ASSEMBLY AND AGGREGATION OF TOBACCO MOSAIC VIRUS IN TOMATO LEAFLETS

Cells of tomato leaflets (Lycopersicum esculentum Mill.) were studied by phase and electron microscopy at various intervals after inoculation with a common strain of tobacco mosaic virus (TMV). Forty-eight hours after inoculation, prior to the development of assayable virus, individual TMV particles, and also particle aggregates, were observed in the ground cytoplasm of mesophyll cells. The most rapid synthesis of virus occurred between 80 and 300 hours after inoculation. Cytological changes during this time were characterized by an increased number of individual particles in the cytoplasm, growth of some aggregates, distortion and vacuolation of chloroplasts, and formation of filaments in the cytoplasm which were approximately four times the size of TMV. These filaments were interpreted as possible developmental forms of the TMV particle. Vacuoles in chloroplasts commonly contained virus particles. Evidence indicated that TMV was assembled in the ground cytoplasm and, in some cases, subsequently was enveloped by distorted chloroplasts.     

ELECTRON MICROSCOPIC STUDIES ON THE DEVELOPMENT OF VESICULAR STOMATITIS VIRUS IN KB CELLS

The development of vesicular stomatitis virus in KB cells was studied by electron microscopy. Sections of infected cells were made 1, 4, 7, 10, and 20 hours after inoculation of the cell cultures, and at the same intervals the supernatant fluid was assayed for virus titer by the plaque test in chick embryo cells. At 10, 14, and 20 hours after inoculation, virus rods were observed attached to cytoplasmic membranes, inside cytoplasmic vacuoles, and attached to the membranes delimiting these vacuoles; they were also found on the surface membrane of the cells. Besides the rods, spherical particles of different sizes and shapes were seen. The possibility that these structures are related to the development of virus rods is discussed. A similarity was noted between the site of maturation of vesicular stomatitis virus rods and that of some other arbor viruses.     

THE UPTAKE AND DEVELOPMENT OF VACCINIA VIRUS IN STRAIN L CELLS FOLLOWED WITH LABELED VIRAL DEOXYRIBONUCLEIC ACID

Vaccinia virus which had its DNA labeled with thymidine-H³ was purified and used as inoculum for L cells growing in suspension. Samples taken over an 8-hour period after infection were studied by light and electron microscopic autoradiography. Within 20 minutes of its being taken up at the cell membrane in phagocytic vesicles, the outer coat of vaccinia becomes disrupted and the virus core containing the labeled DNA passes into the cytoplasmic matrix. Within 1 hour after inoculation the labeled material passes out of the cores into zones of viroplasm, where cores or remnants of cores are gathered and the label becomes more concentrated by 3 hours after inoculation. Most of the label is conserved in the viroplasm areas during the remainder of the experiment. However, 6 hours after inoculation a very small proportion of progeny virus in the cytoplasm, morphologically distinct from the cores of the inoculum, has associated with it labeled material, perhaps derived from the DNA of the inoculum.     

Response of Membrane-bound Mg-activated ATPase of Tobacco Leaves to Tobacco Mosaic Virus

Infectious material was formed at an early stage, and migrated into the mesophyll from the epidermis of tobacco leaves (Nicotiana tabacum cv. Samsun NN) during the period of 1 to 3 hours after inoculation with tobacco mosaic virus (TMV). The activity of membrane-bound Mg²⁺-activated ATPase from the mesophyll was stimulated two to four times within 30 minutes after inoculation with 1.0 microgram per milliliter of TMV. Maximum TMV stimulation of membrane-bound Mg²⁺-activated ATPase activity in epidermis and mesophyll was observed at 0.5 and 3.0 hours after inoculation, respectively. This stimulation was also observed with ultraviolet irradiated TMV (only RNA was destroyed), whereas, the stimulation was not observed with heat-irradiated TMV (both coat and RNA were destroyed). Stimulation equal to that of TMV was observed by inoculation with cucumber green mottle mosaic virus and to a lesser extent with cucumber mosaic virus.

These results illustrate that the stimulus resulting from inoculation with TMV transfers to underlying cells faster than the migration of TMV particles. This stimulus might be closely correlated to the structure of virus, but not to the infectivity of virus.

