Role of verocytotoxigenic Escherichia coli in cattle and buffalo calf diarrhoea

Abstract 273 Strains of Escherichia coli isolated from diarrhoeic and healthy control cattle and buffalo calves in Sri Lanka, were tested for Verocytotoxin (VT) and for heat-stable (ST) and heat-labile (LT) enterotoxins. VT and ST toxigenic E. coli were significantly associated with diarrhoea, accounting for 28% and 18% of diarrhoeic episodes, respectively. LT toxigenic E. coli were not significantly associated with diarrhoea.     

Phosphatidylinositol 4,5-bisphosphate: Light-mediated breakdown in the vertebrate retina

Isolated frog ($\text{Rana}\text{Pipiens}$) retinas were labeled in the dark with either [³²P]PO₄-orthophosphate or $\text{myo}$-[2-³H]inositol for 2.5–4 hrs. After washing the retinas with cold buffer, they were exposed to brief flashes of light (5 secs or 15 secs) and their rod outer segments isolated. Upon separation of labeled phospholipids, a specific decrease in label in phosphatidylinositol 4,5-bisphosphate was observed, whereas there was no significant effect on the labeling of phosphatidylinositol 4-phosphate, phosphatidylinositol, or phosphatidic acid. These results are indicative of a light-activated phosphatidylinositol 4,5-bisphosphate-specific phospholipase C in frog rod outer segments.     

In vitro regeneration of plantlets in Fagraea fragrans Roxb. — a tropical tree

Different vegetative parts of Fagraea fragrans Roxb., a valuable timber tree of South East Asia, were used as explants in in vitro studies.Nodal segments showed the best growth response as numerous adventitious shoots were regenerated in MS medium supplemented with Benzyl adenine (BA, 8.8 um) and 2,4-dichlorophenoxyacetic acid (2,4-D, 0.5 um). Shoot buds also developed from the leaf and root segments that were subcultured. The detailed process of callus growth and differentiation leading to the formation of whole plantlets is described. Uniform plantlets obtained could be transplanted successfully in soil.     

Calcium-dependent activation and deactivation of rod outer segment phosphodiesterase is calmodulin-independent

ATP-dependent activation and deactivation of retinal rod outer segment phosphodiesterase is affected by calcium [Kawamura, S. and Bownds, M. D., J. Gen. Physiol. 77:571-591(1981)]. Our data demonstrate that although calmodulin has been found in rod outer segments [Liu, Y. P. and Schwartz, H., Biochim. Biophys. Acta 526:186-193(1978); Kohnken, R. E. et al, J. Biol. Chem. 256:12517-12522(1981)], this protein is not involved in calcium-dependent phosphodiesterase activation at light levels at which calcium clearly affects this enzyme's activity. Furthermore, calmodulin does not mediate the calcium-dependent deactivation of phosphodiesterase.     

Microelectrode characterization of the basolateral membrane of rabbit S3 proximal tubule

Summary The purpose of this study was to characterize the basolateral membrane of the S3 segment of the rabbit proximal tubule using conventional and ion-selective microelectrodes. When compared with results from S1 and S2 segments, S3 cells under control conditions have a more negative basolateral membrane potential (V _bl=–69 mV), a higher relative potassium conductance (t _K=0.6), lower intracellular Na⁺ activity (A _Na=18.4mm), and higher intracellular K⁺ activity (A _K=67.8mm). No evidence for a conductive sodium-dependent or sodium-independent HCO ₃ ^– pathway could be demonstrated. The basolateral Na–K pump is inhibited by 10^–4 m ouabain and bath perfusion with a potassium-free (0-K) solution. 0-K perfusion results inA _Na=64.8mm,A _K=18.5mm, andV _bl=–28 mV. Basolateral potassium channels are blocked by barium and by acidification of the bathing medium. The relative K⁺ conductance, as evaluated by increasing bath K⁺ to 17mm, is dependent upon the restingV _bl in both S2 and S3 cells. In summary, the basolateral membrane of S3 cells contains a pump-leak system with similar properties to S1 and S2 proximal tubule cells. The absence of conductive bicarbonate pathways results in a hyperpolarized cell and larger Na⁺ and K⁺ gradients across the cell borders, which will influence the transport properties and intracellular ion activities in this tubule segment.     

