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Biomedical subjects

G Kulandaivelu

Publications and source records attributed to G Kulandaivelu.

12 recordsLinked to original sources
PubMed2005

Harmonic scalpel tonsillectomy: a prospective study.

The harmonic scalpel has been in use for tonsillectomy for the last 5-6 years in western Europe and North America. Although some studies have found this technique to be superior to other conventional methods, its use is still not very popular. In this single-blinded prospective study, the intraoperative events and postoperative morbidity after the use of harmonic scalpel in tonsillectomy (HST) was evaluated in 180 cases in two hospitals and compared with conventional steel tonsillectomy (CST) and hemostasis secured by bipolar diathermy or ligatures in 100 cases. Both bipolar diathermy and ligatures were used to control the intraoperative bleeding in all cases of CST and some cases (n =9) of HST. The study was done in two hospitals. Patients were randomized irrespectively of their age, sex, past history or indication for surgery. The total number of patients operated on was 180 for HST and 100 for CST. The surgical duration, intraoperative blood loss and postoperative pain were compared between the patients who only had tonsillectomy done in either group (n =120 in HST and n = 70 in CST). The mean operative time in the HST group was not longer than the CST group, but the intraoperative blood loss was significantly less in the HST group. Postoperative pain was present in all patients in the HST group, but to a lesser extent than in the CST group. There was no major postoperative hemorrhage in the HST group that required surgical attention. HST has the advantage over CST when secondary hemorrhage after tonsillectomy is considered. Thus, following the results of the National Prospective Tonsillectomy Audit (NPTA), it may be safe to say that HST is superior to most other conventional methods in reducing secondary hemorrhage. The use of disposable blades in CST certainly reduces the risk of the transmission of Cruetzfield-Jacob disease (CJD).

Adolescent↗
PubMed2003

Terrestrial ecosystems, increased solar ultraviolet radiation and interactions with other climatic change factors.

Based on research to date, we can state some expectations about terrestrial ecosystem response as several elements of global climate change develop in coming decades. Higher plant species will vary considerably in their response to elevated UV-B radiation, but the most common general effects are reductions in height of plants, decreased shoot mass if ozone reduction is severe, increased quantities of some phenolics in plant tissues and, perhaps, reductions in foliage area. In some cases, the common growth responses may be lessened by increasing CO2 concentrations. However, changes in chemistry of plant tissues will generally not be reversed by elevated CO2. Among other things, changes in plant tissue chemistry induced by enhanced UV-B may reduce consumption of plant tissues by insects and other herbivores, although occasionally consumption may be increased. Pathogen attack on plants may be increased or decreased as a consequence of elevated UV-B, in combination with other climatic changes. This may be affected both by alterations in plant chemistry and direct damage to some pathogens. Water limitation may decrease the sensitivity of some agricultural plants to UV-B, but for vegetation in other habitats, this may not apply. With global warming, the repair of some types of UV damage may be improved, but several other interactions between warming and enhanced UV-B may occur. For example, even though warming may lead to fewer killing frosts, with enhanced UV-B and elevated CO2 levels, some plant species may have increased sensitivity to frost damage.

Climate↗
PubMed1994

Response of senescing wheat leaves to ultraviolet A light: changes in energy transfer efficiency and PS II photochemistry.

Response of senescing leaves of wheat seedlings to ultraviolet A (UVA) radiation (365 nm) has been examined. The results indicate that senescence-induced disorganization of thylakoid membrane, decline in carotenoid-to-chlorophyll energy transfer, and enhancement of lipid peroxidation are furthered by radiation. The senescence-induced decline in photochemical activity of photosystem II further declines on irradiation. UVA does not specifically alter any site other than those damaged by senescence.

Chlorophyll↗
PubMed1985

Oxygenic photoreduction of methyl viologen and nicotinamide adenine dinucleotide phosphate without the involvement of photosystem I during plastid development.

