A biological sampling problem illustrated by the population structure and growth patterns of Sardinella aurita at Tripoli,Libya

Synopsis Sardinella aurita were sampled from catches of the lampara fishery at Tripoli, Libya during October 1979 through to September 1980. Landings consisted mainly of adult fish with large (mode 21–26 cm total length), relatively fast growing 3–5-group individuals in winter and spring and smaller (mode 14–20 cm total length), slow growing 2- and 3-group fish in summer. Gonad growth commenced in April, when the fish were feeding on zooplankton, and continued at the expense of mesenteric fat until July. It is suggested that the older and bigger fish spawn first, probably after having moved westwards, and that this results in spatial and temporal differences in length at age within the population. There was no consistent difference in growth rate between the sexes, but because first maturity in males tends to occur earlier than in females, there were length distribution differences between the sexes in the youngest (2+) age group as sampled.     

Concentrations of steroids in the utero-ovarian vein blood,serially collected from the two sides of individual baboons,during the follicullar phase

The purpose of this study was to determine and compare the follicular phase steroid hormone secretion into the utero-ovarian vein by the ovary with a dominant follicle and the contralateral ovary in the same baboon. Serial utero-ovarian vein blood from both sides was collected in 25 baboons by the use of a laparoscope on alternate days, starting on day 1 or 3 of the cycle and continuing through 2 to 3 days post-ovulation. Approximately 3–4 days before the day of expected ovulation, samples were collected at 8-hr intervals. Steroids estradiol (E₂) and progesterone (P) were measured in all utero-ovarian vein plasma by radioimmunoassay. In the peripheral plasma, E₂, P, LH, and FSH measurements were carried out. Concentrations of steroids were significantly higher on the side of the ovulating ovary by day 5 before ovulation. Individual plots however, indicated that some baboons may establish the dominant side as early as day 11 before ovulation. The preovulatory gonadotropins had a differential effect on the two ovaries. For example, E₂ values on the ovulatory side ovary declined after increases in LH/FSH, whereas on the contralateral side these values had increased. Both sides showed increases in the level of P with the increases in LH. The mean interval from E₂ peak to LH peak was 24 hrs and LH peak to ovulation was 24 hrs.     

Quadriacanthus aegypticus n. sp., a monogenean gill parasite from the Egyptian teleost Clarias lazera

Summary Quadriacanthus aegypticus n. sp., a monogenean from the gills of Clarias lazera inhabiting Nile delta waters in Egypt, is described. The genus Quadriacanthus Paperna, 1961 is reported for the first time in Egypt. Particular attention has been paid to the reproductive system, the digestive system, the anterior adhesive glands, the posterior body glands and haptoral sclerites. Possible functions of the different internal organs are discussed. The diagnosis of the genus Quadriacanthus is emended. ac]19840926     

Induction of 7-ethoxycoumarin o-deethylase activity in cultured human epithelial cells by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD): evidence for TCDD receptor

The responsiveness of 5 human squamous cell carcinoma (SCC) lines derived from tumors of the epidermis and tongue to 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) was assessed by measuring the induction of the cytochrome P1-450-mediated monooxygenase activity, 7-ethoxycoumarin O-deethylase (ECOD). In 4 of the SCC lines the EC50 for this response was approximately 10(-9)M, whereas in one line the EC50 was 10(-10)M. In each of the less sensitive lines a concentration of 10(-10)M TCDD elicited less than 5% of the maximal enzyme activity. Specific binding of radiolabeled TCDD was detected in the cytosol fraction from all the SCC lines. The relative amount of receptor measured in each line correlated with maximally-induced ECOD activity. The data indicate that human cell lines derived from a target tissue for TCDD toxicity contain the TCDD receptor and show differential sensitivity to TCDD analogous to the murine strain differences in sensitivity regulated by the Ah locus.     

Acetylcholine Releases ATP from Varicosities Isolated from Guinea Pig Myenteric Plexus

The effects of cholinergic agonists and antagonists on the release of ATP from isolated myenteric varicosities were studied using a firefly luciferin-luciferase technique. In a previous study, acetylcholine and nicotine released ATP from isolated myenteric varicosities, whereas the muscarinic agonist bethanechol did not. In the present study, release of ATP by acetylcholine was shown to be Ca2+ dependent. d-Tubocurarine competitively antagonized the release of ATP by either acetylcholine or nicotine. Maximal release of ATP by acetylcholine (10(-3) M) was approximately 24% that observed with the depolarizing drug veratridine (5 X 10(-5) M), suggesting either that not all of the varicosities capable of releasing ATP possess nicotinic receptors or that acetylcholine does not depolarize the varicosities to the degree that veratridine does. Tetrodotoxin slightly but significantly reduced ATP release induced by acetylcholine or nicotine, indicating some involvement of Na+ channels in the release process. Finally, 6-hydroxydopamine pretreatment produced a 48% reduction in the acetylcholine-evoked release of ATP, suggesting that much, but possibly not all, of the ATP release occurs from noradrenergic varicosities present in the preparation.     

Design and operation of a simple continuous-culture apparatus

A versatile and simple continuous-culture apparatus is described. With this apparatus, independent control of limiting growth factors and other nutrilites is possible and the conditions of each experiment are reproducible. In view of the synchronized speed of the feeder syringes, flow variation troubles are not encountered. The device allows the performance of growth experiments at different dilution rates simultaneously in a single run which makes the comparison of the results more reliable. The operation of the device has been tested successfully with a study of adenine deaminase induction in yeast.     

Increases in cytokinin levels in Scots pine in relation to chilling and bud burst

Levels of isopentenyladenosine and zeatin riboside were monitored in buds and needles of Scots pine ( Pinus sylvestris L.) seedlings grown under controlled climatic conditions and in field-grown trees. Extracts were purified by immunoaffinity chromatography and high-performance liquid chromatography. Cytokinin levels were quantified with an enzyme-linked immunosorbent assay. The cytokinin content was low in buds and needles of dormant seedlings but increased during dormancy release, reaching peak values in buds just before resumption of shoot growth. Samples collected in the field also showed a marked increase in the levels of cytokinins just prior to bud burst. Further, the biological activity of applied cytokinins in activating the dormant buds of Scots pine is shown. The results indicate a probable role of cytokinins in seedlings during dormancy release.