A study on the lipid distribution pattern in muscles of two teleosts, Arius dussumieri and Ophiocephalus striatus

The muscles of the various regions and zones of the body of the two teleosts, A. dussumieri and O. striatus have been analyzed for lipid contents. There is a significant dorsum-ventral gradient in lipid concentration exhibited by both the fishes with higher lipid values in the ventral aspect of the body, especially the belly flaps. As regards the vertical series, both the fishes exhibit comparatively higher lipid contents at the dorsal aspects of the caudal region and at anterior portion of the dorsal fin area with lower lipid values at cephalic and middle portions of the body. The red muscle of Arius exhibits higher lipid content than the white muscle.

Species composition and abundance of different Macrobrachium species in a natural habitat of Kalu River near Titvala, Maharashtra State

Juveniles of freshwater prawns caught by the traditional cylindrical bamboo traps operated by the local fishermen in a natural habitat of Kalu River near Titvala were sampled every week during September to December 1991 and 1992, to study the composition and relative abundance of different species and their relationship with hydrobiological parameters. The juvenile catch comprised Macrobrachium rosenbergii, M. idella, M. scabriculum and M. bombayensis. Among these M. rosenbergii was more abundant followed by M. idella. It is also observed that high tide catches are more productive than those of low tides.

Nutritional characteristics of the two fermented fish products: Hentak and Ngari of Manipur

Proximate composition and nutritional characteristics of the two fermented fish products Hentak and Ngari of Manipur (India) were evaluated. Percentage of moisture, protein, lipid and ash contents in Hentak and Ngari were respectively: 36.30 versus 36.03; 33.33 versus 38.38; 13.60 versus 13.34 and 11.43 versus 5.49. Digestibility values in feeding trials in laboratory rats for 28 days were 82.37% for Hentak 89.46% for Ngari and that of Casein was 92.69%. The biological value, food conversion ratio and protein efficiency ratio (PER) of Hentak were 96.94, 4.83 and 1.8 respectively and that of Ngari were 97.83, 3.17 and 1.8 respectively. The α amino nitrogen of Hentak and Ngari in Pepsin + Trypsin phase were 28.40 and 28.92 respectively. The TBA number, peroxide value and TVBN were within the acceptable limits.

