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J MacDonald

Publications and source records attributed to J MacDonald.

At least 73 records · Page 4Linked to original sources
PubMed1993

Lack of correlation between interspecific divergence and intraspecific polymorphism at the suppressor of forked region in Drosophila melanogaster and Drosophila simulans.

Levels of DNA sequence polymorphism at the suppressor of forked [su(f)] region in natural populations of Drosophila melanogaster and Drosophila simulans are estimated by restriction map analysis. su(f) is located at the base of the euchromatic portion of the X chromosome where the level of crossing-over per physical length is extremely low. In a survey of 55 alleles from three natural populations of D. melanogaster, only 2 restriction sites of 27 hexanucleotide and 108 tetranucleotide restriction sites scored are polymorphic. Among 103 alleles from three natural populations of D. simulans, just one polymorphic restriction site is found in 109 tetranucleotide-recognizing restriction sites scored. The few polymorphisms in these surveys yield estimates of per site heterozygosities (0.00, 0.0002, and 0.0005, respectively) at least a factor of 10 less than the average observed at loci located in regions of the genome with normal levels of crossing-over. Because under a broad category of models of molecular evolution (including the neutral theory) a correlation between levels of polymorphism and interspecific divergence is expected, the DNA sequence divergence is examined for the su(f) region. Contrary to the predicted correlation, the estimated divergence (0.12 substitution per silent site) is, in fact, greater than that observed at loci in regions of normal crossing-over. According to an alternative hypothesis (hitchhiking effect model) intraspecific polymorphism is swept out of the population in regions of the genome closely linked to rare but selectively favored variants as they quickly go to fixation; the rate of divergence is, however, unaffected by these rare hitchhiking events. Thus, the observed paucity of polymorphism and lack of correlation with divergence are in accord with the theory of the hitchhiking effect and several recent reports of polymorphism and divergence in other genomic regions with reduced crossing-over per physical length.

Animals↗
PubMed1993

Mouse alveolar surfactant: characterization of subtypes prepared by differential centrifugation.

To characterize the properties of alveolar surfactant subfractions obtained from mouse lung by differential centrifugation, lavage fluid, following a preliminary centrifugation at 140 x g for 5 min to yield a cellular pellet (Pc), was sequentially centrifuged at 10,000 x g for 30 min, 60,000 x g for 60 min and 100,000 x g for 15 h; and the resultant pellets, respectively referred to as P10, P60 and P100, were harvested for electron microscopy, phospholipid analysis and surface tension measurements. Ultrastructural differences were observed, in that P10 contained large multilamellated structures which were typical of newly secreted surfactant, P100 contained small unilamellar vesicular structures, typical of catabolic end products of alveolar surfactant and P60 appeared to contain a mixture of structures present in P10 and P100 in addition to numerous, large unilamellar vesicles which were not present in either P10 or P100. Slight but significant differences were found in the phospholipid compositions of the three subfractions but not in the fatty acid composition of their phosphatidylcholine (PC) component. There were no significant differences in their disaturated PC/total PC ratios, but significant differences in their phospholipid/protein ratios. P60 had the highest proportion of phospholipid to protein. P10 and P60 demonstrated surface activity but P100 did not. Total alveolar surfactant phospholipid was evenly distributed among the three fractions. This pattern of distribution was significantly different from that observed in rabbit subfractions prepared by the same procedure. These data indicate that mouse alveolar surfactant consists of three distinct subfractions or subtypes which can be separately and quantitatively isolated by differential centrifugation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

The oral examination: a study of academic and non-academic factors.

The oral examination in psychiatry for final-year medical students at Wellington and Dunedin School of Medicine, University of Otago, was studied. Between December 1989 and April 1990, 40 medical students were videorecorded during such an examination. The transcripts of the recording of each oral, and at a later date the videorecordings, were individually scored by a panel of six research psychiatrists who were experienced examiners. In addition verbal and non-verbal behaviour was rated using visual analogue scales and the students completed personality and anxiety questionnaires. There was a low level of agreement between research psychiatrists in the allocation of oral marks. The oral score was positively associated with the level of confidence of the student and negatively with anxiety in men.

Body Image↗
PubMed1993

A very unusual breast lump.

A 77 year old woman presenting with a malignant phyllodes tumour of of the right breast with exclusively stromal metastases to axillary lymph nodes refractory to both radiotherapy and chemotherapy.

Aged↗
PubMed1992

Project 2000 curriculum evaluation: the case for teacher evaluation.

