Primary literature as a basis for a high-school biology curriculum

Textbooks, research news from the media, and review articles from popular journals are the most common sources of texts used for high-school biology education. We attempted to adopt primary literature as a means of developing scientific literacy among high-school biology majors. For that purpose, we developed and implemented a primary literature-based curriculum in developmental biology. The process of adapting original research articles to the high-school level, as well as a conversational model developed for learning through research articles, are discussed.     

水蕨颈卵器的形成与发育

主要运用电子透射显微镜技术对水蕨(Ceratopteris thalictroides(L.)Brongn)颈卵器形成与发育进行了研究。结果表明:水蕨颈卵器是由原叶体分生组织内颈卵器原始细胞形成的。该原始细胞经2次分裂形成3层细胞,上下两层发育成颈卵器颈部与底部的壁细胞,中层为初生细胞。初生细胞是颈卵器内雌配子发生的第一个细胞,该细胞经2次不等分裂形成1个卵细胞,1个腹沟细胞、1个双核的颈沟细胞。本研究首次阐明了水蕨颈卵器内细胞的发育顺序和特征。     

Primary mesenchyme cell patterning during the early stages following ingression

Sea urchin primary mesenchyme cells (PMCs) ingress into the blastocoel during an epithelial-to-mesenchymal transition (EMT), migrate along the blastocoelar wall for a period of time, and then settle into a subequatorial ring to form the larval skeleton. Fluorescent-marked blastomeres alone, or in combination with blastomere recombination, were used to track the position of PMCs during the early phases of this movement. Micromeres expressing Golgi-tethered GFP (galtase-GFP) were transplanted onto TRITC-stained hosts (in place of the endogenous micromere) to observe the progeny of a single micromere. Galtase-GFP as a Golgi marker is not transferred between PMCs when the syncytium forms. Thus, the position of cells can be followed relative to beginning position for longer periods than previously reported. The PMC progeny of a single micromere do not disperse upon ingression, but instead remain in a closely associated cluster. Generally, progeny of a single micromere remain in the quadrant of origin. In total, greater than approximately 94% of labeled PMCs remain within the local region of ingression. By contrast, when a transplanted micromere is placed at the vegetal plate after removing all 4 host micromeres, the resultant PMCs ingress and migrate into all 4 quadrants. Similarly, if 1 blastomere is injected at the 2-cell stage, and later the 2 unlabeled micromeres are removed at the 16-cell stage, the remaining PMCs ingress into all 4 quadrants of the vegetal plate. We conclude that the normal restriction of PMCs to a quadrant is due to mechanical constraint from other micromere-PMCs. If a labeled micromere is placed ectopically at the macromere/mesomere boundary, the PMC progeny ingress ectopically and migrate longitudinally along the animal-vegetal axis only. Injection of galtase-GFP into one blastomere at the 4-cell stage shows a 2-step pattern of localization. At late mesenchyme blastula and early gastrula stages, greater than 90% of GFP-expressing PMCs remain in the injected quadrant, while at mid- to late-gastrula stage and beyond, more PMCs are found outside the injected quadrant. The migration that sets up the asymmetry of the larval skeleton first occurs around mid- to late-gastrula stages, when some PMCs from an aboral quadrant migrate to the adjacent oral quadrant. In all, these data combined with previous data suggest that freshly ingressed PMCs migrate along a longitudinal path toward the animal pole and back toward the vegetal pole. Beginning at mid- to late-gastrula stage, PMCs utilize oral-aboral cues from the ectoderm for the first time. At this time, some aboral PMCs migrate into the adjacent oral quadrant to assist in the formation of the ventrolateral cluster.     

Influence of cryoprotective agent and cooling rate on frozen and thawed hemocytes from the Mollusk Haliotis tuberculata

Cultures of circulating cells from abalone (Haliotis tuberculata) may be used in fundamental research or in biotechnology. This paper describes attempts to develop a cryoconservation method for these hemocytes in order to constitute a standardized cell stock. Among a panel of five distinct cryoprotective solutions, 10% v/v glycerol ('G solution') was the most effective and better post-thaw recovery was achieved after cooling at 1 degrees C/min than after more rapid cooling (3 degrees C or 9 degrees C/min). In 2-day-old cultures, cell viability, assessed by DNA or protein content, was 83 and 78%, respectively, and metabolic activity, measured by the MTT reduction assay, reached 96%. Viability rates were only slightly reduced after 6 days of culture, suggesting a low proportion of damaged cells among the surviving hemocytes. This study identified a cryoprotective solution and a freezing protocol that allow thawed hemocytes to recover a large part of their viability.     

