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Biomedical subjects

B E Brooker

Publications and source records attributed to B E Brooker.

At least 19 recordsLinked to original sources
PubMed1996

Sampling and transportation of food materials for freeze-fracture from the industrial environment.

A simple holder is described which enables the multiple sampling of food materials for freeze-fracturing in an industrial environment. The holder allows frozen samples to be transferred safely to the laboratory under liquid nitrogen for freeze-fracturing and examination by transmission electron microscopy. The technique has been successfully applied to sampling food from pilot plant and production lines under factory conditions.

Food Handling↗
PubMed1986

Hyperacute Escherichia coli mastitis of cattle in the immediate post-partum period.

The pathology of hyperacute coliform mastitis was studied in 5 post-parturient cows. In all infected quarters infiltration of neutrophils was negligible. In all except one case there was severe damage to the ductular and secretory system, involving most areas of the gland. Bacteria were dense in infected alveoli, and there was evidence of substantial phagocytosis of bacteria by the secretory epithelium. The exception showed a large lesion in the middle of the gland from which the spread was ductular; other infections were consistent with spread via the teat canal. The organisms were largely confined to the ductular/secretary lumen and there was little invasion of the parenchyma. The severity of the disease was considered due to the absence of the inflammatory response seen in mid lactation.

Acute Disease↗
PubMed1985

Ultrastructural features of bovine mammary epithelial cells grown on collagen gels.

Bovine mammary epithelial cells cultured on floating gels of rat tail collagen showed two principal cell types, columnar and squamous, with ultrastructural features resembling secretory and myoepithelial cells respectively. Cultures of freshly prepared cells released alpha-lactalbumin into the culture medium and in some cases contained fat droplets, although these did not appear to be released. No ultrastructural evidence of casein synthesis was observed. A notable feature was the failure to secrete a continuous basement membrane. Intermediate filaments were present in abundance in squamous epithelial cells.

Animals↗
PubMed1984

The adhesion of coagulase negative staphylococci to human skin and its relevance to the bacterial flora of milk.

Twenty-eight isolates of coagulase negative staphylococci were obtained from nipple swabs provided by one non-lactating woman and five nursing mothers. All but two of these isolates were shown by scanning electron microscopy to adhere to the surface of human skin. Experiments with frozen sections of human skin confirmed and extended these results by showing that isolates exhibited one of three patterns of adhesion, suggesting that there are three different adhesion receptors on epidermal cells. It is proposed that adhesion of staphylococci to the nipple and areolar epidermis provides a mechanism whereby large numbers of bacteria, nourished by residues of milk and saliva, are maintained on the surface of the skin.

Adhesiveness↗
PubMed1984

The effect of Escherichia coli endotoxin and culture filtrate on the lactating bovine mammary gland.

The pathogenesis of coliform mastitis was studied by observing pathological changes in lactating glands after infusion of either endotoxin or the sterile culture filtrate (CCF) of the medium in which Escherichia coli strain B117 had been grown. Both infusions produced a rapid and intense inflammatory response by 4 h with a marked increase of serum proteins in the milk. Before dispersing into the milk, neutrophils were attached to the ductular epithelium; highest cell counts in the milk were recorded when the tissue reaction had waned. Oedema of the ductular epithelium occurred, particularly where neutrophils were actively migrating. The infusion of CCF produced, in addition to inflammation, degeneration and necrosis of ductular cells. The smallest lesions healed very rapidly. There was evidence of differing cell susceptibility to the necrotising toxin as well as uneven distribution over the epithelial surface. All changes observed were confined to the regions of the teat and lactiferous sinuses with little effect on the secreting tissue. The role of the necrotising toxin in the natural disease remains undetermined.

Animals↗
PubMed1984

Lesions of gnotobiotic calves experimentally infected with a calicivirus-like (Newbury) agent.

Fourteen gnotobiotic calves were killed 0.5 to ten days after infection with Newbury agent SRV-1 and the changes in small intestinal structure and function were assessed, qualitatively and quantitatively, by light microscopy, scanning and transmission electron microscopy, enzymology and xylose absorption. The first enterocytes detected as infected by immunoperoxidase were those on the sides of villi at the base. Subsequently exfoliation of degenerate enterocytes resulted in stunted villi; mucosal beta-galactosidase activity fell and there was xylose malabsorption. Small intestinal damage, first detected at 12 hours after infection but almost repaired by ten days, was restricted to the anterior half of the small intestine. In the distal small intestine, where no virus-induced damage occurred, villi lengthened--possibly due to increased mitosis of crypt cells stimulated by enteroglucagon release.

