建兰根状茎增殖条件的研究

研究了建兰两个栽培品种的根状茎在固体及液体两种培养方式,以及培养基中有无激素和不同激素浓度配比对增殖及分化的影响。根状茎在液体培养基上的生长量都大于固体培养基上的生长量。根状茎在无激素的培养基上也能增殖。加入激素有促进作用。合适的激素浓度及配比因品种而异。     

影响肝癌周围肥大细胞数量的相关因素研究

探讨影响肝癌周围肥大细胞数量的相关因素及其意义。采用二乙基亚硝胺诱发大鼠肝癌模型。应用光镜,免疫组织化学,核酸原位分子杂交和细胞图像分析技术,检测肝癌细胞转化生长因子β（TGFβ）,血管内皮生长因子（VEGF）,c-fosmRNA的表达与癌周肥大细胞（MS）数量变化的相关性。结果显示肝癌细胞浆中TGFβ,VEGF和c-fosmRNA呈阳性表达,其中TGFβ,c-fosmRNA表达的强度与癌周MC数量变化呈平行关系。而VEGF表达的强度与癌周MC数量变化无关。结果表明：肝癌细胞通过释放TGFβ并通过激活原癌基因（c-fos)以旁分泌方式或癌基因产物影响癌周MC的数量。     

FACTORS AFFECTING THE INTRACELLUALR SYNTHESIS OF KYNURENINE

Near the time of pupation, autofluorescent kynurenine globules appear in the cells in the anterior region of the fatbody of Drosophila melanogaster. It has been reported previously that kynurenine synthesis may be induced in an additional group of fat cells by feeding the precursor tryptophan to Drosophila larvae, and that this induction of kynurenine production viewed within the fat cells is correlated with an increase in tryptophan pyrrolase activity. In the present report, conditions are outlined which result in the appearance of kynurenine in all of the fat cells. The number of cells in the fatbody which contain kynurenine is influenced by the quantity of tryptophan included in the diet, as well as by the developmental stage at the time of treatment and the duration of the feeding period on the inducer. Physical barriers modifying permeability, such as the membranous layer noted surrounding the fatbody, may be a factor in the regulation of the time and nature of the cellular induction of kynurenine synthesis. Another factor to be considered is the possibility of interference with the availability of tryptophan as a substrate or inducer for this synthesis within the cell. It is suggested that the occurrence of pteridines in some of the fat cells may modify the response of these cells to produce kynurenine, since pteridines as electron acceptors can complex with tryptophan as an electron donor. Kynurenine may be produced in the fat cells under in vitro conditions when they are incubated with L-tryptophan, but kynurenine is not formed when fat cells are incubated with D-tryptophan. The in vitro studies further demonstrate that induction of kynurenine synthesis may occur in fat cells isolated from young larvae in contrast, to in vivo conditions in which inducer does not effect an earlier appearance of kynurenine in the larval fatbody.     

SHOOT APICAL MERISTEMS AND MUTATION: FIXATION OF SELECTIVELY NEUTRAL CELL GENOTYPES

Shoot apical meristems are interpreted as either structured, that is having a permanent set of apical initials, or stochastic, having apical initials which represent “... momentary representatives of the continuous meristematic residue at the apex of the relevant layer or zone” (Newman, 1965). The two main parameters of stochastic growth are the average number of apical initials (α) and the number of mitotic cycles (r) of the initials and their daughter cells prior to the random selection of subsequent initials. Mathematical analysis and computer simulation studies of stochastic growth have shown that if one starts with 1 mutant initial and α-1 nonmutant initials, eventually a mosaic plant results. The frequency of shoot apices composed of mutant cells is 1/α and the frequency of shoot apices composed of only nonmutant cells is (1 – α)/α. These asymptotics are only attained after considerable growth, thus mericlinal chimeras can persist for many nodes and give the appearance that a permanent set of initials is present.     

