Cytogenetic changes in peripheral blood lymphocytes of oncology patients

Analysis of home and foreign literature underlies the discussion of the significance of cytogenetic variations (frequency of aberrant cells and SCE-heteromorphism of C-chromatin and brittleness of chromosomes as indices of chromosome instability in oncological patients.     

Cytogenetic study in peripheral blood lymphocytes from asthmatic patients receiving continued therapy with theophylline.

Possible cytogenetic effects of theophylline have been investigated in asthmatic patients undergoing continuous therapy with this drug. Sister-chromatid exchanges (SCE), chromosome aberrations (CA) and proliferating rate indices (PRI) were evaluated in cultured peripheral blood lymphocytes from patients receiving theophylline alone, theophylline plus inhaled beta 2 adrenergic drugs or theophylline in combination with beta 2 adrenergic agents and corticoids. Two samples from each individual were obtained in order to perform a prospective study: before the theophylline medication (sample A) and at a time after the beginning of treatment (sample B). After treatment (66.3 +/- 37.8 days), an increase in SCE was observed without modifications either in PRI or in CA. Patients receiving beta 2 adrenergics or beta 2 adrenergics plus glucocorticoids before and during theophylline treatment, did not respond differently than those on theophylline alone.     

Sister-chromatid exchanges in lymphocytes from patients with Schistosoma hematobium

Sister-chromatid exchange (SCE) frequencies were studied in peripheral blood lymphocytes from 19 patients (13 males and 6 females) with Schistosoma hematobium, prior to the initiation of chemotherapy. The mean frequency of SCE per metaphase for the patients (both sexes) was 10.4 +/- 4.2 which was significantly higher (P less than 0.01) than the mean SCE (6.4 +/- 1.1) score for 35 healthy controls. A highly significant reduction in lymphocyte division and delay in cell-cycle progression as a result of infection were also noticed. These data indicate that infection with S. hematobium could increase SCEs in the host somatic cells.     

Schistosoma mansoni: tracer studies in mice

Mice with patent Schistosoma mansoni infections were injected via the tail vein with peroxidase and Thorotrast, and the ingestion of these tracers by the worms was followed over time. Both tracers are found initially in the crypts of the dorsal tegument of the male; however, the disappearance of the peroxidatic activity from the crypts, presumably by digestion of the peroxidase, occurs prior to the disappearance of the Thorotrast. Only Thorotrast appears in the cecal lumen, and the amount is greater in the female than in the male. Little tracer is ever found between the pair in the gynecophoric canal, and no tracer was ever found in the cytoplasm of the worms. These results suggest that while the tegumental and cecal surfaces are cytoarchitecturally identical in both sexes, they may in fact exhibit functional specializations.     

Uridine phosphorylase from Schistosoma mansoni

Uridine phosphorylase is the only pyrimidine nucleoside cleaving activity that can be detected in extracts of Schistosoma mansoni. The enzyme is distinct from the two purine nucleoside phosphorylases contained in this parasite. Although Urd is the preferred substrate, uridine phosphorylase can also catalyze the reversible phosphorolysis of dUrd and dThd, but not Cyd, dCyd, or orotidine. The enzyme was purified 170-fold to a specific activity of 2.76 nmol/min/mg of protein with a 16% yield. It has a Mr of 56,000 as determined by molecular sieving on Sephadex G-100. The mechanism of uridine phosphorylase is sequential. When Urd was the substrate, the KUrd = 13 microM and the KPi = 533 +/- 78 microM. When dThd was used as a substrate, the KdThd = 54 microM and the KPi = 762 +/- 297 microM. The Vmax with dThd was 53 +/- 9.8% that of Urd. dThd was a competitive inhibitor when Urd was used as a substrate. The enzyme showed substrate inhibition by Urd, dThd (greater than 0.125 mM) and phosphate (greater than 10 mM). 5-(Benzyloxybenzyloxybenzyl)acyclouridine was identified as a potent and specific inhibitor of parasite (Ki = 0.98 microM) but not host uridine phosphorylase. Structure-activity relationship studies suggest that uridine phosphorylase from S. mansoni has a hydrophobic pocket adjacent to the 5-position of the pyrimidine ring and indicate differences between the binding sites of the mammalian and parasite enzymes. These differences may be useful in designing specific inhibitors for schistosomal uridine phosphorylase which will interfere selectively with nucleic acids synthesis in this parasite.     

Study of Schistosoma mansoni isolates from patients with failure of treatment with oxamniquine

After three successive treatments with oxamniquine the continuing elimination of Schistosoma mansoni eggs was observed in patients, who came from various regions of Brazil, with different clinical forms of schistosomiasis. The objective of the present study was to determine the experimental behaviour of five different S. mansoni isolates in Swiss Webster mice that were submitted to treatment with the same drug. The experimental group with failure of treatment showed higher mean number of surviving male worms when it was compared to the group without failure of treatment. These date suggest the possibility of resistance to oxamniquine.     

