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Biomedical subjects

A Abiose

Publications and source records attributed to A Abiose.

At least 19 recordsLinked to original sources
PubMed1998

Blue-yellow colour vision in an onchocercal area of northern Nigeria.

AIM: To determine if the City University Tritan Test is a useful addition to visual function assessment in rural communities in northern Nigeria. METHODS: The study was a cross sectional survey. The participants were 8394 people, aged 5 years and over, living in 37 rural communities, mesoendemic and nonendemic for onchocerciasis, in Kaduna State in northern Nigeria. The main outcome measures were the detection of a defect in blue-yellow colour vision by two criteria: (1) failure with the City University tritan screening plates; (2) failure with the City University grading plates to identify severe tritan defects. RESULTS: 91% of those aged 10 years and above could perform the test. Below this age, there were difficulties in comprehension. The test showed good inter- and intraobserver agreement. After adjustment for confounders the odds of failing the screening plates were significantly increased in the presence of optic atrophy or glaucoma (3.55 (2.48-5.08) and 15.9 (4.22-60.2) respectively). There was a greater increase in the adjusted odds of failing the grading plates in the presence of optic atrophy or glaucoma (5.30 (2.97-9.45) and 8.87 (1.61-48.7) respectively). Cataract had a smaller effect on the screening plates, adjusted odds 1.63 (0.95-2.80). CONCLUSION: Blue-yellow colour vision testing is a useful addition to visual function assessment in those aged 10 years and above in rural northern Nigeria, particularly in the detection of optic nerve disease.

Adolescent↗
PubMed1997

HLA-DQ alleles associate with cutaneous features of onchocerciasis. The Kaduna-London-Manchester Collaboration for Research on Onchocerciasis.

Onchocerciasis is associated with a spectrum of cutaneous changes, ranging from clinically normal skin to acute and chronic pathology. An important aspect of disease expression may be the level of immune response to parasite antigens, which is likely to be regulated by MHC-encoded molecules. We therefore investigated HLA class I and class II phenotypes in Nigerian residents of an area endemic for onchocerciasis. All study subjects were carefully characterized for parasite load and skin pathology. Individuals with depigmentation had increased frequencies of DQA1*0501 and DQB1*0301 compared with persons with normal skin and high microfilarial load (NSHMF) (Odds Ratios 3.6 (95% CI 1.0 to 13.2) and 3.8 (1.0 to 15.2), respectively). Conversely, individuals with depigmentation had a decreased frequency of DQA1*0101 and Cw6 compared with NSHMF (Odds Ratios 0.2 (0.1 to 0.9) and 0.1 (0.02 to 0.8), respectively). When NSHMF subjects were examined by age, a further decrease in DQA1*0501 frequency and increase in DQA1*0101 frequency were observed in older NSHMF individuals. These results strongly suggest that there is an immunogenetic basis for the spectrum of cutaneous presentations in onchocerciasis and that HLA-DQ molecules are associated with the level of immune response to parasite antigens.

Adolescent↗
PubMed1997

Risk factors for optic nerve disease in communities mesoendemic for savannah onchocerciasis, Kaduna State, Nigeria.

Ophthalmic examinations on 6831 individuals aged 5 years or more, living in 34 guinea savannah communities mesoendemic for onchocerciasis, in Kaduna State, Nigeria, revealed a relatively high prevalence (9%) of optic nerve disease (OND). Further investigations were performed to determine what proportion of this burden of OND might be due to onchocercal infection. Information on history of cerebro-spinal meningitis (CSM), past use of diethylcarbamazine (DEC) and chloroquine, consumption of cassava and locally produced alcohol was collected for all individuals by questioning. In addition, a nested case-control study of 81 cases of OND and 136 age and sex-matched controls was performed to investigate whether syphilis or a variety of other neurological disorders were responsible for a substantial proportion of cases of OND. Our data suggest that in this population, onchocercal infection is the single most important cause of OND and may account for 50% of all cases. Some 13% of cases were associated with signs suggestive of glaucoma. DEC use might be responsible for up to 30% of all OND. We found no evidence to suggest that any of the following are important causes of OND in the communities studied: CSM, syphilis, neurological syndromes such as polyneuropathy or other generalized neurological disease, consumption of raw cassava, consumption of locally prepared alcohol.

