The adrenergic agonist tizanidine has differential effects on flexor reflexes of intact and spinalized rat

Tizanidine with its predominant alpha 2-adrenergic properties is a potent myorelaxant drug used clinically in spastic patients. The aim of this study is to analyse further the mechanisms by which this substance exerts its influence on spinal reflexes. It was found that tizanidine dose-dependently diminished flexor reflexes in intact chloralose-anaesthetized rats, and also, but slightly less, in unanaesthetized decerebrate rats. In spinalized rats (1-5 days postoperatively), flexor reflexes were, however, enhanced by tizanidine, especially by the higher doses. Pretreatment with the alpha 2-blocker yohimbine antagonized the depressant action of tizanidine in intact rats whereas the alpha 1-blocker prazosin antagonized the facilitatory action of tizanidine in the spinalized rats. The reflex depression might be explained by a removal of a tonic facilitation of spinal neurons by the descending noradrenergic fibres, because tizanidine is likely to reduce, like clonidine, the spontaneous activity of locus coeruleus neurons by presynaptic autoinhibition. In spinalized preparations, a net facilitatory alpha 1-mediated action may be revealed by the higher doses of tizanidine that would be unopposed by the alpha 2-mediated disfacilitation.

[Value of prophylactic irradiation to supraclavicular areas in small cell lung carcinoma--analysis of 104 patients]

A series of 104 patients with limited small cell lung carcinoma was treated by combination of chemotherapy and radiotherapy from August 1975 to July 1981. 104 patients were divided into three groups: prophylactic irradiation to supraclavicular areas (14 patients), non-prophylactic group (72 patients), non-prophylactic irradiation with positive supraclavicular lymph node metastasis after the treatment (18 patients). The 5 year survival rates of the three groups were 14%, 6% and 0%. Distant metastasis rates after the treatment were 36%, 52% and 61%, respectively. The supraclavicular lymph node metastasis rate after the treatment was higher in patients with intra-thoracic lymph node metastasis before the treatment (25%) than in those without this metastasis (0%). It is suggested that, for small cell lung cancer patients, especially with intra-thoracic lymph node metastasis before the treatment, prophylactic irradiation to the supraclavicular areas be valuable.

Cloning and expression of cDNA for human poly(ADP-ribose) polymerase

cDNAs encoding poly(ADP-ribose) polymerase from a human hepatoma lambda gt11 cDNA library were isolated by immunological screening. One insert of 1.3 kilobases (kb) consistently hybridized on RNA gel blots to an mRNA species of 3.6-3.7 kb, which is consistent with the size of RNA necessary to code for the polymerase protein (116 kDa). This insert was subsequently used in both in vitro hybrid selection and hybrid-arrested translation studies. An mRNA species from HeLa cells of 3.6-3.7 kb was selected that was translated into a 116-kDa protein, which was selectively immunoprecipitated with anti-poly (ADP-ribose) polymerase. To confirm that the 1.3-kb insert from lambda gt11 encodes for poly(ADP-ribose) polymerase, the insert was used to screen a 3- to 4-kb subset of a transformed human fibroblast cDNA library in the Okayama-Berg vector. One of these vectors [pcD-p(ADPR)P; 3.6 kb] was tested in transient transfection experiments in COS cells. This cDNA insert contained the complete coding sequence for polymerase as indicated by the following criteria: A 3-fold increase in in vitro activity was noted in extracts from transfected cells compared to mock or pSV2-CAT transfected cells. A 6-fold increase in polymerase activity in pcD-p(ADPR)P transfected cell extracts compared to controls was observed by "activity gel" analysis on gels of electrophoretically separated proteins at 116 kDa. A 10- to 15-fold increase in newly synthesized polymerase was detected by immunoprecipitation of labeled transfected cell extracts. Using pcD-p(ADPR)P as probe, it was observed that the level of poly(ADP-ribose) polymerase mRNA was elevated at 5 and 7 hr of S phase of the HeLa cell cycle, but was unaltered when artificial DNA strand breaks are introduced in HeLa cells by alkylating agents.

Organochlorine pesticide residues in paddy fish in Malaysia and the associated health risk to farmers

Paddy fish (Trichogaster pectoralis Regan) were collected from five sampling locations in a major paddy-growing area of Malaysia and analysed for organochlorine residues. During the same period, ten farming families, chosen at random from each of the five sampling sites, were interviewed. Information was obtained about the quantity of paddy fish consumed, the amount and type of pesticide used on the paddy-field, and the frequency of application.The pesticide residues found in the fish samples were aldrin/dieldrin, chlordane, HCH, and DDT. Only the projected maximum intake level for aldrin/dieldrin approached the acceptable daily intake as recommended by FAO/WHO; other residue levels were relatively low. However, this study considered only fish; the total daily intake of pesticide residues by the Malaysian paddy farmer may be considerably increased by consumption of other contaminated food.