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D W Gibson

Publications and source records attributed to D W Gibson.

At least 19 recordsLinked to original sources
PubMed2001

Optimization of beta-quantification methods for high-throughput applications.

BACKGROUND: Risk of cardiovascular disease is assessed, in part, by laboratory measurement of the concentrations of several lipoproteins. beta-Quantification is a method of lipoprotein measurement that uses ultracentrifugation to partially separate lipoprotein classes. Although beta-quantification is used largely in clinical and basic research, methods have not been described to allow the analysis of a large number of small-volume specimens with a short turnaround time. We report two variations of the traditional 5-mL method used by the Lipid Research Clinics Program that overcome these shortcomings. METHODS: Two lower-volume modifications of the traditional 5-mL beta-quantification method were developed. The methods used either 1 or 0.23 mL of specimen and required substantially less time for analysis (20 and 6 h, respectively) than the 5-mL method (2.5 days). The goal was to develop ultracentrifugation methods such that the concentration of cholesterol in the bottom fraction, from which LDL-cholesterol concentration is calculated, agreed with the 5-mL method. Fresh serum specimens (n = 45) were analyzed by the three methods to determine comparability of the methods based on the recovery of cholesterol in the bottom fraction after ultracentrifugation. To evaluate intrarun precision, replicate specimens (n = 17) were analyzed in a single run for each method. This experiment also evaluated how quickly the fractions would remix after separation by ultracentrifugation. For the 1-mL method, accuracy of the measurement of LDL- and HDL-cholesterol concentrations and the interrun precision were established by analysis of frozen serum specimens provided by the CDC, which established target values for the pools using reference methods. RESULTS: No clinically significant differences in cholesterol concentrations in the bottom fraction were observed for the 1- and 0.23-mL methods, which had mean biases of 0.8% and 1.5% relative to the 5-mL method, respectively. Intra- and interrun variability was acceptable for each method, e.g., <1.8% for cholesterol in the bottom fraction. Ultracentrifuged specimens were stable for at least 4 h with no evidence of contamination of cholesterol in the bottom fraction. For comparison specimens provided by the CDC, the 1-mL method met the accuracy and precision goals of the National Cholesterol Education Program for the measurement of HDL- and LDL-cholesterol concentrations (goals: total error <13% and <12%, respectively), with total errors of 6.45% and 5.43%, respectively. CONCLUSIONS: Both the 1- and 0.23-mL beta-quantification methods are suitable substitutes for the traditional 5-mL method for use in clinical and basic research for the determination of LDL-cholesterol concentration. Both methods provide much higher throughput and require substantially less specimen volume. The 0.23-mL method can be performed in 1 day, but it is slightly less precise than the 1-mL method. In our laboratory setting, as many as 80 specimens are routinely processed per day using the 1-mL method.

Blood Chemical Analysis↗
PubMed1988

Does dexamethasone suppress the Mazzotti reaction in patients with onchocerciasis?

The Mazzotti reaction is a frequent complication in patients with onchocerciasis being treated with diethylcarbamazine (DEC); and more severe manifestations of this reaction may be unacceptable in many patients. It has recently been demonstrated that prednisone modifies the severity of this reaction and reduces the microfilaricidal activity of DEC. A clinical trial was performed at the National Leprosy Training Center in Wau, Sudan, to evaluate the clinical and histologic effect of the use of corticosteroids in patients receiving DEC. Administration of a low dose of dexamethasone (3 mg/day), begun after onset of the Mazzotti reaction, modifies the progression of the Mazzotti reaction without interfering with the microfilaricidal efficacy of DEC. Pretreatment with low-dose dexamethasone--prior to beginning DEC therapy--prevents the development of the Mazzotti reaction and greatly reduces the microfilaricidal activity. Administration of diphenhydramine, after onset of the Mazzotti reaction, has no effect on the course and intensity of the Mazzotti reaction nor on microfilaricidal activity. We recommend that low-dose corticosteroids be administered in conjunction with DEC--after onset of the Mazzotti reaction--and that they be tapered rapidly.

Adult↗
PubMed1988

Decreased stability of triglycerides and increased free glycerol in serum from heparin-treated patients.

Triglycerides usually are stable in serum. However, for a few patients, we noted marked decreases in measured triglycerides when the same serum specimen was analyzed on successive days. This was found to be ascribable to intravenous administration of heparin. Measured triglyceride in serum of 11 patients being treated with heparin decreased 34% (SD 17%) in samples stored for one day at room temperature. Triglyceride values for sera from control patients remained unchanged. Increases in free glycerol corresponded to the observed decreased in triglycerides. Measurement of free glycerol thus provides a means of recognizing this problem.

Dose-Response Relationship, Drug↗
PubMed1987

Liesegang rings in tissue. How to distinguish Liesegang rings from the giant kidney worm, Dioctophyma renale.

