Review: Low intensity ultrasonics in food technology / Revisión: Ultrasonidos de baja intensidad en tecnología de alimentos

Ultrasonic applications can be classified into low intensity or high intensity applications. The latter are used to modify a process or product with ultrasonics, while in low intensity applications the process or product modifies the ultrasonic signal, thus providing information about the product. Low inten sity ultrasonics in food technology can be used to monitor a process (liquid level, flowmeters) or to determine the quality of food products. Since ultrasonic techniques are rapid, non-destructive, easy to automate and relatively inexpensive, the number of applications is rapidly growing in this field. Ultrasonics can also be considered for use in laboratory testing devices to determine physical and chemical properties of foods. Ultrasonics has been used to determine texture, composition and physical state in liquid and solid foods. The commonly measured ultrasonic parameters are velocity, attenua tion and frequency spectrum composition. Velocity is the parameter used most since it is the simplest and most reliable measurement. This paper reviews the basic principles of ultrasonics, the most suit able techniques for each type of application, the testing devices needed to make measurements and the most interesting applications.

The influence of blanching pretreatments on the quality of dehydrated broccoli stems/ Influencia del tipo de escaldado en la calidad de tallos de bróculi deshidratados

Different blanching treatments were applied to sliced broccoli stems prior to dehydration in order to improve product quality. The pretreatments used were a conventional blanching in water at 100°C, and a stepwise blanching using different temperatures for the first step (50, 55, 60, 65 and 70°C). Five rehydration temperatures were used (25, 40, 55, 65 and 80 °C). Rehydration rate, chlorophyll content and texture of the rehydrated product were evaluated. Rehydration was modeled based on Fick's diffusion equation. A good agreement between the model and the experimental data was obtained when D eff and W e values were identified for each temperature (average percent variation 99.3). Samples stepwise blanched at 60 °C showed, on average, the lowest We and Ea values. Stepwise blanching at 60 and 65 °C and rehydration at 25, 40 and 55 °C were the combinations that gave the firmest product. Stepwise blanching at 50 °C and rehydration between 25 and 65 °C was the combination that preserved the highest chlorophyll content. From these results, it seems difficult to obtain firm samples with high chlorophyll content without any chemical additive.

Ferrochelatase is present in Brucella abortus and is critical for its intracellular survival and virulence

Brucella spp. are pathogenic bacteria that cause brucellosis, an animal disease which can also affect humans. Although understanding the pathogenesis is important for the health of animals and humans, little is known about virulence factors associated with it. In order for chronic disease to be established, Brucella spp. have developed the ability to survive inside phagocytes by evading cell defenses. It hides inside vacuoles, where it then replicates, indicating that it has an active metabolism. The purpose of this work was to obtain better insight into the intracellular metabolism of Brucella abortus. During a B. abortus genomic sequencing project, a clone coding a putative gene homologous to hemH was identified and sequenced. The amino acid sequence revealed high homology to members of the ferrochelatase family. A knockout mutant displayed auxotrophy for hemin, defective intracellular survival inside J774 and HeLa cells, and lack of virulence in BALB/c mice. This phenotype was overcome by complementing the mutant strain with a plasmid harboring wild-type hemH. These data demonstrate that B. abortus synthesizes its own heme and also has the ability to use an external source of heme; however, inside cells, there is not enough available heme to support its intracellular metabolism. It is concluded that ferrochelatase is essential for the multiplication and intracellular survival of B. abortus and thus for the establishment of chronic disease as well.

Expression of major capsid protein VP-1 in the absence of viral particles in thymomas induced by murine polyomavirus

Thymomas induced by polyomavirus strain PTA in mice are known to express the major capsid protein VP-1. Since the expression of a late structural protein such as VP-1 is considered a sign of virus replication, the present work attempted to clarify the implication of the presence of this protein in tumor cells. Electron microscopy of tumors showed a striking absence of viral particles in the vast majority of the cells. However, immunoelectron microscopy of the same samples demonstrated intranuclear VP-1 in most cells despite the absence of viral particles. Very little infectious virus was recovered from tumors. A change in the electrophoretic mobility of VP-1 from thymomas was detected compared with VP-1 from productively infected cells. The data presented in this work prove that the expression of VP-1 in polyomavirus-induced tumors is not synonymous with the presence of infectious virus, suggesting a possible defect in viral encapsidation.