FACTORS AFFECTING EGG-WEIGHT, BODY-WEIGHT AND MOULT OF THE WOODPIGEON COLUMBA PALUMBUS

The heaviest clutches (2 eggs) laid by Woodpigeons Columba palumbus in a Cambridgeshire study area weighed 30% more than the lightest. Yet the variation in egg-weight within clutches was less than 1 %. Irrespective of initial weight, eggs lost weight at the same constant rate during incubation. Heavy eggs hatched more successfully than light eggs and none weighing less than 16 g hatched. There was no correlation between chicks' weight at hatching and their weight at day 6 during the July-September part of the breeding season. The ability to feed crop milk at this stage could compensate for low chick-weight, but this might not be true early in the season. Weight at day 6 was correlated with the weight at day 16 or 17. The growth pattern is discussed. Chicks in broods of one achieved a higher weight at day 17 than those in broods of two. The survival rate both in and after leaving the nest was the same in both brood-sizes. Chick-weight in artificially created broods of three was almost as high as in broods of two, but again data refer to the July-September period when abundant cereal food is available. Survival before and after fledging was lower in broods of three. Clutch- and egg-weight declined from April until September. It is suggested that this is adaptive, in that the adults produce heavier eggs when food supplies are most difficult to collect. The critical period probably occurs during the few days when the adult must produce crop milk and the young cannot be left unattended. Thus egg-weight depends on the female's capacity to acquire nutrients, and is related to the needs of embryonic development and the amount of compensation in nutrient supply which can be provided immediately after hatching. But clutch-size is more related to the bird's ability to feed and rear young to the point of fledging, thereby influencing the number of offspring which survive to leave progeny. Egg-weight and female body-weight were positively correlated in females weighing less than 480 g but not in heavier females. First-year birds did not acquire adult weight until midsummer and they would probably produce light eggs if they could breed before this month. However, their gonads do not recrudesce until July and this prevents them breeding in the spring. Seasonal changes in body-weight and fat content of adults and first-year birds are described and discussed; differences were noted between adult males and females which were considered to be adaptive. The moult is described. It begins in April and continues until November, approximately one pair of primaries being replaced per month. The moult ceases during the winter months, when it is known that food supplies become limiting. Woodpigeons lay light eggs relative to their body-weight but can achieve the extra parental care needed for the altricial chicks by producing crop milk. Because the moult is extended, the energy demands of moulting and breeding combined are relatively low and this enables the Woodpigeon to have a long breeding season and to moult coincidentally.     

FACTORS AFFECTING THE TURNOVER OF CEREBRAL GLYCOGEN AND LIMIT DEXTRIN IN VIVO

The turnover of cerebral glycogen in mice has been investigated by using [U-¹⁴C]glucose as a precursor. The time required for turnover of total glycogen and limit dextrin has been determined in normal animals and animals given phenobarbital or hydrocortisone. In all 3 groups, the turnover time for limit dextrin was twice that of total glycogen. Phenobarbital increased the time for turnover of total glycogen and limit dextrin approximately 2-fold, whereas hydrocortisone diminished the turnover time of both fractions to one-half. The accumulation of glycogen during phenobarbital anesthesia (2·5-fold) is attributed to the decrease in rate of phosphorolysis rather than elevated glycogenesis. The ratio of phosphorylase a to total phosphorylase was significantly decreased in the brains of phenobarbital-treated mice, while the ratio of glycogen synthetase I to total synthetase activity was not affected. The administration of hydrocortisone had no effect on either the phosphorylase or synthetase of mouse brain. A mathematical model was devised to determine the rate constants for incorporation of labelled glucose into brain glycogen and the subsequent loss of radioactivity. Metabolite levels and enzyme activities have been correlated with the observed changes in glycogen turnover.     

FACTORS AFFECTING BREEDING OF RAZORBILLS ALCA TORDA ON SKOKHOLM

A study of the breeding biology of the Razorbill was carried out on Skokholm (South Wales) during 1971-73. Birds ringed or colour ringed before the study began provided additional information upon the effects of age on breeding. Mean laying date was delayed in 1972, compared with 1971; the effect is attributed chiefly to stormy weather which upset colony attendance. Eggs were also smaller in 1972. A seasonal decline in egg size (volume) was noted in all three years, attributed mainly to the later laying of young birds. Egg size increased with age, at least up to the fifteenth year. Eggs lost totalled 30% of those laid; 73% of this total was due to predation by Herring Gulls and of Jackdaws. Most losses (45%) occurred during the first 10 days after laying. Of lost eggs, 25% were replaced, usually 14 days after the loss of the original; only eggs laid and lost early in the season could be replaced. Only 7% of the chicks which hatched failed to fledge. Most (62.5%) chick losses occurred in the first week of nestling life, when chick weight was related to egg size. Afterwards, both growth rate and fledging weight were independent of egg size. The chicks fledging early in the season were heavier than later chicks. Failure to fledge was mainly due to a breakdown in behaviour between parent and young, rather than to predation. Breeding success was highest for birds breeding early in the season, most of which were older, more experienced breeders. These laid early enough to replace an egg if it was lost; they produced large eggs, and their chicks were therefore both heavier than average during the critical first 7–10 days of life, and fledged at a high weight. Thus experience accumulated with age, and the ability to lay early in the season are important for successful breeding in the Razorbill.