Rise In Optical Density Research Articles

Patterns of antibody response, adverse effects, and knowledge regarding COVID-19 vaccine: Findings of a serosurvey among vaccinated individuals in North-Western India

Background: With reference to the National vaccination drive against COVID-19 disease (rolled out on January 16, 2021 by Government of India), this study was undertaken to analyze the patterns of antibody response among fully vaccinated adult individuals, to find the spectrum of adverse events following immunizations and knowledge component of the participants regarding the COVID-19 vaccines as well as its side effects. Materials and Methods: A total of 500 vaccinated individuals (with two doses of Government approved Covishield vaccine) were studied over a period of 9 weeks following the second dose of their vaccine. They were tested for the development of antibodies against SARS-CoV-2 spike protein, using an immunoglobulin G ELISA kit on three occasions, and the seroconversion pattern was analyzed. Results: A postvaccination seroconversion rate of 63.8% (at 2–3 weeks), 83.2% (at 4–5 weeks), and 93.2% (overall seroconversion rate at 8–9 weeks) was found. While 77.4% participants (at 4 weeks) and 65.9% participants (at 8 weeks) showed rise in optical density (OD) values, 7.4% showed a declining in OD values (at 8 weeks) and 6.8% remained seronegative throughout the study period. Sixty-two percent had experienced at least one form of adverse effect postvaccination, which were mostly mild in nature not requiring hospitalization. Conclusion: This study found that the timeline for seroconversion postvaccination by COVISHIELD varies between individuals, with few showing decline in the OD values as well and that majority of the adverse reactions observed in this population were only mild and manageable not requiring hospitalization.

Plant Essential Oils Based Nanoemulsion Formulations and Its Antibacterial Effect on Some Pathogens

Antibiotic resistance is the most challenging problem of concern globally and this is invigorating the need of newer antimicrobial products with potential antimicrobial properties. Plant products, especially plant essential oils produce a large array of secondary metabolites as natural antimicrobials. Use of nanotechnology can add advantages to enhance the antibacterial properties of these essential oils. Present study is focused on development of nanoemulsions from plant essential oils and to study their antibacterial activities. Tea Tree Oil, Thyme Oil, Clove leaf and Cinnamon Essential Oils nanoemulsion was formulated using Tween 20 and Tween 80 respectively using probe ultrasonicator. All the formulated Nanoemulsions were then subjected to physicochemical characterization, stability studies and tested for antibacterial activities using Agar-well diffusion method. Stable nanoemulsion formulation with maximum antibacterial activity then subjected to droplet size measurements and polydispersibility index study. Increase in surfactant concentration resulted in reduction in droplet size when ultrasonication time was constant. Cinnamon oil nanoemulsion 20C4 & 80C4 with pdi index 0.573 and 0.382 and droplet size 272.3nm and 133.6 nm respectively demonstrated maximum antibacterial activity in Agar-well diffusion method against S.aureus, E.coli, and S.typhi. When both nanoemulsions were exposed to bacterial growth curve inhibition study. No potential rise in optical density of test pathogens were observed. The inhibition of bacterial growth may be due to killing action of cinnamon oil nanoemulsion formulations to initial bacterial inoculum added to nutrient broth. The study suggests that nanoemulsion formulations from plant essential oils can be used as natural antimicrobials in variety of products.

Reference dosimetry using radiochromic film

The objectives of this study are to identify and quantify factors that influence radiochromic film dose response and to determine whether such films are suitable for reference dosimetry. The influence of several parameters that may introduce systematic dose errors when performing reference dose measurements were investigated. The effect of the film storage temperature was determined by comparing the performance of three lots of GAFCHROMIC EBT2 films stored at either 4°C or room temperature. The effect of high (>80%) or low (<20%) relative humidity was also determined. Doses measured in optimal conditions with EBT and EBT2 films were then compared with an A12 ionization chamber measurement. Intensity‐modulated radiation therapy quality controls using EBT2 films were also performed in reference dose. The results obtained using reference dose measurements were compared with those obtained using relative dose measurements. Storing the film at 4°C improves the stability of the film over time, but does not eliminate the noncatalytic film development, seen as a rise in optical density over time in the absence of radiation. Relative humidity variations ranging from 80% to 20% have a strong impact on the optical density and could introduce dose errors of up to 15% if the humidity were not controlled during the film storage period. During the scanning procedure, the film temperature influences the optical density that is measured. When controlling for these three parameters, the dose differences between EBT or EBT2 and the A12 chamber are found to be within ±4% (2σ level) over a dose range of 20–350 cGy. Our results also demonstrate the limitation of the Anisotropic Analytical Algorithm for dose calculation of highly modulated treatment plans.PACS numbers: 87.55.Qr; 87.56.Fc