Adolescent↗
PubMed1997

Visual field constriction as a cause of blindness or visual impairment.

Reported are the results of a study of onchocerciasis in communities mesoendemic for savanna onchocerciasis in Kaduna State, northern Nigeria. The study involved 6831 individuals aged > or = 5 years who underwent an extensive screening examination for visual function including Friedmann field analysis. A total of 185 (2.7%) were bilaterally blind by acuity and an additional 28 (0.4%) were blind by visual field constriction. Also 118 (1.7%) individuals were visually impaired by acuity criteria. No criteria for visual impairment by field constriction have been established, and we therefore investigated three potential criteria. As a result, a further 60 (0.9%) individuals were identified with significant visual impairment due to field loss by the various definitions. Small islands of remaining peripheral field occurred in 50 individuals, while 40 individuals had marked reduction of binocular visual field below the horizontal meridian. Concentric visual field constriction to < 20 degrees was found in seven individuals. The WHO definition of blindness currently includes visual field damage criteria for blindness but not for visual impairment. Visual field loss is recognized as a major disability. We hope that these findings stimulate international discussion leading to the development of satisfactory definitions for visual impairment by visual field constriction.

Adolescent↗
PubMed1997

Impact of annual dosing with ivermectin on progression of onchocercal visual field loss.

Reported are the results of a randomized, double-masked, placebo-controlled trial of annual ivermectin dosing in 34 rural communities, Kaduna State, northern Nigeria, where guinea savanna onchocerciasis is mesoendemic. A total of 939 individuals underwent Friedmann field analysis at the first examination and saw at least 19 spots in at least one eye. Of these, 636 (68%) completed a subsequent Friedmann field analysis 2-3 years later. The adjusted incidence rate ratio for the ivermectin group versus the placebo group was 0.64 (95% confidence interval (CI): 0.42-0.98). There was some evidence that the impact of ivermectin was greatest among those who had received one dose of ivermectin. The majority of the deteriorations occurred in eyes that gave evidence of optic atrophy at the first examination. An analysis restricted to individuals with optic atrophy at baseline indicated a reduction of 45% in the incidence of visual field deterioration in the ivermectin group (95% CI: 8-67%). Previous findings have shown that ivermectin has an impact on the incidence of optic atrophy. Our results indicate, for the first time, that ivermectin has a substantial impact on the progression of visual field loss among those with pre-existing optic atrophy.

Adolescent↗
PubMed1996

Morphine-induced venodilation in humans.

Morphine has been extensively used in the treatment of pulmonary edema, and its action is believed to be mediated in part by its ability to produce peripheral venodilation. This study investigated whether opiates produce venodilation in human hand veins and explored the underlying mechanism(s). Fifteen healthy volunteers (11 men and four women) were studied with use of the dorsal hand vein compliance technique. After preconstriction with the selective alpha 1-adrenergic receptor agonist phenylephrine, dose-response curves were constructed to (1) opiate receptor agonists morphine (1 to 30 micrograms/min) or fentanyl (0.07 to 1 microgram/min), (2) a combination of morphine and the mu-opiate receptor antagonist naloxone, and (3) morphine and a combination of histamine (H1 and H2) receptor antagonists. Infusion of morphine caused venodilation in a dose-dependent manner, whereas fentanyl did not produce venodilation. Coinfusion of naloxone and morphine impaired the venodilation only slightly. Coinfusion of the H1- and H2-antagonists completely abolished the venodilatory effect of morphine. These results suggest that the venodilatory effect of morphine is mediated through histamine release and that mu-opiate receptors have little or no involvement in this process.

Adult↗
PubMed1996

Human onchocerciasis in Nigeria: isotypic responses and antigen recognition in individuals with defined cutaneous pathology.