Developmental and genotypic differences in the response of pea stem segments to auxin

The objective of this investigation was to examine the response to exogenous auxin (indole-3-acetic acid; IAA)of stem segments at two developmental stages. The standard auxin response of excised stem segments and intact plants consists of an initial growth response and a prolonged growth response. We found that this biphasic response does not occur in internodes at very early stages. Stem segments of light grown pea of various genotypes were cut when the fourth internode was at 6–13% of full expansion (early-expansion) or at 18–25% of full expansion (mid-expansion). Length measurements of excised segments were made after 48 hours of incubation on buffer with or without auxin. An angular position transducer linked to a computerized data collection system provided high-resolution measurement of growth of stacks of segments incubated in buffer over 20 hours. Early-expansion segments of all genotypes deviated from the standard auxin response, while mid-expansion segments responded in a manner consistent with previous reports. Early-expansion segments of tall, light-grown plants were unique in showing an auxin-induced inhibition of growth. The auxin-induced inhibition correlated with high endogenous auxin content, as determined by HPLC and GC/MS, across genotypes and between early-expansion and mid-expansion segments of tall plants. Measurement of ethylene evolved from stem segments in response to auxin, and treatment of segments with the ethylene action inhibitor, norbornadiene, showed the inhibition to be mediated in part by heightened ethylene sensitivity. Growth of early-expansion segments of dwarf and severe dwarf plants was stimulated by exogenous auxin, but the growth rate increase was delayed compared to that in mid-expansion segments. This is the first time that such a growth response, termed the delayed growth response has been emonstrated. It is concluded that developmental stage and endogenous hormone content affect tissue response to exogenous auxin.     

A scanning electron microscope study of normal and vitrified leaves from Datura insignis plantlets cultured in vitro

The surface anatomy of normal and vitreous leaves of plantlets obtained from Datura insignis Barb Rodr nodal segment cultures was compared using scanning electron microscopy. Normal and vitrified leaves are similar in several ways. They are both amphistomatic, and have similar distributions of glandular and non-glandular trichomes. Stomata have similar length, diameter and distribution in normal and vitreous plants. Immature stomata, which have closed pores, and plugged stomata, which contain an amorphous material between their guard cells, occur in both normal and vitrified leaves. Normal and vitreous leaves differ in the frequency of normal and abnormal stomata. Normal stomata have kidney-shaped guard cells and resemble closely those found in field-grown plants, whereas abnormal stomata have deformed guard cells. Normal stomata represent approximately 80% of the total number of stomata in normal leaves, but only 7% of the total number of stomata in vitreous leaves. Abnormal stomata represent 90% of the total number in vitreous leaves. The deformation of guard cells could possibly be a mechanical impediment to stomatal function.     

渔游蛇(Natrix piscator)的雄性生殖周期及其肾性节的生殖生理学研究:Ⅰ.雄性生殖周期及肾性节的组织学和组织化学

福州近郊分布的渔游蛇睾丸精子发生在10月份达最高峰。全年出现二次雄性激素高峰。肾性节在10月份达发育高峰,其上皮细胞中的分泌颗粒含糖类、缩醛磷脂、酸性磷酸酶和乳酸脱氢酶,不含酸性粘多糖、碱性磷酸酶、琥珀酸脱氢酶或含量(活性)极低。肾性节的组织学变化与睾丸的精子发生活动呈同步性。     

Discrimination of folding types of globular proteins based on average distance maps constructed from their sequences

It has been shown that probable portions which form contacts in a protein can be predicted by means of an average distance map (ADM) as well as regular structures (-helices and -turns) defined as short-range compact regions (Kikuchiet al., 1988a,c). In this paper, we analyze the occurrence of those portions and short-range compact regions on ADMs for various proteins regarding their folding types. We have found out that each folding type of proteins shows characteristic distribution of such parts on ADMS. We also discuss the possibility of the prediction of folding types of proteins by ADMs.