Biomedical subjects
R Clark
Publications and source records attributed to R Clark.
Studies on two patients with concomitant pernicious anemia and immunoglobulin deficiency.
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Blunt head injuries incurred by Marine recruits in hand-to-hand combat (judo training).
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Post-meningitis hydrocephalus treated with ventriculo-atrial shunts.
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The pathologigal physiology of helminth infestations. II. Oesophagostomum columbianum.
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The pathological physiology of helminth infestations. I. Ostertagia circumcincta.
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Some time-correlated reinforcement schedules and their effects on behavior.
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Absence of embryotoxic effects in rats with three quaternary ammonium compounds (cationic surfactants).
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The use of high-frequency oscillatory ventilation (HFOV) and extracorporeal membrane oxygenation (ECMO) in the management of the term/near term infant with respiratory failure.
The use of high-frequency oscillatory ventilation (HFOV) was evaluated as a rescue intervention in 122 consecutive infants meeting criteria for extracorporeal membrane oxygenation (ECMO). Fifty-three percent responded to HFOV and never required ECMO, 3/65 died. Infants who ultimately required ECMO had lower aortic and pulmonary peak flow velocities, and lower pulmonary acceleration, circumferential fiber shortening and shortening fraction than those who were successfully managed with HFOV. The use of HFOV with an appropriate strategy decreased the need for ECMO in this patient population.
Digital mammography: M-channel quadrature mirror filters (QMFs) for microcalcification extraction.
Multiresolution methods are reported for feature extraction in breast cancer screening using digital mammography. The initial application is directed at the detection of microcalcification clusters (MCCs). Quadrature mirror filter (QMF) banks, using both two and three channel are proposed for the first time for both multiresolution decomposition and reconstruction. These filters are specifically tailored for automatic extraction of MCCs. The QMF multiresolution methods are compared to two channel tree structured wavelet transforms (TSWTs) methods previously reported. The QMF filters are preceded by an advanced tree structured nonlinear filter for noise suppression, prior to feature extraction, in order to minimize the false positive (FP) detection rate in digital mammography. The relative performance of these methods were evaluated using both simulated images and fifteen representative digitized mammograms containing biopsy proven microcalcification clusters. Similar high sensitivity (true positive (TP) detection rate (100%) and high specificity (0.6 average false positive (FP) MCC's/image) were observed, substantially better than more traditional approaches using single scale filters. The three channel QMF method, however, demonstrated better detail preservation of MCC's extracted compared to the two channel method. Detail preservation is important for the characterization of MCC's or individual microcalcifications in cancer screening.
The effect of a crude marihuana extract on embryonic and foetal development of the rabbit.
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Harmonisation of rat fetal skeletal terminology and classification. Report of the Third Workshop on the Terminology in Developmental Toxicology. Berlin, 14-16 September 2000.
The initial efforts of the Federal Institute for Health Protection of Consumers and Veterinary Medicine (BgVV) and the Free University of Berlin to standardise terminology in the field of developmental toxicology began in 1995. Procedures were undertaken to harmonise the terminology used by the International Federation of Teratology Societies (IFTS) and the International Programme on Chemical Safety (IPCS). This article reflects these activities and is a report on the Third Workshop on the Terminology in Developmental Toxicology held in September 2000. This Workshop served as a forum to discuss the results of a survey on the classification of skeletal anomalies that had been previously sent to scientists active in the field. Although high agreement was reached among the evaluators for several terms, the use of a number of terms was rather variable. Therefore, the discussions at the workshop among the experts from research institutions, regulatory agencies, and industry were mainly focussed on those terms for which there was disagreement and/or uncertainties and the possible reasons. Pictures provided by the participants for the illustration of "grey zone" anomalies constituted the basis for detailed discussions. In many of the cases with lower agreement, decisions were facilitated by the provision of the corresponding picture. The main reasons for lower agreement were imprecise terms, insufficient knowledge on postnatal consequences, theoretical terms that are unlikely to occur in isolation, and the possibility of observing a range of severity that might be decisive for the classification of either a malformation or variation. The attendees concluded that "grey-zone" anomalies will never disappear completely and that for the assessment, the grade of severity and/or the frequency of the observation can be decisive for the terminology chosen. A Joint IPCS/IFTS Project was proposed to further consensus of terminology and classification and to link these anomalies to pictures at different skeletal sites. In order to support the harmonisation of regulatory decisions, it was proposed to establish a "Clearinghouse" System under the umbrella of the IPCS. The Clearinghouse could be contacted either by the regulatory authorities or by any company to clarify their queries, particularly with regard to registration or authorisation processes. Finally, it was recommended to also carry out a similar survey on "soft tissue anomalies" and "external findings." The results of this survey will be discussed at a Joint IPCS/IFTS Workshop in Berlin in 2002.
