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Biomedical subjects

R N Johnson

Publications and source records attributed to R N Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Accuracy of devices used for self-monitoring of blood glucose.

We measured the inaccuracy of 17 home blood glucose monitors (two visually read, eight colorimetric and seven amperometric). Using strips from a single batch, blood glucose measurements were performed by three medical laboratory technologists on at least 50 capillary blood specimens from patients attending two diabetes clinics. Additional capillary blood was deproteinized and assayed with hexokinase to give a whole blood glucose result. A dedicated glucose analyser was also studied to cross-validate the methodology. At a mean glucose concentration of about 9 mmol/L, monitor readings differed from the reference results by -5.1 to +19.5% with three systems failing to meet the American Diabetes Association guideline for total error of less than 15%. This problem would be alleviated by manufacturers adopting a common policy on calibration and on reporting as a plasma or whole blood value.

Ambulatory Care↗
PubMed1997

Molecular advances in understanding social insect population structure.

Social insects present many phenomena seen in all organisms but in more extreme forms and with larger sample sizes than those observable in most natural populations of vertebrates. Microsatellites are proving very much more informative than allozymes for the analysis of population biological problems, and prolifically polymorphic markers are fairly readily developed. In addition, the male-haploid genetic system of many social insects facilitates genetic analysis. The ability to amplify DNA from sperm stored in a female's sperm storage device enables the determination of mating types long after the death of the short-lived males, in addition to information on the degree of mixing of sperm from different males. Mitochondrial (mt) DNA sequences are also proving important, not only in phylogenetic studies but also in molecular population genetics, as a tracer of female movements. Mitochondrial markers have definitively shown the movement of females between colonies, challenging models giving exclusive primacy to kin selection as the explanation for multiqueen colonies, in Australian meat ants, Iridomyrmex purpureus, and the aridzone queenless ant Rhytidoponera sp. 12. Microsatellite and mtDNA variation are being studied in Camponotus consobrinus sugar ants, showing an unexpected diversity of complexity in colony structure, and microsatellites have shown that transfer of ants between nests of the weaver ant Polyrhachis doddi must be slight, despite an apparent lack of hostility.

Animals↗
PubMed1997

Acute multifocal retinitis.

PURPOSE: To describe the clinical presentation, ophthalmoscopic and fluorescein angiographic findings, and natural history of 14 eyes in nine otherwise healthy, young-to-middle-age adults with idiopathic, acute, multifocal retinitis. METHODS: A retrospective review of the clinical and photographic records of nine patients. RESULTS: Five of the nine patients reported a flu-like illness 1 to 2 weeks before the onset of visual symptoms. Ophthalmoscopic findings included mild vitritis (11 of 14), mild optic nerve edema (seven of 14), macular star (two of 14) or localized neurosensory retinal detachment (two of 14) caused by adjacent focus of retinitis, and small branch-artery occlusion (two of 14). Fluorescein angiography showed early blocking hypofluorescence with late staining hyperfluorescence of all areas of retinitis. In patients with optic nerve edema, the disk showed late leakage. Specific tests for collagen vascular disorders, as well as systemic syphilis and toxoplasmosis titers, were negative in all patients. Five of six patients with histories of cat exposure tested negative for systemic Bartonella henselae antibodies. One patient with a history of cat exposure refused testing. Clinical courses were self-limited, with complete return of vision without treatment in all but one eye, which developed a juxtafoveal scar and localized traction retinal detachment in an area of prior retinitis. CONCLUSIONS: Idiopathic acute multifocal retinitis should be considered in any otherwise healthy, young-to-middle-age adult with acute loss of vision in the presence of multifocal retinitis, particularly when accompanied by an antecedent flu-like illness. Patients with idiopathic acute multifocal retinitis usually have favorable clinical course.

Acute Disease↗
PubMed1997

Indocyanine green videoangiography after acute retinal pigment epithelial tears in age-related macular degeneration.