Studies on the appearance of various electron transport functions were followed during greening of etiolated cucumber cotyledons. Appearance of dichlorodimethoxy-p-benzoquinone, dimethyl quinone, tetramethyl-p-phenylenediamine, dichlorophenol indophenol and ferricyanide Hill reactions were observed after 8h of greening. However, photoreduction of methyl viologen (MV) and nicotinamide adenine dinucleotide phosphate (NADP) was observed from 2h of greening. Variable fluorescence, which is a direct indication of water-splitting function, was observed from 2h of greening in cotyledons, thylakoid membranes and photosystem II (PSII) particles. The decrease in variable fluorescence in the presence of MV (due to rapid reoxidation of Q-) observed from early stages of greening confirmed the photoreduction of MV by PSII. The early development of water-splitting function was further confirmed by the abolition of variable fluorescence in thylakoid membranes and PSII particles by heat treatment and concomittant loss of light dependent oxygen uptake in the presence of MV in heat treated chloroplasts. However, the photoreduction of MV and NADP was insensitive to intersystem electron transport inhibitors, dichlorophenyl dimethylurea or dibromomethyl isopropyl-p-benzoquinone till 8h of greening. Though the oxidation of intersystem electron carrier cytochrome f was observed from early stages of greening, the reduction of cytochrome f was not observed till 8h of greening. All these observations confirm that during early stages of greening MV and NADP are photoreduced by PSII without the involvement of intersystem electron carriers or the collaboration of PSI. Since these observations are at variance with the currently prevalent concept (Z-Scheme) of the photosynthetic generation of reducing power, which requires definite collaboration of the two photosystems, an alternate electron flow pathway is proposed.

Chlorophyll↗
PubMed1977

Characterization of synchronized cultures of Bumilleriopsis filiformis. Changes in cytochrome-f photooxidation and fluorescence induction kinetics.

Activity of the photosynthetic apparatus of synchronized cultures was studied with the xanthophycean alga Bumilleriopsis filiformis, following the kinetics of fluorescence induction and photooxidation of cytochrome f (= cytochrome c-553) of intact cells. During the beginning of the cell-division phase, minimum cellular photosynthetic activity is observed and a maximum after its completion, which is accompanied by corresponding changes in Hill reaction activity and re-reduction of cytochrome f by photosystem II light. At minimum activity, the level of steady state fluorescence was higher than at the maximum. This is due, at least in part, to the diminished electron flow between the two photosystems seemingly caused by decreased photosystem I activity. This explanation was suported by the kinetics of cytochrome-f photooxidation. Thus, electron transport activity of both photosystems appears to vary during the cell cycle.

Cell Division↗
PubMed1976

Site specific inhibition by alpha-benzyl-alpha-bromomalodinitrile (BBMD) of electron transport in spinach chloroplasts.

The addition of alpha-benzyl-alpha-bromomalodinitrile to different controlled states (non-phosphorylating [2]. phosphorylating [3], ATP-inhibited [4] and uncoupled) of photosynthetic electron transport to ferricyanide or benzoquinone demonstrate a significant inhibition in isolated spinach chloroplasts. alpha-Benzyl-alpha-bromomalodinitrile pretreatement of isolated chloroplasts or addition of alpha-benzyl-alpha-bromomalodinitrile at the onset of illumination completely abolished the O2 evolving reaction. The level of the steady state fluorescence in intact chloroplasts showed a alpha-benzyl-alpha-bromomalodinitrile concentration-dependent increase. The gradual decrease in the reoxidation capacity of the reduced quencher, Q with increasing alpha-benzyl-alpha-bromomalodinitrile concentrations provides evidence for an additional inhibitory site for alpha-benzyl-alpha-bromomalodinitrile between the two photosystems.

Ammonia↗
PubMed1976

The 520 nm absorbance changes in Scenedesmus obliquus and its relation to photosystem I.

