Quantitative structure-activity relationship modeling of peptide and protein behavior as a function of amino acid composition

A quantitative structure-activity relationship (QSAR) modeling approach based on the location of each amino acid along three axes obtained by principal component analysis (called z scores) was extended to physical and functional properties of proteins, where the proportion of particular amino acids rather than a precise sequence is the determining factor. Coomassie Brilliant Blue spectral responses to amino acid homopolymers (R = 0.926) and proteins, either as a function of their contents of six basic and aromatic amino acids (R = 0.976) or as a function of the contributions of these amino acids to the three z scores (R = 0.935), were modeled. The ultraviolet absorbance of proteins was modeled in terms of the z score contributions of tyrosine, tryptophan, and cysteine (R = 0.995). Modeling many protein functional properties in this manner appears to be possible. An approach to modeling peptide behaviors that depend on short sequences of amino acids was also considered.     

Comparison of oil and phytosterol levels in germplasm accessions of corn, teosinte, and Job's tears

Seeds of 49 accessions of corn (Zea mays ssp. mays), 9 accessions of teosinte (Zea species that are thought to be ancestors and probable progenitors to corn), and 3 accessions of Job's tears (Coix lacryma), obtained from a germplasm repository, were ground and extracted with hexane. Whole kernel oil yields and levels of four phytonutrients (free phytosterols, fatty acyl phytosterol esters, ferulate phytosterol esters, and gamma-tocopherol) in the oils were measured. Among the seeds tested, oil yields ranged from 2.19 to 4.83 wt %, the levels of ferulate phytosterol esters in the oil ranged from 0.047 to 0.839 wt %, the levels of free phytosterols in the oil ranged from 0.54 to 1.28 wt %, the levels of phytosterol fatty acyl esters in the oil ranged from 0.76 to 3.09 wt %, the levels of total phytosterols in the oil ranged from 1.40 to 4.38 wt %, and the levels of gamma-tocopherol in the oil ranged from 0.023 to 0.127 wt %. In general, higher levels of all three phytosterol classes were observed in seed oils from accessions of Zea mays ssp. mays than in seed oils from accessions of the other taxonomic groups. The highest levels of gamma-tocopherol were observed in teosinte accessions.     

An autoinhibitory mechanism for nonsyntaxin SNARE proteins revealed by the structure of Ykt6p

Ykt6p is a nonsyntaxin SNARE implicated in multiple intracellular membrane trafficking steps. Here we present the structure of the NH2-terminal domain of Ykt6p (Ykt6pN, residues 1 to 140). The structure of Ykt6pN differed entirely from that of syntaxin and resembled the overall fold of the actin regulatory protein, profilin. Like some syntaxins, Ykt6p adopted a folded back conformation in which Ykt6pN bound to its COOH-terminal core domain. The NH2-terminal domain plays an important biological role in the function of Ykt6p, which in vitro studies revealed to include influencing the kinetics and proper assembly of SNARE complexes.     

Clinical features of dilated cardiomyopathy in Great Danes and results of a pedigree analysis: 17 cases (1990-2000)

OBJECTIVE: To determine clinical features of dilated cardiomyopathy (DCM) in Great Danes and to determine whether DCM is familial in this breed. DESIGN: Retrospective study. ANIMALS: 17 Great Danes with DCM. PROCEDURE: Medical records of Great Danes in which DCM was diagnosed on the basis of results of echocardiography (fractional shortening < 25%, end-systolic volume index > 30 ml/m2 of body surface area) were reviewed. Pedigrees were obtained for affected animals, as well as for other Great Danes in which DCM had been diagnosed. RESULTS: Dilated cardiomyopathy appeared to be familial and was characterized by ventricular dilatation, congestive heart failure (left-sided or biventricular), and atrial fibrillation. Pedigree analysis suggested that DCM was inherited as an X-linked recessive trait, but the mode of inheritance could not be definitively identified. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that DCM may be an X-linked recessive trait in Great Danes. Thus, dogs with DCM probably should not be used for breeding, and female offspring of affected dogs should be used cautiously. Male offspring of affected females are at an increased risk of developing DCM and should be evaluated periodically for early signs of disease. Results of pedigree analysis were preliminary and should be used only as a guide for counseling breeders, rather than as a basis for making breeding decisions.     

