Applicability of geomechanical classifications for estimation of strength properties in Brazilian rock masses.

Many authors have been proposed several correlation equations between geomechanical classifications and strength parameters. However, these correlation equations have been based in rock masses with different characteristics when compared to Brazilian rock masses. This paper aims to study the applicability of the geomechanical classifications to obtain strength parameters of three Brazilian rock masses. Four classification systems have been used; the Rock Mass Rating (RMR), the Rock Mass Quality (Q), the Geological Strength Index (GSI) and the Rock Mass Index (RMi). A strong rock mass and two soft rock masses with different degrees of weathering located in the cities of Ouro Preto and Mariana, Brazil; were selected for the study. Correlation equations were used to estimate the strength properties of these rock masses. However, such correlations do not always provide compatible results with the rock mass behavior. For the calibration of the strength values obtained through the use of classification systems, ​​stability analyses of failures in these rock masses have been done. After calibration of these parameters, the applicability of the various correlation equations found in the literature have been discussed. According to the results presented in this paper, some of these equations are not suitable for the studied rock masses.

A comparison of the virulence of three strains of infectious bovine rhinotracheitis virus.

The virulence of three strains of infectious bovine rhinotracheitis (IBR) virus was compared in six-month-old Ayrshire-cross calves. The strains were an isolate from a recent severe outbreak of IBR in Scotland (Strichen strain), the prototype British strain (Oxford strain) and a North American isolate (Colorado strain). The Colorado and Strichen strains produced the characteristic clinical signs and pathological lesions of severe IBR three to four days post infection (p.i.). The Strichen strain was slightly more virulent, possibly as a result of its having been passaged fewer times in tissue culture. In contrast, the Oxford strain produced a mild clinical response with minimal pathological lesions. Virus was recovered from nasal swabs for a longer-period from the calves infected with the Strichen strain (up to 13 days p.i.) and Colorado strain (up to 12 days p.i.) than from the animals infected with the Oxford strain (up to 10 days p.i.). These findings support the suggestion that the recent epidemic of severe IBR in Britain had resulted from the importation of a "new" strain of virus.

Experimental infection of cattle of different ages with infectious bovine rhinotracheitis virus (Strichen strain).

The clinical signs and pathological lesions which developed in various ages of cattle experimentally infected intranasally with the "Strichen" strain of IBR virus were similar to, but generally milder than, those of the field disease. The clinical signs were most severe 4 days after infection and had almost wholly regressed after 12 days. Serum neutralizing antibodies were detected in every animal. Virus was isolated from nasal and ocular swabs for up to 13 days and 10 days, respectively, after infection. The clinical signs and the pathological lesions were more severe in the younger animals.

Reactivation and shedding of bovine herpesvirus 1 following Dictyocaulus viviparus infection.

Three groups of 4 bullocks which had recovered from infectious bovine rhinotracheitis (IBR) were infected 5 months later with Dictyocaulus viviparus larvae. Bovine herpesvirus 1 was recovered from days 7 to 21 post-infection from the nasal secretions of the group given 50 larvae per kilogram and on one occasion from those given 1000 larvae per animal (less than 5 L3 per kg). Virus was not isolated from the animals given 1000 irradiated larvae. Typical clinical signs and lesions of IBR developed in the group from which the virus was isolated regularly.

The ultrastructure of the brush cell in bovine lung.

A cell type with properties similar to those of the brush cell was recognised in the bronchial epithelium of calves. It occurred in small numbers and was not found in airways distal to the small bronchi. The ultrastructural features are described, emphasising the two constant characteristics (i) a dense population of thick apical microvilli and (ii) cytoplasmic filament bundles which extent into the microvilli.

Scanning electron microscopy of the tracheal epithelium of calves inoculated with bovine herpesvirus 1.

Tracheal epithelium was examined by light, scanning electron and transmission electron microscopy at four, five and seven days after calves were infected intranasally with bovine herpesvirus. Similar areas were examined from uninoculated calves. Tracheal epithelial lesions were found in all inoculated calves and their degree of severity did not vary with the interval between inoculation and examination. Extensive loss of cilia leaving areas of tracheal epithelium covered by microvilli was the main feature.

Experimental production of bovine pneumonic pasteurellosis.