Five novel hormone-responsive cell lines derived from murine mammary ductal carcinomas: in vivo and in vitro effects of estrogens and progestins

We have developed an experimental model of mammary carcinogenesis in which the administration of medroxyprogesterone acetate (MPA) to female BALB/c mice induces progestin-dependent ductal metastatic mammary tumors with high levels of estrogen receptor (ER) and progesterone receptor (PR). Through selective transplants in untreated mice, we have obtained progestin-independent variants, still expressing high levels of ER and PR. Primary cultures of the MPA-induced carcinomas C4-HD and C7-HI were set up, and after 3-4 months, several different cell lines were obtained. Four of these, MC4-L1, MC4-L2, MC4-L3, and MC4-L5 were established from C4-HD and a fifth, MC7-L1, from C7-HI. All cells were of epithelial origin, as demonstrated by electron microscopy and by immunocytochemical identification of cytokeratin and cadherin. In vitro MC4-L1, MC4-L3, and MC4-L5 showed a typical epithelial morphology; when transplanted in vivo, they originated metastatic carcinomas with different degrees of differentiation. MC4-L2 and MC7-L1 deviated from the standard epithelial picture; they disclosed a spindle-shaped morphology in vitro and in vivo gave rise to a biphasic spindle cell/tubular carcinoma and an anaplastic carcinoma, respectively; both lines gave rise to metastases. This differential morphology correlated with a higher degree of aggressiveness, as compared with MC4-L1, MC4-L3, and MC4-L5. ERs and PRs were detected by binding, immunocytochemistry, and Western blot. In vitro, MC4-L2 and MC7-L1 were stimulated by MPA (nM to microM) and 17beta-estradiol (nM and 10 nM); no significant stimulation was observed in MC4-L1, MC4-L3, and MC4-L5 under the same experimental conditions. In vivo, MPA significantly stimulated tumor growth in all epithelioid lines but not in MC4-L2 and MC7-L1. A progestin-dependent growth pattern was confirmed for MC4-L1, MC4-L3, and MC4-L5 in successive transplants, whereas MC4-L2 and MC7-L1 behaved as progestin independent. This is the first description of mouse mammary carcinoma cell lines expressing ER and PR. The different in vitro hormone responses as compared with in vivo and the differential effects of 17beta-estradiol in the parental tumors and in cell lines render these lines useful tools for the in vitro and in vivo study of hormone regulation of tumor growth and metastases.

Use of ultrasound to assess Cheddar cheese characteristics

Blocks of Cheddar cheese were matured in temperature-controlled chambers at 5 and 12 degrees C. The ultrasonic velocity increased during maturation ranging from 1657 to 1677 ms-1 at 12 degrees C and from 1684 to 1693 ms-1 at 5 degrees C. The ultrasonic velocity was related to the square root of the deformability modulus and the slope in puncture. The increase of velocity during maturation shows the feasibility of using an ultrasonic device to non-destructively monitor Cheddar cheese maturity. Ultrasound velocity was measured at different temperatures. The velocity decreased with increasing temperature, and from the slope of the first part of the temperature-velocity curves it was possible to non-destructively assess the moisture content of different types of cheese.

Pattern of cytokine receptors expressed by human dendritic cells migrated from dermal explants

