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P Dukes

Publications and source records attributed to P Dukes.

At least 19 recordsLinked to original sources
PubMed2001

Sleep laboratory testing. The important facts.

To test a diagnostic tool's cost effectiveness, timeliness, and accuracy, one must focus on basic information. Merely examining the end results without regard for operating characteristics creates problems for the practitioner and patient alike. If the tool is capable of diagnosing only some of the patients studied, with the disturbing possibility that patients whose diagnoses are missed will not receive care, the practitioner should look elsewhere for a diagnostic tool that performs with greater accuracy despite the additional cost. As the demand for sleep diagnostic testing increases, accuracy and efficiency of diagnostic modalities becomes increasingly important. An alternative tool to standard attended polysomnography would be desirable but is probably unlikely. The results of missing a diagnosis or of mismanaging a patient with SDB can be serious indeed. The practitioner should thoroughly assess the patient and order the appropriate diagnostic study that will provide information that gives the patient the best opportunity for a desirable outcome. Sleepy patients are counting on practitioners everywhere to help them by using all the tools available. Countless mothers driving with children on the roads with these sleepy individuals are counting on the practitioner as well. Therefore, it behooves everyone who manages or wants to manage patients with SDB to offer uncompromising care to the patient with minimal regard to the health insurance industry's cost-cutting strategies. Dentists are and should be an integral part of the team caring for a patient with SDB. As part of the team, the dentist must know what tests to order and why to order them. As a referrer, whether to an otolaryngologist, allergist, pulmonologist, neurologist, or sleep center, the dentist is critical in the early detection of a prevalent nocturnal breathing problem. Many patients will present with early warning signs before related comorbidities develop that are potentially fatal to the patient and to health care economics. As part of the treatment and management team of the patient with SDB, dentists have the opportunity to intervene on their behalf before the disorder worsens. The proper diagnostic tools, when understood and used, will facilitate patient care, minimize risk, and decrease the long-term costs associated with mismanagement or improper diagnosis.

Cost-Benefit Analysis↗
PubMed1993

Identification of Trypanosoma brucei gambiense by PCR amplification of variant surface glycoprotein genes.

We have developed a sensitive and specific method to identify Trypanosoma brucei gambiense using the polymerase chain reaction (PCR) to amplify the gene encoding variant surface glycoprotein (VSG) Antat 11.17. The test was capable of distinguishing T. b. gambiense from T. b. brucei in most foci of gambian sleeping sickness and gave positive results with previously well-characterised Type I T. b. gambiense stocks from Ivory Coast, Nigeria, Cameroon, Congo, Zaire and Sudan. The test gave negative results with T. b. rhodesiense from Zambia, Kenya and Uganda, virulent or Type II T. b. gambiense from Ivory Coast and T. b. brucei stocks from East and West Africa. The test was modified for colorimetric detection in dot blot format by using nested biotinylated primers in a two-step reaction. Comparison of DNA sequences of VSG genes from T. b. gambiense and other T. brucei ssp. stocks showed a high level of homology, suggesting recent gene flow.

Animals↗
PubMed1992

Absence of the LiTat 1.3 (CATT antigen) gene in Trypanosoma brucei gambiense stocks from Cameroon.

Antibodies to the variable antigen type (VAT) designated LiTat 1.3 are common in sera from parasitologically confirmed patients with gambian sleeping sickness. For this reason, LiTat 1.3 has been considered a suitable antigen for detecting Trypanosoma brucei gambiense in the Card Agglutination Test for Trypanosomiasis (CATT; Testryp-CATT, Smith Kline-RIT). However, surveys in the T.b. gambiense endemic focus of Fontem in Cameroon have suggested that expression of LiTat 1.3 might be rare or absent. We show here that the gene for LiTat 1.3 was indeed absent from some T.b. gambiense stocks isolated from this focus, and a LiTat 1.3-like gene was present in others. The divergent gene differed from the cloned version of LiTat 1.3. In addition, antibodies to LiTat 1.3 could not be detected in rabbits infected with either of the two kinds of T.b. gambiense from the Fontem area. We suggest that the absence of LiTat 1.3 expression in this focus may have important implications for the epidemiology and control of sleeping sickness, especially if heavy reliance is placed on the CATT.