Pneumonic pasteurellosis has been reproduced in conventional, weaned, Friesian-cross calves using a strain of Pasteurella haemolytica biotype A, serotype 1 (P haemolytica A1) isolated from a pathologically confirmed incident of bovine pneumonic pasteurellosis. The major clinical findings were pyrexia, hyperpnoea, tachypnoea, nasal discharge and reduced appetite. Fibrinous pneumonia was present in the lungs of animals at necropsy on days 2 and 3 after initial infection while by days 9 and 10 after initial infection many of the areas of fibrinous pneumonia were confined by a fibrous capsule forming well defined nodules. During the experiment natural transmission of the infecting strain of P haemolytica A1 occurred in two control calves which developed a condition identical to that in the artificially infected calves. P haemolytica A1 was repeatedly recovered from the nasopharynx of infected calves and at necropsy throughout the upper and lower respiratory tracts. Seroconversion, as measured by indirect haemagglutination, to the organism developed in all infected calves by days 9 and 10 after initial infection. The clinical, microbiological and pathological findings were identical to those seen in field incidents of bovine pneumonic pasteurellosis involving recently housed, weaned, single-suckled calves.

Immunoglobulin containing cells in the bronchopulmonary system of non-pneumonic and pneumonic calves.

In an examination of the immunoglobulin containing cells in the respiratory mucosa of three-month-old non-pneumonic calves, IgA was found to be the predominant plasma cell type. In calves with cuffing pneumonia there was a marked increase in the plasma cell population in the bronchial wall and IgG1 cells became the major cell type. Similarly in calves with an exudative type of pneumonia IgG1 plasma cells were the significant cell type in the respiratory mucosa but the total number of plasma cells was similar to that found in the non-pneumonic animals. The immunohistochemical results suggest that IgA and, to a lesser extent, IgM are both transported across the mucous membrane via bronchial epithelial secretory cells and submucosal glands.

Experimental production of diffuse pulmonary fibrosis and alveolitis in cattle: the effects of repeated dosage with 3, methyl indole.

Eleven Friesian steers were given 3, methyl indole (3MI) orally at dose rates ranging from 0.1 to 0.3 g/kg. Three of these (group B) received a single oral dose of 0.2 g/kg and subsequently developed respiratory distress. Their plasma 3MI concentrations six hours after dosing were between 2.25 and 7.23 micrograms/ml. The steer with the highest six-hour plasma value died at this stage and the dominant pathological feature was severe pulmonary oedema. The other two steers survived until they were slaughtered 96 hours after dosing; the major pathological findings in them were interstitial emphysema, hyaline membranes and alveolar epithelial hyperplasia. The other eight steers (group C) each received weekly oral doses of 0.1 g 3MI/kg for 10 weeks. One animal died after developing severe respiratory distress following its third dose. Thereafter, the others developed two separate patterns of response. Three steers (subgroup C1) became progressively more tolerant to oral 3MI, even in the face of dose rates increased to 0.2 and 0.3 g/kg during the 11th to 14th weeks of the study and also in the presence of relatively high plasma 3MI concentrations after dosing. One animal was slaughtered after its 10th dose and two after their 14th dose of 3MI; post mortem examinations revealed that their lungs were macro- and microscopically normal. The other steers (subgroup C2) all continued to react after each weekly oral dose of 3MI and their post-dosing plasma 3MI concentrations consistently remained relatively low. Latterly, each of the three steers which survived to the 14th week also exhibited persistent tachypnoea and marked hyperpnoea between dosings. On post mortem examination, in addition to the signs generally associated with acute 3MI toxicity (see above), each of the subgroup C2 steers were found to have diffuse pulmonary fibrosis and an alveolitis. While certain cattle appear to become tolerant to the effects of repeated doses of 3MI, the results of this study clearly demonstrated that, in others, such treatment eventually gives rise to diffuse pulmonary fibrosis and alveolitis.

Some characteristics of a natural infection by parainfluenza-3 virus in a group of calves.

Parainfluenza-3 (Pi3) virus infection in a group of 25 calves is described. The virus was isolated from the lungs of four calve at days 6, 7, 13 and 55 after they were housed together at birth. Intracytoplasmic inclusion bodies were seen by light microscopy in bronchial and bronchiolar epithelial cells of two of these calves. Virus infected cells were detected by electron microscopy in three of the four calves. Haemagglutination inhibition antibodies to Pi3 virus were found in the sera of the calves. Despite the virus being present in the group from one week, a significant increase in antibody titre was found in only two animals although all the calves were in contact with each other during the study period. The pulmonary lesions in the four infected calves consisted of a bronchitis and bronchiolitis with infiltration of the walls and lumena of these structures by neutrophils and an adjacent neutrophil infiltration of alveoli some of which were collapsed.