Antigen (Ag)-specific isotype responses to Onchocerca volvulus Ag (OvAg) were assessed by enzyme-linked immunosorbent assay and immunoblot in 123 residents of a mesoendemic area in northern Nigeria and 16 Nigerians from a nonendemic area. Individuals from an endemic area were divided into six groups on the basis of cutaneous onchocercal pathology: acute papular onchodermatitis (APOD), chronic papular onchodermatitis (CPOD), lichenified onchodermatitis (LOD), atrophy (ATR), depigmentation (DPM) and normal skin, high microfilarial load (NSHMF). Immunoglobulin (Ig)G1-4 levels were all significantly associated with residence in an endemic area after controlling for age and sex (all P values = 0.0001). Both IgG1 and IgG3 were significantly associated with onchocercal clinical category after controlling for age, sex, and microfilarial load (P = 0.0031 and 0.0035, respectively). The IgG1 and IgG3 responses were both highest in LOD and lowest in NSHMF and ATR, respectively. A significant inverse association was found between IgG1 levels and microfilarial load after controlling for age, sex, and clinical category (P = 0.0061). On immunoblotting, 20 (44.4%) of 45 individual onchocerciasis sera contained IgG4 antibodies against a band of 29-31 kD, which was not recognized by pooled sera from individuals with other filarial infections. There was heterogeneity of antigen recognition within each of the onchocercal clinical groups, which together with the small numbers examined by immunoblotting, limits interpretation. Nevertheless, some differences in patterns of antigen recognition were found between the onchocercal groups. The LOD group demonstrated prominent immunoreactivity in IgG1 and IgG3 while a general paucity of low molecular weight reactivity was seen with NSHMF in IgG1-3 subclasses, but there was no specific banding pattern that differentiated NSHMF from those with pathology. Comparison of microfilariae-positive (mf+) and mf- individuals with onchocercal skin disease revealed significantly higher levels of all IgG subclasses and higher overall scores on semiquantitative assessment of immunoblots for IgG1, IgG2, and IgG4 for mf+ individuals. Differing isotypic responses may play a role in the pathogenesis of the clinical spectrum of cutaneous onchocerciasis.

Adolescent↗
PubMed1996

Red-dot card test of the paracentral field as a screening test for optic nerve disease in onchocerciasis.

A new screening test for optic nerve pathology is described, consisting of a series of four red targets presented at an angle of 12 degrees in the paracentral field above and below the horizontal meridian. Nonperception and desaturation of the targets are recorded. Inter-observer variability studies found a kappa value = 0.8. A total of 6831 individuals aged > or = 5 years in communities that were mesoendemic for savanna onchocerciasis in Kaduna State, northern Nigeria, were screened using the test. Of the participants 22% were unable to complete the test; almost two-thirds of these (62%) were aged 5-8 years. After exclusion of those visually impaired or blind according to WHO criteria and those unable to complete the test, the test showed a sensitivity of 40% and a specificity of 98% for optic nerve disease when inability to visualize one or more targets was used as the definition of test failure. The sensitivity increased to 54% with a specificity of 96% when the criterion for failure included desaturation of one or more targets. These values compare favourably with those for other available screening methods. The test took 1-2 minutes to perform and was readily accepted by patients and nurses.

Child↗
PubMed1994

Ivermectin and onchocercal optic neuritis: short-term effects.

In 1982 the macrocyclic lactone, ivermectin, was first tested in human patients with onchocerciasis. It has since undergone phase I to IV trials and is now being widely distributed in onchocercal areas. The previous microfilaricide, diethylcarbamazine citrate (DEC), is known to precipitate or exacerbate active optic neuritis in some onchocercal patients, as part of a wider inflammatory response (the Mazzotti reaction). Ivermectin may also cause a mild reaction, especially in people with high microfilarial loads. Few data are available concerning the effect of ivermectin on active optic neuritis. A large, randomised, double-masked, phase IV trial is reported. Individuals were screened for evidence of optic nerve disease (OND), and those identified as possible cases of OND underwent detailed ophthalmic examination, including fluorescein angiography, before being dosed with ivermectin or placebo. A total of 6831 persons were screened of whom 856 (13%) underwent angiography prior to dosing. At 7-14 days after dosing an attempt was made to re-examine 50% of adults over the age of 20 years, including all those with OND. Six hundred and eighty-eight repeat or new angiograms were performed. During this period, 5 new cases of active optic neuritis and one case of exacerbation of existing optic neuritis were identified. Five of these individuals had received placebo and one ivermectin. Two individuals with optic neuritis before dosing had improved after 7-14 days. One had received placebo, the other ivermectin. Ivermectin does not appear to precipitate or exacerbate optic neuritis at a period of 7-14 days.