Agglutination Tests↗
PubMed1991

Elusive trypanosomes.

Professor Kershaw's encouragement of the development of anion-exchange separation of African trypanosomes from blood led to two decades of activity when, for the first time, considerable progress was made in the intrinsic characterization of these parasites. Such characterization depended on establishing high infections in laboratory rodents. However, the collection of samples from the field was restricted by the failure of certain trypanosomes either to infect, or to multiply adequately in, rodents. More recently, in vitro culture has come to play an increasingly important role in producing material. By obtaining procyclic forms directly from wild tsetse flies, or by transforming low numbers of bloodstream forms in field samples to the procyclic phase in experimental tsetse, trypanosomes of poor or nil infectivity to rodents were readily cultured in the large amounts required for biochemical characterization. A number of specimens of a new kind of Nannomonas, of Trypanosoma simiae, of T. grayi, and of an antigenically distinct T. brucei gambiense were found. Evidence is presented that many other kinds of trypanosome may be eluding isolation by their inability to infect rodents.

Animals↗
PubMed1989

Use of DNA probes to identify Trypanosoma congolense and T. simiae in tsetse flies from The Gambia.

Species- and strain-specific DNA probes were used to identify patent midgut infections in Glossina morsitans submorsitans and G. palpalis gambiensis captured at four sites in The Gambia. 52% of mature Nannomonas infections and 12% of immature infections were identified. Trypanosoma (Nannomonas) simiae accounted for the majority of identified infections in G.m. submorsitans, indicating the importance of distinguishing this species from the closely related T.(N) congolense when assessing the trypanosomiasis challenge to cattle. Both the savannah and riverine-forest groups of T. congolense were present, although the riverine-forest form was found only in G.p. gambiensis at Pirang, an isolated area of forest. Two-thirds of the samples remain unidentified by probes specific for: Trypanozoon; T. congolense savannah, riverine-forest and Kenya coast forms; T. simiae; and T. vivax, probably owing in part to low numbers of trypanosomes. However, the failure to identify several heavy Nannomonas infections, strongly suggests the presence of a further, as yet unknown, kind of Nannomonas.

Animals↗
PubMed1989

Isolation and cultivation in vitro to the infective, metacyclic stage of Trypanosoma (Nannomonas) simiae from Glossina morsitans submorsitans.

Two separate trypanosome isolations were made from a single Nannomonas-infected Glossina morsitans submorsitans from The Gambia. Inoculation of a piglet with the infected hypopharynx produced an infection with Trypanosoma simiae. DNA was isolated from the bloodstream forms to prepare a probe specific for this species. Trypanosomes isolated from the fly midgut were frozen in liquid nitrogen and then cultivated in vitro. Amplification of this population and elimination of a yeast contaminant were achieved by two passages through laboratory G. m. morsitans. Further cultivation in vitro resulted in the production of epimastigotes and, later, metacyclic forms. Two pigs inoculated with cultivated metacyclic forms developed infections with atypical, relapsing parasitaemias and extended survival time. Neither the metacyclic forms, nor bloodstream forms derived from them, infected calves. The identity of various stages of the in vitro cultivated, procyclic-derived stock was confirmed morphologically and with the T. simiae-specific DNA probe.

Animals↗
PubMed1989

Evidence for diploidy in metacyclic forms of African trypanosomes.

The DNA contents of bloodstream form trypanosomes (life cycle stages circulating in the blood of the vertebrate host) of four African Trypanosoma species and of metacyclic forms (the life cycle stage that is injected into the vertebrate by the tsetse fly during its bite) of the same four species were measured by cytofluorometry of individual cells or nuclei. The results showed unambiguously that the metacyclic forms cannot be considered to be products of meiosis containing only half of the DNA of bloodstream forms, in contrast to what was previously reported for Trypanosoma brucei [Zampetti-Bosseler, F., Schweizer, J., Pays, E., Jenni, L. & Steinert, M. (1986) Proc. Natl. Acad. Sci. USA 83, 6063-6064] during an attempt to localize the gametes in the life cycle after experimental evidence of sexual gene exchange in this parasite was reported.

