Error assessment in decision-tree models applied to vegetation analysis

Methods were developed to evaluate the performance of a decision-tree model used to predict landscape-level patterns of potential forest vegetation in central New York State. The model integrated environmental databases and knowledge on distribution of vegetation. Soil and terrain decision-tree variables were derived by processing state-wide soil geographic databases and digital terrain data. Variables used as model inputs were soil parent material, soil drainage, soil acidity, slope position, slope gradient, and slope azimuth. Landscapescale maps of potential vegetation were derived through sequential map overlay operations using a geographic information system (GIS). A verification sample of 276 field plots was analyzed to determine: (1) agreement between GIS-derived estimates of decision-tree variables and direct field measurements, (2) agreement between vegetation distributions predicted using GIS-derived estimates and using field observations, (3) effect of misclassification costs on prediction agreement, (4) influence of particular environmental variables on model predictions, and (5) misclassification rates of the decision-tree model. Results indicate that the prediction model was most sensitive to drainage and slope gradient, and that the imprecision of the input data led to a high frequency of incorrect predictions of vegetation. However, in many cases of misclassification the predicted vegetation was similar to that of the field plots so that the cost of errors was less than expected from the misclassification rate alone. Moreover, since common vegetation types were more accurately predicted than rare types, the model appears to be reasonably good at predicting vegetation for a randomly selected plot in the landscape. The error assessment methodology developed for this study provides a useful approach for determining the accuracy and sensitivity of landscape-scale environmental models, and indicates the need to develop appropriate field sampling procedures for verifying the predictions of such models.     

Whole blood re-calcification time in equine colic

Whole blood re-calcification times were evaluated as a measure of endotoxin-associated coagulopathy in horses. First, the effects of endotoxin concentration and duration of in vitro incubation of citrated whole blood with endotoxin on the whole blood re-calcification time of blood collected from healthy horses were determined. Increasing concentrations or incubation times of endotoxin accelerated the whole blood re-calcification time. This effect was attributed mainly to increased monocyte thromboplastin activity. Second, whole blood re-calcification time, a clotting profile, plasma factor VII activity and plasma endotoxin concentration on blood samples obtained from 35 equine colic patients and 10 healthy horses were determined. Compared with healthy horses, colic patients had a longer mean whole blood re-calcification and prothrombin time, lower per cent factor VII activity and higher mean fibrin degradation products concentration. Within the colic patient group, horses that did not survive had detectable endotoxin in plasma, longer whole blood re-calcification and prothrombin times, and lower plasma factor VII activity, compared with colic patients that survived. These data indicate that colic patients with endotoxaemia experience hypercoagulable states, followed by consumptive coagulopathy. Although the cause of endotoxin-associated coagulopathy is likely multi-factorial, increased expression of monocyte thromboplastin activity may be involved in the pathogenesis of coagulopathy. The whole blood recalcification time is a simple, fast and inexpensive way to detect coagulopathy during endotoxaemia and determine the prognosis for survival.     

Surgical treatment of sacral fracture in a horse

An 8-year-old Arabian stallion had signs of severe tailhead pruritus and slowly progressive loss of tail tone for 3 months. Palpation per rectum and radiography of the sacrocaudal region revealed a transverse, ventrally displaced fracture of the caudal portion of the sacrum. Surgical decompression and tail amputation resulted in complete recovery of athletic and reproductive function. Evidence of cauda equina neuritis was not seen on histologic examination of nerve roots obtained at surgery.     

Radiographic development of canine hip dysplasia.

The radiographic changes observed in the development of CHD in the dog are complex and not fully understood despite years of research. Moderate to severe CHD is relatively easy to diagnose using standard radiographic views and evaluation techniques. However, early detection of mild or borderline CHD continues to be difficult to reliably detect radiographically. Efforts continue to be made to develop new views, techniques, and evaluation methods that will improve the radiographic evaluation of CHD. Until better methods are proven, the standard ventrodorsal leg extended view, evaluated by an experienced reviewer, will remain the method of choice for radiographic detection of CHD.     

Genetic relatedness of disease-associated field isolates of bovid herpesvirus type 4

Eight field isolates of bovid herpesvirus type 4 (BHV-4) were examined by restriction analysis and Southern blot hybridization with respect to their relatedness to one another and to the BHV-4 prototype strain DN-599. Isolates were obtained from cattle exhibiting a range of disease states including abortion, pneumonia, enteritis, metritis, and vaginal blisters. Initial growth studies of all 9 viruses were performed and revealed that the overall rate of virus growth was slow when compared with that of other herpesviruses. Infection with each virus also resulted in the formation of large fused cells, which in addition to the slow growth rate, indicated that the isolates were of the cytomegalovirus type. Further studies to characterize and compare the various BHV-4 isolates were undertaken by obtaining cell-free virus from infected cell populations. Viral isolates were purified and used as a source of BHV-4 DNA. Purified DNA, representing each of the 8 field isolates and the prototype strain DN-599, were each cleaved with 3 restriction enzymes and were separated by agarose-gel electrophoresis, and the resultant fragment patterns were compared. In general, genomic fragments of the field isolates corresponded to those generated by cleavage of DN-599 DNA, with the exception of the abortion-associated isolate 83-3572. Additional minor differences were also seen between DN-599 DNA and DNA from the other field isolates, but the overall restriction patterns were similar. To confirm that all isolates were members of the BHV-4 type, hybridization studies were performed using DN-599.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interactive effects of dietary levels of tryptophan and protein on voluntary feed intake and growth performance in pigs, in relation to plasma free amino acids and hypothalamic serotonin.

