Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 4 uppsatser.

Thesis (doctoral)--Karolinska Institutet, Stockholm, 1987. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (doctoral)--Karolinska Institutet, Stockholm, 1987. / Added t.p. with thesis statement inserted. Includes bibliographical references.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

The dichloromethane extracts (1 mg/ml) of Artemisia pacifica Nutt and Guardiola platyphylla Gray (fam. Asteraceae) separately demonstrated in vitro growth inhibition of Staphylococcus aureus (UA 9-29), Bacillus subtilis (UA 2-27), Klebsiella pneumoniae (UA 3-9) and Candida albicans (UA 97). Each of these extracts were subjected to bioassay-directed solvent extraction and partition in order to obtain concentrated active fractions. Subsequently, the active compounds were isolated and identified from these fractions. Artemisia pacifica Nutt. The active compound was the major component isolated from A. pacifica. By comparing the physical and chemical data with previously reported data, this compound was identified as dehydrofalcarindiol. Dehydrofalcarindiol demonstrated growth inhibition against S. aureus (50 μg/ml), B. subtilis (25 μg/ml), K. pneumoniae (100 μg/ml) and C. albicans (25 μg/ml). Its diacetyl derivative was devoid of activity at 100 μg/ml. Guardiola platyphylla Gray. The active fraction obtained from G. platyphylla contained unstable compounds that decomposed in the presence of air. Size exclusion chromatography (Sephadex LH-20) was used to fractionate the active fraction. Two new sesquiterpenes, the o-catechol derivatives (1S,4S) and (1S,4R)-7,8-dihydroxy-11,12-dehydrocalamenene, were eluted from the column as a mixture. The mixture of their diacetyl derivatives was oxidized with CrO₃ in AcOH. The major oxidation product was identified as (1S)-7,8-diacetyl-4-oxodeisopropylcalamenene, thereby verifying the sole difference to be the configuration at C-4. This sesquiterpene mixture completely inhibited the growth of S. aureus (100 μg/ml), B. subtilis (50 μg/ml), K. pneumoniae (100 μg/ml) and C. albicans (100 μg/ml). After removal of the sesquiterpenes from the active fraction, the remaining compounds displayed the same level of activity. Another six compounds were also isolated from this mixture as acetylated derivatives due to their instability. Their dimeric structures were identified by 2D-NMR techniques (COSY, HETCOR and NOESY). These dimers may be artifacts since they were formed from their o-quinone monomers when kept at room temperature for a week or when heated at 60°C for 4 hours.

Actinomycetes are bacteria belonging to the order of Actinomyceteles and are / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

Antibiotic resistance in bacteria is a growing threat to global health. Many of the genes responsible for resistance are carried on mobile genetic elements which can be transferred laterally between strains and species. The most important of these are conjugative and mobilisable elements including plasmids and integrating and conjugating elements, ICEs. Haemophi/us influenzae is an important human pathogen, which was first identified as carrying antibiotic resistance genes in the 1970s. Much of this resistance is encoded by ICEHin1056, which is present in H. influenzae strains worldwide. The aims of this study were to describe features of the biology of ICEHin1056, with particular reference to the genetic site and control mechanisms responsible for instigating conjugative transfer. The origin of transfer has been localised to a sequence on ICEHin1056 and an environmental stressor initiating conjugative transfer, oxidative stress, has been identified. In addition, detailed phylogenetic analysis has demonstrated ICEHin1056 to be part of a much larger family of mobile genetic elements, widely distributed in proteobacteria and carrying accessory genes responsible for survival in adverse environments, virulence and antibiotic resistance. The ICEs in the family have conserved homology of gene content and synteny of gene arrangement over deep evolutionary time, challenging the accepted paradigm of modular mosaicism of mobile genetic elements. A key event in increasing dissemination of the ICE, acquisition of a phage type integrase gene has also been identified. The findings presented provide significant insight into the behaviour of ICEs and may in future allow predictions about the spread of virulence factors and antibiotic resistance genes, with important implications for human and animal health.