     

Protective action of salicylic acid against bean yellow mosaic virus infection in Vicia faba leaves

In this study, morphological, ultrastructural and physiological modifications of faba bean (Vicia faba cv Giza 461) leaves in response to bean yellow mosaic virus (BYMV) infection and salicylic acid (SA) treatments were examined. Under BYMV stress, leaves showed symptoms including severe mosaic, mottling, crinkling, size reduction and deformations. Three weeks after virus inoculation, photosynthetic rate, pigment contents and transpiration rate were significantly reduced in response to BYMV infection.

Ultrastructural investigations of BYMV-infected leaves demonstrated that most chloroplasts with increased stromal area became spherical in shape and some lost their envelopes, either partially or totally. The internal structures of chloroplast, grana and thylakoids were dilated. Two kinds of inclusions were detected in BYMV-infected leaves: straight or slightly curved bands sometimes coiled or looped at the end, and electron opaque crystals with varied shapes. BYMV-infected cells showed lower chloroplast number in comparison to the control.

Spraying of SA on faba bean leaves helped to reduce or prevent the harmful effects produced after virus infection. Application of 100 μM SA three days before inoculation restored the metabolism of infected leaves to the levels of healthy controls. SA treatment improved plant health by increasing the photosynthesis rates, pigment contents and levels of other parameters studied similar to control values.

Moreover, SA treatment increased plant resistance against BYMV. This was observed through induction of chloroplast number, reduction in percentage of infected plants, decrease in disease severity and virus concentration of plants treated with SA prior to BYMV inoculation. Cells of SA-treated samples showed well-developed chloroplasts with many starch grains and well-organized cell organelles.

The present results provide an overview of the negative effects on faba bean leaves due to BYMV infection from physiological and subcellular perspectives. Also, a role of SA involved in induction of resistance against BYMV infection in bean plants is discussed.     

Virus DNA replication and protein synthesis in Amsacta moorei entomopoxvirus-infected Estigmene acrea cells

Amsacta moorei entomopoxvirus DNA synthesis was detected in Estigmene acrea cells by [³H]thymidine incorporation 12 hr after virus inoculation. Hybridization of ³²P-labeled Amsacta entomopoxvirus DNA to the DNA from virus-infected cells indicated that viral-specific DNA synthesis was initiated between 6 and 12 hr after virus inoculation. A rapid increase in the rate of virus DNA synthesis was detected from 12 to 24 hr after virus inoculation. Amsacta entomopoxvirus protein biosynthesis in E. acrea cells was studied by [su35S]methionine incorporation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Extracellular virus and virus-containing occlusion bodies were first detected in virus-infected cell cultures 18 hr after virus inoculation. Thirty-seven virus structural proteins, ranging in molecular weight from 13,000 to 208,000 were detected in both occluded and nonoccluded forms of the virus. The biosynthesis of virus structural proteins increased rapidly from 18 to 34 hr after infection. A major viral-induced protein corresponding in molecular weight to viral occlusion body protein (110,000) was detected approximately 24 hr after virus inoculation.     

Pathway of vesicular stomatitis virus entry leading to infection

The entry of vesicular stomatitis virus into Madin-Darby canine kidney (MDCK) cells was examined both biochemically and morphologically. At low multiplicity and 0 °C, viruses bound to the cell surface but were not internalized. Binding was very dependent on pH. More than ten times more virus bound at pH 6.5 than at higher pH values. At the optimal pH, binding failed to reach equilibrium after more than two hours. The proportion of virus bound was irreproducible and low, relative to the binding of other enveloped viruses. Over 90% of the bound viruses were removed by proteases. When cells with pre-bound virus were warmed to 37 °C, a proportion of the bound virus became protease-resistant with a half-time of about 30 minutes. After a brief lag period, degraded viral material was released into the medium. The protease-resistant virus was capable of infecting the cells and probably did so by an intracellular route, since ammonium chloride blocked the infection and slightly reduced the degradation of viral protein.When the entry process was observed by electron microscopy, viruses were seen bound to the cell surface at 0 °C and, after warming at 37 °C, within coated pits, coated vesicles and larger, smooth-surfaced vesicles. No fusion of the virus with the plasma membrane was observed at pH 7.4.When pre-bound virus was incubated at a pH below 6 for 30 seconds at 37 °C, about 40 to 50% of the pre-bound virus became protease-resistant. On the basis of this result and previously published experiments (White et al., 1981), it was concluded that vesicular stomatitis virus fuses to the MDCK cell plasma membrane at low pH.These experiments suggest that vesicular stomatitis virus enters MDCK cells by endocytosis in coated pits and coated vesicles, and is transported to the lysosome where the low pH triggers a fusion reaction ultimately leading to the transfer of the genome into the cytoplasm. The entry pathway of vesicular stomatitis virus thus resembles that described earlier for both Semliki Forest virus and fowl plague virus.     