Biological productivity of Lake Towada,a north temperate,oligotrophic, kokanee fishery lake

During the Lake Towada survey from April through October 1998, we measured primary production at shore and offshore stations, and calculated crustacean zooplankton production from samples collected at the offshore station. We then analyzed these data and compared them with commercial fishery data in order to discuss the energy flow in this lake where kokanee (Oncorhynchus nerka) fisheries are one of the main businesses. At all stations, primary production was relatively high: 150–300mgCm^–2day^–1 in April–mid-June and lower at ca. 100mgCm^–2day^–1 thereafter. The variation in primary productivity could largely be explained by multiple regression models that included phytoplankton biomass and ambient nutrient conditions as independent variables. Among zooplankton, rotifers had their peak abundance in May, before the crustacean zooplankton (Daphnia longispina, Bosmina longirostris, and Acanthodiaptomus pacificus) population was well established. D. longispina dominated the crustacean zooplankton community in terms of biomass and production; their production during the study period made up 80% of crustacean community production (19.6gdry-wtm^–2), which was 40% of primary production during the survey. In July, when the abundance of D. longispina was particularly high, their daily production slightly exceeded daily primary production, which resulted in ca. 30% and 75% reduction in the amount of particulate organic carbon and chlorophyll a, respectively, during this period. The community ingestion rate of crustacean zooplankton, calculated from their daily production (D. longispina accounted for 90%) and the assumption that their gross production efficiency (K₁) was 60%, could roughly explain this reduction of particulate matter, corroborating previous studies that the grazing of D. longispina can significantly improve the water transparency of this lake. The catch of kokanee and pond smelt (Hypomesus transpacificus nipponensis, another important fish in the lake) during the survey corresponded to 1.1% of crustacean community production, and corresponded to 0.45% of the primary production, which is one of the highest recorded values. Bearing in mind that D. longispina was the major food item of planktivorous fish such as kokanee and pond smelt, the present study suggests that the energy transfer from phytoplankton to zooplankton to fish is outstandingly efficient, compared with other aquatic ecosystems, when D. longispina dominates in the lake.     

Monitoring method for pre- and post-liver transplantation in patients with primary hyperoxaluria type I

Differential diagnosis of primary hyperoxaluria type I (PH1) may become difficult once end-stage renal failure and anuria have occurred. Here we describe a rapid and sensitive method to simultaneously quantify glycolate and oxalate in plasma using a stable isotope dilution and gas chromatography-mass spectrometry. The results are provided within 2 h. The linearity of the method was validated up to 200 micromol/l of these compounds and the inter-assay precision for glycolate and oxalate was 2.4 and 2.6%, respectively (n=5), when the control plasma was spiked with 50 micromol/l of glycolate and oxalate. For healthy subjects, 1.0 ml of plasma was required and 0.1 ml for the PH1 patients. Using this method, plasma levels in non-PH1 patients under hemodialysis and in healthy subjects were determined. This method proved to be useful when used for differential diagnosis of PH1 and for monitoring the plasma levels of glycolate and oxalate in two PH1 patients before and after dialysis and liver transplantation. Plasma glycolate in these patients was dramatically decreased after liver transplantation, but plasma oxalate decreased more slowly due to remobilization of the calcium oxalate stores deposited throughout the body.     

Continuing dental care for Highlands elderly: current practice and attitudes of dental practitioners and home supervisors

Objective : To investigate current practice and attitudes of Highland dentists and home supervisors to continued dental care of elderly residents. Methods : A cross‐sectional questionnaire was designed to survey the current practice and attitudes of Highland dentists and residential care supervisors in their provision of dental care for the elderly at home and in long stay accommodation. Results : The response rate was 94% of dentists and 79% of homes. Despite 86% of dentists providing domiciliary care and 93% of homes transport to a surgery, no more than a quarter of residents had had contact with a dentist in the previous year. The distribution of residents varied with dependant individuals living in nursing units and the least dependant in residential homes. Only 1% of all residents were totally bed bound. Domiciliary patients were less likely to receive continuing care compared with those seen in a surgery and 75% of homes had to initiate dental care. In terms of patient referral, the majority of GDPs would refer uncooperative patients, salaried dentists would refer those with complex medical histories and community dentists would refer those requiring complex treatments. A dental assessment was undertaken in 46% of homes and 81% of these kept a record of dental care. Conclusion : This study highlights the need for a co‐ordinated, seamless continuing dental care service, tailored to the actual needs of the elderly individuals it is designed to serve, particularly in a remote and rural area.     