Development of a functional scoring system in dogs with acute spinal cord injuries

OBJECTIVES: To develop and compare the reliability of 2 methods of scoring pelvic limb gait in dogs recovering from thoracolumbar spinal cord injuries and to use this scoring system to determine the rate and level of functional recovery of dogs with acute thoracolumbar intervertebral disk herniations. ANIMALS: 46 dogs with spinal cord injuries resulting from intervertebral disk herniations. PROCEDURE: Dogs' gaits were videotaped at different time intervals after injury. In phase 1 of the study, the stages of recovery of pelvic limb function were identified, and a numeric scoring system was devised to reflect that recovery. In phase 2, pelvic limb gait was scored by different observers, using a numeric and a visual analog scale. Intra- and interobserver coefficients of variability of both methods were compared. In phase 3, pelvic limb function was scored, using the numeric scale at various intervals after acute thoracolumbar disk herniations. RESULTS: The numeric scale was significantly more reliable than the visual analog scale when both intra- and interobserver coefficients of variability were evaluated. Dogs that were paraplegic with no deep pain sensation recovered at different rates during the first 3 months, whereas dogs that were paraplegic with deep pain sensation typically recovered within 1 month of injury. CONCLUSIONS: Pelvic limb gait of dogs recovering from thoracolumbar spinal cord injuries can be reliably quantified, using a numeric scale. This scale will facilitate the performance of clinical trials aimed at improving the outcome of acute spinal cord injuries.     

Use of echocardiography for the diagnosis of heartworm disease in cats: 43 cases (1985-1997)

OBJECTIVE: To determine the usefulness of echocardiography in the diagnosis of heartworm disease in cats and to compare this modality with other tests. DESIGN: Retrospective study. ANIMALS: 43 cats with heartworm infection that had echocardiographic examinations at 2 veterinary teaching hospitals between 1985 and 1997. Twenty-two of these 43 cats also underwent radiography of the thorax and heartworm antibody and heartworm antigen testing. PROCEDURE: Cats were determined to be infected with Dirofilaria immitis infection on the basis of 1 or more of the following findings: positive modified Knott or antigen test result, echocardiographic evidence of heartworm disease, or confirmation of the disease on postmortem examination. The percentage of echocardiographs in which heartworms were evident was compared with the percentage of radiographs in which pulmonary artery enlargement was evident and results of antigen or antibody tests in cats in which all tests were performed. RESULTS: Overall, heartworms were detectable by use of echocardiography in 17 of 43 cats, most often in the pulmonary arteries. In the 22 cats in which all tests were performed, antibody test results were positive in 18, antigen test results were positive in 12, and pulmonary artery enlargement was evident radiographically and heartworms were identifiable echocardiographically in 14. Heartworm infection was diagnosed exclusively by use of echocardiography in 5 cats in which the antigen test result was negative. CONCLUSIONS AND CLINICAL RELEVANCE: Although echocardiography was less sensitive than antigen testing, it was a useful adjunctive test in cats that had negative antigen test results in which there was a suspicion of heartworm disease. The pulmonary arteries should be evaluated carefully to increase the likelihood of detection of heartworms echocardiographically.     

Treatment of dogs infected with Hepatozoon americanum: 53 cases (1989-1998)

OBJECTIVE: To determine clinical and pathologic findings before and after short-term (group 1) and long-term (group 2) treatment in dogs with Hepatozoon americanum infection. DESIGN: Retrospective study. ANIMALS: 53 dogs with H. americanum infection. PROCEDURE: Medical records of dogs that were treated for hepatozoonosis diagnosed on the basis of meront or merozoite stages in skeletal muscle were reviewed. RESULTS: Circulating gametocytes of H. americanum were identified in 12 of 53 dogs. Dogs were treated with various drugs, including toltrazuril, trimethoprim-sulfadiazine, clindamycin, pyrimethamine, and decoquinate. Mean WBC counts prior to treatment were 85,700 and 75,200 cells/microl in groups 1 and 2, respectively, and 1 month after initiation of treatment were 12,600 and 14,600 cells/microl, respectively. Initial response to treatment was excellent in all dogs. Twenty-three of 26 dogs in group 1 relapsed at least once and died within 2 years; mean (+/- SD) survival time was 12.6+/-2.2 months. Twenty-two of 27 group-2 dogs survived; 11 dogs had no clinical signs and were still receiving decoquinate (mean duration of treatment, 21 months), 11 dogs had no clinical signs after treatment for 14 months (range, 3 to 33 months; mean survival time, 39 months [range, 26 to 53 months]), 2 dogs were lost to follow-up, and 3 dogs were euthanatized because of severe disease. CONCLUSIONS AND CLINICAL RELEVANCE: Although no treatment effectively eliminated the tissue stages of H. americanum, treatment with trimethoprim-sulfadiazine, clindamycin, and pyrimethamine followed by long-term administration of decoquinate resulted in extended survival times and excellent quality of life.