Distribution of Pasteurella haemolytica in the respiratory tracts of carrier calves and those subsequently infected experimentally with Dictyocaulus viviparus.

Distribution of Pasteurella haemolytica in the respiratory tracts of calves with no apparent clinical signs of illness and those infected experimentally with Dictyocaulus viviparus was determined so as to define carrier sites for this organism. The calves had been positive by nasopharyngeal swab for either P haemolytica A2 or A1 for at least two months or for over a month, respectively, before slaughter. P haemolytica A1 was acquired following horizontal spread from other infected calves. It was observed post mortem that P haemolytica A1 or A2 resided in the tonsils and retropharyngeal lymph nodes of calves of both groups. In addition to these sites, P haemolytica A1 was also isolated from the right cranial lung lobe of one of the calves from the D viviparus infected group although there was no evidence of pasteurella associated pneumonia. It was concluded that tonsil and retropharyngeal lymph nodes appear to be the most important carrier sites for P haemolytica when compared to other tissues of the bovine respiratory tract.

Mycoplasmas and cuffing pneumonia in a group of calves.

The mycoplasmas found in the lungs of 20 calves, housed together for six months, and the related pulmonary pathology are reported. Twelve calves had cuffing pneumonia and in this group there was a significantly higher isolation frequency of Mycoplasma dispar and Ureaplasma spp compared with the non-pneumonic group. Mycoplasma bovirhinis and Acholeplasma laidlawii were isolated from the lungs of calves in both groups. Mycoplasma arginini was not recovered from the lungs of any calf. The significance of the peribronchiolar lymphocytic accumulation in the lungs of the non-pneumonic animals and their differentiation from peribronchiolar lymphocytic cuffs is discussed.

Sequential lesions of experimental bovine pneumonic pasteurellosis.

A strain of Pasteurella haemolytica biotype A serotype 1, which had been isolated from a pathologically-confirmed outbreak of bovine pneumonic pasteurellosis, was used successfully to reproduce the disease in conventional calves. The development of the various pathological features was studied at regular intervals following infection. The acute inflammatory reaction which had developed by day 2 after initial infection was characterised by flooding of the alveoli by oedema and neutrophils together with a mild degree of bronchiolar epithelial necrosis. This progressed to an acute exudative fibrinous pneumonia with extensive involvement of the interlobular septa and often with pleurisy. Subsequently, these pulmonary lesions became walled off by fibrous tissue which became infiltrated by plasma cells and lymphocytes. At this stage organisms could be demonstrated only within these nodules in the lung tissue.

Experimental production of infectious bovine keratoconjunctivitis.

The left eyes of 10 conventional dairy cross calves were inoculated with a pathogenic strain of Moraxella bovis and lesions of infectious bovine keratoconjunctivitis developed in nine of these eyes. M bovis was isolated from all inoculated eyes and lesions developed in five out of 10 eyes which had become naturally infected. The clinical and microbiological findings were similar to those described in field cases.

Pasteurella species isolated from the bovine respiratory tract and their antimicrobial sensitivity patterns.

Pasteurella haemolytica biotype A, serotype 1 (P haemolytica A1) was the most commonly isolated Pasteurella species from 80 calves examined at necropsy from 40 outbreaks of respiratory disease, the majority of which were pathologically confirmed as bovine pneumonic pasteurellosis (transit fever; shipping fever). Similarly, nasopharyngeal swabs from in-contact and apparently healthy calves indicated the widespread presence of P haemolytica A1. Pasteurella multocida and other serotypes of P haemolytica A1 were found including six isolations of P haemolytica T10, a fairly common pathogen in sheep. Approximately two-thirds of the isolates were tested for their antimicrobial sensitivity patterns and the degree of sensitivity for P haemolytica A1, the most frequently isolated serotype, was chloramphenicol (100 per cent), sulphamethoxazole trimethoprim (98 per cent), oxytetracycline (80 per cent), ampicillin (85 per cent), penicillin (82 per cent), streptomycin (3 per cent) and lincomycin (1 per cent).

Clinical and epidemiological features of 15 incidents of severe infectious bovine rhinotracheitis.