Animals↗
PubMed1988

Species-specific DNA probes for the identification of African trypanosomes in tsetse flies.

We have obtained 5 specific DNA probes for African trypanosomes of the subgenera Trypanozoon and Nannomonas. Each probe consists of one repeat unit of the major repetitive DNA (satellite DNA) of each species or intra-specific group. One probe hybridized with all members of subgenus Trypanozoon (except T. equiperdum which was not tested). In subgenus Nannomonas, one probe recognized T. simiae, but 3 probes were needed to identify all stocks of T. congolense available. Each of the 3 latter probes recognized trypanosomes from one of the 3 major groups of T. congolense previously defined by isoenzyme characterization, i.e. savannah, forest and Kenya coast types. As few as 100 trypanosomes could be unequivocally identified by dot blot hybridization and individual trypanosomes could be identified by in situ hybridization. We show how this simple methodology can be used in the field for the identification of immature and mature trypanosome infections in tsetse.

Animals↗
PubMed1986

Extrachromosomal inheritance of susceptibility to trypanosome infection in tsetse flies. II. Susceptibility of selected lines of Glossina morsitans morsitans to different stocks and species of trypanosome.

Two lines of Glossina m. morsitans, selected for susceptibility and refractoriness to infection with a single stock of Trypanosoma congolense, have now been shown to be susceptible or refractory to different stocks of T. congolense and, also, to different stocks of T. b. brucei and T. b. gambiense. The mean midgut infection rates of the susceptible line obtained in different experiments with T. congolense, T. b. brucei and T. b. gambiense were, respectively, 66%, 56% and 55%; the corresponding mature (hypopharynx or salivary gland) infection rates were 37%, 23% and 0%. The highest mature infection rates obtained in individual experiments with susceptible flies were 65% (T. congolense) and 40% (T. b. brucei). Mean T. congolense and T. b. brucei midgut infection rates obtained with the refractory line were 29% and 33% respectively, the mature infection rates being 12% and 7%, all significantly lower than the corresponding rates in the susceptible line. Development of midgut infections in susceptible flies appears to take place irrespective of trypanosome stock or form. There is some evidence to suggest that higher infection rates can be obtained with flies infected and maintained on mammals rather than on in vitro feeding systems. Susceptible flies matured a significantly greater proportion of their midgut T. congolense and T. b. brucei infections than did the refractory line, which suggests that maturation of infections is influenced by the susceptibility status of the fly. However, the apparent inability of these flies to develop mature infections of a major T. b. gambiense genetic grouping suggests that maturation of infections established in the midgut is a phenomenon primarily associated with trypanosome genotype.

Animals↗
PubMed1985

Extrachromosomal inheritance of susceptibility to trypanosome infection in tsetse flies. I. Selection of susceptible and refractory lines of Glossina morsitans morsitans.

Differences in susceptibility to infection with Trypanosoma congolense between F1 families of Glossina morsitans morsitans indicated that susceptibility is maternally inherited in this species of tsetse fly. Twelve F1 families, six selected for susceptibility and six selected for refractoriness to infection, have been bred for up to 13 generations. The reciprocal differences demonstrated in the F1 generation persisted in these selected families over many generations, indicating that susceptibility/refractoriness to T. congolense infection is extrachromosomally inherited in G. m. morsitans. Repeated 'backcrossing' to males of the opposite strain showed that infection rates within families were independent of the contribution of the male parent. Susceptible families had a mean midgut infection rate of 76.9% and a mature (hypopharyngeal) infection rate of 47.9%. In the refractory families 88.9% of the flies failed to develop an infection, 11.1% had midgut infections and only 6.3% developed mature infections. Levels of midgut infection remained remarkably constant within families over generations, whether refractory or susceptible, while maturation rates varied between generations and between sexes. Males matured a significantly greater proportion of midgut infections than females in the susceptible families. It is suggested that the inheritance of susceptibility/refractoriness relates primarily to the establishment of midgut infections in G. m. morsitans, and that maturation of midgut infections is dependent upon environmental factors such as diet, and differences between sexes probably reflecting differences in rates of bloodmeal digestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Arsenic and old taxa: subspeciation and drug sensitivity in Trypanosoma brucei.

