Ecological studies on Culex tritaeniorhynchus as a vector of Japanese encephalitis

In the Republic of Korea, light-trap assessments and collections from cows and pigs after sunset were highly successful in monitoring the seasonal abundance of C. tritaeniorhynchus, the primary vector of Japanese encephalitis. The dates and duration of the population peaks at semirural suburbs of Seoul and Pusan were markedly different from those at a rural rice-growing site. The main breeding sites in these three areas were, respectively, swamps, marshes, and ricefields. The overall adult densities were the lowest at the rice-growing site where agricultural pesticides were extensively used. A short period of man-vector contact occurred at each study site at low densities when the natural population was at its peak. These vector monitoring techniques, coupled with information on antibodies in swine, represent a simple but valuable surveillance system.

The effects of betel-nut chewing on the buccal mucosa: a histological study

Sixty-two "leukoplakias" from the cheeks of betel-nut chewers in West Malaysia were studied histologically. Ten biopsies were from non-tobacco betel-nut chewers. An amorphous von Kossa positive layer was seen on the keratin surface in 42 specimens. Tobacco did not appear essential for its formation, and it appeared to be significantly associated with parakeratosis. Its possible significance as a cuticle-like layer prolonging contact between carcinogens and the mucosa is discussed.Parakeratosis appeared to be the most common form of cornification seen, and the mitotic activity in parakeratinized leukoplakias appeared to be significantly greater than orthokeratinized leukoplakias.Comparison with studies on other population samples using different quids suggested that severe histological changes were more likely to be seen when tobacoo-containing quids were chewed as compared to non-tobacco-containing quids.An attempt to correlate the histological changes seen with the clinical habit in leukoplakias from chewers using tobacco-containing quids suggested that epithelial atrophy appeared to be significantly related to the duration of the habit but not to the "intensity" of the habit.

The effects of betel-nut chewing on the buccal mucosa of 296 Indians and Malays in West Malaysia. A clinical study

Changes in the buccal mucosa of 296 Indian and Malay betel-nut chewers in Perak, West Malaysia, were studied clinically. 167 out of 212 Indian subjects incorporated tobacco in their quids, while 45 out of 84 Malay subjects incorporated. "Gambir". The Indians appeared to show a higher proportion of mucosal changes, particularly when tobacco was used. "Gambir" did not appear to be potent in the production of mucosal changes. Comparison with studies in other parts of the world suggested comparable findings with respect to both tobacco and non-tobacco chewing samples, and there would appear to be some evidence that tobacco-containing quids are likely to produce a higher proportion of mucosal changes as compared to non-tobacco-containing quids. An attempt to demonstrate a dose-effect relationship by dividing the subjects into "slight" and "heavy" chewers did not yield significant differences between these two categories in each of the groups.

Metal complexes of tridentate hybrid ligands. I. Cobalt and nickel conlplexes of ligands containing the donor sequence As-N-O

The interaction of the new tridentate ?hybrid? ligand, N-o- dimethylarsino-phenylsalicylaldimine (As-N-O), with cobalt(II) salts leads to the formation of cationic octahedral cobalt(III) complexes of the type [Co(As-N-O)2]+. No cobalt(II) complex entities containing the ligand could be isolated. With nickel(II) salts three types of octahedral complexes were obtained: (a) [Ni(As-N-O)2],H2O, (b) Ni(As-N- O)X,-xH2O (X = Cl, Br, or NCS), (c) [Ni2(As-N-O)3ClO4]. Electronic spectra, conductivity measurements, and magnetic data have been used to determine the structure of the complexes isolated. The ?hybrid? ligand appears to operate overall as a relatively weak field ligand.

Clay Sols versus Clay Gels: Biological Activities Compared

Clay gels were prepared by extrusion of sodium-Wyoming bentonite pastes through a small orifice. Clay sols were prepared from the gels by rapping on the laboratory bench for disturbance. Lettuce seeds germinated faster, microbes generated more heat, and corn seedlings absorbed more (22)Na in the sols than in the gels. These differences in biological activity are attributable to changes in water properties and ion activities that accompany transformation from gelsol.

Decreased Ca2+ uptake by sarcoplasmic reticulum after coronary artery occlusion for 60 and 90 minutes

Dogs were placed on total cardiopulmonary bypass and the anterior descending branch of the left coronary artery was occluded for the duration of 15 min, 60 min or 90 min. In some experiments the coronary perfusion was restored after the occlusion. Fragments of sarcoplasmic reticulum were isolated from ischemic and nonischemic cardiac tissue and the Ca 2+ transport mechanism of the reticulum was studied. The Ca 2+ uptake of reticulum fragments obtained from cardiac tissue ischemic for 15 min was not impaired compared to the nonischemic control hearts. However, ischemia for 60 or 90 min caused impairment of Ca 2+ uptake by the sarcoplasmic reticulum isolated from the ischemic tissue. The functional damage brought by coronary occlusion for 60 min could be reversed by the restoration of coronary circulation after the occlusion, but after occlusion for 90 min it was irreversible.

Spectral and biological changes induced in nicotinic acid and related compounds by ultraviolet light

1. Irradiation of nicotinic acid, nicotinamide, nicotinamide N-oxide, N'-methyl-4-pyridone-3-carboxamide, reduced nicotinamide-adenine dinucleotide and pyridine with ultraviolet light at 253.7mmu leads to striking spectral changes. 2. Nicotinic acid and nicotinamide are broken down to photosensitive intermediates which in turn undergo photodecomposition. 3. A major photoproduct of [7-(14)C]nicotinic acid is radioactive and absorbs ultraviolet light, but is inactive as a growth factor for Candida pseudotropicalis. 4. Irradiation of nicotinamide gives rise to small quantities of a biologically active photoproduct having the same R(F) as nicotinic acid. A second photoproduct is also formed, but its identity has not yet been established. 5. Irradiation of nicotinamide N-oxide leads to the formation of several photoproducts, one of which has the same R(F) as nicotinamide, absorbs ultraviolet light, and is biologically active. 6. Evidence is presented that irradiation of ethanolic solutions of N'-methyl-4-pyridone-3-carboxamide gives rise to acetaldehyde. 7. Irradiation of reduced nicotinamide-adenine dinucleotide in the presence of acetaldehyde leads to the formation of oxidized nicotinamide-adenine dinucleotide, which in turn can break down to nucleotide and/or nucleoside (depending on the conditions of the reaction). 8. The quantum yields of photolysis and the molar photosensitivities have been determined for N'-methyl-4-pyridone-3-carboxamide and nicotinamide N-oxide. 9. The possible biological significance of these photoreactions is discussed in relation to photosynthesis, visual-pigment metabolism and ultraviolet-light-induced cell damage. 10. A four-step theory is presented for the biochemical evolution of oxidation-reduction systems, involving photoactivated transformations of pyridine derivatives.