoculated with 16 well-known fungal, bacterial, and viral pathogens of tomato. Athelia rolfsii, Botryotinia fuckeliana, Oidium sp., Phytophthora infestans, and Sclerotinia sclerotiorum caused typical symptoms and sporulated abundantly on Micro-Tom. Micro-Tom was resistant to Alternaria alternata, Corynespora cassiicola, and Fusarium oxysporum. When Micro-Tom was inoculated with 17 isolates of Ralstonia solanacearum, many isolates induced wilt symptoms. Agrobacterium tumefaciens also was pathogenic, causing crown galls on stem tissue after needle prick inoculation. In Micro-Tom sprayed with Pseudomonas syringae pv. tomato, P. s. pv. tabaci, or P. s. pv. glycinea, bacterial populations did not increase, and yellow lesions appeared only on leaves sprayed with P. s. pv. tomato. Tomato mosaic virus, Tomato aspermy virus, and Cucumber mosaic virus systemically infected Micro-Tom, which developed symptoms characteristic of other cultivars of tomato after infection with the respective virus. These results indicated that Micro-Tom was generally susceptible to most of the important tomato pathogens and developed typical symptoms, whereas certain pathogens were restricted by either hypersensitive resistance or nonhost resistance on Micro-Tom. Therefore, an assortment of Micro-Tom–pathogen systems should provide excellent models for studying the mechanism of susceptible and resistant interactions between plants and pathogens.     

Indole-3-acetic acid biosynthesis in <Emphasis Type="Italic">Aciculosporium take</Emphasis>, a causal agent of witches' broom of bamboo

 Aciculosporium take (Ascomycota; Clavicipitaceae) is a causal agent of witches' broom of bamboo plants. The symptoms of this disease are believed to be induced by plant hormones, particularly auxins. Indole-3-acetic acid (IAA) was identified in cultures of this fungus in an l-tryptophan-supplemented liquid medium. IAA production was confirmed on 30 isolates of A. take from various hosts and locations at levels up to 1 mg/l. The biosynthetic pathway of IAA in A. take culture was examined by analyzing intermediate products and by feeding experiments. The results showed that the indole-3-pyruvic acid pathway (l-tryptophan → indole-3-pyruvic acid → indole acetaldehyde → IAA) was the dominant pathway in A. take. Received: June 3, 2002 / Accepted: July 25, 2002     

Identification of the core motif of the BRCA2 C-terminal RAD51-binding domain by comparing canine and human BRCA2

Mammary tumors are the most common tumors in women and non-spayed female dogs. One of the reasons for mammary tumors is mutations of the tumor suppressor gene, BRCA2. BRCA2 participates in homologous recombination repair by interacting with the RAD51 recombinase. BRCA2 has two RAD51-binding domains, consisting of BRC repeats and the C-terminal RAD51-binding domain, respectively. Although several studies have addressed the function of the C-terminal RAD51-binding domain of human BRCA2, the amino acid sequences required for the RAD51-interaction activity remain unclear. In this study, the C-terminal RAD51-binding domains of canine and human BRCA2 were compared; the canine domain displayed a weaker interaction with RAD51. This difference was attributed to the C-terminal portion of the domain via a comparison between canine and human domains. Furthermore, peptides shorter than those previously reported displayed RAD51-interacting activity, and a core motif of this domain consisting of 25 amino acids was identified. Since a mutation (S3323N) was reported in the core motif of this domain, the effect of this mutation was evaluated. The mutant exhibited similar RAD51-binding activity as that of the wild-type protein, suggesting that the mutation was functionally neutral. These data suggested that the C-terminal portion of the BRCA2 C-terminal RAD51-binding domain influenced its RAD51-interaction activity, and a minimum core motif of 25 amino acids was identified in this domain. These data may help clarify BRCA2 function, as well as the tumorigenic effects of BRCA2 mutation.     

Mesh-like vascular changes in copper deficiency-induced rat cardiomyopathy

The pathological effects of copper deficiency (COD) are well known. However, the pathogenesis of cardiomyopathy resulting from COD remains unclear. In this study, aimed to elucidate the pathogenesis of COD-induced cardiomyopathy by examining the morphology of the cardiovascular system in copper-deficient rats using histopathology, immunohistochemistry, and scanning and transmission electron microscopy. Changes detected in the myocardium and interstitium were consistent with those reported for COD. Morphological changes included mesh-like changes in the capillary endothelial cells that appear to be a novel finding in COD-induced cardiomyopathy. These changes are hypothesized to result from abnormal vascular remodeling following damage to the basement membrane and due to the mechanical effects of myocardial contractions. Although cardiomyopathy may be associated with microcirculatory disorders arising from these lesions, further investigations are necessary to demonstrate a causal relationship between the pathogenesis of cardiomyopathy and the contribution of these lesions to disease progression.     

Effect of relationships among clinical mastitis incidence,reproductive performance,and culling rate on the lifetime of dairy cows at Hiroshima University Farm

Farm managers' decision to cull dairy cows is based on the cows' milk production, history of disorder(s), and reproductive performance, each of which affects dairy cows' lifetime (herd life and productive lifespan). We investigated the relationships among the incidence of clinical mastitis (CM), the reproductive performance, and the culling rate. We also assessed the effects of these relationships on the lifetimes of dairy cows, using the records made before and after the introduction of an automatic milking system (AMS) at Hiroshima University Farm. Milk yield, CM incidence density, and culling rate of dairy cows increased after the AMS introduction. The CM incidence was associated with an elongation of the calving interval in cows with the same parity. CM in the 1st parity might have caused the reductions of the cows' lifetime and their parity at culling. A higher age at first calving (AFC) was associated with an increase in culling rate but did not lead to a significant decrease in lifetime. Investigations of the factors mediating CM in the 1st parity or AFC with CM incidence or culling rate in the later stages might contribute to the control of lifetime of dairy cows.     

Development of a Simple Method for Evaluation of Water Absorption Rate and Capacity of Rice Flour Samples

A simple method employing a commercially available canister was developed for the determination of mode of water absorption of rice flour samples. The samples prepared by four different grinding methods were used to analyze water absorption. The total amount of water in a flour sample was described by using an exponential model. Capacity and rate of water absorption of the samples were determined, and the relationship to baking quality of partially substituted rice bread was investigated. The water absorption was highly dependent on the method of grinding. Flours produced by wet jet‐milling of the grains, which absorbed a small amount of water at high speed, were most suitable for rice bread. The method was applicable to other food powders, provided that flour particles do not stick together or swell immediately upon contact with water.