Fifteen incidents of infectious bovine rhinotracheitis (IBR) were studied in herds distributed widely throughout northern Britain. Fattening beef animals (10 outbreaks), dairy cattle (four outbreaks) and suckler beef cows (one outbreak) were affected and all bar one incident occurred in housed cattle during the winter. The first signs of illness noticed were a reduced appetite, dullness, coughing and oculonasal discharge. In 13 of the incidents they were observed in cattle purchased from a market within the previous four weeks. In every outbreak, affected animals developed a serous nasal discharge which became purulent in severe cases. In the early stages the nasal mucosa was congested but later yellow-brown diphtheritic plaques developed. In such animals halitosis was always detected. Soft coughing was frequently heard but pneumonia was rarely confirmed ante mortem. Conjunctivitis and ocular discharge were a major finding in 13 incidents and, in severely affected cases, conjunctival oedema was seen. The drooling of saliva was noticed in 14 incidents but congestion of the oral mucous membranes was the only abnormality found on examination of the oral cavity. Diarrhoea was a consistent feature in one outbreak. As a result of contracting this disease beef cattle failed to put on weight for a period of one to eight weeks and the milk yield of lactating dairy cattle decreased markedly. The morbidity rate was high, being more than 90 per cent in 10 incidents. The mortality rate varied considerably but 7 to 8 per cent of the animals died, or were culled, in three outbreaks. The clinical signs were most severe on intensive units with a high turnover of cattle.

The pathological features of severe cases of infectious bovine rhinotracheitis.

In recent outbreaks of infectious bovine rhinotracheitis (IBR) in Britain a proportion of the animals affected developed a severe clinical disease characterised, at necropsy, by widespread damage to the respiratory tract. They had necrotising rhinitis, pharyngitis, laryngotracheobronchitis with extensive pseudomembrane formation and severe pneumonia with or without interstitial emphysema. Renal infarction was seen in approximatley half of the cases. The central nervous system was not affected in any of the 25 animals with severe IBR examined in this study. Tissues from the respiratory tract of 14 animals were examined for the presence of bovine herpesvirus 1 and the virus was isolated from the nasal passages of 11 and the lungs of four. Mycoplasma bovis was frequently isolated in large numbers from both the upper and lower respiratory tract.

Effect of anti-prostaglandin therapy in experimental parainfluenza type 3 pneumonia in weaned, conventional calves.

An acute pneumonia was induced experimentally in 10, 10- to 12-week-old conventional calves by administration into the upper airways of a pathogenic strain of parainfluenza type 3 (PI3) virus. The experimental calves had been selected on the basis of freedom from clinical evidence of respiratory and other diseases, freedom from current infection by PI3 virus as judged by repeated nasopharyngeal swabbing and freedom from earlier PI3 virus infection as judged by their lack of significant levels of serum antibody to that virus. The infection procedure was deemed to have been successful in that infection was established with subsequent seroconversion, clinical signs of a febrile pneumonia arose soon after the administration of virus, histopathological changes characteristic of PI3 pneumonia developed and the presence of PI3 virus antigen was demonstrated by immunofluorescence in association with those lesions. Treatment of five of the pneumonic calves was carried out on days 1, 2 and 3 of the trial using the anti-prostaglandin compound flunixin meglumine and that treatment appeared to be of benefit in that in the test calves there was a prompt cessation of coughing with fewer fevers and lower respiratory rates as compared with the untreated controls. The drug did not appear to influence PI3 infection rates but its administration was associated with a marked reduction in the extent of pulmonary consolidation, probably as the result of its known ability to limit the acute inflammatory response.

Applicability of geomechanical classifications for estimation of strength properties in Brazilian rock masses

ABSTRACT Many authors have been proposed several correlation equations between geomechanical classifications and strength parameters. However, these correlation equations have been based in rock masses with different characteristics when compared to Brazilian rock masses. This paper aims to study the applicability of the geomechanical classifications to obtain strength parameters of three Brazilian rock masses. Four classification systems have been used; the Rock Mass Rating (RMR), the Rock Mass Quality (Q), the Geological Strength Index (GSI) and the Rock Mass Index (RMi). A strong rock mass and two soft rock masses with different degrees of weathering located in the cities of Ouro Preto and Mariana, Brazil; were selected for the study. Correlation equations were used to estimate the strength properties of these rock masses. However, such correlations do not always provide compatible results with the rock mass behavior. For the calibration of the strength values obtained through the use of classification systems, ​​stability analyses of failures in these rock masses have been done. After calibration of these parameters, the applicability of the various correlation equations found in the literature have been discussed. According to the results presented in this paper, some of these equations are not suitable for the studied rock masses.