Adolescent↗
PubMed1994

Distribution and aetiology of blindness and visual impairment in mesoendemic onchocercal communities, Kaduna State, Nigeria. Kaduna Collaboration for Research on Onchocerciasis.

During a field trial of ivermectin in Kaduna State, 6831 people age 5 years and above, living in 34 mesoendemic onchocercal communities in Kaduna State, northern Nigeria, were examined for ocular disease. Visual function assessments included tests of visual acuity and visual fields. A total of 185 individuals (2.7%) were bilaterally blind by acuity criteria with a further 28 blind by field constriction. The overall prevalence of blindness was 3.1%. A further 118 individuals were visually impaired by WHO criteria. Examination for the cause of blindness revealed that 43% of eyes in bilaterally blind patients were blind due to onchocerciasis. A further 11% were blind from optic atrophy much of which was probably onchocercal in origin. Glaucoma was the next most common cause of blindness in the bilaterally blind (11%). Only 6% of eyes were blind from cataract as the primary cause. In the visually impaired population cataract was the most common primary cause of impaired/blind eyes (31%), followed by onchocerciasis (19%) [corrected].

Adolescent↗
PubMed1993

Reduction in incidence of optic nerve disease with annual ivermectin to control onchocerciasis.

The safety and efficacy of ivermectin in the prevention of blindness from onchocerciasis have been established in many studies that have addressed the drug's effects on the front of the eye. We undertook a study with sufficient statistical power to detect an effect on optic nerve disease (OND), probably the main cause of blindness in the disorder. The trial was based in 34 mesoendemic communities in Kaduna State, Nigeria. Villagers aged 5 years and older were randomly assigned annual dosing with ivermectin or placebo for 3 years. Participants underwent medical and ophthalmological examinations before the first, third, and fourth treatments. 3522 villagers aged 15 and older were re-examined at least once. Skin-snip samples were taken at baseline for calculation of microfilarial load. The outcome measure was development of disc pallor accompanied by objective evidence of deterioration in visual function; 116 subjects (45 ivermectin-treated, 71 placebo-treated) showed such changes during the trial. The incidence rate ratio (ivermectin vs placebo) was 0.90 (95% CI 0.54-1.51) for subjects with loads of 0-10 mf (microfilariae) per mg skin and 0.52 (0.29-0.93) for subjects with more than 10 mf/mg. The incidence rate ratio varied little when account was taken of age, sex, presence of pre-existing disc pallor in one eye, previous use of diethylcarbamazine citrate, or doses of ivermectin or placebo received. There was evidence that ivermectin reduced the incidence of OND in subjects with microfilarial loads above 10 mf/mg but had little effect in those with lower loads. Sustained annual delivery of ivermectin could prevent a substantial proportion of onchocercal blindness in mesoendemic communities.

Adolescent↗
PubMed1993

A clinical classification and grading system of the cutaneous changes in onchocerciasis.

Although onchocerciasis is one of the most important diseases of the skin and eye in the tropical world, to date there has been no formal consensus regarding the description and terminology of skin lesions. Furthermore, the contribution of cutaneous pathology to the morbidity and socio-economic effects of the disease has been largely neglected. We present a clinical classification and grading system for recording the cutaneous changes of onchocerciasis, and propose that this system be used as a standard method of description to convey clinical information between workers in all endemic areas to assist local and comparative research.

Acute Disease↗
PubMed1993

An immunohistochemical analysis of onchocercal nodules: evidence for an interaction between macrophage MRP8/MRP14 and adult Onchocerca volvulus.

