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Biomedical subjects

C L Gross

Publications and source records attributed to C L Gross.

13 recordsLinked to original sources
PubMed2005

Broom and honeybees in Australia: an alien liaison.

Facilitative interactions between non-indigenous species are gaining recognition as a major driver of invasion success. Cytisus scoparius (L.) Link (Fabaceae), or Scotch broom, is a cosmopolitan invasive shrub that lacks the capacity for vegetative reproduction and is a good model to study facilitative interactions. Its success in pioneer environments is determined by constraints on its reproduction. We determined whether pollinators were required for seed set in C. scoparius at Barrington Tops, NSW, Australia, where the species has infested ca. 14,000 ha across the plateau. Field and laboratory experiments showed that C. scoparius is an obligate outcrossing species at Barrington Tops. Monitoring of plants (10.7 h) showed that the flowers of C. scoparius have to be tripped to effect seed set and the only pollinator to do this was the introduced honeybee, Apis mellifera L. Most floral visits by honeybees result in fruit set (84 %) and because fruits have many ovules (10 - 18 per ovary) a single bee on an average foraging day can effect the production of over 6000 seeds. A review of C. scoparius pollination across four continents revealed major differences in pollen quantity, which may explain differences in the efficiencies of honeybees as pollinators of C. scoparius. The incorporation of pollinator management in an integrated approach for the control of C. scoparius is discussed.

Animals↗
PubMed2003

Floral structure, breeding system and fruit-set in the threatened sub-shrub Tetratheca juncea Smith (Tremandraceae).

Tetratheca juncea Smith (Tremandraceae) has undergone a range contraction of approx. 50 km in the last 100 years and is now listed as a vulnerable sub-shrub restricted to the central and north coast regions of New South Wales, Australia. There are approx. 250 populations in a 110 km north-south distribution and populations are usually small with fewer than 50 plants/clumps. The reproductive ecology of the species was studied to determine why seed-set is reportedly rare. Flowers are bisexual, odourless and nectarless. Flowers are presented dependentally and there are eight stamens recurved around the pistil. Anthers are poricidal, contain viable pollen and basally contain a deep-red tapetal fluid that is slightly oily. Thus flowers are presented for buzz pollinators, although none were observed at flowers during our study. The species was found to be facultatively xenogamous with only one in 50 glasshouse flowers setting seed autogamously, i.e. without pollinator assistance. Field studies revealed fertile fruit in 24 populations but production varied significantly across sites from exceedingly low (0.6 fruits per plant clump) to low (17 fruits per plant clump). Fruit-set ranged from 0 to 65 %, suggesting that pollen vectors exist or that autogamy levels in the field are variable and higher than glasshouse results. Fruit production did not vary with population size, although in three of the five populations in the south-west region more than twice as much fruit was produced as in populations elsewhere. A moderately strong relationship between foliage volume and fruit : flower ratios suggests that bigger plants may be more attractive than smaller plants to pollinators. A review of Tetratheca pollination ecology revealed that several species are poorly fecund and pollinators are rare. The habitat requirements for Tetratheca, a genus of many rare and threatened species, is discussed.

Australia↗
PubMed2002

The pollination ecology of Grevillea beadleana McGillivray, an endangered shrub from northern New South Wales, Australia.

Grevillea beadleana (Proteaceae) is an endangered species known from five populations in northern New South Wales, Australia. The reproductive ecology of G. beadleana was compared in two populations with a ten-fold difference in the number of plants. Grevillea beadleana was found to be self-compatible in both populations and an examination of pollen viability and stigma maturation revealed that the species is protandrous. Flowering within inflorescences is acropetallous. In the first season plants in the largest population produced approx. ten-fold more inflorescences than those in the smaller population and, although the number of flowers per inflorescence did not vary significantly between populations the first season, the larger population produced more fruit per inflorescence than the smaller population. However, fruit to flower ratios were less than 0.2 in both seasons and populations. In both populations the number of fruit was significantly greater at the proximal end of the inflorescence, where flowers open first, compared with medial and distal positions. Several bird species were observed visiting flowers, although few birds were recorded foraging at plants in the smaller population. Within both populations, birds tended to make more within- than between-plant visits. Self-compatibility, acropetally and proximal fruit-set, combined with the predominantly within-plant movement of honeyeaters, suggests inbreeding may be common within both populations of G. beadleana. Pollination and fruiting success are discussed for G. beadleana and breeding systems among rare and common taxa in Grevillea are reviewed.

Animals↗
PubMed1997

L-oxothiazolidine 4-carboxylate pretreatment of isolated human peripheral blood lymphocytes reduces sulfur mustard cytotoxicity.