低磷胁迫对高等植物中膜脂含量及分布影响的研究

　磷脂酰甘油(PG)是类囊体膜中唯一的磷脂, 并具有独特的结构。其甘油的sn-2位上总是连接着一个棕榈酸 (16:0) 或反式十六碳烯酸 (16:1tans)。很多研究表明, PG在维持类囊体膜的结构与功能方面具有重要的作用。然而，一些研究表明，在缺磷培养条件下，蓝藻、衣藻和拟南芥中PG含量下降，同时双半乳糖甘油二酯(DGDG)和硫代异鼠李糖甘油二酯(SQDG)含量上升，这一现象似乎表明在缺磷条件下，DGDG和SQDG可以取代PG。在本工作中，我们在叶片、类囊体膜和光系统II水平上研究了缺磷对小麦和黄瓜膜脂组成和含量的影响，特别是缺磷对PG含量影响的机理，以阐明PG与其它甘油脂的关系和其在类囊体膜中的功能。 　　通过对生长在不同磷营养水平条件下9天龄和16天龄小麦叶片中光合膜脂含量的分析，发现在磷缺失培养条件下，小麦光合膜脂的相对含量发生了很大变化，这种变化与小麦叶龄密切相关。在16天龄小麦植株中，第一片叶为老叶，第二片叶为较老叶，而第三片叶为新叶，PG和单半乳糖甘油二酯(MGDG)在叶片中的相对含量从新叶到老叶逐渐下降，而DGDG和SQDG含量逐渐上升;在磷缺失条件下，16天龄小麦第一叶片中PG的含量(2.5%)远远低于其在9天龄小麦第一叶片中的含量(5.5%)。这些结果说明，磷缺失引起小麦叶片中脂含量的变化不仅与脂合成有关，而且与PG的降解有关：新生叶片中PG含量减少的主要原因是由于磷供应不足, 从而影响了PG的合成;而PG的降解则是老叶中PG含量下降的主要原因。 　　由于植物叶片中有部分PG并不分布于类囊体膜中，并且PG是类囊体膜中唯一的磷脂，为了阐明缺磷对类囊体膜脂含量的影响，利用黄瓜作为实验材料， 提取了缺磷和对照条件下黄瓜叶片中的类囊体膜和PSII颗粒，并对其中的脂进行了分析，以期在叶片、类囊体膜和PSII颗粒三个不同层次上来分析缺磷对黄瓜膜脂的影响。结果表明： 1. 黄瓜幼苗的缺磷培养可显著改变叶片中膜脂的组成, 表现为所有磷脂含量的下降和DGDG、SQDG含量上升。 2. 对不同叶位中脂含量的分析表明，在缺磷条件下，随着叶片年龄的增加，叶片中磷脂的含量是逐渐下降的并且低磷处理使新生叶中PC和PE的下降幅度明显高于PG，而PG含量的下降只有在老叶中才明显表现出来。由于PC和PE是质膜、内质网膜和线粒体膜等膜系统的主要组成成分，而叶片中PG主要存在于类囊体膜中。这说明，在新生叶中，缺磷对于其类囊体膜外其他膜系统中磷脂的影响要大于类囊体膜;并且在磷缺失条件下，老叶磷脂中的磷可以运送到新叶中被重新利用。 3. 缺磷引起叶片类囊体膜脂含量的变化与叶片类似, 即PG含量的降低伴随着DGDG和SQDG含量的升高。然而，与叶片中不同的是，缺磷使类囊体膜中MGDG含量轻微下降。在植株生长过程中，缺磷导致老叶类囊体膜中PG含量的下降幅度远远大于新生叶中的下降幅度，而伴随着PG含量的下降，老叶类囊体膜中SQDG和DGDG的含量要远远高于新叶中两种脂的含量。这说明，在叶片生长过程中，缺磷条件下类囊体膜脂中DGDG和SQDG含量的上升可以弥补PG含量的下降。 4. 尽管缺磷使类囊体膜中的PG含量有较大幅度的下降, 但是叶绿素荧光动力学和PSII光合放氧活性都没有受到显著的影响。这些结果说明缺磷胁迫并没有对PSII的功能产生显著的影响。进一步研究发现, 在缺磷黄瓜植株中, PSII中PG的含量仍然维持在一个较高的水平。这些结果表明, 缺磷可以导致类囊体膜中某些区域中的PG大幅度降低, 但是对分布在PSII中的PG含量则影响较小。缺磷对类囊体膜脂组成及分布在不同区域PG的影响说明了类囊体膜中的PG可能存在着两种类型: 一些PG分子在类囊体膜中仅仅起结构作用, 当这些PG分子缺少时, 其它脂特别是SQDG可以替代PG; 而另一些PG分子在PSII的结构和功能中起重要的作用, 具有其它脂类分子不可取代的功能。

INFLUENCE OF ATMOSPHERIC COMPOSITION ON THE ABRASIVE WEAR OF TITANIUM AND Ti-6Al-4V.

A pin-on-disc apparatus has been used to investigate the wear and friction (sliding force) behavior of metals on bonded silicon carbide and alumina papers under conditions of controlled atmospheric composition. The wear rates of both commercial purity titanium and the alloy Ti-6%Al-4%V tested in air were found to remain constant with time, in contrast with the behavior of other metals tested under similar conditions, which exhibited a progressive decrease in wear rate with increasing number of passes along the same track. It is proposed that the concentration of interstitial nitrogen and oxygen in the worn metal surface, which largely determines its mechanical properties, strongly influences both the ductility of the abraded material and the force of adhesion between the metal and the abrasive particles. Parallels are drawn between abrasive wear and machining to illustrate the importance of oxygen at the interface between workpiece and tool surfaces.

Ecophysiological response of Nerita oryzarum (Recluz), a gastropod, to variations in temperature, pH and salinity

During ecophysiological investigations on an intertidal gastropod, Nerita oryzarum (Recluz), of Mumbai shore, various biochemical changes could be recorded. Glycogen and lipid contents of N. oryzarum were found to decrease, whereas, water content increased with decreasing salinity. The rate of oxygen consumption declined with the decrease in salinity and also in highly acidic (pH 2) as well as highly alkaline (pH 10) sea water. The observed variations in the rate of oxygen consumption and changes in biochemical composition in the animal with changes in salinity, pH and temperature are probably the process of physiological and biochemical adjustments to the fluctuating environmental conditions in the intertidal region.

