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Biomedical subjects

D Jackson

Publications and source records attributed to D Jackson.

At least 127 records · Page 7Linked to original sources
PubMed1996

The multicultural workplace: comfort, safety and migrant nurses.

The changing composition of Australian society has resulted in the reality of a multicultural workplace. With this comes the need to examine issues related to cultural wellbeing within an occupational setting. Migrant women nurses from non-English speaking backgrounds participated in this phenomenological study, which examined their experiences working as nurses within the New South Wales health care system. Participants described traumatic experiences around entering the nursing work environment. Familiar and comfortable roles such as being a woman, a colleague and a nurse were altered and made uncomfortable by the imposition of disturbing and unfamiliar roles. This discomfort was compounded by what was experienced as an uncomfortable and perilous work environment. The task for these women became one of finding sanctuary and comfort and finally, of establishing a place for themselves. This paper will take the reader on the journey from being a stranger to finding a place and will raise issues for discussion surrounding culture and safety in the nursing workplace.

Adaptation, Psychological↗
PubMed1995

Aromatic L-amino acid decarboxylase immunoreactive cells in the rat striatum: a possible site for the conversion of exogenous L-DOPA to dopamine.

The efficacy of L-dihydroxyphenylalanine (L-DOPA) in ameliorating the symptoms of Parkinson's disease (PD) is attributed to its conversion to dopamine (DA) by the enzyme aromatic L-amino-acid decarboxylase (AADC) in the striatum. Although the site of this conversion in the DA-denervated striatum has yet to be identified, it has been proposed that L-DOPA could be converted to DA at non-dopaminergic sites containing AADC. In the present study, we used immunocytochemical techniques to examine the localization of AADC and DA in the striatum of rats with a unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal dopaminergic projection. In the DA-denervated striatum, we observed AADC-immunoreactive (-IR) cells with morphological characteristics similar to a class of small aspiny interneuron. Although usually obscured by a dense plexus of AADC-IR fibers, these cells could also occasionally be detected in the intact striatum. Acute administration of L-DOPA to DA-denervated animals elicited contralateral rotational behavior as well as a pronounced c-fos protein immunoreactivity in the striatum ipsilateral to the lesion. Following acute administration of L-DOPA, but not after acute saline, DA-IR cells were detected in the denervated striatum. These DA-IR cells are similar in morphology and were found in the same location as the AADC-IR cells. These results strongly suggest the existence of a class of AADC-containing striatal cells that can form DA from exogenous L-DOPA in the rat. In the DA deafferented striatum, DA produced by these cells from exogenous L-DOPA could be released to exert physiological effects on DA receptive tissue. It is possible that similar cells could contribute to the efficacy of L-DOPA in the treatment of Parkinson's disease.

Animals↗
PubMed1995

Homeobox genes in the functioning of plant meristems.

The maize homebox gene knotted1 (kn1) is expressed in vegetative and floral meristems and is down-regulated at the site of primordia formation. kn1-related genes from maize and other species also show meristem-specific expression and offer additional tools for studying the activities of shoot meristems. Members of this gene family are expressed early in embryogenesis, providing molecular markers for meristem initiation. Ectopic expression of either kn1 or a related Arabidopsis gene, KNAT1, causes dramatic alterations in Arabidopsis and tobacco leaf morphology. Most significantly, meristems form on the leaf, producing small shoots. We discuss whether the phenotypes can be interpreted as changes in positional information or timing of determination.

Gene Expression Regulation, Plant↗
PubMed1995

Ultrabithorax protein is necessary but not sufficient for full activation of decapentaplegic expression in the visceral mesoderm.

To elucidate the mechanisms by which homeotic selector (HOM) genes specify the unique features of Drosophila segments, we have analyzed the regulation of decapentaplegic (dpp), a transforming growth factor (TGF)-beta superfamily member, and have found that the Ultrabithorax (Ubx) HOM protein directly activates dpp expression in parasegment 7 (PS7) of the embryonic visceral mesoderm. Other factors are also required, including one that appears to act through homeodomain protein binding sites and may be encoded by extradenticle (exd). The exd protein binds in a highly co-operative manner to regulatory sequences mediating PS7-specific dpp expression, consistent with a genetic requirement for exd function in normal visceral mesoderm expression of dpp. A second mechanism contributing to PS7 expression of dpp appears not to require Ubx protein directly, and involves a general visceral mesoderm enhancer coupled to a spatially specific repression element. Thus, even in an apparently simple case where visceral mesoderm expression of the dpp target gene mirrors that of the Ubx HOM protein, full activation by Ubx protein requires at least one additional factor. In addition, a distinct regulatory mode not directly involving Ubx protein also appears to contribute to PS7-specific expression.