Soft‐Surface DNA Nanotechnology: DNA Constructs Anchored and Aligned to Lipid Membrane

Soft‐Surface DNA Nanotechnology: DNA Constructs Anchored and Aligned to Lipid Membrane

Comparative Sensitivity of Seven Marine Microalgae to Cumulative Exposure to Ultraviolet-B Radiation with Daily Increasing Doses

A comparative study of the relative sensitivity to ultraviolet radiation (UVR) among seven marine microalgae from the classes Cyanophyceae (Synechococcus sp.), Rhodophyceae (Porphyridium cruentum), Cryptophyceae (Rhodomonas salina), Prymnesiophyceae (Isochrysis galbana), Bacillariophyceae (Chaetoceros sp.), Chlorophyceae (Dunaliella salina), and Prasinophyceae (Tetraselmis suecica), was carried out. Daily exposure for 4 h over a 4-day period with daily increasing doses of UVR (mainly ultraviolet-B, UV-B) led to a continuous decrease in the effective quantum yield (φPSII) in Rhodomonas salina, Chaetoceros sp. and Isochrysis galbana. In contrast, Tetraselmis suecica did not show a significant inhibition over the 4-day period of exposure. Synechococcus sp., Dunaliella salina and Porphyridium cruentum were able to restore, at least partially, the values of φPSII during the recovery period (white light only, 20 h), even though a significant decrease in φPSII was also measured in these algae after each exposure. Relative inhibition, defined here as the decrease in φPSII after exposure as compared to the value before exposure and normalised to the latter value (RI = ∆φ PSII /φ PSII ), was fitted against UV-B irradiance according to an equation of the type y = 1 ‐ (a x) c e -bx , where y is RI, x is the UV-B irradiance (W m ‐2 ), and a, b and c are constants determined from the fit, using unweighted and weighted irradiances. From the fit, the UV-B irradiance for 50% relative inhibition of φ PSII (RI = 0.5, E 50 [W m ‐2 ]), was calculated for each alga. Rhodomonas salina and Isochrysis galbana exhibited the lowest values of E50 (0.21 and 0.25, respectively, for unweighted irradiance), being the most sensitive algae to UV-B, while the highest value was calculated for Dunaliella salina (0.47 for unweighted irradiance). The E50 could not be calculated for Tetraselmis suecica since this alga showed an RI maximum of 0.1, and was therefore considered as a species which was highly tolerant of UV-B. A rise in optical density of each algal cell suspension at 680 and 750 nm, as well as in chlorophyll a content determined from methanolic extracts, was evident over the experimental period in all of the species except for Isochrysis galbana and Rhodomonas salina. In these two algae, in contrast to the other species, there was a notable increase in the carotenoid/chlorophyll a ratio, although this had negligible effects for the protection against deleterious UV-B. The phycobilin/chlorophyll a ratio showed a gradual decrease with time in the three phycobilin-containing algae, but it was particularly evident in R. salina after the third day of exposure.

Streptococcus pneumoniae serotype 4 outbreak in a home for the aged: report and review of recent outbreaks.