Wadge Bank trawl fishery studies. Pt. 3. Nature and composition of the resident population

The demersal stock of the Wadge Bank is known to be made up of two major groups, namely the resident and migrant stocks (Sivalingam 1966b). It is necessary to analyse the two groups separately in order to correctly interpret the changes in relative abundance of the demersal fish stocks of the Bank. The object of this paper is to present the nature of the resident stock and discuss its changes in composition from 1945 to 1960. That of the migrant population will be presented later. The significance of this analysis has been discussed earlier (Sivalingam 1966a).

Fluctuations in species composition of Penaeid prawns in estuaries

During a study of the distribution of penaeid prawns in Sri Lanka waters a difference was noticed in the species composition from one estuary to another. Moreover, a marked monthly fluctuation in the relative abundance of the different penaied species was also observed. This indicated migratory behaviour. In order to study this phenomenon in the different species of prawns, regular samples of prawns were collected from two estuaries on the south-west coast of Sri Lanka, namely at Moratuwa/Panadura and at Negombo. The investigation was spread over a period of three years from 1957-1959.

The freshwater zooplankton of Sri Lanka, with a discussion of tropical freshwater zooplankton composition

Based on the study of over 500 zooplankton samples collected in Sri Lanka during 1965-1974, the species composition from different habitats is analysed. The zooplankton assemblage is typically tropical with relatively few species of Cladocera and Copepoda. The Rotifera include a large number of species of the genus Brachionus. The limnetic zooplankton resembles the pond zooplankton closely in that all the eurytopic species found in the different types of habitats, including ponds; also occur in the limnetic zooplankton. The large Cladocera belonging to the genus Daphnia are very rare. In general, large zooplankters are absent. The size composition of the zooplankton has a smaller range than in temperate regions. This is due to the absence of large-sized zooplankton species. The reasons for the differences in species variety and size composition between zooplankton of temperate and tropical regions is perhaps due to a number of factors. These include the effects of high and uniform temperatures, food availability and predation by fish and invertebrates.

A comparative study of the morphometrics and the proximate composition of two edible molluscs Crassostrea cuculata (Born) and Perna perna (L.)

The morphometrics and the bio-chemical characteristics of Crassostrea cuculata and Perna perna were studied. In the oyster, the length was found to be positively correlated with breadth and total body weight. There was also a positive relationship between the total body weight and the total muscle weight. In the mytilid the total body weight was positively correlated with length and total muscle weight. The muscle weight was also found to be highly correlated with the length. In both animals the relationship between the length and the total body weight was curvilinear. In the oyster, the protein content was found to increase with the total body weight and the total muscle weight. In the mytilid the protein content increased not only with the total body weight but also with the length. In both animals, the relative content of protein is higher than that of carbohydrates, lipids and ash.

Nutritional evaluation of some small coastal fish in Sri Lanka

Small pelagic fish play a very important role in human nutrition and health. Lipids of these fish differ remarkably from plant and other animal lipids. The aim of the study was to describe the proximate composition of thirty-three small pelagic fish species commonly available in Sri Lanka. Fish species were collected from Negombo and Chillaw fish landing sites and subjected to analysis for moisture, ash, protein and total lipid content. Tiger tooth croaker (Otolithus ruber) was found to have the highest moisture percentage (80.0%) followed by Clarias sp. (78.9%), Indian anchovy (Steloporus indicus) and Comerson's anchovy (Stelophorus commersonii), (78%). The lowest percentage of moisture, 69.4%, was recorded in white sardinella (Sardinella albella). Indian ilisha (Ilisha melastoma) was found to have the highest amount of ash (10.1%) followed by Otolithus sp. (8%) and big-eye barracuda contained the least amount (2.5%). Carassius Carassius, pick handle barracuda (Sphyraena jello) and Indian mackerel (Rastrelliger kanagurta) contained higher amounts of protein, 24.3, 20.6 and 19.2% respectively. The lowest protein content (10.1%) was found in Indian scad (Decapterus russelli). The protein content of the fish was in the range of 13-15%. The results revealed that the small fish are moderate protein sources. The total lipid content varied between 0.6-8%. White sardinella recorded the highest percentage of lipid (8%) where tiger tooth croaker contained the lowest percentage (0.6 %). The study showed high fatty species to contain low amount of moisture and vice versa establishing an inverse relation between fat and moisture quantitatively.