Further studies of genetic variation in Schistosoma mansoni

Genetic studies on the human blood fluke Schistosoma mansoni were undertaken using starch gel electrophoresis to detect new gene loci and allelic variation. The number of enzyme staining systems useful with S. mansoni was increased from 14 to 34. It was found that unmated female worms stained as well as male worms. Three new polymorphic loci, fructose biphosphatase (FBP), gly-leu dipeptide peptidase (PEP-4), and glyceraldehyde-3-phosphate dehydrogenase (G3PDH) were detected. This brings the known number of polymorphic loci to 10 for this species. One locus (FBP) was found to be polymorphic in the PR-1 strain of S. mansoni. This strain was previously reported to be invariant.     

Cytogenetic studies of blood lymphocytes of cosmonauts after long-ter, space flights

An analysis was performed of unstable chromosomal aberrations in peripheral blood of 36 cosmonauts after long-term space missions on "Mir" orbital station. 25 cosmonauts were examined before their flights to score spontaneous yields of cytogenetical damage. In all cases the doses absorbed by crews during space flights did not exceed permissible levels of irradiation, adopted for cosmonauts. The frequencies of chromosomal-type aberrations after space missions were found to increase significantly compared to the pre-flight levels. The yields of dicentrics and centric rings on the average were as high as 0.12 +/- 0.02 and 0.47 +/- 0.06% before and after the 1st flight, 0.18 +/- 0.05 and 0.71 +/- 0.11% before and after the 2nd flight respectively. During the inter-flight periods, usually lasted 1.5-2 years, the yields of chromosome damage lowered, but did not reach their spontaneous values. After each next flight the yields of chromosome aberrations increased again. The cytogenetical damage detected in cosmonauts' peripheral blood lymphocytes after chronic action of low doses of space radiation points out a possible increase in risks of stochastic effects in distant future for crews after long-term space missions.     

Schistosoma mansoni: ultrastructural studies on the esophageal secretory granules.

The posterior portion of the esophageal gland of Schistosoma mansoni produces a granule that is highly structured internally. Each granule consists of arrays of membrane-bound tubules enclosed by a membrane. Cytochemical tests indicate that the granules are not reactive for cytochrome c-oxidase but du react for macromolecular carbohydrates. It is believed that the granules are synthesized in the Golgi complex and are secreted at the base of the luminal amplifications of the esophagus. Colchicine treatment results in an accumulation of granules in the cyton region. Their physiological function is still undetermined, but it is hypothesized that they are involved with early stages of digestion of host red blood cells.     

Cytogenetic studies on three pheochromocytomas derived from patients with von Hippel-Lindau syndrome

Summary Chromosomal analyses of three pheochromocytomas from patients with von Hippel-Lindau syndrome are reported. One pheochromocytoma revealed a normal karyotype, another tumor showed a trisomy 7 as the only chromosomal abnormality, whereas in a further sample a polyclonal chromosome constitution was detected. In addition to a normal 46,XX cell line, four distinct chromosomally abnormal cell lines could be identified. One cell line revealed partial trisomy for the long arm of chromosome 1 and additionally exhibited the phenomenon of telomeric association. Most interestingly, three further cell clones showed rearrangements of chromosome 3 including the region where the von Hippel-Lindau gene was mapped; three rearrangements resulted in a partial or total trisomy of 3p. Our findings are discussed in relation to previously reported cytogenetic and molecular results regarding von Hippel-Lindau syndrome.     

Leucine aminopeptidase of the human blood flukes, Schistosoma mansoni and Schistosoma japonicum

An array of schistosome endoproteases involved in the digestion of host hemoglobin to absorbable peptides has been described, but the exoprotease responsible for catabolising these peptides to amino acids has yet to be identified. By searching the public databases we found that Schistosoma mansoni and Schistosoma japonicum express a gene encoding a member of the M17 family of leucine aminopeptidases (LAPs). A functional recombinant S. mansoni LAP produced in insect cells shared biochemical properties, including pH optimum for activity, substrate specificity and reliance on metal cations for activity, with the major aminopeptidase activity in soluble extracts of adult worms. The pH range in which the enzyme functions and the lack of a signal peptide indicate that the enzyme functions intracellularly. Immunolocalisation studies showed that the S. mansoni LAP is synthesised in the gastrodermal cells surrounding the gut lumen. Accordingly, we propose that peptides generated in the lumen of the schistosome gut are absorbed into the gastrodermal cells and are cleaved by LAP to free amino acids before being distributed to the internal tissues of the parasite. Since LAP was also localised to the surface tegument it may play an additional role in surface membrane re-modelling.