Genetic Diversity of Microcystin Producers (Cyanobacteria) and Microcystin Congeners in Aquatic Resources across Africa: A Review Paper

Microcystins are produced by multifaceted organisms called cyanobacteria, which are integral to Africa's freshwater environments. The excessive proliferation of cyanobacteria caused by rising temperature and eutrophication leads to the production and release of copious amounts of microcystins, requiring critical management and control approaches to prevent the adverse environmental and public health problems associated with these bioactive metabolites. Despite hypotheses reported to explain the phylogeography and mechanisms responsible for cyanobacterial blooms in aquatic water bodies, many aspects are scarcely understood in Africa due to the paucity of investigations and lack of uniformity of experimental methods. Due to a lack of information and large-scale studies, cyanobacteria occurrence and genetic diversity are seldom reported in African aquatic ecosystems. This review covers the diversity and geographical distribution of potential microcystin-producing and non-microcystin-producing cyanobacterial taxa in Africa. Molecular analyses using housekeeping genes (e.g., 16S rRNA, ITS, rpoC1, etc.) revealed significant sequence divergence across several cyanobacterial strains from East, North, West, and South Africa, but the lack of uniformity in molecular markers employed made continent-wise phylogenetic comparisons impossible. Planktothrix agardhii, Microcystis aeruginosa, and Cylindrospermopsis raciborskii (presently known as Raphidiopsis raciborskii) were the most commonly reported genera. Potential microcystin (MCs)-producing cyanobacteria were detected using mcy genes, and several microcystin congeners were recorded. Studying cyanobacteria species from the African continent is urgent to effectively safeguard public and environmental health because more than 80% of the continent has no data on these important microorganisms and their bioactive secondary metabolites.

Polycythemia Rubra Vera Presenting as Unilateral Clubbing Due to Left Subclavian Artery Thrombosis

We report the case of a 29 year old male who presented with burning pain in the tips of fingers of left hand and recurrent episodes of amarausis fugax. Examination revealed polycythemia, unilateral clubbing with positive Adson's test in left upper limb. Evaluation revealed thrombosis of the left subclavian artery in CT angiography. Polycythemia rubra vera was found to be the underlying cause.

Acute optic neuritis following infection with chikungunya virus in southern rural India

OBJECTIVES

To define acute optic neuritis following infection with chikungunya virus (CHIKV) and to determine the efficacy of treatment with corticosteroids of acute optic neuritis.

METHODS

This was an observational study involving 10 patients, who were confirmed cases of infection with CHIKV with acute optic neuritis in one or both eyes. A complete ophthalmic examination was performed in all cases. All 10 patients were treated with intravenous methylprednisolone for 3 days, followed by oral prednisolone for 2 weeks, thereafter reducing the dose of prednisolone over 1 month.

RESULTS

Of the 10 patients in the study, seven were male and three female. Seven patients had unilateral optic neuritis and three patients had bilateral optic neuritis. Initial visual acuity in the affected eyes ranged from perception of light to visual acuity of 6/6. After treatment, nine out of 10 patients improved to visual acuity of 6/12 or better. Color vision became normal in eight patients in our study. After treatment, a relative afferent pupillary defect persisted in four patients and six patients had normal pupils. A statistically significant improvement in vision was found after treatment (p ≤ 0.001). Visual field (HFA FF 120) examination showed various types of defect. Visual fields returned to normal in four patients, while the remaining six patients had persistent diffuse visual field defects.

CONCLUSIONS

CHIKV infection may cause acute-onset of visual loss due to acute optic neuritis. Prompt recovery of vision may follow steroid therapy. Physicians should be aware of the possibility of acute optic neuritis following CHIKV infection so that a preventable cause of vision loss can be treated effectively.

