DNA SYNTHESIS, MITOSIS, AND DIFFERENTIATION IN PANCREATIC ACINAR CELLS IN VITRO

Pieces of mouse embryonic pancreatic epithelium cultured in an inductive situation in vitro, or when examined at critical times in vivo, show a gradient of zymogen granule accumulation. Cells located internally in explants, or in central acini in vivo, show this overt differentiation first. As the epithelia age, the more peripheral cell population proceeds in a similar differentiation. Observations of autoradiograms of H³-thymidine-labeled tissues indicate that the first cells which cease incorporating the DNA-precursor are in the central regions that differentiate first. In older explants, thymidine incorporation is largely restricted to the periphery of the tissue as zymogen appears in the internal cells. Evidence suggests that cells or nuclei which have replicated DNA move inward before dividing. Some daughter cells apparently return peripherad to divide again, whereas others remain centrally where they undergo differentiation. During at least the first 24 hours of these maturational changes, mesenchyme has a stimulatory effect upon epithelial thymidine-incorporation frequencies. The presence of a post-DNA-synthetic population is seen in the form of a group of nonlabeling central cells that remains intact in the midst of a labeled epithelium for as long as 48 hours in vitro (from 72 to 120 hours). If explants are treated with 5-bromodeoxyuridine for any 24-hour segment of the 0 to 72-hour period, before the non-incorporating population arises, no subsequent overt zymogen formation occurs. If explants are treated continuously from 72 to 120 hours, on the other hand, zymogen still forms in some internal cells. Presumably, this differentiation is limited to the postmitotic population as revealed in the thymidine autoradiograms.     

新疆的芍药属

产于我国新疆的芍药属Paeonia L.植物虽然种类不多,但分类上却一直未予澄清。按《FL.URSS》(Tom.7)有两种,P.anomala L.和P.hybrida Pall.,按Stern(1946)有一种,包括两个变种,即P.anomala L.和P.anomala var.intermedia(C.A.     

REPRODUCTION IN FEMALE MANATEES OBSERVED IN SARASOTA BAY, FLORIDA

Resightings of recognizable individual Florida manatees, Trichechus manatus latirostris , in Sarasota Bay provided information on life history and reproductive parameters. These parameters have been documented at winter aggregation sites, but few data existed for Florida's west coast at non-winter sites. Life history data are needed to estimate annual reproduction and survival rates and construct population models for manatees along west central Florida. Observations of 113 recognizable manatees of known sex sighted between 1993 and 1997 indicated a 1: 1 sex ratio. Fifty-three females produced at least 55 calves during five years of observation. Two large, presumably sexually mature females were never observed with calves in over five years of monitoring. Not surprisingly, several reproductive parameters matched those measured in previous studies at winter sites with a mean of 1.8 seasons of calf dependence, 2.2 seasons between births, and age of sexual maturity at 3–4 yr. Birth rates, fecundity, and proportions of females with calves varied only slightly among investigations.     

海南岛兴隆地区某些药用植物中的微量元素

本文研究海南兴隆地区１２种不同类型药用植物微量元素的生物吸收系数（Ａｘ）及其含量水平变化特性,结果表明不同科、属、种植物对同一元素的吸收量差异显著,以Ｍｇ＞Ａｌ＞Ｆｅ＞Ｍｎ＞Ｚｎ＞Ｃｕ为序;同属不同品种植物在不同生境中对微量元素的生物吸收系数各有差别,海南槟榔（Ａｘ０．３０×１０－６、１２．５１×１０－６）＞泰国槟榔（Ａｘ０．２９×１０－６、１１．５９×１０－６＞云南槟榔（Ａｘ０．２７×１０－６、１１．５６×１０－６）,元素间吸收量相比以Ｍｏ＞Ｚｎ＞Ｃｕ＞Ｍｎ＞Ｎｉ为例;同种植物不同器官微量元素的吸收量也是不同的,例如巴戟天的含量以根（２１８．４８×１０－６＞叶（１１５．１９×１０－６）＞茎（１１３．０２×１０－６）。植物与土壤中元素含量消长变化关系密切,相比之下,植物中Ｆｅ、Ｍｎ、Ｚｎ含量均高于Ｃｕ、Ｐｈ、Ｎｉ。绞股蓝（１８９．２６）＞巴戟天（１６９．０４）＞益智（１６１．７０）＞槟榔（１５５．８８）。     

INTERACTION OF LEUCINE, GLUCOSE, AND KETONE METABOLISM IN RAT BRAIN IN VITRO

Brain cortex slices from fed, 48 h and 120 h fasted rats were incubated and ¹⁴CO₂ was measured from (a) [U-¹⁴C]glucose (5 mm ) either alone or in the presence of l -lcucine (0.1 or 1 mm ), and (b) [U-¹⁴C]leucine or [l-¹⁴C]leucine at 0.1 or 1 mm with or without glucose (5 mm ). In other experiments, sodium dl -3-hydroxybutyrate (3-OHB) or acetoacetate (AcAc) at 1 or 5 mm were added in the above incubation mixture. The rate of conversion of [U¹⁴C]glucose to CO₂ was decreased 20% by leucine at 1 mm and 30–50% by 3-OHB at 1 or 5 mm but not by leucine at 0.1 mm . The effects of 3-OHB and of leucine (1 mm ) were not additive. The effects of leucine were similar in the fed and fasted rats. The rate of conversion of [U-¹⁴C]leucine or [l-^,4C]leucine to ¹⁴CO₂ at 0.1 mm and 1.0 mm was increased by glucose (35%) in the fed or fasted rats. Ketone bodies in the absence of glucose had no effect on leucine oxidation. However, the stimulatory effect of glucose on the rate of conversion of leucine to CO₂ was inhibited by 3-OHB at 5 mm . These results suggest that (a) leucine in increased concentrations (1 mm ) may reduce glucose oxidation by brain cortex while itself becoming an oxidative fuel for brain, and (b) leucine oxidation by brain may be influenced by the prevailing glucose and ketone concentrations.     

江苏苏州绰墩遗址孢粉记录与太湖地区的古环境

根据绰墩遗址考古资料和孢粉分析,认为古遗址中的孢粉组合受人类活动影响较大,太湖地区新石器文化的兴衰与该区地势、气候、海平面变化以及太湖碟形湖盆体系的发育有密切关系,绰墩遗址中之所以形成较为丰富的文化内涵,与其较高的地势有关。     

云南滇池、洱海及泸沽湖的放线菌

分离了云南的滇池、洱海及泸沽湖的底泥及水样的放线菌,并对它们的数量、组成及生物学特性作了研究。