Animals↗
PubMed1984

Progressive pathology of severe Escherichia coli mastitis in dairy cows.

An investigation was made using light and electron microscopy of the progressive pathological changes in nine experimental and two natural cases of severe Escherichia coli mastitis in dairy cows. The duration of infection varied from 18 hours to 13 days. Epithelial lesions were not found in glands which had been infected for more than 24 hours. However, the epithelia of the sinuses and large ducts became hyperplastic after 60 hours of infection and by six days hyperplasia was extensive on the crests of folds. The leucocyte response in the lumina of the glands and subepithelial tissue showed a progressive change from an acute neutrophil reaction to a chronic mononuclear cell infiltration within the first 36 hours of infection. The only changes affecting the secretory tissue occurred after six days of infection and were typical of mammary gland involution which was probably a direct consequence of anorexia.

Animals↗
PubMed1984

An ultrastructural study of the sinus epithelium in the mammary gland of the lactating ewe.

The teat and lactiferous sinus epithelium from the mammary glands of 23 lactating ewes was examined by light and electron microscopy. Most of the sinus epithelium consisted of two layers of non-secretory cells but, in the lactiferous sinus, cells with the same ultrastructural features as alveolar secretory cells were also found. Secretory cells sometimes occupied more than 50% of the total area of the sinus. Many non-secretory cells in the lactiferous sinus possessed a single cilium but they were less common in the teat sinus. 'Accessory glands', which opened directly into the lumen of the gland, were found beneath the epithelium in both the teat and the lactiferous sinuses. From their ultrastructure it was clear that these glands consisted of normal secretory alveoli and that they produced normal milk components. It is suggested that the mixed population of secretory and non-secretory cells in the lactiferous sinus provides unique material for the experimental study of many aspects of mammary gland physiology.

Animals↗
PubMed1983

Pseudopod formation and phagocytosis of milk components by epithelial cells of the bovine mammary gland.

The non-secretory epithelial cells which line the teat and lactiferous sinuses of the bovine mammary gland produce prominent pseudopodia which are able to ingest milk fat globules and casein micelles by phagocytosis. In the lactating gland, pseudopodia are uncommon and the phagocytosis of milk components less active than in the dry glands of cows which have not been milked for 2-3 weeks. Inside phagocytic vacuoles, casein micelles show morphological changes which suggest that digestion is taking place and the presence of acid phosphatase in vacuoles containing milk fat globules indicates that they too are degraded. The differences between lactating and dry glands in their phagocytic activity are reflected by corresponding differences in the number of epithelial cells containing acid phosphatase activity and in the intracellular distribution of the enzyme. It is suggested that the phagocytosis of milk components from the lumen of the dry gland assists in the resorption of milk and that the phagocytic potential of epithelial cells may, under some circumstances, play a role in the protection of the gland from invading bacteria.

Acid Phosphatase↗
PubMed1983

The effect of Escherichia coli endotoxin and culture filtrate on the dry bovine mammary gland.

The mammary glands of eight non-lactating dairy cows were infused with either endotoxin or the sterile culture filtrate in which Escherichia coli had been grown (CCF). Animals were necropsied at intervals up to 24 h after infusion. Only mild inflammation of the teat and lactiferous sinuses occurred after 4 h, subsiding gradually to 24 h. After mixing dry cow secretion with either endotoxin or CCF, an intense inflammatory response was produced on inoculation of quarters of a lactating cow; CCF also produced necrosis of the epithelium. Thus, dry gland secretions do not inhibit the effect of filtrate or endotoxin. It was concluded that the refractory nature of the gland to these toxins in the non-lactating animal is due to the changes which occur in the ductular epithelium during involution.

Animals↗
PubMed1982

Culture of bovine mammary epithelial cells on collagen gels.

A method for the isolation of lobules of acini from bovine mammary gland and their storage in liquid nitrogen is described. After further dissociation of freshly prepared or frozen lobules, clumps of cells are obtained which attach to collagen gels and give rise to colonies which, on morphological criteria, appear predominantly epithelial. Storage for up to 6 months did not adversely affect viability. Increase in colony area involved cell division, was more rapid in air than in 95% oxygen and was enhanced by fetal calf serum.

Animals↗
PubMed1982

Incidence of rotavirus in artificially reared pigs and some effects of diarrhoea on the physiology and histology of the gastrointestinal tract.