A primitive social circuit: vasotocin-substance P interactions modulate social behavior through a peripheral feedback mechanism in goldfish

At its core, the polyvagal theory proposes that peptides affect simple social behaviors through influences on hindbrain autonomic processes. To test this mechanism, we compared the effects of fore- and hindbrain infusions of vasotocin (VT) on social approach behavior in goldfish. VT infusions into the 4th ventricle, which ink infusions verified did not move rostrally to the forebrain, inhibited social approach at a lower dose than did infusions into the 3rd ventricle, which did diffuse to the hindbrain. Thus, VT actions in the hindbrain appear to modulate this simple social behavior. We then identified a population of substance P (SP)-immunoreactive cells in the hindbrain that are encapsulated by putative VT terminals, and determined that those cells project to the periphery. Injecting SP peripherally, as with infusing VT centrally, inhibited social approach, and peripheral injections of an SP antagonist, but not central infusions, abolished the behavioral effects of central VT infusions. We therefore propose that VT inhibits social approach by activating SP cells in the hindbrain, which then induce changes in body state that feed back to the brain. Central VT infusions did not inhibit feeding, suggesting that this VT mechanism selectively affects appetitive social responses. Because VT projections to the hindbrain are highly conserved in vertebrates, influences on peripheral feedback processes like the one we have described in goldfish may reflect how VT affected simple social behaviors in ancestral vertebrates and thus preadapted members of this peptide family to play increasingly complex roles in social and emotional regulation in modern animals.

Lattice strain and lattice expansion of nanoparticles of MgAl2O4 as a function of particle size

Reduction in the physical dimension of a crystalline solid lead to regular changes in the lattice constants. The lattice expansion or contraction in nanoparticles depend on a number of factors like nature of atoms in the interior, surface atoms, surface surroundings, dangling bonds, and oxygen concentration on the surface. XRD patterns of nanoparticles of MgAl2O4 having average particle size 7 nm, 9 nm, and 19 nm show that lattice parameters undergo contraction or repulsion along different planes. The lattice contraction along with lattice expansion is possible since the morphology of the particle is not spherical which is evident from the SEM micrographs. Lattice expansion is observed mainly in nanocrystals having covalent or ionic bonds. The existence of ionic bonds is evident from the IR spectrum. Along planes where there is no deficiency of oxygen, contraction is observed while where there is deficiency of oxygen lattice expansion is observed. As the particle size increases due to heating most of the planes show lattice contraction and on further heating due to the excess oxygen accumulation in interstitial positions lattice expansion is observed along most of the planes. The reason for the observation of lattice strain or lattice expansion may be due to the electrostatic attraction or repulsion between ions along different planes.

Splenic abscess in a boy with isolated levocardia

Levocardia with situs inversus is a rare condition. We present the case of a fourteen-year-old boy with congenital cyanotic heart disease, isolated levocardia and splenic abscess. It is the first report of both these conditions occurring in the same person.

Caffeine ameliorates radiation-induced skin reactions in mice but does not influence tumour radiation response

Intramuscular administration of caffeine at a dose of 80 mg kg(-1) body weight to the gastrocnemius muscles of Swiss mice 5 min prior to local irradiation (35 Gy) of the leg delayed the progression of radiation-induced skin reactions in such animals. While 90% epilation with reddening of the skin was noted in animals treated with radiation alone, animals pretreated with caffeine suffered only partial hair loss with slight reddening of the skin on the 16th and 20th days post-irradiation. Beyond the 28th day, damage scores in irradiated feet for both the groups were similar (score 3) and remained unchanged until the 32nd day and then decreased and disappeared completely in both treatment groups by the 40th day after irradiation. In addition, the effect of caffeine on the radiation response of a mouse fibrosarcoma was investigated. Results showed that intratumoral administration of caffeine at a dose of 80 mg kg(-1) body weight 5 min prior to local exposure of tumours to 10 Gy of 60Co gamma-rays did not influence the response of tumours to radiation. The present study thus showed that although caffeine ameliorated radiation-induced skin reactions in the mouse leg, it did not affect the tumour radiation response, indicating its potential application in cancer radiotherapy.