A Research Report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirement for the degree of Master of Science in Medicine in the branch of Plastic and Reconstructive Surgery / Introduction: Chronic wounds are commonly associated with biofilms and exaggerated inflammation resulting in non-healing: “Bioflammacides” are a recently described group of compounds used in the treatment of chronic and recalcitrant wounds.“Bioflammacides” target biofilms and inflammation aiding a change in the wound environment enabling cutaneous wound healing. Aim: This study aims to evaluate the effects of two targeted “active” topical dressings: a bioflammacide gel (Flavonix®), and a nanocrystalline silver sheet (Acticoat®), on the wound healing events in an in vivo rat chronic wound model. 
Methods: A chronic wound model was created in 128 Sprague-Dawley rats, modifying previously described methods by combining burn and excisional wounds. Wounds were inoculated with a bacteria broth (Pseudomonas
aeruginosa 
and
 Staphylococcus 
aureus) on POD 7; Flavonix®, Acticoat® 
and a negative control. An additional non-inoculated control group (no bacterial or other broth) was included. Eight animals were assigned to each group at each time point.The study was conducted over 21 days and the categorical variables assessed were epithelial gap, cellular proliferation at the wound edge at days 10,14 and 21 semi-quantitative culture for bacterial load at Days 10 and 21: Both Acticoat® and Flavonix®
showed improved wound healing compared to the control group. Epithelial gap distances were significantly different between the Acticoat® group and the negative control group at Day 21 (p
=
0.0350) (8mm
vs.
12.8mm).
Cellular profileration profiles were most modulated in the Flavonix®
treated group at Day 21 in iii comparison to the negative control group (p=0.013) (1.45
vs.
8.65). Bacterial load based on semi-quantitative culture showed significant differences in Pseudomonas aeruginosa counts at POS 21 with all treatment groups except Acticoat® but failed to show a significant change with the Staphylococcus aureus counts in any groups Conclusion: Flavonix® and Acticoat®
both demonstrated similar effects on wound healing events in our chronic wound model with significant differences being noted between the treated groups and negative controls n epithelial gap reduction and cellular proliferation profiles. Bacterial burden in the form of a mixed species biofilm was not convincingly altered by any of the treatment groups, but this did not alter the wound in its ability to close suggesting that inflammatory balance plays an important role as a common pathway in cutaneous healing