Herpesvirus simiae infection in Macaca radiata

Forty of 79 bonnet macaques (Macaca radiata) housed in an outdoor structure became infected with a respiratory disease, and 16 died. The most conspicuous lesions were those of hemorrhagic interstitial lobar pneumonia and focal hepatic necrosis with monocytic infiltration and eosinophilic intranuclear inclusions. A virus, in high titer, was obtained from the lung and liver of two fatal cases (10⁷ TCID₅₀ × gram of tissue) by inoculating tissue homogenates in primary vervet monkey kidney, BSC-1, and MA104 cell cultures. The cytopathic effect was identical with that induced by Herpesvirus simiae in the same cell cultures. Similar cellular changes were seen in LLC-MK2 cell cultures. Infected cells contained eosinophilic intranuclear inclusions, and intranuclear herpes-like virus particles were seen by electron microscopy. The virus could not be passed serially in mice by the intracerebral route of inoculation. Bonnet monkeys (herpes antibody-free), inoculated intravenously with the virus, developed vesicular lesions on the arms, face, hands, and soles of the feet; and the virus was recovered from the vesicular fluid. All lesions disappeared within three weeks after inoculation, and the animals later recovered. On the basis of host range, cytopathic effect, electron microscopy, mouse susceptibility, and the results of neutralization tests in tissue cultures, the virus was identified as Herpesvirus simiae.     

Ultrastructural changes of organelles in coleoptile cells during anaerobic germination of rice seeds

Summary Ultrastructural changes of organelles, especially those of mitochondria in rice seedlings germinated under strictly anaerobic conditions were investigated.The embryos of dry seeds had slightly modified mitochondria, characterized by an electron transparent matrix with few cristae and electron opaque patches. These mitochondria developed normally for 48 hours irrespective of whether oxygen was present or not. However, after 72 hours' germination under anaerobic conditions vesiculation of the cristae developed and progressed greatly for the subsequent 24 hours and most of the spaces in the mitochondrion became occupied with vacuolated cristae. Vesiculation seemed to be the effect of cessation of energy supply from the mitochondria themselves.Ultrastructural changes of other organelles such as the plastids and endoplasmic reticulum were also observed after 96 hours under anaerobic conditions.     

指状青霉Penicillium digitatum侵染柑橘果实的细胞学研究

采用电子显微镜技术系统研究了指状青霉Penicillium digitatum对柑橘果实的侵染过程及超微结构特征。结果表明室温条件下,接种12h后,伤口附近的分生孢子开始萌发产生芽管;然后从伤口处直接侵入果实表皮细胞内;接种24h后,受侵染果实细胞中的菌丝向相邻细胞扩展蔓延,寄主细胞壁开始消解,质壁分离,细胞内含物及各类细胞器凝集,颜色加深,最后完全消解,伤口部位的果皮开始变软,伤口处的菌丝向外生长;84h后伤口处病斑软化,部分长出白色的霉层;96h后病斑软化面积直径达3cm,白色霉层面积逐渐扩大;120h后白色霉层中间伤口处霉层颜色加深变为灰绿色;144h后整个果实变软腐烂。果胶质标记结果表明,菌丝侵入果实后产生果胶酶并降解柑橘细胞壁中的果胶,使得细胞壁松弛,软化腐烂。     

狂犬病毒鼠脑复壮后的典型形态恢复及感染细胞内的形态发生学

[目的]观察比较鼠脑复壮前后狂犬病毒的形态变化,并观察病毒感染BHK-21细胞后不同时间的形态发生情况.[方法]以保存时间较长的SRV9毒株为原始材料,经乳鼠脑传代复壮后接种BHK-21细胞,浓缩、纯化后观察.[结果](1)未经复壮的病毒中DI粒子占较高比例,典型粒子只占少数,而复壮后典型粒子所占比例升高到病毒粒子总数的90%.(2)感染24h后在细胞浆内可以观察到典型病毒粒子,其数量随着培养时间的延长而增加.带毒传代之后的培养过程中细胞内病毒数量增加不明显.(3)病毒可以在细胞内的空泡膜表面以多种方式成堆出芽.[结论](1)鼠脑复壮可恢复狂犬病毒中典型粒子所占比例.(2)带毒传代1～2次时为狂犬病毒收获的最佳时机.(3)本研究为狂犬病毒的装配机制补充了数据.     

