Trichodinids (Ciliophora: Trichodinidae) on Rocky-tidal Fishes from the Baja California Peninsula, Mexico.

Information regarding trichodinid ectoparasites on marine fishes of North America is relatively scarce. In this study, 5 ciliate species from the family Trichodinidae were found associated with 8 fish hosts from the rocky intertidal zone of the western coast of the Baja California Peninsula (BCP), Mexico. All of the host-parasite relationships recorded here are new. Furthermore, 3 of the trichodinid species found are recorded for the first time for Mexico. Trichodinids taxa do not show a noticeable distributional gradient along the BCP, which suggests a wide-continuous distribution of the species throughout the study area.

Evaluation of a new type of direct digital radiography machine.

OBJECTIVE: To evaluate a recently developed low-dose, large-field, direct digital X-ray scanning system for medical use. METHOD: Radiation dose, image quality, diagnostic capability and clinical utility of the unit were compared with those of conventional radiography. RESULTS: Radiation doses ranged from 3% to 5% of conventional radiographic values, and a mean of 1 line-pair per millimetre could be detected. Ease of use, anatomical coverage and tolerance to patient motion were advantages. However, image quality was inferior to that of conventional radiographs, with limited fine detail visibility and penetration. Only 67 of 156 (42.9%) pathological features seen on conventional radiographs were detected, including 13 of 41 fractures (31.7%) and 11 of 18 pneumothoraces (61.1%). CONCLUSION: Although image quality and diagnostic performance were not ideal, potential roles in triage, foreign body detection and possibly screening were promising. Radiographic factors may have affected sensitivity. This machine demonstrated useful attributes that may, with improvement, be beneficial in the imaging of trauma and other patients.

A review of the fractal image coding literature.

Fractal image compression is a technique based on the representation of an image by a contractive transform, on the space of images, for which the fixed point is close to the original image. This broad principle encompasses a very wide variety of coding schemes, many of which have been explored in the rapidly growing body of published research. While certain theoretical aspects of this representation are well established, relatively little attention has been given to the construction of a coherent underlying image model that would justify its use. Most purely fractal-based schemes are not competitive with the current state of the art, but hybrid schemes incorporating fractal compression and alternative techniques have achieved considerably greater success. This review represents a survey of the most significant advances, both practical and theoretical, since the publication of Jacquin's (1990) original fractal coding scheme.

Analysis of partial gag and env gene sequences of HIV type 1 strains from southern Africa.

PIP: HIV-1 is spreading at an exponential rate in southern Africa, with a current doubling time of approximately one year. An estimated 2 million of South Africa's 36 million population are already infected with HIV. Information on the extent of variability of HIV-1 sequences in the region is important for the development of vaccines, the evaluation of new therapies, and for structure/function studies of the viral genome and proteins. The authors isolated and partially sequenced local strains of the virus. The first strain sequenced was determined to be a new subtype of HIV-1, designated subtype C(2). HIV-1 subtypes B and D are also circulating within southern Africa. The derived phylogenetic trees for the various strains are presented. It is possible that southern African HIV-1 strains have evolved from Central African ones during their spread southward over time and geographic distance. The data on HIV-1 env and gag gene variability presented in this paper have implications for the design of vaccines intended for use in southern Africa and India. The results also establish new limits of variability for the virus, by extending the phylogenetic tree along a new branch.^ieng

Evaluation of commercially available assays for antibodies to HIV-1 in serum obtained from South African patients infected with HIV-1 subtypes B, C, and D.

Between 1984 and 1990, virus was routinely isolated and serum collected from patients diagnosed at hospitals in the Western Cape as suffering from AIDS or AIDS-related conditions (ARC). From these, 17 virus strains were selected at random for sequencing and molecular characterisation of the env gene. The strains were previously characterised as belonging to HIV-1 subtypes B, C and D. The purpose of the present study was to evaluate retrospectively the serological diagnosis of HIV-1 in these 17 South African patients. Thirteen anti-HIV screening assays, including 7 rapid/simple test devices (RTDs), 4 enzyme-linked immunosorbent assays (EIAs) and 2 Western immunoblot assays were evaluated. Using commercial EIAs, 16 serum samples were HIV antibody-positive and these results were confirmed by Western immunoblot analysis. Serum from one terminal AIDS patient was found negative with all the serological tests. Some RTDs gave false negative antibody reactions on specimens from patients infected with subtype D strains. To investigate the false negative antibody reactions, the polymerase chain reaction (PCR) was used to amplify, clone and sequence proviral DNA from the immunodominant gp41 region from 7 of the HIV-1 strains. Two patients, both subtype D strains (D214 and D482) with false negative results in the RTDs, showed a significant amino acid substitution, i.e., substitution of a histidine residue for leucine at env position 607. It was concluded that although there were false negative RTD reactions on patients with HIV-1 subtype D strains, the commercial EIAs tested are sensitive and are able to detect patients infected with HIV-1 subtypes B, C and D that are present in South Africa.