Animals↗
PubMed1995

Computerized consensus diagnosis: a classification strategy for the robust analysis of MR spectra. I. Application to 1H spectra of thyroid neoplasms.

We introduce and apply a new classification strategy we call computerized consensus diagnosis (CCD). Its purpose is to provide robust, reliable classification of biomedical data. The strategy involves the cross-validated training of several classifiers of diverse conceptual and methodological origin on the same data, and appropriately combining their outcomes. The strategy is tested on proton magnetic resonance spectra of human thyroid biopsies, which are successfully allocated to normal or carcinoma classes. We used Linear Discriminant Analysis, a Neural Net-based method, and Genetic Programming as independent classifiers on two spectral regions, and chose the median of the six classification outcomes as the consensus. This procedure yielded 100% specificity and 100% sensitivity on the training sets, and 100% specificity and 98% sensitivity on samples of known malignancy in the test sets. We discuss the necessary steps any classification approach must take to guarantee reliability, and stress the importance of fuzziness and undecidability in robust classification.

Adenocarcinoma, Follicular↗
PubMed1995

A feedback controlled silicon microprobe for quantitative mechanical stimulation of nerve and tissue.

The ability to apply and control the force and force velocity of mechanical stimulation is essential for the study of mechanoelectric transduction and adaptation processes. Silicon micromachining technology was used to produce miniature (20-70 microns wide) mechanical microprobes. Passive polysilicon, piezoresistive, force sensing elements were deposited onto the boron-doped epitaxial silicon and the individual devices were chemically etched from the bulk wafer. These microprobes display a linear force versus output voltage relationship. Stimulation forces up to 2 mN can be generated with a measurement resolution of 1.5 microN. The probes were mounted onto circuit board holders and their output sent to a proportional-integral controller which drives an electromagnetic actuator. By using this force-feedback control circuit coupled to a PC it is possible to define any stimulus wave form pattern and independently control and measure the actual stimulus force and velocity. A computer controlled 3-axis stepper motor (0.025 micron step capability) manipulator is used to position the silicon microprobe-actuator assembly relative to the mechanoreceptive field. Sensor feedback control coupled to the 3-axis stepper motor manipulator allows automatic touchdown control and/or preloading of the probe prior to stimulation. Three-dimensional topographic manipulator feedback position control allows automated receptive field mapping.

Action Potentials↗
PubMed1995

Antiemetic efficacy of a droperidol-morphine combination in patient-controlled analgesia.

STUDY OBJECTIVES: To evaluate the antiemetic effectiveness and side effects of adding low-dose droperidol to morphine delivered via a patient-controlled analgesia (PCA) device. DESIGN: Randomized, double-blind, clinical study. SETTING: University-affiliated women's hospital. PATIENTS: 60 healthy women, 18 to 60 years of age, who underwent total abdominal hysterectomy with a standardized anesthetic regime. INTERVENTIONS: After surgery, the control group (n = 20) had access via PCA to two cartridges, each containing morphine 1 mg/ml and saline 1 ml. The two treated groups (n = 20 each) had access via PCA to either droperidol 0.5 mg or droperidol 1 mg added to two cartridges containing morphine 1 mg/ml. MEASUREMENTS AND MAIN RESULTS: Preoperative data, including each patient's history of nausea and vomiting with and without previous anesthesia, motion sickness, smoking, and alcohol intake, and date of her last menstrual period, were obtained. All patients received a standardized anesthetic with droperidol 0.5 mg given at closure of the peritoneum. Among those patients who received droperidol added to morphine for their postoperative analgesic regimen, fewer required rescue antiemetic medication (p < 0.05, test of trend in proportions), and they had a lower incidence of vomiting (p < 0.05, test of trend in proportions), as well as a decrease in the number of times a rescue antiemetic was needed during the 24-hour postoperative period (linear trend, p = 0.013). CONCLUSIONS: An intermittent intake of low-dose droperidol with morphine given via a PCA delivery system in two treatment groups gave evidence for a dose-response relation between the amount of droperidol added and the proportion of patients needing a rescue antiemetic. The same result applied to the proportion of patients having an emetic episode and the number of times a rescue antiemetic had to be administered. There was no evidence that the low dose of droperidol added to morphine delivered via a PCA device increased unwanted side effects.

Adolescent↗
PubMed1995

CD44 expression and modulation on human neuroblastoma tumours and cell lines.