Different reasons account for the lack of information about the expression of cytokine receptors on human dendritic cells (DC): (a) DC are a trace population; (b) the proteolytic treatment used to isolate DC may alter enzyme-sensitive epitopes; and (c) low numbers of receptors per cell. In the present work the expression of cytokine receptors was analysed by flow cytometry on the population of dermal DC (DDC) that spontaneously migrate from short-term culture dermal explants. DDC obtained after dermal culture were CD1alow, CD1b+, CD1c+, human leucocyte antigen (HLA)-DR+, CD11chigh, CD11b+ and CD32+. The DC lineage was confirmed by ultrastructural analysis. DDC expressed interleukin (IL)-1R type 1 (monoclonal antibody (mAb) hIL-1R1-M1; and 6B5); IL-1R type 2 (mAb hIL-1R2-M22); IL-2R alpha chain (mAb anti-Tac; and hIL-2R-M1) and IL-2R gamma chain (mAb 3B5; and AG14C). DDC did not stain for IL-2R beta chain using four mAbs recognizing two different epitopes of IL-2R beta (mAb 2R-B; Mik-beta 1; and CF1; Mik-beta 3, respectively). DDC were also positive for the cytokine binding chains (alpha chains) of IL-3R (mAb 9F5); IL-4R (mAb hIL-4R-M57; and S456C9); and IL-7R (mAb hIL-7R-M20; and R3434). DDC showed low levels of IL-6R alpha chain (mAb B-F19; B-R6; and B-E23) and its signal transducer gp130 (mAb A2; and B1). DDC strongly expressed interferon-gamma receptor (IFN-gamma R) (mAb GIR-208) and were negative for IL-8R (mAb B-G20; and B-F25). All DDC were highly positive for granulocyte-macrophage colony-stimulating factor receptor (GM-CSFR) alpha chain (mAb hGM-CSFR-M1; SC06; SC04, and 8G6) and to a lesser extent for the common beta chain of GM-CSFR, IL-3R and IL-5R (mAb 3D7). On the other hand, reactivity was not found for granulocyte colony-stimulating factor receptor (G-CSFR) (mAb hGCSFR-M1) nor macrophage colony-stimulating factor receptor (M-CSFR) (mAb 7-7A3-17) confirming the DC lineage of DDC. As previously reported for lymphoid DC, DDC expressed tumour necrosis factor receptort (TNFR) 75000 MW (mAb utr-1; hTNFR-M1; and MR2-1) but lacked TNFR 55000 MW (mAb htr-9; MR1-1; and MR1-2). In summary, DDC express receptors for a broad panel of cytokines, even receptors for cytokines whose effects on DC are still unknown (i.e. IL-2R alpha gamma; IL-6R alpha/gp 130; IL-7R alpha gamma).

Intramammary immunization with live-attenuated Staphylococcus aureus: microbiological and immunological studies in a mouse mastitis model

Mammary infection was induced in lactating mice by intramammary injection of Staphylococcus aureus. Histopathological analysis revealed infiltration and lesions of varying magnitude that were still apparent 21 days after the challenge. Concomitantly, viable S. aureus was recovered from infected mammary glands. Mice were immunized by the intramammary route with 5 x 10(6) colony forming units of a temperature-sensitive mutant of S. aureus and subsequently received a boosting injection seven days later. On day 14 mice were challenged by the intramammary route with the wild-type strain. Intramammary immunization induced a significant increase in milk IgA (P < 0.05), serum IgG (P < 0.05) and serum IgA (P < 0.05) on the day of the challenge, when compared with non-immunized mice. Immunization decreased significantly (P < 0.01) the number of S. aureus colony forming units recovered 96 h after intramammary challenge. In conclusion, the feasibility of immunizing locally with temperature-sensitive S. aureus to induce immunity in the mouse mammary gland was demonstrated. The mouse model of mastitis is proposed as a useful system for screening temperature-sensitive S. aureus strains to be utilized in the development of a vaccine.

Tumor necrosis factor alpha plus interleukin 1 beta treatment protects granulocytopenic mice from Pseudomonas aeruginosa lung infection: role of an unusual inflammatory response

We have recently demonstrated that treatment with interleukin 1 beta (IL-1 beta) plus tumor necrosis factor alpha (TNF alpha) protects granulocytopenic hosts from Pseudomonas aeruginosa aerosol challenge. In this study we characterized the inflammatory response induced by P. aerugionsa in granulocytopenic mice treated with 2,000 U IL-1 beta plus 2,000 U TNF alpha. Treatment with the nonsteroidal anti-inflammatory agent piroxicam abolished both the protective effect of cytokine treatment and the increase in myeloperoxidase (MPO) pulmonary activity. Histopathological studies revealed that, after aerosol challenge with P. aeruginosa, treatment with these cytokines induced migration and extravasation of mononuclear cells of immature appearance into the lung parenchyma. These cells contained MPO in their cytoplasm and displayed phagocytic capacity. Resident alveolar macrophages exhibited signs of activation and appeared in reduced numbers in bronchoalveolar lavage fluid. We suggest that the inflammatory response promoted by low TNF alpha plus IL-1 beta doses may be one mechanism responsible for protection of granulocytopenic hosts from P. aeruginosa aerosol challenge.