To describe a pneumonia outbreak caused by Streptococcus pneumoniae among residents of a home for the aged and to review contemporary pneumococcal outbreaks. Epidemiological investigation. S pneumoniae isolates were serotyped and analyzed by pulsed-field gel electrophoresis. Paired sera were tested for antibodies to pneumococcal surface adhesin A protein (PsaA, a 37-kDa cell-wall protein). Pneumococcal outbreaks reported in the last decade in English were reviewed. Pneumonia developed in 18 of 200 residents. In 11 (61%), a pneumococcal etiology was demonstrated. S pneumoniae, serotype 4, was isolated from the blood cultures of 3 patients; all isolates were indistinguishable by pulsed-field gel electrophoresis. Pneumococcal involvement was established in 2 by sputum culture and latex agglutination of parapneumonic fluid and in 6 others by a twofold rise in optical density of serum antibody reactive to PsaA. Pneumococcal immunization had not previously been received by any patient; mortality was 22%. No additional cases were noted following administration of pneumococcal vaccine and antibiotic prophylaxis with penicillin or erythromycin. Twenty-six outbreaks of invasive pneumococcal disease since 1990 were reviewed. Twelve occurred in the United States, and serotypes 23F, 14, and 4 accounted for 8 (67%) of 12 outbreaks. All confirmed serotypes in US outbreaks are included in the 23-valent vaccine. More than one half of pneumococcal outbreaks worldwide involved elderly persons in hospitals or long-term-care facilities. A pneumococcal pneumonia outbreak occurred among unvaccinated residents of a residential facility for the aged. Institutionalized elderly persons are at risk of outbreaks of pneumococcal disease and should be vaccinated.

Vesicle-micelle transition of phosphatidylcholine and octyl glucoside elucidated by cryo-transmission electron microscopy

Vesicle-micelle transition structures of egg phosphatidylcholine (PC) and octyl glucoside (OG) mixtures were observed in the vitrified hydrated state by cryo-transmission electron microscopy (cryo-TEM) and correlated with the macroscopic and molecular changes previously associated with micellization monitored by 90 degrees light scattering and resonance energy transfer between fluorescent lipid probes. Several distinct structural changes occurred as OG was added to the PC vesicles. First, the average vesicle size decreased from 160 nm to less than 66 nm with no apparent change or decrease in optical density (OD). Then, associated with a small rise in OD, samples with open vesicles were observed coexisting with pieces of lamellae and long cylindrical micelles; more micelles were seen at higher [OG]. This mixture of vesicles and cylindrical micelles occurred in the region of the phase diagram previously attributed to vesicle opening, and possibly vesicle size increase. At higher [OG], small spheroidal micelles coexisting with cylindrical micelles correlated with a decrease in OD and changes in the fluorescence signal. At high [OG] when the solution appeared clear, spheroidal micelles were the dominant structure. By using cryo-TEM, a technique which preserves the original microstructure of fluid systems and provides direct images at 1 nm resolution, we have elucidated the vesicle-micelle transition and identified intermediates not known previously in the PC/OG system.

Lysis and protoplast formation of group B streptococci by mutanolysin.

Group B streptococci, refractory to previously tested muralysins under physiological conditions, were successfully converted to protoplasts by use of a recently describede N-acetyl muramidase, mutanolysin, derived from a streptomycete. Purified enzyme was effective, but crude preparations, although degrading cell walls, simultaneously produced peculiar effects of cytoplasmic coagulation, retention of cell shape, loss of some intracellular enzymes, and a rise in optical density. Addition of purified mutanolysin to the array of muralysins (group C streptococcal phage-associated lysin, lysozyme), previously successful in preparing protoplasts of different streptococci, now makes possible enzymatic preparation of protoplasts of streptococci of groups A, B, C. D. G, and H.

Bacterial kill rates of amoxycillin and ampicillin at exponentially diminishing concentrations simulating in vivo conditions

The responses of bacteria exposed to amoxycillin and ampicillin were studied at continuously decreasing levels with half-life values similar to those which could occur in vivo. For Escherichia coli, the kill-rates were higher with amoxycillin than with ampicillin. The bactericidal response was exponential. With an antibiotic half-life of one hour, the amoxycillin first order inactivation rate was 3.544 h-1 and the viable cell half-life was 0.196 h; the respective values for ampicillin were 2.341 h-1 and 0.296 h. With an antibiotic half-life of five hours, the inactivation rate was 0.704 h-1 corresponding to a viable cell half-life of 0.985 h for amoxycillin compared to 0.358 h-1 and 1.937 h respectively for ampicillin. Comparison of viable counts and photometric monitoring showed that the former is the preferable method for recording the bacterial response to these beta-lactam antibiotics. During the phase of exponential kill, a plateau occurred in the optical density values. This was due in part to an increased biomass per cell. During the recovery phase, the number of viable cells started to increase several hours sooner than did the rise in optical density. For Staphylococcus aureus,the rates of kill were similar with both agents. Amoxycillin had a long bacteriostatic phase which was not seen with ampicillin. This led to a longer lasting antibacterial effect and reduction to a lower total count with amoxycillin. With staphylococci, the viable counts and the photometric responses were parallel.