The kinetics (region of seconds) of the light-induced 520 nm absorbance changes and its dark reversal have been studied in detail in the wild type and in some pigment and photosynthetic mutants of Scenedesmus obliquus. The following 5 lines of evidence led us to conclude that the signal is entirely due to the photosystem I reaction modified by electron flow from Photosystem II. Gradual blocking of the electron transport with 3(3,4-dichlorophenyl)-1,1-dimethylurea resulted in diminution and ultimate elimination of the biphasic nature of the signal without reducing the extent of the absorbance change or of the dark kinetics. On the contrary, blocking electron flow at the oxidizing side of plastoquinone with 2,5-dibromo-3-methyl-6-isoprophyl-p-benzoquinone or inactivating the plastocyanin with KCN, prolonged the dark reversal of the absorbance change apart from abolishing the biphasic nature of the signal. Action spectra clearly indicate that the main signal (I) is due to electron flow in Photosystem I and that its modification (Signal II) is due to the action of Photosystem II. Signal I is pH independent, whereas Signal II demonstrates a strong pH dependence, parallel to the O2-evolving capacity of the cells. Chloroplast particles isolated from the wild type Scenedesmus cells demonstrated in the absence of any added artificial electron donor or acceptor and also under non-phosphorylation conditions the 520 nm absorbance change with approximately the same magnitude as whole cells. The dark kinetics of the particles were comparatively slower. Removal of plastocyanin and other electron carriers by washing with Triton X-100 slowed down the kinetics of the dark reversal reaction to a greater extent. A similar positive absorbance change at 520 nm and slow dark reversal was also observed in the Photosystem I particles prepared by the Triton method. Mutant C-6E, which contains neither carotenoids nor chlorophyll b and lacks Photosystem II activity, demonstrates a normal signal I of the 520 nm absorbance change. This latter result contradicts the postulate that carotenoids are the possible cause of the 520 nm absorbance change.

Chlorophyll↗
PubMed1974

Physiological studies with isolated leaf cells: early products of photosynthesis and their metabolic interconversions.

A number of plants have been surveyed with respect to isolation by mild grinding in large quantities of leaf cells. The extent of recovery of mesophyll cells per unit leaf area was found to vary with plant species and the method of grinding. Greater than 70% recovery was obtained from the leaves of Canna indica L., Crotalaria Laburnifolia L., and Thunbergia grandiflora Roxb.By pulse-chase time course experiments, the photosynthetically fixed primary carbon compounds of bean leaf cells were not converted into the ethanol-insoluble fraction. About 25% of total (14)C-photoassimilates were found to leak out into the incubation medium. In contrast, Euglena and Chlorella cells incorporated their primary photosynthetic products into cellular macromolecules and the amount of "leak" was very little. (14)C-Leucine supplied to the bean cells was absorbed readily and incorporated into the trichloroacetic acid insoluble fraction.

Journal Article↗
PubMed1969

Photosynthetic studies with leaf cell suspensions from higher plants.

A technique for obtaining intact mesophyll cell suspensions derived from higher plant leaves is described. A large number of taxonomically unrelated plants were found suitable for cell ;extraction' including several plant species from monocotyledonous group.The absorption spectra of leaf cells in suspension differed only slightly from that of Chlorella cells. The higher plant cells respired and photosynthesized in aqueous solutions very much like algal cell suspensions. Only osmotically intact cells photosynthesized maximally and their activity was stimulated by 2 to several fold by the addition of bicarbonate to the medium. The isolated cells when stored at low temperature with proper aeration maintained their initial activity for a minimum of 9 hr. Cells stored at the room temperature (27 +/- 2 degrees ) lost their activity rather rapidly. The isolated cells were physiologically intact as tested by their metabolic response to diverse inhibiting chemicals and growth regulating substances.

Journal Article↗
PubMedDate not supplied

Ultrastructural changes in in vitro ageing spinach chloroplasts.

Ultrastructural changes in in vitro ageing spinach chloroplasts have been studied in detail. Prolonged storage caused swelling of the chloroplasts due to the increase in the thickness and spacing of the thylakoid membranes. The increase in the thickness of the membrane is partly accompanied by the release of lipids. Addition of crystalline bovine serum albumin was found to stabilize the membrane structures. Storage of the chloroplasts at 77 degrees K even though it resulted in complete breakage of the whole chloroplasts, maintained the thylakoid structures in a highly intact form.

Aging↗