We have used a panel of MoAbs to investigate the phenotype of macrophages and other leucocytes infiltrating onchocercal nodules. Nodules were removed from individuals at the end of the second year of a community-based, placebo-controlled trial of annual ivermectin chemotherapy in northern Nigeria. No significant differences were seen in the distribution and phenotype of leucocytes in nodules from ivermectin- and placebo-treated individuals. Live adult worms were only seen in nine of the 21 nodules examined. Three regions were clearly discernible within nodules containing both live and dead worms; an outer fibrovascular capsule (zone A), an inner adult worm bundle with surrounding hyaline extracellular matrix interspersed with solitary cells (zone B), and a dense cellular infiltrate surrounding and in contact with a variable proportion of the worm (zone C). Macrophages were the predominant cell type in all zones of the nodule. Those in zone B were distinguished by their dendritic morphology and strong reactivity with MoAbs directed against class II molecules, FcRI (CD64) and CD68, whereas macrophages in zone C were larger, more heterogeneous in shape, and were distinguished by strong reactivity with MoAbs directed against CR4 (CD11c, CD18) and MRP8/MRP14, and with MoAb24. T cells were found primarily in zones A and C, whilst eosinophils were found in only six nodules. A unique staining pattern was seen using MoAbs reacting with the calcium-binding protein MRP8/MRP14. Most macrophages in zones A and B were negative; however, where the occasional positive macrophage was seen in zone B, MRP8/MRP14 was also found around the cell and on the neighbouring worm surface, giving the impression that MRP8/MRP14 was being secreted onto the adult worm. Macrophages in zone C were also MRP8/MRP14-positive, and often the whole infiltrate was surrounded with extracellular MRP8/MRP14, with greatest concentration seen adjacent to the worm. MRP8/MRP14 was not identified on the surface of microfilariae (MF) within the same nodules. Since MRP8/MRP14 was seen on the adult worm in the absence of a leucocytic infiltrate, it may have an early role to play in the immune response to Onchocerca volvulus.

Animals↗
PubMed1993

Ivermectin dose assessment without weighing scales.

Described are two alternatives to the weighing of patients for assessing the dose of ivermectin for use in mass chemotherapy campaigns against onchocerciasis. The first method uses height to separate patients into four dosing categories (1/2, 1, 11/2 and 2 tablets), while the second involves estimating one of these dosing categories according to an individual's physical appearance, without making any measurements. Data for the height-based method were obtained from 6373 people who were taking part in a placebo-controlled trial of ivermectin in northern Nigeria. Use of an arbitrary trade-off of approximately 100 people "overdosed" for every person "underdosed" would lead to 0.5% of the population being underdosed by 1/2 tablet, 46.5% being dosed correctly, 51.7% being overdosed by 1/2 tablet, and 1.2% being overdosed by 1 tablet. The physical appearance approach involved three observers and 779 subjects. A total of 82% of the observers' estimates were "correct", with all the incorrect dosing deviating by only 1/2 tablet from the dose that the subjects should have received.

Adult↗
PubMed1985

Childhood malignancies of the eye and orbit in northern Nigeria.

One hundred four histologically proven malignant tumors of the eye and orbit in children seen in Guinness Eye Clinic, Kaduna, Nigeria between 1975 and 1982 are presented. Retinoblastoma and Burkitt's lymphoma account for the majority of the tumors. The data are compared with those from Ibadan, Nigeria. Burkitt's lymphoma occurs less frequently in Kaduna, whereas the incidence of retinoblastoma is almost the same. Chloroma, which was not seen in Ibadan, accounted for 2.9% of the current series. Factors that may be contributory to the observed differences are discussed.

Adolescent↗
PubMed1984

Neurofibromatosis of the head and neck: clinical presentation and treatment.

The clinical features of neurofibromatosis of the head and neck in 28 Nigerians are presented. The disease produced varying degrees of cosmetic and functional deformity. Total excision of the lesions, where feasible, with skin grafting, when indicated, gave satisfactory cosmetic and functional results. Incomplete excision was unsatisfactory for all eyelid and other more extensive lesions. Intraoperative bleeding was prominent and postoperative follow-up poor.

Adolescent↗
PubMed1983

Cryosurgery in the management of vernal keratoconjunctivitis.

Forty-eight eyes of patients with bulbar vernal conjunctivitis and eight eyes of patients with severe tarsal vernal conjunctivitis were treated with cryopexy. A pointed probe with tip temperature of -35 degrees C was used for the bulbar application, while a round-ended probe with tip temperature of -70 degrees C was used for tarsal application after excision of large cobblestones. Immediate results were highly impressive, while observation over 36 months in some of the patients showed long-term relief or very marked reduction in frequency of exacerbations. Cryotherapy avoids the long-term use of topical corticosteroids in vernal conjunctivitis and is preferable in our largely illiterate population. This study shows that the method is effective and safe.

Betamethasone↗