Thesis (Ph.D. (Virology))--University of the Witwatersrand, Faculty of Health Sciences, 2012 / The majority of HIV-1 infections around the world occur via sexual intercourse and women, especially in developing countries, are disproportionately affected. Recently a number of strategies have been proposed to control the spread of HIV, among these the use of microbicides to prevent the sexual transmission of the virus. A clinical trial of 1% tenofovir gel that conferred up to 39% protection provided a proof-of-concept that an anti-HIV microbicide is feasible. Various other compounds, acting at different stages of HIV-1 life cycle, are also being investigated as potential microbicides. These include the lectins Griffithsin (GRFT), cyanovirin-N (CV-N) and scytovirin (SVN). GRFT was isolated from the red algae griffithsia sp. while CV-N and SVN were isolated from the blue green alga Nostoc ellipsosporum and the cyanobacterium Scytonema varium, respectively. These lectins bind mannose-rich glycans found on the surface of HIV-1 envelope and act as entry inhibitors. Although HIV-1 subtype C is the main cause of infections around the world, almost all studies conducted with GRFT, CV-N and SVN are based on subtype B viruses. The Chapter Two sought to establish the neutralization sensitivity of HIV-1 subtype C viruses to the three lectins, using both a cell line and primary cells, and compared this sensitivity to subtype B. This Chapter also examined mannose-rich glycans on HIV-1 that are involved in GRFT, CV-N and SVN binding. The conclusion from this study was that the neutralization of subtype C viruses by these lectins is similar to subtype B and that the 234 and 295 mannose-rich glycans were involved in their interaction with the virus. In general these data supported further studies on the use of GRFT, CV-N and SVN for prevention of HIV-1 subtype C sexual transmission. In Chapter Three, the ability of GRFT to expose the CD4 binding site (CD4bs) on HIV-1 gp120 is explored. I found that this exposure resulted in the enhancement of HIV-1 binding to plates coated with anti-CD4bs antibodies b12 and b6 or the CD4 receptor mimetic CD4-IgG2. This lectin also synergized with b12 and HIVpositive plasma containing antibodies to the CD4bs to neutralize the virus. Furthermore, the glycan at position 386, which shields the CD4bs, was shown to be involved in both GRFT enhancement of HIV-1 binding to b12 and b6 and in the synergistic interaction between the lectin and these antibodies. The importance of this study is that it investigated in details the effect of GRFT binding on HIV-1 envelope and also suggests this lectin can be used in combination with anti-HIV-1 antibodies to synergistically enhance the anti-viral activity. In Chapter Four I investigated GRFT, CV-N and SVN inhibition of the virus binding to the DC-SIGN receptor and their inhibition of the DCSIGN transfer of HIV-1 to target cells. These lectins only moderately inhibited the virus binding to the receptor while they potently inhibited its transfer to target cells. However, the inhibition of transfer was stronger when the virus bound the lectins after binding the DC-SIGN receptor compared to when it bound the lectins prior to binding the receptor. These three lectins can, therefore, inhibit the sexual transmission of HIV-1 since the DCSIGN- mediated transfer of the virus to susceptible cells is pivotal to this mode of transmission. Chapter Five is an investigation of the ability of HIV-1 subtype C to escape GRFT, CV-N and SVN, which involved growing the virus under escalating concentrations of these compounds. This was to know how this virus behaves under conditions of continuous exposure to the lectins. I found that HIV-1 subtype C became increasingly resistant to the lectins and viral envelope sequence analysis showed that this was associated with the deletion of mannose-rich glycans on gp120. Furthermore, of the 11 potential mannose-rich glycosylation sites on gp120 seven (230, 234, 241, 289, 339, 392 and 448) were involved in GRFT, CV-N and SVN resistance. Thus, the conclusion was that although these three lectins are potent inhibitors of HIV-1 infection, the virus is also able to escape their neutralization by deleting mannose-rich glycans on its envelope. However, the fact that escape to these lectins involved multiple deglycosylation and was only partial suggests that HIV-1 subtype C escape from GRFT, CV-N and SVN in a microbicide formulation may not be an easy process. We discuss the implications of these findings in Chapter Six and suggest future studies that could complement data presented in this thesis. Overall our data show that GRFT, CV-N and SVN can prevent the sexual transmission of both free and DC-SIGN associated HIV-1 particles and supports further development of these lectins as microbicides against HIV-1.

Thesis (DTech(Chemistry)) --- Cape Technikon, Cape Town, 1996 / A new general synthetic strategy for the synthesis of benzo[c]pyranquinones, with a view to making the route more generally applicable to the synthesis of naturally occurring naphtho[2,3-c]pyranquinones of potential importance as antimicrobial agents, has been developed. This synthetic approach afforded, inter alia, the natural products, is oeleutherin and hongconin (as their racemates) in good overall yield. A new high-yielding synthetic route for the synthesis of 1,5-dimethoxy-4naphthol, 2-allyl-5-methoxy-I,4-naphthoquinone and 3-acetyl-5-methoxy-I,4naphthoquinone, all ofwhich are key intermediates in several laboratory routes to naturally occurring naphtho[2,3-c]pyranquinones, has also been developed. A key-step in their formation is respective methylation, allylation or acetylation of a common intermediate Diels-Alder adduct. A feasible route to a naphtho[2,3-c]pyranone was developed. This model route is envisaged to be generally applicable for the synthesis of higher oxygenated naphtho[2,3-c]pyranones by virtue ofthe nature of the conditions and reagents used in this synthetic route. The target quinones and some of their precursors were evaluated for antimicrobial activity and specificity in vitro. This showed that the benzo[c]pyranquinones have a broader specificity spectrum than their naphtho[2,3-c] or naphtho[2,3-b] analogues.