Liesegang rings (LRs) are periodic precipitation zones from supersaturated solutions in colloidal systems. They are formed by a process that involves an interplay of diffusion, nucleation, flocculation or precipitation, and supersaturation. Examples include LRs of calcium carbonate in oölitic limestone (in nature), LRs of silver chromate in gelatin (in vitro), and LRs of glycoprotein in pulmonary corpora amylacea (in vivo). Here we describe LRs in lesions from 29 patients--mostly lesions of the kidney, synovium, conjunctiva, and eyelid. The LRs formed in cysts, or in fibrotic, inflamed, or necrotic tissue. The LRs in this study varied greatly in shape and size, measuring 7-800 microns. Special stains and energy-dispersive radiographic analysis or scanning electron microscopy revealed that some LRs contained calcium, iron (hemosiderin), silicon, and sulfur. Some pathologists have mistaken LRs for eggs, larvae, or adults of the giant kidney worm, Dioctophyma renale. D. renale is a large blood-red nematode that infects a variety of fish-eating mammals, especially mink. Fourteen documented infections of humans have been recorded, usually with adult worms expelled from the urethra. The adult worms are probably the largest helminth to parasitize humans. Eggs of D. renale are constant in size (60-80 microns X 39-47 microns), contain an embryo, and have characteristic sculpturing of the shell. Liesegang rings should not be mistaken for eggs, larvae, or adults of D. renale, or for any other helminth.

Chemical Precipitation↗
PubMed1984

A diagnostic "patch test" for onchocerciasis using topical diethylcarbamazine.

There is great need for a simple, inexpensive, and sensitive diagnostic test for onchocerciasis, especially in endemic areas where trained personnel and laboratory facilities are limited. Diethylcarbamazine (DEC) was applied as a "patch test" to the skin of 45 patients with onchocerciasis in the Southern Sudan. 75 tests were done on these 45 patients, and 69 (92%) were positive. A positive reaction was a papular eruption beneath the patch. Histopathological studies of the skin beneath the patch revealed the microscopic features of a severe Mazzotti reaction, including degenerating microfilariae in the upper dermis and within epidermal eosinophilic abscesses.

Administration, Topical↗
PubMed1984

Mycobacterium ulcerans in Liberia: a clinicopathologic study of 6 patients with Buruli ulcer.

Two patients with Buruli ulcer (infection by Mycobacterium ulcerans) in the Foya region of Liberia have recently been reported. We describe three more patients which together with the two original patients establish the Mayor River basin as an endemic area of Buruli ulcer. We also describe a patient from the St. Paul River basin. This disease, unrecognized in Liberia before 1978, now seems to be widespread in Liberia and has been reported in neighboring Sierra Leone and observed in Ivory Coast as well. The possibility of Buruli ulcer appearing in other regions of West Africa should be anticipated. Diagnosis involves finding acid-fast bacilli in smears of the exudate from typical lesions or by finding in biopsy specimens the characteristic zone of coagulation necrosis containing acid-fast bacilli. The bacillus, Mycobacterium ulcerans, stains readily with the Ziehl-Neelsen (ZN) and Fite-Faraco (FF) procedures. Treatment is excision when the lesion is small and by debridement and grafting, combined with heat and chemotherapeutic agents when the lesion is large.

Adult↗
PubMed1984

Deposition of eosinophil granule major basic protein onto microfilariae of Onchocerca volvulus in the skin of patients treated with diethylcarbamazine.

We investigated the association between eosinophil degranulation, as evidenced by the deposition of granule major basic protein (MBP), and the killing of microfilariae of Onchocerca volvulus in vivo following treatment with diethylcarbamazine (DEC). Utilizing an immunofluorescence procedure for the cellular and extracellular localization of eosinophil MBP in formalin-fixed, paraffin-embedded tissues, we studied skin biopsies from onchocerciasis patients before and during treatment with topically or orally administered DEC. Before DEC, there was little or no inflammatory response in either dermis or epidermis and microfilariae were essentially intact. Immunofluorescent staining for MBP revealed some filamentous fluorescence associated with dermal collagen fibers, very few eosinophils, and no fluorescence in association with intact microfilariae. In contrast, during treatment with DEC, immunofluorescent staining for MBP revealed extensive eosinophil infiltrates in both dermis and epidermis with numerous intraepidermal eosinophil abscesses containing degenerating microfilariae. An intense extracellular immunofluorescence for MBP surrounded degenerating microfilariae in the dermis and epidermis in both the presence and absence of eosinophil infiltrates as early as 4.5 hours after starting therapy. Many intact nondegenerating microfilariae were also present, but they did not show immunofluorescent staining for MBP nor a surrounding inflammatory infiltrate. The results show that immediately following administration of DEC, eosinophils localize and degranulate around microfilariae in the skin and release granule MBP onto or in close proximity to the parasite's surface. Because of the striking association between eosinophil localization, degranulation, and deposition of MBP onto microfilarial surfaces, and the degeneration of microfilariae in the skin, these observations support the hypothesis that the eosinophil, through helminthotoxic granule proteins such as MBP, damages the microfilariae of O. volvulus.