Functional specialisation and polyphenism in aphid olfactory sensilla

Electroantennogram (EAG) responses to the aphid sex pheromone components, (1R,4aS,7S,7aR)-nepetalactol and (4aS,7S,7aR)-nepetalactone, and a plant volatile, (E)-2-hexenal, were investigated at three different positions (5/6th, 4/5th and 3/4th inter-segmental regions) along the antennae of four different morphs in two host-alternating aphid species, Aphis fabae Scopoli and Rhopalosiphum padi (L.). Position-dependent and morph-specific EAG responses were elicited in both species. The nepetalactol and nepetalactone isomers elicited large EAG responses at all three recording positions in males of both species, such that primary rhinaria as well as secondary rhinaria appeared to respond. Asexual female morphs showed relatively smaller EAG responses to these compounds. The secondary rhinaria, which have been reported as sex pheromone receptors in males, were not very different in their number and distribution between gynoparae and alate virginoparae, but the gynoparae showed significantly larger EAG responses to nepetalactol and nepetalactone. The alate virginoparae showed EAG responses that were similar to those of apterous virginoparae, which lack secondary rhinaria. Taking the EAG response profiles together with the distribution of the secondary rhinaria, it is suggested that the function of secondary rhinaria differs between the morphs. Secondary rhinaria appear to detect sex pheromone components in males and gynoparae but not in the alate virginoparae. If they are functional in the latter morph, they are likely to play a role in detecting specific, but as yet unknown, volatile compounds. Some 30 plant volatiles were tested but none evoked an EAG response that could be allocated to the secondary rhinaria. In contrast to the very different EAG response profiles to the pheromone compounds between morphs, EAG responses to (E)-2-hexenal were similar in all forms and both species. These findings suggest that this plant volatile was detected only by the two primary rhinaria, which are common to all morphs. The present study showed that EAG responses were not a simple summation of receptor potentials between recording and reference electrodes in aphids. The localised distribution pattern of olfactory receptor neurones around the recording electrode was also likely to contribute to the EAG responses.     

4,4'-diisothiocyano-2 ,2'-stilbenedisulfonate protects cultured cerebellar granule neurons from death

We examined the effects of 4,4′-diisothiocyano-2,2′-stilbenedisulfonate (DIDS), an inhibitor of the chloride-bicarbonate exchangers and chloride channels, on death in cultured cerebellar granule neurons. Various stimuli, such as reduction of extracellular K⁺ concentration, removal of growth factors, and staurosporine treatment, induced cell death. This death was blocked by DIDS in a dose dependent manner. In the presence of DIDS, the cells exposed to such stimuli did not show DNA fragmentation, but retained the ability to exclude trypan blue and to metabolize MTT to formazan. On the other hand, pretreatment of the cells with DIDS did not show any protective effects. The neuroprotective effect of DIDS was not influenced by extracellular Na⁺, Cl⁻, HCO₃⁻ or Ca²⁺ concentrations, although reduction of extracellular Cl⁻ or Ca²⁺ concentrations per se induced neuronal death. Other chloride-bicarbonate exchange blockers like 4-acetamido-4′-isothiocyanatostilmene-2,2′-disulfonic acid (SITS) or 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNDS) showed no significant effects on neuronal survival under these death-inducing stimuli. Dimethylamiloride, an inhibitor of the Na⁺/H⁺ exchanger, did not influence neuronal death induced by these stimuli. Cells undergoing death showed gradual intracellular acidification, and DIDS did not inhibit this response, although DIDS (2 mM) per se induced transitory acidification followed by recovery within 10 min. DIDS did not influence intracellular Ca²⁺ or Cl⁻ levels during the lethal process. DIDS suppressed the cleavage of caspase-3 in the cells exposed to the death-inducing stimuli. These findings suggest that the neuroprotective effect of DIDS is mediated by a novel mechanism other than by nonselective inhibition of transporters or channels, and that DIDS blocks the death program upstream of caspases and downstream of all of the activation processes triggered by various stimuli.     

Primary cilia in vertebrate corneal endothelial cells

The presence of primary cilia in corneal endothelial cells of a range of species from six non-mammalian vertebrate classes (Agnatha, Elasmobranchii, Amphibia, Teleostei, Reptilia and Aves) is examined by scanning and transmission electron microscopy. Our aim is to assess whether these non-motile cilia protruding into the anterior chamber of the eye are a consistent phylogenetic feature of the corneal endothelium and if a quantitative comparison of their morphology is able to shed any new light on their function. The length (0.42-3.80 microm) and width (0.12-0.44 microm) of the primary cilia varied but were closely allied with previous studies in mammals. However, interspecific differences such as the presence of a terminal swelling in the Teleostei and Amphibia suggest there are functional differences. Approximately one-third of the endothelial cells possess cilia but the extent of protrusion above the cell surface varies greatly, supporting a dynamic process of retraction and elongation. The absence of primary cilia in primitive vertebrates (Agnatha and Elasmobranchii) that possess other mechanisms to control corneal hydration suggests an osmoregulatory and/or chemosensory function.