Mechanism of reappearance of contact sensitivity to DNCB in desensitized guinea pigs.

The different immunologic activities of lymph node and spleen cells as compared to peritoneal exudate cells were studied in temporarily desensitized, DNCB-contact-sensitive guinea pigs. Lymph node (and spleen) lymphocytes: (a) transfer contact sensitivity to syngeneic recipients when harvested at the time of unresponsiveness; (b) are only temporarily inactivated in tolerant recipients by the desensitizing procedure; (c) enter the lymph node (or spleen) compartments in a higher proportion than peritoneal exudate cells; (d) are not susceptible to inactivation in vitro; and (e) are not permanently desensitized when released into the circulation by an intravenous injection of Bordetella pertussis vaccine. These results indicate that the resistance of primed lymph node cells to the desensitizing procedure may account for the reappearance of contact sensitivity in desensitized guinea pigs.

Mechanism of densensitization in DNCB-contact sensitive guinea pigs.

Contact sensitivity to dinitrochlorobenzene (DNCB) in guinea pigs could be rapidly suppressed by intravenous injection of dinitrobenzene sulfonic acid sodium salt (DNBSO3). This suppression is transient and antigen-specific. Macrophages from desensitized animals are not inactivated as shown by their ability to react, both in vivo and in vitro to lymphokines produced in a separate system. Therefore, effector lymphocytes are considered the target for the desensitizing antigen. Using an adoptive transfer system it was demonstrated that effector lymphocytes are inactivated by a direct effect of the hapten. Since this inactivation can be reversed by trypsin treatment, a receptor blockade of effector lymphocytes is proposed as the mechanism of desensitization of DNCB-contact sensitive guinea pigs. This does not exclude the possibility that additional mechanisms such as suppressor cells, compartmentalization or endogenous proliferation of lymph node lymphocytes may play an additional role.

Studies on contact sensitivity to chromium in the guinea pig. The role of valence in the formation of the antigenic determinant.

Guinea pigs sensitized with either the trivalent chromium chloride or the hexavalent potassium dichromate are capable of reacting in vivo and in vitro to challenges with both chromium salts. This double reactivity is retained also after repeated restimulations with only 1 of these chromium compounds. From the failure to select lymphocytes directed specifically against a chromium determinant of a particular valence it is concluded that by sensitization with chromium salts of different valences a common determinant or closely related determinants are formed. It is suggested that this determinant is formed by chromium in the trivalent form.

In vitro DNA synthesis in lymphocytes from guinea pigs epicutaneously sensitized with DNCB.

Lymph node lymphocytes from guinea pigs sensitized with the hapten homogenized in Freund's complete adjuvant or pretreated with cyclophosphamide shortly before an epicutaneous sensitization are capable of responding in vitro to a larger set of antigenic preparations than the lymphocytes from only epicutaneously sensitized animals. This may be due to a formation of a larger set of antigenic determinants when the hapten was homogenized in Freund's complete adjuvant or to a formation of a larger repertoire of lymphocytes capable of recognizing these determinants as it might be the result of pretreatment with cyclophosphamide. These procedures may also change the proportion of responding cells in the lymphocyte suspensions.

Antigen-specific T-cell lines in DNCB-contact sensitivity in guinea pigs.

Expanded DNP-specific guinea pig T cells exhibit enhanced in vitro and in vivo activity as demonstrated by DNA synthesis and systemic adoptive transfer of contact sensitivity. Moreover, expanded lymphocytes are capable of accomplishing local passive transfer of contact sensitivity and producing interleukin 2, vascular permeability-increasing and macrophage migration-inhibiting factors. Expansion of hapten-specific lymphocytes offers a suitable model for studying eliciting mechanism of allergic contact dermatitis in humans.

Induction of contact sensitivity to a broad variety of allergens with haptenized macrophages.

Using guinea pigs an analysis could be made of various aspects of contact sensitivity (CS) induced by subcutaneous injection of syngeneic haptenized macrophages (oil-induced peritoneal exudate cells, PEC) as compared to epicutaneous sensitization. Very little PEC-bound hapten (dinitrochlorobenzene, or oxazolone) is needed for optimum sensitization. Nevertheless, both sensitization methods induce a state of CS that may last for over 6 months, give rise to hapten-specific antibodies with a similar isotype distribution, and show susceptibility to cyclophosphamide pretreatment. In addition, time courses and microscopic appearance of skin test reactions after either way of sensitization are identical. CS to a broad variety of physicochemically different antigens, including nickel, penicillin, and acrylates, is readily induced by syngeneic PEC, haptenized following a standardized procedure. As Freund's complete adjuvant is known to cause serious side effects like ulceration and long-lasting granuloma formation, immunization with haptenized PEC should now be considered as a clean and effective alternative in experimental CS studies.

Self molecules in induction of hypersensitivity and tolerance in DNCB contact sensitivity in the guinea pig.