Project 2000 has changed the role of nurse teachers. Thus evaluation of Project 2000 should incorporate a theoretical framework that not only evaluates the individual school/college of nursing curriculum but also enhances the teachers' professional development. This paper suggests that teacher professional development would be enhanced by teacher self-evaluation (action research). A collaborative approach between teachers and an evaluation co-ordinator would ensure that the quality of the curriculum is maintained (MacDonald 1991). It is argued that the implementation of monitored innovation would fulfil the criteria for the developing school/college of nursing put forward by Holly et al (1989).

Curriculum↗
PubMed1992

Molecular cloning and expression of ptxA, the gene encoding the 120-kilodalton cytotoxin of Actinobacillus pleuropneumoniae serotype 2.

The genetic determinants of the 120-kDa cytotoxin of Actinobacillus pleuropneumoniae serotype 2 were isolated from a lambda DNA library by a plaque immunoblot technique. Expression of the 120-kDa polypeptide was confirmed by Western immunoblot analysis of infected Escherichia coli cell lysates, which were shown to be toxic for porcine alveolar macrophages in vitro. The genetic determinants of the toxin were subcloned into the plasmid vector pUC18. This plasmid (pPTX1) directed the synthesis and secretion of the active 120-kDa cytotoxin in E. coli. The recombinant toxin was indistinguishable from native cytotoxin from A. pleuropneumoniae serotype 2 with respect to molecular size, reaction in Western blot analysis, heat lability, cytotoxic activity, and neutralization by serum antibody. A restriction endonuclease cleavage map of pPTX1 was prepared, and deletion mutants were used to locate the minimal region of DNA required for production of intracellular toxin; this gene was termed ptxA. Southern hybridization analysis with a 1.7-kb PvuII fragment located within the ptxA gene revealed sequences with a high degree of homology in serotype reference strains 2, 3, 4, 6, and 8. Other reference strains did not contain sequences that were recognized by this probe. However, related sequences (greater than 71% homology) were detected in Actinobacillus actinomycetemcomitans and A. equuli. Weak hybridization was observed between the ptxA probe and pLKT5, which carries the lktAC genes of Pasteurella haemolytica, and between the ptxA probe and pAPH1, which carries the structural gene for type II hemolysin from A. pleuropneumoniae. The isolation of the genetic determinants of this cytotoxin will enable investigations of the structure and organization of the ptx DNA region and further analysis of its role in the pathogenesis of pleuropneumonia.

Actinobacillus↗
PubMed1992

The history of ventriculoscopy: where do we go from here?

With the availability of better endoscopes, improved lighting and increased instrumentation, the use of ventriculoscopy and ventriculostomy in the management of hydrocephalus is becoming increasingly more common. Neurosurgeons recognized the potential for endoscopic surgery early in this century, but were frustrated in many of their attempts at treatment due to the poor quality of the instruments available. Nevertheless, much progress has been made, and the stage was set for better results with modern instrument design. This paper reviews the history of endoscopes in neurosurgery and ponders the direction these instruments will take us in the near future.

Cerebral Ventricles↗
PubMed1992

An investigation of bacterial causes of arthritis in slaughter hogs.

Joints from 153 arthritic and 80 normal slaughter hogs were examined by culture for presence of bacteria. Although none of the normal joints yielded bacteria, 37% of the disease joints were positive for bacterial growth. Of 67 bacterial isolates obtained, 45% were Erysipelothrix rhusiopathiae. Occurrence of other bacteria in order of their frequency was Streptococcus suis (16%), Actinomyces pyogenes (10%), Mycoplasma spp. including 3 M. hyorhinis isolates (7%), staphylococci (7%), Streptococcus spp. (6%), and organisms of uncertain significance (7%).

Actinomyces↗
PubMed1992

Risk management.

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Hospital Administration↗
PubMed1991

Projections of the tectospinal tract to the upper cervical spinal cord of the cat: a study with the anterograde tracer PHA-L.