Caffeine protects mice against whole-body lethal dose of gamma-irradiation

Administration of caffeine (1,3,7-trimethylxanthine), a major component of coffee, to Swiss mice at doses of 80 or 100 mg/kg body weight 60 min prior to whole-body lethal dose of gamma-irradiation (7.5 Gy) resulted in the survival of 70 and 63% of animals, respectively, at the above doses in contrast to absolutely no survivors (LD-100/25 days) in the group exposed to radiation alone. Pre-treatment with a lower concentration of caffeine (50 mg/kg) did not confer any radioprotection. The protection exerted by caffeine (80 mg/kg), however, was reduced from 70 to 50% if administered 30 min prior to irradiation. The trend statistics reveal that a dose of 80 mg/kg administered 60 min before whole-body exposure to 7.5 Gy is optimal for maximal radioprotection. However, caffeine (80 mg/kg) administered within 3 min after irradiation offered no protection. While there is documentation in the literature that caffeine is an antioxidant and radioprotector against the oxic pathway of radiation damage in a wide range of cells and organisms, this is the first report demonstrating unequivocally its potent radioprotective action in terms of survival of lethally whole-body irradiated mice.

Antitumor effect of pre-transplantation local hyperthermia and augmentation by dietary unsaturated fat

Antitumor effects of pre-transplantation hyperthermia and its correlation to immunological changes in the host animals and enhancement by dietary unsaturated fat have been studied. Leg muscles of mice were locally heated (41 degrees-43 degrees C, 40 min) and fibrosarcoma cells were inoculated into the heated and unheated sites and tumor growth time was determined. Spleen cell activity and plasma levels of interleukins (IL1 and 2) [RIA kits] were assessed. Muscle and tumor fatty acid profiles were modified by feeding mice with unsaturated fat supplemented diet and analysed by GLC. Pre-transplantation hyperthermia suppressed the tumor growth on both heated and unheated contralateral legs of mice. These effects were associated with increased spleen cell activity and plasma levels of IL1 and 2. Diet rich in unsaturated fat altered the fatty acid profiles of the leg muscles and tumors and inhibited tumor growth. It also potentiated the antitumor effect of pre-transplantation hyperthermia. In conclusion, mild local hyperthermia induces both direct and abscopal antitumor effects which may be ascribed to stimulation of host's antitumor immune responses and these effects are augmented by unsaturated fat supplemented diet.

Antitumor effects of local hyperthermia on a mouse fibrosarcoma

Local hyperthermia at 41-43 degrees C for 40 min prior to transplantation of a fibrosarcoma reduced its growth on the heated as well as the unheated contralateral legs of mice. The growth retardation was most pronounced in the unheated leg at 16 days interval between hyperthermia and tumor cell inoculation and was noticeable even at 22 days while in the heated leg it disappeared by the time. Inhibition of tumor growth was also independent of temperature and of the heating time at 43 degrees C. These results thus indicate that local hyperthermia induces both direct and abscopal antitumor effects which may probably be the result of a systemic effect of hyperthermia in the host animal.

Effects of local hyperthermia on the tissue levels and toxicity of three radiosensitizers in mice

The toxicity of the radiosensitizers misonidazole (MISO), demethylmisonidazole (DEMISO) and pimonidazole (PIM) in mice can be affected differently when combined with local hyperthermia at 43 degrees C for 30 min. At a dose of 1 mg/g, only MISO plus heat resulted in 50% lethality in animals over a period of 7 days post-treatment, whereas 100% survival was observed in the case of DEMISO and PIM. The enhanced lethality may be associated with the production of toxic intermediates of MISO. Heat did not affect the levels of DEMISO in the tissues studied (plasma, brain and tumour), whereas those of PIM were markedly lowered in tumour but not affected in brain for up to 4 h after combined treatment. MISO was found to be decreased in the tumour at all times but affected differently in brain after 1 and 2 h, initially decreasing and then increasing significantly. In all cases the treatment sequence, i.e. sensitizer plus heat or vice-versa, did not affect the rate of survival. At a dose of 2 mg/g, DEMISO plus heat was found to be more toxic when DEMISO was given first (25% survival) compared to 58% on reversal. However, the levels of DEMISO in the tissues were not affected by heat. Thus, it would appear that there is no correlation between parent drug levels measured in plasma, tumour or brain and hyperthermia-induced drug lethality.