Pigs reared on a milk substitute from two days old often developed diarrhoea, but suckled littermates remained healthy. Only in a few pigs was diarrhoea associated with the presence of rotavirus. Rotavirus was also present in some healthy pigs, and was associated with a reduction in villus length. Pigs with diarrhoea usually had an increased amount of digesta in the stomach and a reduction in lactase activity in the small intestine but villus length was unchanged. There was no evidence of lactose malabsorption.

Animals↗
PubMed1982

Pathogenesis of experimental bovine mastitis following a small inoculum of Escherichia coli.

Mastitis was produced in four quarters of two lactating cows by the inoculation of 50 or 200 viable Escherichia coli. Changes were investigated by light microscopy and scanning electron microscopy. After 10 hours the changes were confined to the superficial layer of the epithelium of the teat and lactiferous sinuses; single cells or small groups of cells were damaged and were being extruded from the tissue. By 14 hours there was extensive necrosis and sloughing of the epithelial cells which did not extend beyond the basement membrane, and an intense inflammatory response associated with the epithelial damage. The somatic cells in the milk, mainly polymorphonuclear leucocytes, increased 40 to 250 times and strongly inhibited the survival of E coli. Epithelial damage appeared first in the ventral portions of the gland and then extended through the lactiferous sinus to the large ducts and secreting tissue. This pattern of damage together with the failure to observe bacteria attached to the epithelia was consistent with the production of diffusible toxins by the organisms.

Animals↗
PubMed1981

Attachment of Streptococcus faecium, to the duodenal epithelium of the chicken and its importance in colonization of the small intestine.

The counts of Streptococcus faecium SY1 in the duodenums of gnotobiotic chicks exceeded the counts in their crops, indicating that multiplication was occurring in the anterior small intestine. This growth was related to adhesion to the gut wall which could be demonstrated by viable counts of macerated washed duodenal tissue. Scanning electron microscopy demonstrated that adhesion occurred in restricted areas on the surface of the villus, and transmission studies showed the presence of a thick extracellular layer on the bacterium. Attachment of S. faecium SY1 was confirmed in vitro by using chicken duodenal brush borders. The washings, produced during the preparation of the brush borders, increased the number of S. faecium adhering to the brush borders. This enhancing effect was due to the presence of trypsin in the duodenal washings. However, the effect was not dependent on the enzymatic activity of the trypsin molecule. The initial adhesion was not prevented by pretreatment of the brush borders with soy bean trypsin inhibitor. There were, therefore, two adhesion systems operating, only one of which was dependent on trypsin. Pretreatment of brush borders with trypsin digested them, but they remained intact in the presence of S. faecium SY1, indicating that the enzymatic activity was being inhibited. This effect was specific for the adhering strain of S. faecium SY1; the nonadhering S. faecium strain CRS23 and an adhering strain of Lactobacillus sp. were inactive, as was strain SY1 when adhesion was prevented by including sodium periodate in the test system. The colonizations of the gut by strains of S. faecium of differing adhesive abilities were compared. The nonadhering strain CRS23 showed reduced ability to colonize the duodenum, but the penicillin-resistant mutant of S. faecium SY1, which had reduced adhesive ability but could still attach to a lesser degree, was able to colonize the duodenum as efficiently as the parent strain.

Anaerobiosis↗
PubMed1980

The early pathogenesis of bovine mastitis due to Escherichia coli.

The pathogenesis of coliform mastitis was studied after infusing each of ten lactating quarters of three dairy cows with a large dose (ca. 1 x 10(9) colony-forming units) of virulent Escherichia coli strain B117. This approach was adopted first to maximize the chance of observing microscopic lesions in the tissues of a gland and secondly to overwhelm the differences that might be shown between animals in their response to the infection. The infected glands were examined at intervals of up to 4 h after infection by scanning and transmission electron microscopy and by light microscopy. The earliest lesions were seen after 1 h and consisted of necrosis and sloughing of the epithelial cells of the teat and lactiferous sinuses. After 2 h this was more severe, and was followed by an intense neutrophil response. Neutrophils migrated through the epithelial lesions and at first remained attached to the epithelial surface, forming large mounds. This resulted in gross underestimation of the number of cells in the lumen of the gland when neutrophils in the secretion were counted. At no stage was there evidence of attachment of organisms to the epithelial cells. Tissue damage did not extent beyond the basement membrane, which helps to explain the rapid clinical resolution seen in most field cases of the disease. There was considerable variation in the degree of response shown by the three cows, and also within the infected glands, where the damage was most severe in the lactiferous and teat sinuses. It seems unlikely that all aspects of the disease could be attributed to endotoxin.

Animals↗