AN ELECTRON MICROSCOPE STUDY OF THE DEVELOPMENT OF A MOUSE HEPATITIS VIRUS IN TISSUE CULTURE CELLS

Samples taken at different intervals of time from suspension cultures of the NCTC 1469 line of mouse liver—derived (ML) cells infected with a mouse hepatitis virus have been studied with the electron microscope. The experiments revealed that the viruses are incorporated into the cells by viropexis within 1 hour after being added to the culture. An increasing number of particles are found later inside dense cytoplasmic corpuscles similar to lysosomes. In the cytoplasm of the cells from the samples taken 7 hours after inoculation, two organized structures generally associated and never seen in the controls are observed: one consists of dense material arranged in a reticular disposition (reticular inclusion); the other is formed by small tubules organized in a complex pattern (tubular body). No evidence has been found concerning their origin. Their significance is discussed. With the progression of the infection a system of membrane-bounded tubules and cisternae is differentiated in the cytoplasm of the ML cells. In the lumen of these tubules or cisternae, which are occupied by a dense material, numerous virus particles are observed. The virus particles which originate in association with the limiting membranes of tubules and cisternae are released into their lumen by a "budding" process. The virus particles are 75 mµ in diameter and possess a nucleoid constituted of dense particles or rods limiting an electron transparent core. The virus limiting membrane is sometimes covered by an outer layer of a dense material. In the cells from the samples taken 14 to 20 hours after inoculation, larger zones of the cell cytoplasm are occupied by inclusion bodies formed by channels or cisternae with their lumens containing numerous virus particles. In the samples taken 20 hours or more after the inoculation numerous cells show evident signs of degeneration.     

The Life Cycle of Isospora felis Wenyon, 1923, a Coccidium of the Cat*

SYNOPSIS. A pure strain of Isospora felis derived from a single oocyst was used to study the endogenous cycle. One and a half to two-month-old laboratory-reared, coccidia-free kittens were used thruout the study. The endogenous stages occurred in the epithelial cells of the distal parts of the villi in the ileum and occasionally duodenum and jejunum. All stages lay above the host cell nucleus. There were 3 asexual generations. The 1st generation schizonts were 11–30 by 10–23 μ when mature and contained 16–17 banana-shaped merozoites 11–15 by 3–5 μ. They became mature in 96 or sometimes in 120 hours. The 1st generation merozoites entered new host cells, rounded up and formed 2nd generation schizonts. These formed within themselves 2–10 or more spindle-shaped bodies resembling 1st generation merozoites in shape and size. These were 2nd generation merozoites. They were uninucleate 120 hours after inoculation, but by 144 hours they became larger, multinucleate and some lost their elongate shape and became ovoid. They were then 3rd generation schizonts. They were 12–16 by 4–5 μ. Each formed up to 6 or more banana-shaped merozoites 6–8 by 1–2 μ. The 3rd generation schizonts and merozoites developed within the same host cell and parasitophorous vacuole as the 2nd generation schizonts and merozoites. Mature schizonts containing only 3rd generation merozoites appeared 144 hours after inoculation, were most abundant 168 hours after inoculation, and might be present as late as 216 hours after inoculation. They were 14–36 by 13–22 μ and contained 36 to more than 70 merozoites. The 3rd generation merozoites entered the sexual cycle. The mature microgametocytes were 24–72 by 18–32 μ and contained a central residuum and a large number of microgametes 5–7 by 0.8 μ with 2 posteriorly-directed flagella. The mature macrogametes were 16–22 by 8–13 μ. Gametogony occurred 144–216 hours after inoculation. The prepatent period was 168–192 hours and the patent period 10–11 days. Peak oocyst production occurred on the 6th day of the patent period.     