Combined effects of X rays, Ro 03-8799, and hyperthermia on growth, necrosis, and cell proliferation in a mouse tumor

A mouse adenocarcinoma was treated with 20 Gy X rays, hyperthermia (30 minutes at 43 degrees C), Ro-03-8799, or a combination of two or three of these agents. Combined treatments increase growth delay in the tumor and this was greatest with the combination of all three modalities. Extensive amounts of necrosis were observed after the combined treatments. This effect was most pronounced after treatment modalities including hyperthermia. On the other hand, the radiation-induced micronucleus formation was more enhanced by the sensitizer than by hyperthermia. After X irradiation and combined treatments with X rays a G2-block was observed in DNA-histograms. Tetraploid cells appeared in large amounts that started DNA synthesis followed by necrosis. From these tumors it was impossible to obtain regular DNA-histograms. Tumor regression is a combined result of reduced cell renewal, increased cytogenetic damage, and development of necrosis.

Growth, cell proliferation and morphological alterations of a mouse mammary carcinoma after exposure to X-rays and hyperthermia

A C57 mouse mammary carcinoma was irradiated with 10, 20 or 30 Gy of X-rays or heated to 43 degrees C for 30 min preceded or not by exposure to 10 Gy. Tumour growth, cell proliferation kinetics, induction of micronuclei and morphological changes in necrosis and vascular density were simultaneously determined. Treatment with radiation and/or hyperthermia produced only a delay in tumour growth of between 1 and 3.8 days. However, the effects of the treatments became more apparent when the amounts of muscle and necrosis were deducted from the originally measured tumour volume. Radiation-induced G2 block of the cells was observed at 12 h after irradiation alone. After the combined treatment, however, the G2 block was delayed beyond 12 h. Moreover, 24 h after the various treatments, the proportion of S-phase cells decreased considerably although the formation of micronuclei showed only a marginal increase. However, the ratio of S-phase cells to micronuclei was significantly reduced during this period. Whereas the amount of necrosis was markedly enhanced 5 days following treatment with 10 Gy plus heat, as well as after 30 Gy, no alterations in the density of small blood vessels could be observed during this period. These results clearly demonstrate that the apparent changes in tumour volume after X-rays and hyperthermia do not truly reflect the response of the constituent cells and that there are many other factors, for instance cell proliferation and morphological alterations, that influence the effects of radiation and hyperthermia on tumours.

Recovery from sublethal damage by acutely hypoxic tumour cells in vivo and in vitro

The ability of acutely hypoxic tumour cells to recover from sublethal damage following irradiation in vivo and in vitro has been measured using a single tumour system. The methods of assay were tumour growth delay, local tumour control and tumour cell survival in vitro following treatment in vivo or in vitro. Tumours in vivo or cells in vitro rendered acutely hypoxic during irradiation were irradiated with either single doses or two doses 24 hours apart. Cells left in situ had a greater capacity for recovery than those treated either in vivo or in vitro and then assayed in vitro. It is suggested that tumours may not show a systematically reduced capacity for recovery relative to normal tissues, unless chronically hypoxic tumour cells have a reduced capacity for recovery and determine the response. However, the results imply that deductions as to the ability of tumour cells to recover from sublethal damage (whether chronically hypoxic or not), which rely on in vitro assays, may underestimate the extent of recovery.

Modification of radiation effects in single-cell systems by membrane-binding agents

Chlorpromazine sensitized E. COLI B/r, thymocytes and Yoshida ascites-tumour cells to 60Co gamma-rays, preferentially, under hypoxic conditions, Residual sensitization was observed in E. coli B/r. The radiosensitization by chlorpromazine was found to be due to the reaction of radiolytically-induced hydroxyl radicals with the sensitizer. When both procaine HCI and chlorpromazine were present during anoxic irradiation of E. coli B/r, there was no additive effect. But the addition of procaine HCL after irradiation to cell sensitized by chlorpromazine had an effect that was significantly greater than that produced even by oxygen. A similar effect was observed when lignocaine or tetracaine was used in place of procaine. The possible mechanisms involved in radiosensitization by chlorpromazine and in the post-irradiation effect of local anaesthetics in cells sensitized to 60Co gamma-rays by chlorpromazine are discussed.