The effect of treatment with interleukin-1 and tumor necrosis factor on Pseudomonas aeruginosa lung infection in a granulocytopenic mouse model

The efficacy of treatment with interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF alpha) on Pseudomonas aeruginosa pneumonia was evaluated in a granulocytopenic mouse model. Combined intravenous administration of 2000 U IL-1 beta plus 2000 U TNF alpha significantly diminished mortality from aerosol challenge with P. aeruginosa. Mice treated with IL-1 beta, TNF alpha, or both also exhibited a significant enhancement in pulmonary clearance of P. aeruginosa. Combined cytokine administration induced an increase in the pulmonary content of myeloperoxidase activity. Mature leukocytes were not detected in either circulation or bronchoalveolar lavage fluid from granulocytopenic, cytokine-treated mice. In conclusion, IL-1 beta and TNF alpha treatment exhibited a synergistic protective effect from pulmonary P. aeruginosa challenge in granulocytopenic hosts, probably due to enhancement of nonspecific antibacterial mechanisms.

Infection by polyomavirus of murine cells deficient in class I major histocompatibility complex expression

Embryonic fibroblasts and kidney epithelial cells from beta 2-microglobulin-deficient mice were as infectible by polyomavirus as cells from normal littermates were, as judged by expression of nuclear viral capsid antigen, development of cytopathic effects, and yields of infectious virus. We conclude that expression of intact class I major histocompatibility complex molecules is not essential for polyomavirus infection.

Susceptible adult murine model for Junin virus

The adult mouse model had been considered resistant to Junin virus (JV) infection. However, we found that C3H/HeJ murine strain proved highly susceptible up to 5 months of age to intracerebral inoculation with the prototype XJ JV strain, showing neurological signs and 80-90% mortality within 13 days. Neutralizing antibodies (Nt Ab) were absent, but low immunofluorescent Ab levels (1:5) were detected as from day +7. The virus could only be rescued by coculture of brain samples with Vero cells. Histopathological findings were consistent with the suckling mouse model and with a delayed-type hypersensitivity reaction. XJ inoculation by extraneural routes failed to cause disease, however, it induced Nt Abs. Ic infection with XJCL3 strain of JV attenuated for man and guinea pig, but not for mouse, induced high Nt Ab levels but not mortality. In either case, mice resisted ic XJ challenge. Thus, C3H/HeJ is the first adult mouse model susceptible to JV.

Mouse mammary tumors induced by medroxyprogesterone acetate: immunohistochemistry and hormonal receptors

Mammary adenocarcinomas induced by medroxyprogesterone acetate (MPA) in female BALB/c mice were investigated as to their morphology and immunohistochemistry and their content of steroid, prolactin (PRL), and epidermal growth factor (EGF) receptors. Histologically, these tumors were mainly of ductal origin, since hyperplastic alveolar nodules were observed only in 3 cases. No viral particles were encountered in electron microscopic studies. Estrogen and/or progesterone, PRL, and EGF receptors were detected in MPA-induced tumors, as well as in the occasional spontaneous mammary tumors of multiparous females. EGF was detected, by a radioimmunoassay, in the cystic fluid of 12 mammary adenocarcinomas. MPA treatment was found to induce uterine secretory changes, glandular cystic hyperplasia, and eventually deciduomas that stained strongly for desmin and to a lesser degree for vimentin, suggesting a muscular differentiation. Consequently, MPA-induced adenocarcinomas can be considered as ductal tumors that possess estrogen and/or progesterone, PRL, and EGF receptors. Whether MPA induces tumor growth directly via progesterone receptors remains to be investigated.

Abrogation of Junin virus encephalitis by critical cyclophosphamide timing and dosage

Junin virus-induced encephalitis in suckling mouse is a delayed-type hypersensitivity reaction, whose immunopathologic nature has been proven by suppressing the thymus-dependent response. Cyclophosphamide (CY) given at day +6 post-infection (p.i.) has been shown to modulate infection, presumably by TDTH lymphocyte inactivation. To determine critical timing and i.p. drug dose, brain histology and survival were studied in 3-day-old Balb/c mice, inoculated i.c. with Junin virus. Optimal protection was achieved with a non-toxic, 50 mg/kg CY dose at day 6 p.i. (+6): no brain tissue damage was detected in animals killed at day +12, when the necropsied controls exhibited widespread lesions. Other timings (day +3, +4, +5) proved less effective. As regards alternative dosage at day +6, 30 mg was useless, and severe leptomeningitis was evident, whereas 40 mg significantly lowered mortality, and lesions were much milder and less constant. It seems that the 50 mg/kg CY dose must be administered at a critical time p.i. to inactivate sensitized TDTH lymphocytes and to reduce mortality and CNS pathology significantly.