The effects of dietary level of tryptophan (TRP) and CP content and composition on voluntary feed intake, growth performance, and carcass characteristics in finishing pigs were studied in two experiments, with an equal number of females and castrated males. In Exp. 1, involving 120 Large White pigs from 44 to 99 kg BW with ad libitum access to feed, six treatments were compared according to a 2 x 3 factorial arrangement: 1) two levels of TRP (.09 and .13%), suboptimal and optimal for growth, respectively, 2) three types of CP supply (a 12.5% CP diet based on corn-soybean meal, and adequately balanced for essential amino acids [EAA] other than TRP; 15.7% CP diet with additional protein from corn gluten meal; 16.2% CP diet with additional nonessential amino acids [NEAA, in the form of L-glutamic acid.HCl and glycine], and the same levels of EAA as in the 12.5% CP diet. In Exp. 2, including four of the six previous factorial combinations (.09 and .13% TRP, 12.3 and 15.8% CP with additional protein), 32 pigs of 50-kg initial BW were used during 21 d, and further observations on meat quality characteristics, plasma free amino acid levels, and serotonin concentrations in the posterior hypothalamus were made. The major observed effects were interactions of different magnitude according to sex between TRP level and the amount and the composition of additional CP. At the suboptimal level of .09% TRP, the increase in protein content severely decreased daily feed intake and growth compared with the .13% level, especially in females. Conversely, the addition of NEAA at both TRP levels had little effect on daily feed intake and growth. Deficiency of TRP exerted a significant increase of pH in adductor femoris and semimembranosus muscles measured 45 min and 24 h postmortem, but only in females. Voluntary feed intake, as affected by dietary TRP and CP levels, was linearly related with concomitant changes in TRP to large neutral amino acids (TRP:LNAA) ratio both in feed and in plasma, which in turn was directly associated to hypothalamic serotonin concentration. It was concluded that an overly low concentration of serotonin in the hypothalamus, especially in females, as a result of TRP:LNAA imbalance, could be involved in the reduction of voluntary feed intake.     

Bronchial cartilage dysplasia with multifocal lobar bullous emphysema and lung torsions in a pup.

Bronchial cartilage dysplasia is believed to have caused lobar bullous emphysema in a 5-month-old Chow Chow that had exercise intolerance, progressive dyspnea, and episodic cough. Radiography of the thorax revealed hyperlucency of the left hemithorax, displacement of the mediastinum and heart to the right, and flattening of the diaphragm. The pup died shortly after the radiographs were obtained. Necropsy revealed massive hyperinflation with 180 degrees torsion of the cranial portion of the left cranial lung lobe, and hyperinflation with less than 180 degrees torsion of the right accessory lung lobe. Histologic examination of the affected lung lobes revealed a lack of bronchial cartilage, loss and displacement of alveolar walls, and bulla formation that resembled congenital (infantile) lobar emphysema of human beings. In this pup, lung lobe torsions may have been predisposed by bronchial cartilage dysplasia.     

Effects of sterol biosynthesis-inhibiting (SBI) fungicides on cytochrome P-450 oxygenations in fungi

The fungicides miconazole, fenarimol, and etaconazole block ergosterol biosynthesis in fungi by inhibiting sterol 14α-demethylation, which is mediated by a cytochrome P-450 enzyme. The sensitivity of cytochrome P-450-dependent hydroxylation or demethylation of several substrates to these fungicides and similar compounds was compared to that of fungal growth and sterol 14α-demethylation. Demethylation of p-chloro-N-methylaniline (PCMA) by sporidia of Ustilago maydis and 11α-hydroxylation of progesterone by Aspergillus nidulans were relatively insensitive to these compounds and to metyrapone. The ability of a sterol 14α-demethylation-deficient mutant to demethylate PCMA indicates that this substrate is not demethylated by the sterol 14α-demethylation system of U. maydis. The 14α-hydroxylation of progesterone by cells of Curvularia lunata was quite sensitive to the three fungicides, and also to metyrapone and isopropylphenylimidazole. This system was less sensitive to the three fungicides than sterol 14α-demethylation, but was appreciably more sensitive than PCMA demethylation. A study of progesterone 14α-hydroxylation in cell-free preparations of C. lunata showed the reaction to be inhibited by CO, and to be competitively inhibited by low concentrations of miconazole. These data suggest that the primary action of sterol biosynthesis-inhibiting (SBI) fungicides is competitive inhibition of sterol/steroid-type cytochrome P-450 enzymes rather than interference with the function of sterol carrier proteins or enzyme-modulating phospholipids.     

The Effect of R Factor Transfer on Bacterial Growth Rates an in Vitro Study

It has been studied whether R factor transfer had an inhibitory effect on the growth rate of Escherichia coli in mixed cultivation. A total of 39 antibiotic resistant E. coli strains were grown together with E. coli K12 W 3132 as prospective recipient. Thirteen crosses turned out successfully. When comparing generation times for these crosses with those of negative crosses no difference could be demonstrated. This, however, does not exclude that R factor transfer impairs bacterial growth capacity at a level which can not be detected in a short-term experiment.