The goal of the present experiments was to re-examine the spinal projections of neurons in the superior colliculus (SC) of the cat by taking advantage of the high sensitivity of the anterograde tracer, phaseolus vulgaris leucoagglutinin (PHA-L). In seven experiments, multiple injections of PHA-L into different regions of the SC labelled a total of 172 axons in the predorsal bundle; yet only 11 tectospinal tract (TST) axons were found in the upper cervical spinal cord. Collaterals emerging from these axons were rare and arose exclusively from TST axons with a diameter of less than 1 micron. Individual collaterals had different termination zones: some terminated in the lateral part of lamina V and VI after taking a dorsolateral course through lamina VII and VIII; others terminated in the medial part of lamina VII. One collateral terminated within lamina IX and the ventral part of lamina VIII. The combined termination of all collaterals was densest in lamina VII and dorsal lamina VIII. A small number of boutons were also found in the lateral parts of laminae V and VI, and in lamina IX and immediately adjacent regions in lamina VIII. Compared to axons belonging to other spinal descending systems, individual TST axons give rise to much simpler intraspinal collaterals with relatively few boutons. This feature, together with the relative paucity of TST axons, suggests that direct connections from the SC to neurons in the upper cervical spinal cord are sparse. Furthermore, our results are consistent with electrophysiological studies that show that few, if any, neck motoneurons receive monosynaptic connections from TST neurons. Projections to neck motoneurons must therefore involve a relay, either through other descending pathways, such as the reticulospinal system, or via local segmental interneurons.

Animals↗
PubMed1991

Control of embryonic motoneuron survival in vivo by ciliary neurotrophic factor.

During development of the nervous system, neurons in many regions are overproduced by proliferation, after which the excess cells are eliminated by cell death. The survival of only a proportion of neurons during normal development is thought to be regulated by the limited availability of neurotrophic agents. One such putative trophic agent is ciliary neurotrophic factor (CNTF), a polypeptide that promotes the survival of ciliary, sensory, and sympathetic neurons in vitro. In contrast to the results of in vitro studies, however, the daily treatment of chick embryos in vivo with purified human recombinant CNTF failed to rescue any of these cell populations from cell death, whereas CNTF did promote the in vivo survival of spinal motoneurons. Thus, CNTF may not act as a neurotrophic agent in vivo for those embryonic neurons (especially ciliary neurons) on which it acts in vitro. Rather, CNTF may be required for in vivo survival of motoneurons.

Animals↗
PubMed1991

Phase II study of pibenzimol in pancreatic cancer. A Southwest Oncology Group study.

Twenty-three patients with advanced pancreatic adenocarcinoma were treated with Pibenzimol utilizing a daily intravenous schedule for five days. There were no objective responses seen. The major toxicity was pancreatic with grade 3 hyperglycemia in eleven patients. Pibenzimol is inactive in patients with advanced pancreatic adenocarcinoma.

Adenocarcinoma↗
PubMed1991

Characterization of prostate cancer, benign prostatic hyperplasia and normal prostates using transrectal 31phosphorus magnetic resonance spectroscopy: a preliminary report.

We assessed the ability of 31phosphorus (31P) transrectal magnetic resonance spectroscopy to characterize normal human prostates as well as prostates with benign and malignant neoplasms. With a transrectal probe that we devised for surface coil spectroscopy we studied 15 individuals with normal (5), benign hyperplastic (4) and malignant (6) prostates. Digital rectal examination, transrectal ultrasonography and magnetic resonance imaging were used to aid in accurate positioning of the transrectal probe against the region of interest within the prostate. The major findings of the in vivo studies were that normal prostates had phosphocreatine-to-adenosine triphosphate (ATP) ratios of 1.2 +/- 0.2, phosphomonoester-to-beta-ATP ratios of 1.1 +/- 0.1 and phosphomonoester-to-phosphocreatine ratios of 0.9 +/- 0.1. Malignant prostates had phosphocreatine-to-beta-ATP ratios that were lower (0.7 +/- 0.1) than those of normal prostates (p less than 0.02) or prostates with benign hyperplasia (1.1 +/- 0.2, p less than 0.01). Malignant prostates had phosphomonoester-to-beta-ATP ratios (1.8 +/- 0.2) that were higher than that of normal prostates (p less than 0.02). Using the phosphomonoester-to-phosphocreatine ratio, it was possible to differentiate metabolically malignant (2.7 +/- 0.3) from normal prostates (p less than 0.001), with no overlap of individual ratios. The mean phosphomonoester-to-phosphocreatine ratio (1.5 +/- 0.5) of prostates with benign hyperplasia was midway between the normal and malignant ratios, and there was overlap between individual phosphomonoester-to-phosphocreatine ratios of benign prostatic hyperplasia glands with that of normal and malignant glands. To verify the in vivo results, we performed high resolution magnetic resonance spectroscopy on perchloric acid extracts of benign prostatic hyperplasia tissue obtained at operation and on a human prostatic cancer cell line DU145. The extract results confirmed the differences in metabolite ratios observed in vivo. We conclude that transrectal 31P magnetic resonance spectroscopy can characterize metabolic differences between the normal and malignant prostate.

Adult↗
PubMed1991

AIDS update 1991.

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Acquired Immunodeficiency Syndrome↗