Resistance to the trypanocidal drugs atoxyl and tryparsamide was traditionally considered to be a diagnostic feature of rhodesian sleeping sickness and, consequently, of Trypanosoma rhodesiense. In examining the tryparsamide sensitivity of 13 isoenzymically defined stocks of the subgenus Trypanozoon, typical West African stocks showed no greater drug sensitivity than did those of East and Central Africa. The greatest resistance to tryparsamide was shown by two stocks isolated in the Ivory Coast. There was no evidence of strain differences in drug sensitivity to melarsoprol (Mel B) among 26 tested populations; none the less, differential melarsoprol sensitivity was evident in clones from a single mixed population. By contrast, isoenzymically defined West African stocks appeared to be less sensitive to pentamidine and diminazene aceturate (Berenil) than were typical East African stocks. Drug sensitivity was measured in a novel in vivo test designed to minimize the influence of host-parasite interactions, in particular trypanosome penetration of drug-inaccessible sites and host-antibody induced remission of parasitaemia. Drug effect was expressed as the DS0.1, the dose required to suppress parasitaemia to 0.1% of that in untreated control mice.

Animals↗
PubMed1984

A "healthy carrier" of Trypanosoma rhodesiense: a case report.

A case of a 56-year-old, healthy carrier of Trypanosoma rhodesiense infection was identified in a total village survey for trypanosomiasis. All initial laboratory tests were negative for trypanosomes but two blood-inoculated mice were both positive 11 days after inoculation. The epidemiological significance of human healthy carriers of trypanosomes is discussed.

Carrier State↗
PubMed1984

Maintenance of Glossina morsitans morsitans on antiserum to procyclic trypanosomes reduces infection rates with homologous and heterologous Trypanosoma congolense stocks.

Three experimental groups of male Glossina morsitans morsitans were infected at their first feed with procyclic forms of different stocks of Trypanosoma congolense and subsequently maintained on a diet containing rabbit antiserum to one of these stocks. Control flies were similarly infected but were then maintained on normal rabbit serum. Dissection of the flies 19-21 days post infection showed a reduction in both immature and mature infection rates in all groups fed on antiserum by comparison with control flies. These results suggest that vaccination with a single procyclic T. congolense strain could reduce transmission of both homologous and heterologous T. congolense strains which might, in certain epidemiological circumstances, provide an alternative or additional control method for African trypanosomiases.

Animals↗
PubMed1984

A field comparison of seven diagnostic techniques for human trypanosomiasis in the Luangwa Valley, Zambia.

One serological and six parasitological techniques for diagnosing human trypanosomiasis were compared with regard to sensitivity, specificity, positive and negative predictive values, and practicality in field application in the Luangwa Valley of Zambia. Seven (0.64%) trypanosomiasis cases were diagnosed parasitologically in a survey of 1093 people from 19 villages. The indirect fluorescent antibody test (IFAT) was more sensitive but less specific than the parasitological techniques, detecting 71% of the confirmed cases in the first round of testing. Rat inoculation, the Giemsa stained thick film and miniature anion-exchange/centrifugation (mAEC) were all more sensitive than wet blood film examination, microhaematocrit centrifugation and wet film examination of the buffy coat after microhaematocrit centrifugation. The comparison indicated that the most effective, practical combination of techniques for survey in the Luangwa Valley was IFAT screening followed by examination of seropositive patients by rat inoculation and the mAEC (or stained thick film) in parallel format. Calculation of positive and negative predictive values showed that trypanosomiasis point prevalence measured in this way would still be underestimated by approximately 60%, indicating the need to improve IFAT specificity and parasitological sensitivity. Although only one of the seven patients diagnosed in the survey presented with signs and symptoms indicating possible trypanosomiasis, no evidence of a population of "healthy carriers" was found.

Adolescent↗