Dissolution of Autographa californica nuclear polyhedrosis virus polyhedra by the digestive fluid of Trichoplusia ni (Lepidoptera:Noctuidae) larvae

The dissolution of polyhedra of Autographa californica nuclear polyhedrosis virus by digestive fluid collected from 5th stage Trichoplusia ni larvae was studied in vitro. Observations were made at timed intervals using phase contrast microscopy, and scanning and transmission electron microscopy. Dissolution occurred rapidly and in a detectable sequence. Under phase contrast, most polyhedra lost their refringence by 0.5 min. The polyhedra became rounded in appearance with small protuberances on the surface and Brownian movement was observed within. After 1 min, the envelope of most polyhedra had ruptured, releasing the enclosed virions. The protuberances were also observed under the scanning electron microscope after digestion for 0.5 min. Many shell fragments devoid of internal contents were seen after more lengthy digestion. Internal structural changes were revealed by electron microscopy. After 1 min of exposure, polyhedra were observed in all stages of dissolution. By 3 min, only virions, scattered about in heterogeneous material, could be distinguished.     

ELECTRON MICROSCOPE OBSERVATIONS ON THE SURFACE ADENOSINE TRIPHOSPHATASE-LIKE ENZYMES OF HELA CELLS INFECTED WITH HERPES VIRUS

HeLa cells infected with herpes simplex virus have been examined in thin sections by electron microscopy after cytochemical staining for the presence of surface enzymes splitting adenosine triphosphate. As with uninfected HeLa cultures (18), the opaque enzyme reaction product was localized at the plasma membranes of about half the cells, tending to be present where there were microvilli and absent on smooth surfaces. Where mature extracellular herpes particles were found in association with cell membranes showing the enzyme activity, they were invariably likewise stained, and conversely, those mature particles which lay close against cells without reaction product at the surface were themselves free of it. Particles found budding into cytoplasmic vacuoles were also always without opaque deposit since this was never seen at vacuolar membranes, even in cells having the activity at the surface. The enzyme reaction product thus provided a marker indicating the manner in which the particles escape from cells and mature by budding out through cellular membranes, carrying, in the process, a portion of the latter on to themselves to form the outer viral limiting membrane. In some instances, virus particles were observed with more opaque material covering them than was present at the cell membrane with which they were associated. This finding has been taken as evidence for a physiological waxing and waning of surface enzyme activity of adenosine triphosphatase type. The fine structure of the mature extracellular virus as prepared here, using glutaraldehyde fixation, is also recorded. The observations and interpretations are discussed in full.     

Pathology of mosquito iridescent virus of Aedes taeniorhynchus in cell cultures of Aedes aegypti.

An electron microscopical study was conducted on the pathology of the mosquito iridescent virus (MIV) of Aedes taeniorhynchus in monolayer cultures of Aedes aegypti cells. The sequence of events in the pathology, from the initiation of attachment through maturation and release, is presented.MIV attaches to cells and is taken up by the process of viropexis (phagocytosis) within 15 min after inoculation. Intact virions are released into the cytoplasm at 30–60 min by disruption of the phagocytic vesicles. Discrete foci of replication (viroplasm) develop in the cytoplasm within 1 day after infection. Progeny virus is assembled in the viroplasm within 2 days after infection and later appears at the cell surface, where it acquires an envelope from the plasma membrane upon budding from the cell. Virus does not accumulate to form aggregates in the cytoplasm; instead, it buds from the cell after assembly.     

A new strain of Drosophila that inhibits the development of symptoms in imagoes infected with sigma virus

A strain of Drosophila melanogaster bearing the mutant gene ebony has been found to slow the development of symptoms (carbon dioxide sensitivity) in adult flies inoculated with sigma virus, a member of the rhabdovirus group. This inhibition is made evident by comparing mean incubation times of the virus in ebony and wild-type (Oregon) flies. The increase in mean incubation time in ebony flies has ranged from about 3 to 8 days, depending on the virus strain, amount of virus injected, and the age of the flies at the time of inoculation. This delay in development of symptoms appears to be due to a dominant autosomal gene, although further work is needed to confirm this. When accumulation of infectious virus after inoculation is compared in ebony and Oregon flies, there seems to be no inhibition of multiplication in ebony at the level of the entire fly. The relationship of this work to current theories on the mechanism of symptom production by sigma virus is discussed.     