PURPOSE: To determine the features of combined fluorescein and indocyanine green videoangiography after acute retinal pigment epithelial tears associated with age-related macular degeneration. METHODS: We performed combined fluorescein and indocyanine green videoangiography in three eyes of three patients 2 days to 2 months after the development of tears of the retinal pigment epithelium. RESULTS: The area of exposed choroid in a retinal pigment epithelial tear shows intense hyperfluorescence in fluorescein videoangiography; in contrast, this area demonstrates near-normal choroidal fluorescence on an indocyanine green videoangiogram. The folded and retracted flap of retinal pigment epithelium in a retinal pigment epithelial tear discloses marked hypofluorescence on the fluorescein videoangiogram; in contrast, this flap of retinal pigment epithelium displays varying degrees of hyperfluorescence on the indocyanine green videoangiogram. CONCLUSIONS: The angiographic differences between fluorescein and indocyanine green result from the distinct biophysical properties of these two dyes as well as from the differential penetration of their fluorescence through such pigmented structures as retinal pigment epithelium. Compared with fluorescein videoangiography, indocyanine green videoangiography allows better visualization of choroidal neovascular membranes within the rolled-up and retracted flap of the retinal pigment epithelial tear.

Acute Disease↗
PubMed1997

Grid laser photocoagulation for macular edema in bilateral juxtafoveal telangiectasis.

OBJECTIVE: The purpose of the study is to report the efficacy of laser photocoagulation treatment for macular edema in bilateral juxtafoveal telangiectasis (BJT). DESIGN: The study design was a retrospective, clinical study. PARTICIPANTS: The authors observed 14 patients with BJT, studying the visual acuities and retinal changes of treated and untreated eyes. MAIN OUTCOME MEASURES: Visual acuity, presence of macular edema, and associated retinal findings were measured. RESULTS: Of 28 eyes, 10 (8 patients) received 15 laser photocoagulation treatments for macular edema. Neither treated nor untreated eyes had visual improvement of two or more lines. After treatment, five eyes (50%) had increased retinal vascular distortion develop, three (30%) had new draining retinal venules, five (50%) had intraretinal fibrovascular tissues, and four (40%) had retinal and preretinal hemorrhages develop. CONCLUSIONS: Grid laser photocoagulation therapy for macular edema in patients with BJT appears to neither improve nor stabilize long-term visual acuity. In addition, treatment is associated with retinal pigment epithelial changes, increased postoperative retinal vascular distortion, postoperative vascularized retinal scars, and postoperative retinal hemorrhages. These changes, however, do not appear to cause a further loss of vision.

Aged↗
PubMed1997

Outpatient postoperative fluid-gas exchange after early failed vitrectomy surgery for macular hole.

BACKGROUND: Vitrectomy surgery with fluid-gas exchange and prone positioning has been shown to close macular holes and improve vision. In those eyes that have failed surgery, repeat vitrectomy has been advocated. As an alternative, the authors performed an outpatient postoperative fluid-gas exchange on eyes when the macular hole failed to close after vitrectomy surgery. METHODS: The authors reviewed all cases of failed vitrectomy surgery for macular holes that underwent a postoperative fluid-gas exchange. Eyes were considered to have failed initial surgery if a rim of subretinal fluid surrounded an open full-thickness macular hole. RESULTS: Twenty-three consecutive eyes underwent outpatient fluid-gas exchange 1 week to 8 weeks after vitrectomy surgery. In 17 eyes (74%), fluid-gas exchange resulted in flattening and closure of the macular hole. In all 17 eyes, visual acuity improved 2 or more lines, with 8 (35%) of the 23 eyes achieving 20/50 or better visual acuity. CONCLUSIONS: Postoperative fluid-gas exchange may achieve successful closure of macular holes and improve vision in eyes that have failed surgery for full-thickness macular holes and should be considered as a cost-effective alternative to repeat vitrectomy.

Aged↗
PubMed1997

Phlebotomine sandflies of Kenya (Diptera: Psychodidae). V. Phlebotomus (Paraphlebotomus) mireillae n.sp.