Dinitrophenylated macrophages are efficient inducers of contact sensitivity and of tolerance to dinitrochlorobenzene, depending on the mode of application. Contact sensitivity induced by an intradermal injection of DNP-M phi is genetically restricted, whereas tolerance induced by an intravenous injection is, in guinea pigs, not under control. This tolerance is complete in the majority of animals, but is reversed by DNCB in Freund's complete adjuvant and prevented by pretreatment with cyclophosphamide. Tolerance induced by an intravenous injection of the unconjugated hapten is not reversed by DNCB in FCA, but is abrogated by an intradermal injection of DNP-M phi. This abrogation does not occur, however, when DNCB in FCA is applied simultaneously with the DNP-M phi. In further experiments, it is demonstrated that the genetic restriction of induction of contact sensitivity by DNP-M phi is on the level of antigen recognition and is not due to the nonidentity of the Ia structures on macrohages used for induction and the Ia structures involved in elicitation of contact sensitivity.

Resistance of gram-negative bacteria to antibiotics in large calf agglomerations.

The antibiotic resistance of E. coli, Citrobacter, Enterobacter-Klebsiella and Pseudomonas aeruginosa strains isolated from calves was tested. A high proportion of multiresistance was found even in E. coli strains isolated from newborn calves. Gram-negative bacteria isolated from animals in three large calfhouses were almost 100% resistant to ampicillin, tetracyclines and sulphonamides. Multiresistance was general and varied from 5 to 12 antibiotics among different strains. Initial high sensitivity to antibiotics which had never been used before was observed. Antibiotic resistance rapidly increased after use started. The usefulness of antibiotics in E. coli induced diarrhea is questioned and oral rehydration is appraised.

Polycyclic aromatic isothiocyanate compounds as fluorescent labeling reagents.

Polycyclic aromatic isothiocyanates were synthesized in an attempt to produce new fluorescent agents for protein labeling and for use in microanalytical techniques. The relative fluorescence of these reagents, the required intermediates, and the derivatives were established. Of the compounds evaluated, the 9-acridine derivatives were the most promising.

Rabies epizootiology and control methods in Czechoslovakia.

In Czechoslovakia from 1976-1980. 26,306 animals from 44 different species were examined for rabies. A total of 3270 rabies cases were diagnosed during this period. Foxes account for 90% of all cases. Rabies in domestic animals is reported only sporadically. Rabies was permanently established in the mountainous border regions up to the year 1975. Since 1976 the wave of rabies has gradually spread to the interior of the country. The border mountains did not restrict the movement of foxes, which are responsible for carrying the disease, towards the interior. The river Vltava has stemmed the spreading of rabies for more than two years but it cannot be considered an absolute natural barrier. A bounty of 150 Crowns is paid for every fox handed over to the Veterinary Service. In districts with rabies incidence the gassing of fox dens is carried out. The principal measures relating to domestic animals are the compulsory, and charge free, vaccination of dogs in the whole country.

Induction of tolerance to DNCB-contact sensitivity in guinea pig fetuses.

1. Female guinea pigs made tolerant before pregnancy do not transfer tolerance to their offspring. This result favours the concept of cellular mechanism of tolerance. 2. Guinea pig fetuses become tolerant when exposed to the tolerogen in the last two weeks of pregnancy. This is due to active tolerization by the tolerogen passing the placental barrier. 3. Fetuses exposed to the antigen earlier did not develop tolerance. This is due to immunological immaturity rather than to insufficiently developed vascularization. No functional active depot of tolerogen is formed. 4. Guinea pigs become immunologically mature between the 54th and 61st day of fetal live.

[Induction and synchronization of pregnancy in cows]. / Indukce a synchronizace porodu u krav.

Inductions and synchronizations of parturitions by the analogue PG F2alpha, Cloprostenol, were tested in cows under production conditions. The average time from induction to delivery is 40.5 hours (33-49 hours). No significant relation exists between the length of gravidity and the time of delivery induction (correlation coefficient = -0.325). A scheme was proposed from the system of calving days in cows to organize synchronized parturitions. In production conditions the induction and synchronization of cow parturitions cannot be recommended because amnions are retained frequently (69.7%). No relationship was demonstrated between gravidity length at the time of delivery induction and the order of parturition in the cow (first-calver-cow).

[Induction of labor and its synchronization in hogs]. / Indukce porodu a jejich synchronizace u prasnic.

The authors describe the synchronization of farrowing by the induction of parturition with a prostaglandin F2alpha analogue (Cloprostenol). The time sequence of the beginning of parturitions was recorded in 147 sows after administration of 175 microgram Cloprostenol. 93.7% of the parturitions take place between the 14th and 39th hour after administration, the peak time being between the 24th and 27th hour (31.2%). The schedule of the farrowing days is described as a prerequisite for a qualitative change in the organization of work in large pig herds.

[Effect of tylosin in pigs]. / Ucinek tylosinu u prasat

The effect of tylosine and sulphadimidine, chlortetracycline, and bacitracin in feed was studied in 1275 piglets from 120 litters; the values obtained were compared with the control group given no antibiotics. Three Tylan injections were applied to a half of the animals on the 2nd, 5th, and 28th day after birth. The Tylan program did not lead to any significant reduction of piglet mortality before the 50th day of life. In neither of the groups did Tylan injections reduce mortality at the level of statistical significance. From the age of 56 days, the Tylan-application program provides statistically significant weight gains, as compared with other groups. The group with Czechoslovak antibiotics had the same weight as the group fed without antibiotics. The occurrence of pathological and anatomic findings on lungs showed no statistically significant differences in the two groups. The presence of tylosine in blood could not be ascertained after the oral application of even much higher doses than those used in the Tylan-application program. Small incidence of rhinitis does not allow for drawing any conclusions concerning the effects of Tylan.