Sulfur mustard (HD, mustard gas) is a vesicant chemical warfare agent for which there is no specific medical countermeasure. A potential approach to combating the debilitating effects of this agent is the use of compounds that can react with this material before it interacts with critical macromolecules. Glutathione (GSH), a tripeptide that exists in high concentrations in cells, reacts with HD and is involved in HD detoxification. Pretreatment of human peripheral blood lymphocytes (PBL) with 10 mmol/L L-oxothiazolidine-4-carboxylate (OTC), a "masked" cysteine precursor, increased intracellular glutathione levels 25-50% over control values. Pretreated PBL were harvested, washed, and exposed to 10, 50, or 100 mumol/L HD. Flow cytometry was used to measure cytotoxicity by propidium iodide uptake. Pretreatment of PBL with OTC led to small decreases in cytotoxicity after HD exposure. However, treatment of cells with OTC after HD exposure was not beneficial. Compounds that can modulate GSH levels within the cell may help to reduce the cytotoxicity of HD when used a pretreatment.

Antidotes↗
PubMed1992

Development of an antibody that binds sulfur mustard.

An antibody that binds bis(2-chloroethyl) sulfide (sulfur mustard) was developed. The immunizing antigen was prepared from the hapten 4-(2-chloroethyl)benzoic acid covalently bound to keyhole limpet hemocyanin (KLH). The antibody was monitored by a solid phase enzyme-linked immunosorbent assay (ELISA). The test antigen consisted of a second hapten, 8-chlorocaprylic acid, covalently bound to bovine serum albumin (BSA). The test antigen was absorbed to the wells of 96-well plates. The immunizing and test antigens contain a common chloroethyl moiety. Thiodiglycol, the principal hydrolysis product of sulfur mustard, does not react with the antibody. This antibody, because of its specificity, has the potential to be a valuable tool for mustard research and forensic detection.

Animals↗
PubMed1990

The use of human epidermal keratinocytes in culture as a model for studying the biochemical mechanisms of sulfur mustard toxicity.

Human epidermal keratinocytes in culture were studied to evaluate their usefulness in demonstrating toxic events following exposure to sulfur mustard. Exposure of keratinocytes to sulfur mustard over a concentration range of 1-1000 microM HD, reduced NAD + levels from 96% to 32% of control levels. When keratinocytes were exposed to a concentration of 300 microM HD, NAD + levels began to fall at 1 hour and reached a plateau of 47% of control levels at 4 hours. Niacinamide, an inhibitor of the enzyme poly(ADP-ribose) polymerase, partially protected mustard-exposed cells against NAD + depletion. It also protected cellular viability as assessed by vital staining 24 hours after exposure. This protection was not seen in long-term (72 hr) cultures. These studies suggest that human epidermal keratinocytes in culture can serve as a useful in vitro model for research into the biochemical mechanisms of sulfur mustard-induced cutaneous injury.

Cell Survival↗
PubMed1987

2,2'-Dichlorodiethyl sulfide (sulfur mustard) decreases NAD+ levels in human leukocytes.

2,2'-Dichlorodiethyl sulfide (sulfur mustard, HD) extensively alkylates DNA in a concentration-dependent manner in many cell types. We have proposed a biochemical hypothesis that explains HD-induced injury by linking DNA alkylation and DNA breaks with activation of poly(ADP-ribose) polymerase, resulting in depletion of cellular NAD+. This hypothesis was tested by treating human leukocytes with HD to determine whether NAD+ depletion occurred as predicted. These cells demonstrated a decrease in NAD+ levels which was dependent on both concentration of HD and time after exposure. Inhibitors of poly(ADP-ribose) polymerase or substrates for NAD+ synthesis were able to prevent the HD-induced NAD+ decrease.

Granulocytes↗
PubMed1986

Regulation by serine esterase of histamine release from human leukocytes--I. Direct release of histamine by the serine esterase inhibitors diisopropyl fluorophosphate (DFP) and soman (GD).

The serine esterase inhibitor diisopropyl fluorophosphate (DFP) had been reported previously to inhibit IgE-dependent histamine release. Recently, it has been demonstrated that lower concentrations of DFP enhance IgE-dependent histamine release and inhibit desensitization. This manuscript describes the abilities of several esterase inhibitors to cause release of histamine from human leukocytes (basophils), by a process that is IgE-independent. This esterase inhibitor-induced histamine release appears to be by a non-cytotoxic mechanism that requires calcium and is temperature dependent. These histamine release processes occurred over a longer period of time than IgE-dependent release. Direct release of histamine by these small molecular weight inhibitors and inhibition of desensitization both suggest that one or more serine esterases are involved in the regulation of histamine release from human basophils.

Edetic Acid↗
PubMed1985

Sulfur mustard lowers nicotinamide adenine dinucleotide concentrations in human skin grafted to athymic nude mice.