Histological study of the responses of two Vitis vinifera cultivars (resistant and susceptible) to Plasmopara viticola infections

Leaves of Vitis vinifera L. cvs. Chasselas (susceptible) and Solaris (resistant) were inoculated with Plasmopara viticola. Samples were then examined by scanning electron microscopy, light and epifluorescence microscopy. On the resistant cv. Solaris, stomatal deposits, identified as callose, were visible around the germinating zoospores 7 h after inoculation. Twenty-four hours after inoculation, infected stomata exhibited secretions that enveloped the zoospores. At this time, infected stomata were surrounded by necrotic tissues. At 120 h after inoculation, undefined material was deposited on the cuticle in the necrotic areas. Stomata in the vicinity of the infection sites contained callose deposits in and around the stomatal openings, but no necrotic zones were observed. On the sensitive cv. Chasselas neither secretion nor callose deposits were observed. Sporangiophores emerged about 96 h after inoculation and were fully developed 24 h later. Sporulation through small stomata-like apertures present all along the primary vein was also observed on the upper leaf surface. The role of stomatal callose deposits in the defense reactions of the Solaris grapevine cultivar against P. viticola is discussed.     

Accumulation of beta-Fructosidase in the Cell Walls of Tomato Roots following Infection by a Fungal Wilt Pathogen

Active defense in plants is associated with marked metabolic alterations, but little is known about the exact role of the reported changes in specific activity of several enzymes in infected plant tissues. β-Fructosidase (invertase), the enzyme that converts sucrose into glucose and fructose, increases upon infection by fungi and bacteria. To understand the relationship between fungal growth and β-fructosidase accumulation, we used an antiserum raised against a purified deglycosylated carrot cell wall β-fructosidase to study by immunogold labeling the spatial and temporal distribution of the enzyme in susceptible and resistant tomato (Lycopersicon esculentum) root tissues infected with the necrotrophic fungus, Fusarium oxysporum f. sp. racidis-lycopersici. In susceptible plants, the enzyme started to accumulate in host cell walls about 72 hours after inoculation. Accumulation occurred only in colonized cells and was mainly restricted to areas where the walls of both partners contacted each other. In resistant plants, accumulation of β-fructosidase was noticeable as soon as 48 hours after inoculation and appeared to reach an optimum by 72 hours after inoculation. Increase in wall-bound β-fructosidase was not restricted to infected cells but occurred also, to a large extent, in tissues that remained uncolonized during the infection process. The enzyme also accumulated in wall appositions (papillae) and intercellular spaces. This pattern of enzyme distribution suggests that induction of β-fructosidase upon fungal infection is part of the plant's defense response. The possible physiological role(s) of this enzyme in infected tomato plants is discussed in relation to the high demand in energy and carbon sources during pathogenesis.     

Prevalence of antimicrobial resistance among bacterial pathogens isolated from cattle in different European countries: 2002–2004

Background

Acute phase proteins haptoglobin (Hp), serum amyloid A (SAA) and lipopolysaccharide binding protein (LBP) have suggested to be suitable inflammatory markers for bovine mastitis. The aim of the study was to investigate acute phase markers along with clinical parameters in two consecutive intramammary challenges with Escherichia coli and to evaluate the possible carry-over effect when same animals are used in an experimental model.

Methods

Mastitis was induced with a dose of 1500 cfu of E. coli in one quarter of six cows and inoculation repeated in another quarter after an interval of 14 days. Concentrations of acute phase proteins haptoglobin (Hp), serum amyloid A (SAA) and lipopolysaccharide binding protein (LBP) were determined in serum and milk.

Results

In both challenges all cows became infected and developed clinical mastitis within 12 hours of inoculation. Clinical disease and acute phase response was generally milder in the second challenge. Concentrations of SAA in milk started to increase 12 hours after inoculation and peaked at 60 hours after the first challenge and at 44 hours after the second challenge. Concentrations of SAA in serum increased more slowly and peaked at the same times as in milk; concentrations in serum were about one third of those in milk. Hp started to increase in milk similarly and peaked at 36–44 hours. In serum, the concentration of Hp peaked at 60–68 hours and was twice as high as in milk. LBP concentrations in milk and serum started to increase after 12 hours and peaked at 36 hours, being higher in milk. The concentrations of acute phase proteins in serum and milk in the E. coli infection model were much higher than those recorded in experiments using Gram-positive pathogens, indicating the severe inflammation induced by E. coli.

Conclusion

Acute phase proteins would be useful parameters as mastitis indicators and to assess the severity of mastitis. If repeated experimental intramammary induction of the same animals with E. coli is used in cross-over studies, the interval between challenges should be longer than 2 weeks, due to the carry-over effect from the first infection.