Adult↗
PubMed1984

Evaluation of heat-sealed ultracentrifuge tubes in the isolation of plasma lipoproteins.

An initial step in the measurement of the concentration of lipids in plasma lipoproteins by the Lipid Research Centers' protocol is the separation of very low density lipoproteins from low density and high density lipoproteins by ultracentrifugation. We compared the performance of heat-sealed centrifuge tubes to the conventionally capped centrifuge tubes required by the protocol in terms of the separation and recovery of cholesterol and triglyceride. No significant differences in either parameter were found, however the heat-sealed tube required much less time to prepare and eliminated the need for periodic replacement of relatively expensive cap parts. We recommend the use of heat-sealed tubes for the routine separation of plasma lipoproteins.

Hot Temperature↗
PubMed1983

Sowda--onchocerciasis in north Yemen: a clinicopathologic study of 18 patients.

Sowda is an unusual form of onchocerciasis in Yemenites that differs from African onchocerciasis. Clinical and pathological studies were performed on 18 patients in Yemen Arab Republic (North Yemen). Biopsies of skin and lymph nodes were taken, and then processed at the Armed Forces Institute of Pathology, Washington, D.C. The most striking clinical features were swollen, darkened, pruritic, papular skin changes that were usually limited to one leg, more rarely to one arm, and large soft regional lymph nodes. Dermal changes were deeper and more diffuse than in African onchocerciasis, with many large fibroblasts and plasma cells. Microfilariae of Onchocerca volvulus were much rarer in skin from Yemenites with sowda. When patients were treated with diethylcarbamazine, the dermatitis became suddenly worse as the microfilariae degenerated and provoked acute inflammation. The dermatitis decreased after several days of treatment. Enlarged lymph nodes from sowda have shown follicular hyperplasia, in contrast to follicular atrophy and perivascular fibrosis that are characteristic of lymph nodes from cases of African onchocerciasis. Cell-mediated and humoral immunity may be more active in sowda than in African onchocerciasis.

Adolescent↗
PubMed1983

Sowda-type onchocerciasis in Guatemala.

The usual pattern of onchocercal dermatitis in Africans and Guatemalans is a generalized and symmetrical dermatitis located on legs, arms and trunk. These patients appear to be anergic, with depressed immune responses and numerous microfilariae in the skin. In contrast, "sowda" is an unusual type of onchocercal dermatitis found in Yemenites and in a minority of African patients. Here the dermatitis is localized and asymmetrical - typically confined to one limb or one region of the body. Patients with sowda appear to be hypergic, with active humoral and cellular immune responses; microfilariae are rare or absent. This study describes two Guatemalan patients with sowda-type dermatitis. The diagnosis in these two patients is based on the asymmetrical papular pruritic dermatitis, rare or absent microfilariae, a positive Mazzotti reaction, and histopathologic changes characteristic of the sowda-type onchocercal dermatitis.

Adult↗
PubMed1982

Noninvasive evaluation of bile leakage.

Three patients had internal biliary leakage demonstrated by hepatobiliary scintigraphy. In two, it was secondary to trauma and in one patient, it was related to spontaneous bile leakage of unknown causation. Although ultrasound of the abdomen is a highly accurate modality for the detection and anatomic localization of cystic collections, the ultrasonic features of a biloma are identical to those of other cystic lesions in the abdomen. In many patients, hepatobiliary and gallium scintigraphy ca help in the differentiation between biloma and abscesses. These patients stressed the need for hepatobiliary imaging, multiple projections and delayed views for the detection and localization of abnormal collections of bile. The biliary excretion of gallium should be taken into consideration when interpreting these scans.

Adult↗
PubMed1978

Onchocercal lymphadenitis: Clinicopathologic study of 34 patients.

Clinicopathological studies on lymph nodes of 32 Africans with onchocerciasis--some complicated by hanging groin and elephantiasis of the genitalia--revealed atrophic lymphoid tissue, lymphoedema, chronic inflammation and fibrosis. We identified microfilariae of Onchocerca volvulus in nodes of 24 of 32 Africans (75%). There microfilariae were most numerous in the capsule and in the fibrous tissue of the medulla, but smaller numbers were also found within lymphoid tissue, in dilated lymphatics and in blood vessels. We believe that in Africians, antigens released from microfilariae of O. volvulus lead to the deposition of immune complex in tissues, which in turn causes inflammation and fibrosis and eventually obstructive lymphadenitis. This causes hanging groin and, possibly, also elephantiasis. A distinctive pattern of perivascular fibrosis contains "fibrinoid material" that we interpret as immune complexes involving microfilarial antigens. In contrast, nodes from two Yemenites with severe onchocercal dermatitis of the lower limbs (sowda) had hyperplastic follicles, minimal fibrosis and no microfilariae.

Adolescent↗