A spectrophotometric procedure for quantitation of antibody directed to bacterial antigens

A spectrophotometric procedure was developed to study the reaction of whole Streptococcus mutans 6715 cells with purified IgG antibody directed to the group-specific antigen of these organisms. The nature of the reaction was studied by combining different concentrations of antibody with 10 8 formalin-killed S. mutans 6715 cells and monitoring the optical density at 530 nm periodically for up to 24 hr. The curves obtained by plotting the observed optical density values against time were characterized by three phases: an initial rise, a plateau and a fall. The optical density changes were related to the number and size of cell aggregates present at various times during the procedure. Aggregated cells, primarily those in intermediate-size complexes (21–150 cells) appeared to contribute to initial rise in optical density, while further changes appeared to most closely correspond to the formation and subsequent sedimentation of the larger-size complexes (> 150 cells). Apparent rate constants calculated for the formation of intermediate size aggregates did not significantly vary with antibody concentration, while the rate constants for large aggregate formation increased dramatically with increases in antibody concentration. Spectrophotometric analyses performed with 14 different antibody concentrations ranging from 7·6 to 380 μg/100 μl showed that a linear relationship existed, after 1 min of reaction, between the log of the antibody concentration and the change in optical density. This relationship, coupled with the demonstration that serum components did not contribute to the effects of antibody on bacterial cells, indicated that the concentration of antibody in immune serums could be measured. Comparison of the spectrophotometric procedure with direct elution of antibody from cells, using 5 different serum samples, showed a mean per cent difference between the 2 methods of 6·5% (range 0·9–16·1%). Further comparison of the spectrophotometric procedure with the reversed radial immunodiffusion technique (4 serums tested) showed a mean per cent difference of 10·4% (range 0·3–30·3%). The spectrophotometric procedure was at least as accurate as the other procedures utilized and had the distinct advantage of permitting determinations to be made after 1 min of reaction.

Effect of temperature on the mutual adhesion of preaggregation cells of the slime mould, Dictyostelium discoideum.

ABSTRACT The mutual adhesion of slime-mould cells was investigated at 24 and 1 °C in stirred and unstirred medium. Adhesion was induced by adding sodium chloride and followed by recording the diminution in optical density of the cell suspension associated with the formation of cell aggregates. It was found that: (1) when cells, previously stored at 1 °C, were stirred in distilled water at 24 °C the optical density of the suspension increased; (2) when sodium chloride was added after this increase, the optical density fell as cells adhered to each other; (3) both the increase in optical density and subsequent adhesion were reversibly inhibited at 1 °C; and (4) the rise in optical density was a prerequisite for adhesion. Comparison of cell shape and volume at the 2 temperatures suggested that the rise in optical density was due to (a) extension of pseudopodia and a consequent change from a spherical to an irregular shape, and (b) an increase in mean cell volume of about 17%. Observations on the formation of adhesions in still medium at 24 °C showed that initial contacts were formed either by microspikes or by rounded parts of the cell surface. The cell surfaces then flattened against each other, thereby increasing the area of contact. No flattening occurred at 1 °C. Microspikes were present on the surfaces of both cold and warm cells and contained longitudinal fibrils. It is suggested that adhesion of these cells is inhibited in the cold in stirred medium because the cells are unable to expand areas of mutual contact. Cold adhesions are, therefore, weak and easily disrupted by shearing forces. The inability to expand adhesive contacts may be due to the inhibition of cell motility at low temperature.

