ABSTRACT
331 primary school students studying from Nursery classes to Class IV in 2 randomly selected schools in Naxalbari Village in Darjeeling district of West Bengal were tested for visual acuity (VA), Vitamin A deficiency (VAD) and Bitot's spot. 329 students could be tested for visual acuity whereas all 331 students were tested for VAD and Bitot's spot. The prevalence of abnormal Visual Acuity (VA) (VA < 6/9 in any eye) in this study group was 3.65% and it was highest in 7-8 years age group in both the sexes contributing to 75% of the total students having abnormal VA. All these children fell within 50th percentile of weight and height for their respective age and sex. Hindu & ST children accounted for 91.67% & 50% abnormal VA respectively; however, when presence of abnormal VA was compared with its absence between 2 sexes, Hindu and Muslim students and in different castes, no statistically significant differences were found (p > .05). Students of Class-I and Class-II contributed 25% and 50% respectively and together accounted for 75% of abnormal VA. Prevalence of VAD was 8.16%. Among sufferers of VAD Hindus (81.48%) and ST (51.85%) were the main contributors; the differences between presence and absence of VAD in 2 sexes, among 3 religious groups were not statistically significant (p > .05); however, differences among ST and NonSCST groups, and again SC, ST and Non-SCST groups were statistically significant (p < .05). Prevalence of Bitot's spot was 3.63%. Among the students having Bitot's spot, females (58.33%) outnumber the males (41.67%); but the difference between presence and absence of Bitot's spot in 2 sexes was not statistically significant (p > .05). 83.33% each of Hindus and STs had Bitot's spot. No SC and no Muslim student had this spot; the differences between presence and absence of Bitot's spot between Hindu and Christian students were statistically significant (p < .01); similarly when the findings were considered between ST and NonSCST students the difference was found to be statistically highly significant (p < .001).
Subject(s)
Child , Child, Preschool , Female , Humans , India/epidemiology , Male , Prevalence , Religion , Rural Health Services/organization & administration , Visual Acuity , Vitamin A Deficiency/epidemiologyABSTRACT
MB78, a virulent bacteriophage of S. typhimurium does not allow other bacteriophages like P22 and 9NA to multiply in its presence. The exclusion of P22 by MB78 is found to be due to competition for common binding site(s) in the host cell membrane. As a result, P22 DNA fails to replicate in presence of MB78 DNA. Further, the sedimentation profile of P22 DNA in cells infected simultaneously with P22 and MB78 suggested fragmentation of P22 DNA. This may also contribute to the exclusion phenomenon.
Subject(s)
Bacteriophage P22/physiology , Bacteriophages/pathogenicity , Virulence , Virus ReplicationABSTRACT
Bacteriophage MB78 is a virulent phage of Salmonella typhimurium. The viral DNA is 42 kb in size and seems to be circularly permuted. We show that viral DNA replication is through concatemeric DNA formation which is subsequently converted into full length DNA through headful packaging. A restriction map of MB78 DNA for six restriction endonucleases e.g. BgIII, PvuII, ECORI, ClaI, SalI and SmaI has been constructed. The yield of certain fragments in less than molar amount is explained in terms of permutation and the headful mechanism of packaging. The packaging site (pac site) has been suggested.
ABSTRACT
The transport of α-methyl-D-glucoside and two aminoacids, L-phenylalanine and L-leucine by a temperature sensitive fatty acid requiring mutant of Salmonella typhimurium was studied under conditions of supplementation with cis or trans-unsaturated fatty acids. The results of such experiments definitely establish a relationship between the fatty acids composition of the membrane and the transport property of the cells. Cells grown in the presence of trans–unsaturated fatty acids cannot transport so efficiently as compared to the cis-unsaturated fatty acid-grown cells except linolelaidic acid, a trans-transunsaturated fatty acid. Protein: phospholipid ratio of the membrane also varies significantly under such conditions. The affinity of L-phenylalanine transport carrier for the substrate changes remarkably in cells grown in the presence of different cis or trans-unsaturated fatty acids and indicate the possible role of membrane lipids in membrane assembly as well as regulation of the activity of L-phenylalanine transport system.
ABSTRACT
The effects of changes in fatty acid composition of the cell membrane on different biological functions of Salmonella typhimurium have been studied with the help of a temperature sensitive fatty acid auxotroph which cannot synthesise unsaturated fatty acids at high temperature. On being shifted to nonpermissive temperature the cells continue growing for another one and half to two generations. The rates of protein and DNA syntheses run parallel to the growth rate but the rate of RNA synthesis is reduced. Further, there is a gradual reduction in the rate of transport of exogenous uridine and thymidine into the soluble pool. The transport process can be restored by supplementing the growth medium with cis-unsaturated fatty acids but not trans-unsaturated ones although the growth of the cells is resumed by supplementation with either cis or trans-unsaturated fatty acids. However, supplementation with trans, trans-unsaturated fatty acids leads to only partial recovery of the transport process. The rate of oxygen uptake is also affected in cells grown in the presence of the trans-unsaturated fatty acids, elaidic acid and palmitelaidic acid. Analysis of cells grown under different fatty acid supplementation indicate that fatty acid composition of the cell membrane, especially the ratio of unsaturated to saturated fatty acids varies with temperature shift and supplementation of the growth media with fatty acids.