The human CD44 cell surface glycoprotein has been involved in a variety of functions including lymphocyte homing, extracellular cell matrix attachment and tumour metastasis. A large family of variants or isoforms, generated by alternative splicing of a single gene, has been reported to be involved in the malignant process, by conferring metastatic potential to non-metastatic cells. Neuroblastoma is a tumour characterised by an aggressive and metastatic behaviour in advanced stages, with amplification of the MYCN protooncogene. In this report, we show that the CD44 standard molecule was highly expressed in the majority of tumours of stages 1-3, in all stage 4s and ganglioneuromas, but only in a subset of stage 4 tumours. A lack of CD44 expression was observed in all MYCN amplified stage 4 tumours, thus demonstrating a highly significant inverse relationship between MYCN amplification and CD44 expression in neuroblastoma. In addition, the expression of 4 different CD44 isoforms was measured on all specimens and was always found to be negative. Using neuroblastoma cell lines and MYCN expressing transfectants, we show that CD44 expression by neuroblastoma cell lines is not directly related to MYCN amplification, but is associated to the stage of differentiation or lineage, and to the tumorigenic properties of the cells. In addition, CD44 expression can be upmodulated parallel to differentiation or maturation as induced by retinoic acid, bromodeoxyuridine or phorbol ester. In contrast, cytokines such as IFN gamma, TNF alpha, or growth factors such as bFGF, SCF and TGF beta were ineffective in modulating CD44 expression.

Biomarkers, Tumor↗
PubMed1995

Constructing nursing practice: country of origin, culture and competency.

This study explored the everyday experiences of a group of overseas qualified female nurses from non-English speaking backgrounds (NESB) entering the New South Wales health-care system. Migrant women from a variety of NESB participated by describing their experiences in the hospital environment as qualified nurses. Analysed data suggest that the experience of being a migrant woman has a profound effect on how these nurses construct nursing practice. National wealth and the dominant government ideologies operating in a nurse's country of qualification shape the practice of nurses. Nursing therefore is socially and culturally constructed, yet nurses seeking to practise in New South Wales (and other parts of Australia) are assessed against the Australian Nursing Council (Inc) competencies. Do these competencies support the current ideology of multiculturalism or do they reflect a monocultural view of the world? This paper raises questions concerning the use of competencies as an assessment tool for locally qualified and overseas qualified nurses.

Adaptation, Psychological↗
PubMed1995

Effects of racist provocation and social support on cardiovascular reactivity in African American women.

It has been speculated that exposure to the chronic stress of racism contributes to the high rates of hypertension among African Americans. Social support may buffer the effects of stress on cardiovascular (CV) health by attenuating stress-induced CV responses that have been linked to hypertension. In this study we investigated the effects of racism and social support on CV reactivity in African American women. Participants showed greater increases in CV and emotional responses while responding and listening to racist provocation. Augmented blood pressure (BP) persisted through recovery following racial stress. Participants receiving no support showed the greatest increases in anger during racist provocation. No significant effects were seen for support on CV reactivity. These results provide some of the first evidence that interactive confrontation with racism elicits significant increases in CV reactivity and emotional distress. Furthermore, individuals receiving less support may be at greater risk for the potentially health-damaging effects of racial stress. These findings may have significant implications for the health of African Americans.

Journal Article↗
PubMed1995

Regulation of growth and dissemination of a human lymphoma by CD44 splice variants.

CD44 is a polymorphic cell surface glycoprotein, currently proposed to be the principal cell surface receptor for hyaluronan. However, different isoforms of CD44, expressed in human lymphoid tumor cells, appear to have distinct effects on the ability of the cells to attach to hyaluronan-coated surfaces and on their capacity to form tumors in vivo. In the present study, we address the mechanisms that may regulate CD44 isoform-dependent adhesion to hyaluronan. We use a human Burkitt lymphoma, stably transfected with six different alternatively spliced human CD44 isoforms, to determine their potential hyaluronan binding and tumor growth promoting roles. We show that transfectants expressing CD44 splice variants that contain variable exons 6-10, 7-10 and 8-10 adhere to hyaluronan-coated surfaces weakly and that corresponding tumor formation in vivo is delayed with respect to CD44-negative parental cell-derived tumors. Abundant shedding of these three isoforms may play a significant role in determining the rate of tumor development. Transfectants expressing variable exon 3, on the other hand, fail to display CD44-mediated adhesion to hyaluronan, but form bone marrow tumors rapidly following intravenous injection. These observations suggest that different mechanisms regulate CD44-mediated adhesion and tumor growth, and provide evidence that expression of exon v3 may confer novel ligand-binding properties.

Alternative Splicing↗
PubMed1995

Genetic and molecular analysis of patterning in plant development.

Phyllotaxy, or leaf arrangement, and leaf shape are two products of patterning mechanisms in plants. We have isolated a family of plant homeobox genes that provide tools to study both of these components. Expression patterns of the homeobox genes appear to predict leaf initiation sites; the ectopic expression of these genes affects leaf shape. We have isolated a recessive mutation, abphyl, that changes the phyllotaxy of maize from alternate to opposite. Analysis of mutant plants suggests that the gene product regulates meristem size. We consider the possible roles of gene expression and physical constraints in establishing pattern.