Magneto-Optical Properties of Sputtered Mn5Ge3 Films

The Faraday rotation and optical absorption of ferromagnetic Mn5Ge3 thin films have been measured in the visible and near infrared. Apart from a gradual rise in optical density in the near uv, the absorption is featureless to 2.5 μ. The Faraday rotation behaves similarly. At 500 mμ the room-temperature absorption coefficient α and the 5°K saturation rotation F are 3.5×105 cm−1 and 2.1×105 deg/cm, respectively. The rotation decreases with rising temperature and vanishes at 40°C which agrees well with the bulk Curie temperature of 37°C. The in-plane coercive field Hc decreases monotonically with temperature as Tc is approached. For a 900-Å-thick film Hc is 260 Oe at 0°C. The dependence of magnetic and magneto-optical properties on film structure is discussed.

Kinetics of the oxidation of hydrogen peroxide by aquocerium(IV) ions in aqueous perchlorate media

The rapid reaction of aquocerium(IV) ions with hydrogen peroxide has been investigated in perchlorate media by the stopped-flow technique. Oscilloscope traces show a rapid initial rise in optical density followed by a rapid decay. The initial rise is ascribed to the formation of cerium(IV)–hydrogen peroxide complexes and the subsequent decay is explained by an inner-sphere electron transfer. The rate of decay is independent of the initial [CeIV], of [H2O2], of [Ce]III, and of acidity, confirming that an intermediate complex with a high formation equilibrium constant exists, The activation energy for the rate-determining electron transfer is very low.

Kinetics of the oxidation of quinol by aquocerium(IV) ions in aqueous perchlorate media

The rapid reaction of aquocerium(IV) ions with quinol has been investigated in aqueous perchlorate media by the stopped-flow technique. The oscilloscope traces show a very rapid initial rise in optical density followed by a rapid decay. The rate of decay is of the first order in [CeIV]Total and of zero order in [quinol]. The rate constant is independent of acidity in the range 0·2–2·0M-HClO4. The rapid initial rise in optical density suggests the formation of an intermediate complex, and the interpretation of the kinetics of the decay also requires such a complex with a high formation equilibrium constant. The kinetics of the decay are compared with the kinetics of the oxidation of quinol by FeIII, MnIII, and CoIII.

The kinetics of the oxidation of hydrazoic acid by aquocerium(IV) ions in aqueous perchlorate media

The rapid reaction of CeIV with hydrazoic acid in perchlorate media has been followed by use of the stopped-flow technique. Oscilloscope traces show a rapid rise in optical density followed by a slower, but still rapid, decay: the rise is ascribed to the formation of CeIV–hydrazoic acid complexes, and the decay to the oxidation of hydrazoic acid. A detailed kinetic study of the latter reaction shows that it is of the first order in [CeIV] and zero order in both [H+] and [HN3]: the consumption ratio Δ[CeIV]/Δ[HN3]= 1·0. These kinetic orders contrast with those found for the oxidation of hydrazoic acid by other cations, and they are discussed in terms of mechanisms involving hydrazido- and azido-complexes. The low value for the activation energy contrasts with the values obtained for the oxidation of hydrazoic acid by other cations.

An Abnormal Pattern of Adenosine Diphosphate-Induced Platelet Aggregation in Acute Myocardial Infarction

SummaryPlatelet aggregation as induced by A.D.P. has been studied using the fragiligraph. With this instrument continuous registration for 60 min of the aggregation - disag gregation - behaviour of platelet rich plasma (P.R.P.) has become practicable and a number of parameters of the curves could then be defined and analysed. Specimens from 24 male patients with acute myocardial infarction and 14 normal controls were compared. P.R.P. of the controls exhibited a short phase of an initial rise in optical density (O.D.) lasting 10-20 sec, a phase of decreasing O.D. (5 min), pointing to platelet aggregation and a phase of disaggregation afterwards. The samples of the myocardial patients differed clearly in several aspects : in most of them (18) the initial rise in O.D. was absent and aggregation started immediately; it was though slower but reached a greater extent. The time of maximum aggregation was significantly greater in the patients and there was no overlap with the controls. Coarse aggregates were clearly visible. Final disaggregation was either minimal or absent. At a concen tration of A.D.P. 0.59 γ/ml, the aggregation curve was biphasic in most patients, whereas it was monophasic in the controls. The curves obtained were mathematically analysed including the definition of a parameter called “aggregation time”, τ, and an attempt was made to clarify several of the properties of the curves in terms of platelet behaviour.