Classification terms in developmental toxicology: need for harmonisation. Report of the Second Workshop on the Terminology in Developmental Toxicology Berlin, 27-28 August 1998.
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Transient reversion of ras oncogene-induced cell transformation by antibodies specific for amino acid 12 of ras protein.
The proteins encoded by the ras oncogene are thought to trigger expression of the transformed phenotype in some types of cancer cells. In human cells, the ras protein family consists of several members including normal (proto-oncogene) and mutant (oncogene) forms. In general, the proto-oncogene forms are thought to be involved in the normal growth control of cells, while the mutant forms (which apparently result from somatic mutation of the normal ras genes) appear to be responsible, in part, for the loss of normal growth control. On microinjection into living normal cells, the purified ras oncogene protein (p21) induces a characteristic loss of growth control in cells within several hours. The mutant forms of the different ras proteins typically contain a single amino-acid change, usually at position 12 or less frequently at position 61. Here we report that microinjection of antibodies specific for amino acid 12 of the oncogenic v-Ki-ras protein into cells transformed by this protein causes a transient reversion of the cells to a normal phenotype. The fact that this antibody inhibits binding of GTP to the v-Ki-ras protein supports the notion that GTP binding is essential to the transforming function of this oncogene product.
Streptococcus pneumoniae endocarditis presenting as an epidural abscess.
Streptococcus pneumoniae is an important pathogen in many serious infections, such as pneumonia, sinusitis, and meningitis. It uncommonly causes infective endocarditis and only rarely produces spinal epidural abscesses. This report describes a patient who had pneumococcal infection presenting as an acute epidural abscess and who was subsequently found to have endocarditis. S. pneumoniae was cultured from both blood and abscess material. A high level of clinical suspicion of endocarditis is important in all cases of bacteremic pneumococcal illness; patients with such an illness and back pain may harbor potentially catastrophic epidural abscesses.
Psychiatric diagnosis and uncooperative behavior in nursing homes.
The prevalence of psychiatric disorders and behavioral disturbances in nursing homes is high, but the relationship between the two is unknown. We studied 454 new admissions who were diagnosed by research psychiatrists using DSM-III-R criteria and compared patients who nursing staff designated as cooperative or uncooperative by psychiatric diagnosis and use of restraints and neuroleptics. Uncooperative patients (n = 79; 17.4%) had a variety of psychiatric disorders (total, 87.3%) but particularly had dementia syndromes complicated by delusions, depression, or delirium (44.3%). Uncooperative patients were more frequently restrained and prescribed neuroleptics. Determining the origins of behavior disorders in patients with psychiatric disorders in nursing homes may reduce behavior disturbances.
The development of suture anchors for use in soft tissue fixation to bone.
Soft tissue fixation to bone is a basic technique of orthopaedic surgery for which a multitude of devices have been developed. A new class of orthopaedic devices termed "suture anchors" has been developed to secure soft tissues to bone using suture material. The suture anchor is designed to allow quick and secure fixation without the need for extensive exposure. This device was tested using in vitro and in vivo models and found to be comparable with standard transosseous and two-pronged stable techniques. This device should prove useful in allowing the versatility of suture fixation of soft tissues to bone without the technical requirements of constructing transosseous suture tunnels.
Modernization and status change among aged men and women.
This study investigates the differences between the relationship between elderly occupational status and modernization for men and women. Consonant with previous findings, it finds that economic development is associated with relative losses of elderly men in professional and technical occupations. Augmenting those findings, however, it finds an even stronger association between development and such losses for women. In accounting for the differences, several explanations are advanced and tested, using data from fifty-one nations.