A new species of the sandfly subgenus Paraphlebotomus Theodor from Kenya is described and named Phlebotomus mireillae. The type locality is Utut Reserve, near Gilgil, Nakuru District. The description is based on 10 males and 10 females reared from individual egg batches of wild-caught females. Males of the new species differ from nine other species of the subgenus by the shape of the aedeagus, which is straight, not curved or hooked. They are separated from the remaining three species by other differences in the aedeagus, and in the style and coxite process. Female P. mireillae have backwardly pointing spines inside the distal quarter of the spermathecal ducts, a character not previously described for phlebotomine sandflies. Additional characters which distinguish females of the new species from others of the subgenus are differences in the pharyngeal armature and spermathecae and the lengths of the third antennal segment and labium.

Animals↗
PubMed1997

Ring retinal pigment epithelial window defect of the macula in central serous chorioretinopathy.

PURPOSE: Central serous chorioretinopathy is usually a benign disorder, in which resolution of serous subretinal fluid and return to a visual acuity of 20/40 or better is the normal outcome. In unusual cases of central serous chorioretinopathy, chronic subretinal fluid can lead to permanent retinal pigment epithelial depigmentation. In this report, we describe a ring-like (bull's eye) pattern of retinal pigment epithelial atrophy associated with central serous chorioretinopathy. METHODS: We examined eight patients (nine eyes) with central serous chorioretinopathy in whom retinal pigment epithelial window defects encircling the fovea developed. RESULTS: The average duration of symptoms before recognition of a circular window defect was 6 years. Visual acuity at the time of documentation of the ring-like window defect was 20/40 or worse in seven of nine (77%) eyes. Although laser photocoagulation treatment was performed in six of the nine eyes, vision improved two or more lines in only one eye (17%). CONCLUSION: Chronic central serous chorioretinopathy can cause a ring-like (bull's eye) pattern of retinal pigment epithelial window defects encircling the fovea. This pattern of retinal pigment epithelial window defect when seen in patients with central serous chorioretinopathy may indicate that a patient has a more severe form of central serous chorioretinopathy.

Adult↗
PubMed1996

Echographic findings in benign reactive lymphoid hyperplasia of the choroid.

BACKGROUND: Benign reactive lymphoid hyperplasia is an uncommon uveal tumor. Misdiagnosis may lead to unnecessary enucleations. Clinical evaluation alone is usually not sufficient to diagnose this tumor. OBJECTIVE: To evaluate the utility of standardized echography in the recognition of this disease. METHODS: Retrospective review of the medical and echographic records of 6 patients with choroidal involvement of benign reactive lymphoid hyperplasia. RESULTS: Extraocular episcleral lymphoid nodules were present in 5 of the 6 patients and were usually seen as a late manifestation of the disease. Two patients had repeated echography after treatment of the tumor and showed marked regression of the episcleral nodules. CONCLUSIONS: A combination of clinical and echographic findings can assist in the accurate diagnosis of this rare uveal tumor. The presence of episcleral nodules on standardized echography supports the diagnosis.

Aged↗
PubMed1996

Fibrovascular tissue in bilateral juxtafoveal telangiectasis.

OBJECTIVE: To study the natural history and retinal findings associated with the intraretinal and subretinal fibrovascular tissues that develop in the late phases of bilateral juxtafoveal telangiectasis. METHODS: The records of 10 patients (11 eyes) with bilateral juxtafoveal telangiectasis who developed these fibrovascular tissues were examined. RESULTS: Throughout the follow-up period (average 44 months), only 2 eyes (18%) lost 2 or more lines of vision; the final visual acuities were similar for the eyes both with and without fibrovascular tissues. Sixty-four percent of fibrovascular tissues showed little to no growth. Eyes with fibrovascular tissue commonly had retinal pigment epithelial hyperplasia (72%), draining retinal venules (82%), and retinal vascular distortion (64%). CONCLUSIONS: Fibrovascular tissues of bilateral juxtafoveal telangiectasis have little proliferative potential and minimal effects on visual acuity. Nevertheless, these fibrovascular tissues do remodel over time, leading to retinal vascular distortion. Given these benign findings, the role of laser photocoagulation treatment of these tissues is questionable.

Aged↗
PubMed1996

Vitrectomy in eyes with peripheral retinal angioma associated with traction macular detachment.