In vitro effect of sodium phenobarbital and diethylnicotinamide (coramine) on the protein binding of bilirubin

Summary 1. The effect of various anions on the protein binding of bilirubin was studied in 14 sera with indirect bilirubin levels ranging from 9 to 30 mg/100 by analysis of their spectral curves. Addition of sulfisoxazole, salicylate, and caffeine sodium benzoate all produced a decrease in protein bound bilirubin, reflected as a fall in optical density at 460 to 465 nm; with a corresponding increase in free bilirubin reflected as a rise in optical density at 420 to 440 nm. 2. No change was seen with either phenobarbital or diethylnicotinamide (Coramine). These findings suggest that the effect of the latter two drugs in lowering serum bilirubin levels is not the result of a redistribution of bilirubin secondary to competitive uncoupling of the bilirubin from its protein binding sites.

Action of heat on pyrethrum extract: The isomerisation of pyrethrins to isopyrethrins

AbstractThe thermal isomerisation of the pyrethrins to isopyrethrins has been studied, the progress of the reaction being followed by the rise in optical density at 2700 Å and the fall at 2300 Å. The isomerisation is a first‐order reaction with 106k equal to 4·58 and 481 at 125° and 195° respectively; these values give E* = 24,610 cal. mol.−1; log A = 8·17; ΔS* = −21·8 cal. deg.−1.In normal (unheated) pyrethrum extract the ratio of the optical densities at 2700 Å and 2300 Å is 0·08; in pyrethrum extract which has been fully isomerised by heat this ratio is 0·62.The biological activities of normal and of partially and completely isomerised pyrethrum extract have been examined by three methods (two on flies and one on grain weevils). Extract in which the pyrethrins have been completely isomerised to isopyrethrins has approximately one‐half of the lethal, and one‐quarter of the knockdown, activity of normal extract on houseflies.Pyrethrum extract which has been submitted to heat treatment shows no loss in biological activity if the ratio of the optical density at 2700 Å to that at 2300 Å has not risen above 0·095.

Effect of blood platelets on heparininduced clearing reaction.

The relationship between the fall in optical density and the rise in glycerol concentration which occur during heparin-induced clearing was studied in platelet-rich and in platelet-poor post-heparin plasmas. This relationship as determined by the significance of the regression coefficients was highly significant with both plasmas. The effect of platelets on clearing was studied in three system containing either fasting plasma or post-heparin plasma or a mixture of both plasmas. In each system platelets inhibited clearing as measured by fall in optical density but did not inhibit lipolysis as measured by production of glycerol. Addition of platelet-poor fasting plasma to platelet-poor post-heparin plasma inhibited lipolysis but did not inhibit clearing. It is concluded that there may be at least two inhibitors against clearing, one associated with platelets and one present in plasma, which inhibit optical clearing and lipolysis, respectively. When fasting plasmas were incubated with substrate endogenous clearing occurred frequently, but sometimes a rise in optical density and a decrease in glycerol concentration were found, suggesting reversal of enzymatic processes.

Cytological and chemical studies of the growth of protoplasts of Bacillus megaterium.

Aeration of protoplasts of Bacillus megaterium in a succinate buffered nutrient broth led to marked growth similar to that already described by McQuillen, and the degree of chromatin synthesis in these growing forms prompted a combined cytological and chemical study. Growth was followed by phase contrast and by Feulgen stains, as well as by lipide phosphorus, nucleic acid, and protein analyses. In slide cultures, growth and compression led to monstrous flattened forms with readily visible, but coalescent nuclear structures. In fluid cultures, the protoplasts grew as phase dense spheres. Orderly reproduction of apparently discrete nuclear bodies was observed during the initial hours of spherical growth, but in older cultures, the chromatin arrangement tended to be more haphazard and was influenced by the concentration of Mg ions. In the same medium, protoplasts free of lysis showed a linear rise in optical density, while vegetative cells exhibited an exponential increase. However, protoplasts were able to synthesize DNA at the same rate as vegetative cells, but their increase of RNA was always less. Thus, as they grew, the ratio RNA/DNA fell. The lipide P increased in proportion to the expanding surface. With growth and lysis, large amounts of water-insoluble slime accumulated. Analyses indicate it to be a phospholipoprotein material containing some RNA.