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Biomedical subjects

R H Markham

Publications and source records attributed to R H Markham.

15 recordsLinked to original sources
PubMed2002

Pest management in traditional maize stores in West Africa: a farmer's perspective.

Farmers in the Republic of Benin have few resources to invest in protection of stored maize, and prophylactic pesticide application is often recommended by extension and development agencies. Neither the efficacy nor profitability of such an application in traditional maize storage facilities has been addressed quantitatively. In this study, existing management options for stored maize were evaluated monthly over 6 mo in central and southern Benin with respect to their effects on grain injury and on densities of Prostephanus truncatus (Horn) and Sitophilus zeamais Motschulsky. P. truncatus infested 54% of the experimental stores in the study even though Teretrius nigrescens (Lewis), a natural enemy introduced against P. truncatus, was well established in the region. S. zeamais was the most common pest, found in 85% of the experimental storage facilities. Prophylactically treated maize was, on average, worth more than untreated maize for month 1 through 5 in southern Benin, after taking into account market price, pesticide costs, percentage grain damage and weight loss, but maize storage was not profitable overall. No difference was observed between treatments in central Benin. After 6 mo treated storage facilities were not significantly different from untreated storage facilities in terms of either percentage damage or profit in either region. A rapid scouting plan intended to provide farmers with a means for identifying storage facilities at greatest risk of severe P. truncatus infestation was field validated. Given that unsafe pesticide use is prevalent in Benin, research and extension services should clearly state the limitations to prophylactic treatment and increase the effort to educate farmers on appropriate pesticide use, store monitoring and marketing.

Animals↗
PubMed2002

Resistance in accessions of cowpea to the coreid pod-bug Clavigralla tomentosicollis (Hemiptera: Coreidae).

Laboratory and screenhouse experiments were conducted to identify antibiosis and tolerance in four wild accessions of cowpea, Vigna unguiculata subsp. dekindtiana, to Clavigralla tomentosicollis Stål, the most damaging pod-sucking bug on cultivated Vigna genotypes in West Africa. The wild accession TVnu 151 showed antibiosis resistance, causing >50% mortality of the nymphs within 3 d of placing them on pods. Nymphs died more quickly on TVnu 151 than on TVnu 72, the wild and resistant control of the V. vexillata species which affected the weights of surviving insects to a much greater degree than TVnu 151. The three other accessions of the subspecies dekindtiana (TVnu 369, TVnu 517, and TVnu 707) did not cause significant mortality to the bugs, but rather extended their developmental time, with surviving adults showing lower weights and slower oviposition rates than those on the susceptible control IT84S-2246. Wild accessions affected male and female bugs differently, resulting in differential survival. This was reflected by the sex ratio which was male biased on the wild accessions (1:0.3-1:0.9), and female biased on IT84S-2246 (1:1.5). No evidence of tolerance was found in the four accessions of V. unguiculata subsp. dekindtiana. Overall, seed traits seemed to be the major resistance component in these wild accessions.

Animals↗
PubMed2001

The Effects of an entomopathogenic fungus, Beauveria bassiana (balsamo) vuillemin (hyphomycetes), on Prostephanus truncatus (horn) (Col.: Bostrichidae), Sitophilus zeamais motschulsky (Col.: Curculionidae), and grain losses in stored maize in the Benin Republic.

A fungal entomopathogen, Beauveria bassiana, was used to treat maize ears placed in traditional grain stores against Prostephanus truncatus in a field experiment conducted from September 1997 to March 1998 in the Benin Republic, West Africa. Treatments included oil-based spray with and without conidia, maize stored with and without the husk, and stores with and without artificial infestation. Additional treated ears kept in insect-proof cages under field conditions were sampled weekly and exposed to insects to estimate the virulence and persistence of the pathogen during the storage season. P. truncatus densities were significantly lower in treatments that included conidia, although densities were high in all artificially infested treatments and grain losses were severe. The effect of the pathogen was modeled with an exponential decay function and incorporated in a published P. truncatus simulation model. The effects of hypothetical pathogens with different virulence and persistence characteristics were evaluated in terms of insect density and percentage grain loss.

Animals↗
PubMed2000

Grain injury models for Prostephanus truncatus (Coleoptera: Bostrichidae) and Sitophilus zeamais (Coleoptera: Curculionidae) in rural maize stores in West Africa.

Prostephanus truncatus (Horn) and Sitophilus zeamais Motschulsky have been reported as the two most serious pests of stored maize in sub-Saharan Africa and smallholder farmers are in urgent need of guidelines for their proper management. In this article we investigate the injury rates attributable to these two species in terms of percentage weight loss and percentage grain damage, and we derive functional response models for the two species on maize. The models successfully described the progression of grain injury in an extensive data set compiled from previously published studies, comprising 46 time series of data relating maize injury and insect pest density. The grain injury models can be used in conjunction with predictive models of pest population dynamics to guide the development of integrated management strategies for postharvest maize pests in West Africa and comparable regions elsewhere.