Amino Acid Sequence↗
PubMed1995

Nursing texts and lesbian contexts: lesbian imagery in the nursing literature.

Using textual analysis, this paper locates and explicates the images of lesbians that have been presented in introductory nursing texts. The author argues that these images, when presented as 'text', adopt a veil of objectivity and neutrality. Textbooks have power and authority, they legitimize the opinions of authors which are often unsupported by evidence. In the case of lesbians, the use of language in texts effectively re-pathologizes that which has been de-pathologized for over 20 years. Implications for scholarly practice are drawn from the findings of this paper.

Australia↗
PubMed1995

OB-GYN Consultants and Sharp the BirthPlace: an exemplar of nurse-midwife and obstetrician interdependence and integration.

The "co-management" model of perinatal care as practiced at OB-GYN Consultants and Sharp The BirthPlace maximizes the practice strengths of both nurse-midwives and obstetricians. The nurse-midwife is the primary provider for 95% of the clients; high-risk women are referred to the physician as appropriate. The model provides extensive health education and an option of a freestanding birth center for low-risk women. In the face of rapid health care changes, which emphasize cost effectiveness, this model has appealing features for managed care systems.

Birthing Centers↗
PubMed1994

Stimulation and inhibition of angiogenesis by placental proliferin and proliferin-related protein.

In many mammalian species, the placenta is the site of synthesis of proteins in the prolactin and growth hormone family. Analysis of two such proteins, proliferin (PLF) and proliferin-related protein (PRP), revealed that they are potent regulators of angiogenesis; PLF stimulated and PRP inhibited endothelial cell migration in cell culture and neovascularization in vivo. The mouse placenta secretes an angiogenic activity during the middle of pregnancy that corresponds primarily to PLF, but later in gestation releases a factor that inhibits angiogenesis, which was identified as PRP. Incubation of placental tissue with PLF led to the specific binding of this hormone to capillary endothelial cells. Thus PLF and PRP may regulate the initiation and then the cessation of placental neovascularization.

Animals↗
PubMed1994

CD44H expression by human neuroblastoma cells: relation to MYCN amplification and lineage differentiation.

The human CD44 cell surface glycoprotein has been involved in a variety of functions including lymphocyte homing, extracellular cell matrix attachment, and tumor metastasis. Due to the alternative splicing of the single gene, a large family of different variants or isoforms is generated. Several reports have indicated an up-regulation of CD44 variant (v) isoforms in malignant process, conferring metastatic potential to non-metastatic cells. Neuroblastoma is a tumor characterized by an aggressive and metastatic behavior in advanced stages with amplification of the MYCN protooncogene. In this report we show that the CD44 standard molecule is highly expressed in 100% of stage I-III, IVs neuroblastomas and ganglioneuromas but only in a subset of stage IV tumors. In contrast, no expression of CD44 was detected on MYCN amplified stage IV tumors, thus demonstrating a highly significant negative relationship between MYCN amplification and CD44 expression in neuroblastoma. The expression of CD44 on neuroblastoma cultured cell lines was not shown to be related to MYCN amplification but rather linked to the S-type, schwann/glial differentiation lineage. Immunochemical analysis of tumor samples with anti-CD44v3 and -v6 antibodies and Northern blot analysis of mRNA from cell lines with probes spanning exons 4-10 did not reveal any expression of splice variants on neuroblastomas of all stages and cell lines, thus ruling out a major role of these isoforms in neuroblastoma progression and metastasis.

Blotting, Northern↗
PubMed1994

Postural tremor of Parkinson's disease.

Previous studies have reported the resting tremor (RT) of Parkinson's disease to occur at frequencies between 3-7 Hz and to be characterised by an alternating pattern of electromyographic (EMG) bursting activity between opposing muscles. A postural tremor (PT), of higher frequency (> 6 Hz) and with a synchronous pattern of EMG activity, has also been previously described in Parkinson's disease. We investigated the electrophysiological and pharmacological properties of both the RT and PT of 11 patients with Parkinson's disease and 10 patients with essential tremor in a double-blind, placebo-controlled study of L-Dopa/benserazide and propranolol. Tremor amplitude and frequency were assessed via bidirectional accelerometry, and the pattern of activation of the antagonist muscles of the forearm was determined with use of surface EMG. In the Parkinson's disease group studied, the frequency, EMG pattern of bursts, and response to L-Dopa were similar for the two tremors (median improvement of RT by 70% and PT by 61%). Despite some overlap between the Parkinson's disease and essential tremor groups in the electrophysiology of the tremor, there was no such dramatic pharmacological response in the latter group. These results suggest that the RT and PT of Parkinson's disease share a common pathophysiology and are distinct from essential tremor.

Adult↗