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S Macdonald

Publications and source records attributed to S Macdonald.

65 records · Page 4Linked to original sources
PubMed1975

Sexual reproduction in the monogenean Diclidophora merlangi: tissue penetration by sperms.

Copulation between pairs of adult Diclidophora merlangi detached from the host was frequently observed. The spined penis of one animal always attaches to a second worm at a latero-ventral position posterior to the genital openings. There is no vagina. The sperms travel between the cells of the recipient to reach the seminal receptacle. The ultrastructure of the sperm is described. Positions of adult D. merlangi on the gills of the host would facilitate pairing for sperm transfer.

Animals↗
PubMedDate not supplied

Novel word acquisition in children with Down syndrome: does modality make a difference?

Signing is a commonly used intervention technique for children with cognitive impairments who have expressive language delays. Novel word learning in three conditions (signed only, spoken only, signed and spoken combined) was compared for children with Down syndrome (2;1 to 5;2) and mental-age matched control children (1;4 to 2;6). Spontaneous imitations and responses to production and comprehension probes were examined after 5, 10, and 15 word exposures. No group differences in frequency of imitations or productions were obtained. The frequency of imitations was highest in the combined condition. Probed productions were infrequent, although novel words were produced most often in spoken and combined conditions. For both imitated and probed productions in the combined condition, the spoken portion was almost exclusively produced. Across conditions, children with Down syndrome comprehended fewer words than did control children. The evidence for and explanations of the facilitative effect of signs and the advantage of dual-method presentation are discussed.

Child↗
PubMedDate not supplied

Aggression and the termination of "rituals": a new variant of the escape function for challenging behavior?

Aggression and stereotyped behaviors are not uncommon among people with intellectual disabilities and they are often treated separately as operant behaviors. In this single case study, it is argued that the function of a young woman's aggressive behavior appeared to be that of avoiding or escaping the termination of a chain of complex stereotyped behavior (or "ritual"). She became aggressive only when this chain of stereotyped behavior was terminated and the aggression appeared to extinguish when it no longer led to escape from the termination of the "ritual". It is suggested that this is an example of a complex interaction between two behaviors and that it illustrates the need for very careful analysis of the functions of challenging behavior. Furthermore, it is proposed that the lengthening list of variables already documented as determinants of challenging behavior (provision of attention (verbal and physical), mechanical restraint, sensory or tangible events, escape from demands or from social attention, denials, escape from intrusive medical procedures, escape from task difficulty) be lengthened to include the possibility of escape from (or avoidance of) the interruption of a chain of complex stereotyped behavior or "ritual".

Adult↗
PubMedDate not supplied

Patient tolerance of cervical esophageal metallic stents.

PURPOSE: To demonstrate that proximal esophageal stenoses and tracheoesophageal fistulas can be adequately palliated with use of metallic stents without significant foreign-body sensation. MATERIALS AND METHODS: Between June 1994 and March 1999, 22 patients with lesions within 3 cm of the cricopharyngeus were treated by placement of metallic stents. The series was reviewed retrospectively. Twenty patients had surgically unresectable malignant lesions, two patients had benign disease. Ten patients had associated tracheoesophageal fistulas. In all, the upper limit of the stent was between C5 vertebral body inferior endplate and the T2 vertebral body superior endplate. The case-notes were reviewed until patient death (range, 6-198 days), or to date in the two surviving patients with benign disease. RESULTS: Immediate technical success was 93% (27 of 29). Dysphagia scores improved from a median of 3 to 2 after stent placement. Eighteen of 22 (82%) patients reported no foreign-body sensation. There have been no cases of proximal migration, periprocedural perforation, or deaths. The two patients with benign disease experienced significant complications. CONCLUSION: Lesions in proximity to the cricopharyngeus can be successfully palliated without significant foreign-body sensation in the majority of patients with use of metallic stents. The authors urge caution in placing stents in patients with benign disease.

Adult↗
PubMedDate not supplied

Sampling bulk consignments of dried figs for aflatoxin analysis.

The between-box aflatoxin distribution for a bulk consignment of whole dried figs (11 tons) has been established by the individual analysis of 200 boxes (analysed as single samples of 12 kg each of homogenized material) randomly selected from a total of 850 boxes. The within-box aflatoxin distribution for three boxes was investigated by the analysis of 12 subsamples in each case made up of packets of figs totalling 1 kg in weight. Of the 200 boxes, 134 contained less than 10 micrograms/kg total aflatoxins whereas the highest level found was 227 micrograms/kg. The highest level of aflatoxins found in a single 1 kg unit was 2063 micrograms/kg. The batch average aflatoxin contamination determined on the basis of a single 20 kg homogenized sample (20 x 1 kg subsamples) was 33 micrograms/kg, compared to a level of 15 micrograms/kg calculated as the average of 200 determinations. Evaluations are made of different possible ways of sampling and the confidence that can be associated with each of these is estimated.

Aflatoxins↗
PubMedDate not supplied

Novel synthetic organosulfur compounds induce apoptosis of human leukemic cells.

It has been well documented that natural organosulfur compounds (OSCs) derived from plants such as garlic, onions and mahogany trees possess antiproliferative properties; however, the essential chemical features of the active OSC compounds remain unclear. To investigate the association between OSC structure and growth inhibitory activity, we synthesized novel relatives of dysoxysulfone, a natural OSC derived from the Fijian medicinal plant, Dysoxylum richii. In this study, we have examined the antiproliferative effects of these novel OSCs on a model human leukemic cell system and show that the compounds segregate into three groups. Group I, consisting of compounds A, B, G and J, did not affect either cell proliferation or the cell cycle profile of the leukemic cell lines. Group II, consisting of compounds F and H, induced the cells to undergo apoptosis from the G2/M phase of the cell cycle. Group III, consisting of compounds C, D, E and I, decreased cell proliferation and induced apoptosis throughout the cell cycle. The apoptotic agonists of Group II and III shared a common disulfide moiety, essential for leukemic cell cytotoxicity. Interestingly, Group II compounds did not affect cell viability of normal human diploid cells, suggesting the regions flanking the disulfide group contributes to the specificity of cell killing. Thus, we provide evidence that structure-activity analysis of natural products can identify novel compounds for the development of new therapeutics that can trigger apoptosis in a tumor-specific manner.

Antineoplastic Agents, Phytogenic↗
PubMedDate not supplied

Vision 2000. A critique.

Explore the source record for details and available documents.

Continuity of Patient Care↗
PubMedDate not supplied

Introduction of high-alcohol beer in Ontario: preliminary observations on its use by underage drinkers.

Preliminary data are reported on the use of high-alcohol beer by underage drinkers in Ontario. Students in grades 11 and 12 with a valid driver's licence completed a questionnaire between January and May, 1994 (i.e., between three and seven months after the introduction of high-alcohol beer). About one-half of students who had drunk alcohol within the previous four weeks reported consuming high-alcohol beer within that period. In this group, males were much more likely to report high-alcohol beer consumption in the previous month. Both male and female high-alcohol beer consumers drank alcohol more frequently, got drunk more frequently, and drank five or more drinks on the same occasion more frequently than non-consumers. One reason for trying high-alcohol beer, "wanted a higher alcohol content", was endorsed by more than one-third of high-alcohol beer consumers. Our data suggest that the users of high-alcohol beer among this underage drinking sample tend to be heavier drinkers and more likely to experience alcohol-related problems.

Adolescent↗