Animals↗
PubMed1996

A simple snare for transscleral fixation of dislocated intraocular lenses.

PURPOSE: The construction and use of a surgical snare in retrieving and securing posterior chamber intraocular lenses is described. METHODS: The snare consists of a 10-O polypropylene suture threaded into a 25-gauge retrobulbar needle. This is used after a pars plana vitrectomy to retrieve the dislocated intraocular lens. The needle attached to the polypropylene suture is used to secure the lens haptic 1.5 mm behind the limbus. Two snares are used to secure the two lens haptics. CONCLUSIONS: The snare is easy to make with readily available materials. The use of this snare involves less intraocular and extraocular manipulations than other described methods.

Foreign-Body Migration↗
PubMed1992

Results of intraocular lens implantation in paediatric aphakia.

Intraocular lenses were implanted in 16 eyes of 13 patients with congenital cataract, and visual progress was plotted using a preferential-looking technique. Initial surgery was by lens aspiration with preservation of the posterior capsule, and subsequent posterior capsulotomy without anterior vitrectomy. Poly-HEMA posterior chamber lenses were used, usually as a primary procedure but in four cases as a secondary procedure after contact lens failure. No serious complications were encountered. Most eyes achieved a very significant visual improvement, and none were worse than preoperatively. Residual refractive error was highly unpredictable, but did not exceed 6 dioptres. The importance of rigorous occlusion therapy is stressed. With close follow-up, this procedure offers an effective and safe method for the correction of unilateral paediatric aphakia, and, in selected cases only, for bilateral aphakia.

Cataract↗
PubMed1981

Retinal detachment surgery without cryotherapy.

A series of cases of retinal detachment treated without the application of cryotherapy at the time of surgery has been studied. The omission of cryotherapy while not interfering with retinal reattachment, carries the risk of redetachment at a later date. Macular pucker may still occur in spite of the absence of cryotherapy.

Cryosurgery↗
PubMed1979

Retinal detachment surgery without cryotherapy.

The authors have performed 43 retinal detachment operations omitting the use of cryotherapy or any other type of retinal adhesion. Only a full thickness buckling procedure has been performed with drainage of subretinal fluid in some cases. The cases were carefully selected and the follow-up period has been from 1 to 3 1/2 years. Redetachment has not occurred if the original hole was free of traction (round holes) but has so far occurred in 3 cases where traction was present.

Cryosurgery↗
PubMed1977

Severe persistent inclusion conjunctivitis in a young child.

A 14-month-old girl had inclusion conjunctivitis although there had been no signs or symptoms that required medical attention in her first year. By 2 1/2 years of age, the child had extensive pannus and corneal scarring that severely reduced vision. The infection was caused by a genital strain of Chlamydia trachomatis, TRIC type E, that was probably acquired at birth. Although genitally transmitted chlamydial strains normally cause a self-limiting inclusion conjunctivitis in areas where trachoma is not endemic, this case illustrates that they may occasionally cause severe trachoma. Possibly local idoxuridine (IDU) treatment (administered to this patient before the correct diagnosis was made) contributed to the severity of this infection.

Child, Preschool↗
PubMed1977

Retinal detachment surgery. Buckling procedures and drainage of subretinal fluid.

The encircling procedure, while still an important part of succesful retinal detachment surgery, has been found to be unnecessary in a wide variety of retinal detachments which can be more simply treated by local buckles. A much more important aspect of the detachment procedure, however, is the avoidance where possible of drainage of subretinal fluid.

Drainage↗
PubMed1977

Double--blind clinical trial of adenine arabinoside and idoxuridine in herpetic corneal ulcers.

The results are reported of a fully controlled randomized double-blind clincial trial of adenine arabinoside and idoxuridine ointment in sixty patients with herpetic ulceration of the cornea. Although both antivirals showed a trend towards superiority over placebo, the therapeutic effect did not reach statistical significance in spite of the known efficacy in laboratory animals. Further studies in rabbits are reported; these indicate that systemic immunity may play a role in combating virus proliferation in recurrent disease, and it is considered this disguises the efficacy of topical antiviral therapy in clinical trials, thus necessitating an estimated requirement for approximately fifty patients per treatment group to obtain significant effects. It is concluded that an antiviral is valuable in the treatment of ulcerative herpetic keratitis, particularly in primary disease and in the presence of systemic and local immunosuppression after the use of topical adrenocorticosteroid. In recurrent disease, where a trigger factor is known, experience has shown that therapy can be profitably administered before the onset of clinical disease.

Adolescent↗
PubMed1977

Current status of prophylaxis of retinal detachment.

Our indications for prophylaxis may be summarized as follows: (1) All symptomatic holes. (2) All holes in aphakic eye. (3) All holes in fellow eyes. (4) Lattice degeneration in fellow eyes, even when holes are not present. (5) Holes in snail-track degeneration. (6) The fellow eye of one with a giant tear. (7) Asymptomatic holes in myopic eyes except those within the vitreous base. (8) Some large asymptomatic holes in non-fellow or aphakic eyes.

Cataract↗