PURPOSE: Peripheral angiomas have been associated with epiretinal membranes and traction retinal detachment. The authors investigated the timing, results, and complications of vitreous surgery to remove the retinal traction and treat the peripheral vascular tumor. METHODS: The authors reviewed the results of ten eyes that had undergone vitrectomy for macular pucker and/or traction retinal detachment. These eyes had either preoperative or intraoperative treatment of the peripheral tumor. RESULTS: Patients were followed 4 to 95 months. Six eyes had nonfamilial peripheral acquired retinal hemangioma, three had von Hippel angiomas, and one had multiple large peripheral retinal angiomas associated with extensive retinal telangiectasis. Four eyes received cryotherapy and/or laser photocoagulation 2 to 3 months before surgery. In the remaining six eyes, initial treatment to the peripheral angioma was performed at the time of vitreous surgery. At final follow-up, all eyes were attached without retinal traction. Vision improved in all eyes; six (60%) achieved 20/50 or better visual acuity. Complications included recurrent epiretinal membrane (n=3); nonregressed angiomas (n=3); increased nuclear sclerosis (n=2); and retinal detachment (n=1). CONCLUSION: Vitreous surgery, when applied to epiretinal membranes or traction retinal detachments associated with peripheral vascular tumors, has a good chance of improving vision. Treatment of the hemangioma, before or during vitrectomy, usually results in tumor regression.

Adult↗
PubMed1996

Non-invasive diagnosis of infarct artery patency after acute myocardial infarction by use of serial plasma troponin T concentrations: importance of measurement of peak levels.

OBJECTIVE: To confirm the validity of a previously described method for assessment of infarct artery patency involving serial measurements of creatine kinase activity by use of troponin T concentration as an independent plasma marker. DESIGN: Streptokinase (1.5 x 10(6) units) was given intravenously to 60 patients within 6 h of onset of prolonged chest pain and ST segment elevation, and blood was taken for measurement of troponin T concentration at baseline and at 1, 2, 3, 4, 8, 12, 16, 20, and 24 h after starting treatment. Coronary arteriography was performed at 2.6 (SD 0.3) h. Plasma troponin T concentration was assessed by two methods: (1) as the absolute rise between 0 and 3 h; and (2) as the proportion of the total rise (from baseline to peak) over the same period. Accuracy for prediction of infarct artery patency, assessed by receiver operating characteristic curves, was compared for both methods of assessment using troponin T and was in turn compared with previously reported results on the same patients using serial measurements of creatine kinase activity. RESULTS: Sufficient values for prediction of patency using troponin T were available in 53 patients. A rise in troponin T between 0 and 3 h to > or = 9% of peak concentration predicted angiographic patency with sensitivity of 94% and specificity of 100%. By contrast, at the optimum cutoff for absolute rate of rise (0.5 micrograms/l/h) sensitivity was only 66% and specificity 86%. Comparable figures for creatine kinase were 92% and 91% (> or = 20% of peak by 3 h) and 62% and 78% (150 IU/l/h). Receiver operating curves confirmed better predictive accuracy for proportions over absolute rates of rise for both markers (P < 0.01). CONCLUSIONS: For accurate diagnosis of infarct artery patency using plasma markers it is necessary to express the rate of rise as a proportion of the peak level. Analysed in this way, both creatine kinase and troponin T are suitable for use in randomised trials of new thrombolytic or adjuvant drugs.

Adult↗
PubMed1995

Indocyanine green angiography of acute multifocal posterior placoid pigment epitheliopathy.

PURPOSE: To understand the pathophysiology of acute multifocal posterior placoid pigment epitheliopathy (AMPPPE). METHODS: Indocyanine green (ICG) angiography was used for three patients, four eyes with acute AMPPPE and four eyes with healed AMPPPE. RESULTS: The angiographic photographs demonstrated widespread choroidal hypofluorescence of the active and healed lesions. CONCLUSIONS: Although the pathogenesis and histopathology of AMPPPE are unknown, the literature suggests that AMPPPE may represent an inflammatory reaction, possibly a delayed-type hypersensitivity reaction. The ICG choroidal hypofluorescence in AMPPPE is probably due to partial choroidal vascular occlusion secondary to occlusive vasculitis.

Acute Disease↗