Methods for investigation and estimation of individual chemosensitivity of tumors (review)

A review of the current methods for the estimation of tumor sensitivity to antiblastomic drugs is presented. Methods for the in vitro and in vivo cultivation of tumor cells are discussed. Among them the following methods are reviewed: the method for the cultivation of tumor heterotransplants in diffusion chambers and its various modifications, the method for the cultivation of human tumors under the kidney capsule, the method for the cell cultivation in primary short-term suspensions, the methods using enriched media, the methods for the cell cultivation on acetate cellulose fibres, in monolayers, etc.     

Termination within oligo(dT) tracts in template DNA by DNA polymerase gamma occurs with formation of a DNA triplex structure and is relieved by mitochondrial single-stranded DNA-binding protein

Xenopus laevis DNA polymerase gamma (pol gamma) exhibits low activity on a poly(dT)-oligo(dA) primer-template. We prepared a single-stranded phagemid template containing a dT41 sequence to test the ability of pol gamma to extend a primer through a defined oligo(dT) tract. pol gamma terminates in the center of this dT41 sequence. This replication arrest is abrogated by addition of single-stranded DNA-binding protein or by substitution of 7-deaza-dATP for dATP. These features are consistent with the formation of a T.A*T DNA triplex involving the primer stem. Replication arrest occurs under conditions that permit highly processive DNA synthesis by pol gamma. A similar replication arrest occurs for T7 DNA polymerase, which is also a highly processive DNA polymerase. These results suggest the possibility that DNA triplex formation can occur prior to dissociation of DNA polymerase. Primers with 3'-oligo(dA) termini annealed to a template with a longer oligo(dT) tract are not efficiently extended by pol gamma unless single-stranded DNA-binding protein is added. Thus, one of the functions of single-stranded DNA-binding protein in mtDNA maintenance may be to enable pol gamma to successfully replicate through dT-rich sequences.     

Role of the B cell antigen receptor in antigen processing and presentation. Involvement of the transmembrane region in intracellular trafficking of receptor/ligand complexes

To study the role of the B cell Ag receptor (membrane-bound Ig [mIg]) in Ag processing and presentation, we have generated several Ig transfectants that express transfected TEPC-15 idiotype (T15-Id) mIgM with phosphorylcholine (PC)-binding specificity. The wild-type Ig transfectant is able to present a specific Ag (e.g., PC-conjugated hen egg-white lysozyme [PC-HEL]) more efficiently than a nonspecific Ag (HEL) to a T cell hybridoma recognizing an epitope on the HEL molecule. A substitution in the entire spacer, transmembrane, and cytoplasmic region of mIg with an equivalent region of I-A alpha chain completely abolishes this mIg-enhanced Ag presentation. Experiments with the wild-type and substituted variant Ig transfectants suggest that this substitution may interfere with normal intracellular trafficking of mIg after cross-linking with specific Ag or antibodies specific for the mIg (anti-T15-Id mAb). Prolonged treatment of the wild-type Ig transfectants with specific Ag or anti-T15-Id mAb reduces the surface expression of T15-Id mIgM and leads to an accumulation of T15-Id mIgM inside the cells. The reduced surface expression and the elevated cytoplasmic accumulation of T15-Id mIgM are not observed in the variant Ig transfectant. Despite the ability of the variant to endocytose ligands similarly to the wild-type Ig transfectant, this variant displays a higher rate of recycling of the mIg/ligand complexes back to the cell surface and a lower rate of degradation of the ligands. These abnormalities may be responsible for the deficiency in mIg-mediated enhancement of Ag presentation in the variant Ig transfectant. Therefore, our results suggest that the transmembrane region of mIg is involved in intracellular trafficking of receptor/ligand complexes and that proper delivery and handling of internalized Ag are required for the enhanced presentation of specific Ag by B cells.     

The effect of the vole subspecies of the plague microbe on the viability of Callopsylla caspia fleas]

When infected with cultures of plague microbe reared at 28 C the experimental fleas showed no reliable differences in the mortality as compared to control ones. By contrast, the infection with agent cultures reared at 37 C as well as the infection on agonizing white mice caused a statistically reliable increase in the mortality in insects of both sexes. In the groups of fleas infected on white mice the most intensive mortality was observed during the first 24 hours after the infectious feeding that, apparently, is connected with the effect of toxins present in the blood of agonizing animals.     

Mast cell involvement in the rat paw oedema response to 1,8-cineole, the main constituent of eucalyptus and rosemary oils

The present studies tested the ability of 1,8-cineole to produce inflammatory oedema in the hind paw of the rat and verified the possible involvement of mast cells in the response. Subplantar injection of 1,8-cineole (10, 15 and 20 microl/paw) induced a dose-dependent paw oedema which was apparent within 30 min. At higher doses the oedema effect was persistent, peaked at 2 h, and then decreased gradually but was still pronounced at 24 h post injection. In contrast, the oedema produced by mast cell degranulator compound 48/80 (10 microg/paw) had a rapid onset with a peak effect at the first hour, followed by a gradual decrease thereafter and at 24 h post injection it was almost absent. The oedema response to 20 microl 1,8-cineole was significantly inhibited throughout its time-course in rats pretreated with antihistaminic and antiserotonergic drugs such as diphenhydramine, methysergide and cyproheptadine or with ketotifen, a mast cell stabilizer. A more effective blockade of the oedema response was, however, observed in rats depleted of mast cell granules by systemic treatment with compound 48/80. Furthermore, 1,8-cineole was able to cause rat peritoneal mast cell degranulation (94%) in vitro, in a concentration as low as 0.3 microl/ml, which was almost comparable to that produced by 0.1 microg/ml of compound 48/80. The data provide evidence of a key role for the mast cell in 1,8-cineole-induced hind paw oedema in the rat.     

Posterior fossa decompression without duraplasty in infants and young children for treatment of Chiari malformation and achondroplasia

Some children with Chiari malformation and achondroplasia require posterior fossa decompression that typically includes expansion of the dural tube with duraplasty. Infants and young children, however, may have a more distensible dura mater than do older patients. Furthermore, the structures that compress the hindbrain of young patients may be the bone and abnormally thickened atlantooccipital membrane, i.e., dural band, rather than the dura mater. We have treated 7 children who had Chiari malformation or achondroplasia with posterior fossa decompression without duraplasty. All children were symptomatic; 3 had Chiari-I malformations, 2 Chiari-II malformations, and 2 achondroplasia. The age range was 3 months to 2.5 years (mean 15.1 months). The exent of tonsillar herniation and other hindbrain anomalies was assessed on preoperative magnetic resonance imaging. The infants with Chiari-II malformations underwent cervical laminectomies, whereas the other young children with Chiari-I malformations or achondroplasia underwent suboccipital craniectomy as well as cervical laminectomy. In Chiari malformation, the dural band was divided; in achondroplasia, there was no identifiable dural band. Following bony decompression and division of the identifiable dural band, immediate expansion of the stenotic region with visible cerebrospinal fluid space posterior to the neural elements could be ascertained by intraoperative ultrasonography. During a follow-up period ranging from 4.5 months to 4 years (mean 22 months), all patients made improvements in their symptoms, 3 having complete resolution of their symptoms. This preliminary experience indicates that in children 2 years of age or younger, posterior fossa bony decompression without duraplasty can be effective treatment for Chiari malformations or achondroplasia.