Human skin grafted to athymic nude mice shows a decrease in nicotinamide adenine dinucleotide (NAD+) concentrations when exposed to sulfur mustard (HD). The lowering of NAD+ is dependent on both dose of HD and time after exposure. When HD is applied to grafted skin at 127 micrograms/cm2, the decrease in NAD+ begins immediately after exposure, approaches minimal values by 4 hr. NAD+ returned to normal within 18 hr. With higher concentrations of HD, NAD+ concentrations fall precipitously within 4 hr, reach a minimum value at 18 hr, and seem to remain at this depressed value for at least 72 hr. NAD+ loss appears to precede and be proportional to tissue injury. Pretreatment of mice with 3-aminobenzamide, a specific inhibitor of poly(ADP-ribose) polymerase, seems to lessen the effect of HD. At higher concentrations of HD, human grafts from mice pretreated with 3-aminobenzamide show significant protection from loss of NAD+ levels after 4 hr.

Animals↗
PubMed1985

Histamine release by esterase inhibitors. The regulation of histamine release from human leukocytes of allergic and non-allergic individuals by the serine esterase inhibitors diisopropyl fluorophosphate and pinacolyl methylphosphorofluoridate.

The serine esterase inhibitor diisopropyl fluorophosphate (DFP) has been shown to inhibit IgE-dependent histamine release. Recently, it has been demonstrated that lower concentrations of DFP enhanced IgE-dependent histamine release and inhibited desensitization. This manuscript describes the ability of another esterase inhibitor, pinacolyl methylphosphorofluoridate (soman), to directly cause release of histamine from human leukocytes (basophils) by a process that is IgE-independent. This release process requires calcium and is also temperature-dependent but occurs over a longer period of time than IgE-dependent release. These data suggest that there is a serine esterase which controls histamine release, and inhibition of this esterase causes histamine release.

Enzyme Inhibitors↗
PubMed1985

Molecular basis for mustard-induced vesication.

A biochemical hypothesis explaining the generation of pathology in human skin by mustard gas (HD) is presented which links the initiation of DNA damages to local alterations of metabolism and subsequent development of blisters. The proposed sequence involves HD alkylation of purines in DNA which are processed to form apurinic sites. Apurinic endonucleases act at these sites to produce backbone breaks in DNA which cause activation of the chromosomal enzyme poly(ADP-ribose)polymerase. This enzyme utilizes NAD+ as a substrate and, at vesicating doses of HD, would deplete the cells of their NAD+ content. The depletion in NAD+ would cause inhibition of glycolysis, and the resulting accumulation of common intermediates would stimulate the NADP+-dependent hexosemonophosphate shunt (HMS). Such stimulation of the HMS has been associated with DNA damage and enhancement of protease synthesis and release. These proteases could be responsible for development of subepidermal blisters which result from fluid accumulation in the cavity created by separation of the moribund basal cell layer from the basement membrane--a characteristic feature of HD-exposed human skin. Partial validation of this biochemical hypothesis has been achieved. DNA alkylated with either monofunctional or bifunctional sulfur mustards, followed by spontaneous or enzymatic depurination, was shown to be sensitized to degradation by apurinic endonuclease. Studies on the effect of HD on human skin grafted to athymic nude mice demonstrated dose- and time-related decreases in NAD+ levels. These decreases in NAD+ levels preceded and correlated to the predicted severity of pathology. The participation of poly(ADP-ribose)polymerase activity in the HD-induced NAD+ loss was substantiated by prevention of this loss in the presence of inhibitors of the enzyme. Additional supporting evidence for the proposed mechanism was obtained at the cellular level by studies which utilized human leukocytes. The subsequent involvement of the HMS and proteases in HD-induced vesication is discussed.

Animals↗
PubMedDate not supplied

Biochemical manipulation of intracellular glutathione levels influences cytotoxicity to isolated human lymphocytes by sulfur mustard.

Glutathione (GSH) is the major nonprotein thiol that can protect cells from damage due to electrophilic alkylating agents by forming conjugates with the agent. Sulfur mustard (HD) is an electrophilic alkylating agent that has potent mutagenic, carcinogenic, cytotoxic, and vesicant properties. Compounds that elevate or reduce intracellular levels of GSH may produce changes in cytotoxicity induced by sulfur mustard. Pretreatment of human peripheral blood lymphocytes (PBL) for 72 hr with 1 mM buthionine sulfoximine (BSO), which reduces intracellular GSH content to approximately 26% of control, appears to sensitize these in vitro cells to the cytotoxic effects of 10 microM HD but not to higher HD concentrations. Pretreatment of PBL for 48 hr with 10 mM N-acetyl cysteine (NAC), which elevates intracellular glutathione levels to 122% of control, appears to partially protect these in vitro cells from the cytotoxic effects of 10 microM HD but not to higher HD concentrations. Augmentation of intracellular levels of glutathione may provide partial protection against cytotoxicity of sulfur mustard.

Acetylcysteine↗