Biomedical subjects

L Hall

Publications and source records attributed to L Hall.

At least 55 records · Page 3Linked to original sources

PubMed1998

Sequence analysis of a variety of primate fertilin alpha genes: evidence for non-functional genes in the gorilla and man.

The sperm surface fertilin complex was first described in the guinea pig where it was found as a heterodimer of alpha and beta subunits, both of which were proposed to play a role in sperm-oolemma recognition and plasma membrane fusion during fertilisation. Whilst the beta subunit is apparently testis-specific, the finding of low levels of fertilin alpha in nonreproductive tissues has cast some doubt on a unique role in fertilisation. Moreover, the absence of a functional fertilin alpha gene in the human would imply that this gene product is not absolutely essential for fertilisation, although it could play a facilitatory role. We now describe the organisation and sequence of the fertilin alpha genes in a range of primates, including the great apes, and find that the gorilla gene, like that of the human, is non-functional.

ADAM Proteins↗

PubMed1998

MRI measurement of brain tumor response: comparison of visual metric and automatic segmentation.

An automatic magnetic resonance imaging (MRI) multispectral segmentation method and a visual metric are compared for their effectiveness to measure tumor response to therapy. Automatic response measurements are important for multicenter clinical trials. A visual metric such as the product of the largest diameter and the largest perpendicular diameter of the tumor is a standard approach, and is currently used in the Radiation Treatment Oncology Group (RTOG) and the Eastern Cooperative Oncology Group (EGOG) clinical trials. In the standard approach, the tumor response is based on the percentage change in the visual metric and is categorized into cure, partial response, stable disease, or progression. Both visual and automatic methods are applied to six brain tumor cases (gliomas) of varying levels of segmentation difficulty. The analyzed data were serial multispectral MR images, collected using MR contrast enhancement. A fully automatic knowledge guided method (KG) was applied to the MRI multispectral data, while the visual metric was taken from the MRI films using the T1 gadolinium enhanced image, with repeat measurements done by two radiologists and two residents. Tumor measurements from both visual and automatic methods are compared to "ground truth," (GT) i.e., manually segmented tumor. The KG method was found to slightly overestimate tumor volume, but in a consistent manner, and the estimated tumor response compared very well to hand-drawn ground truth with a correlation coefficient of 0.96. In contrast, the visually estimated metric had a large variation between observers, particularly for difficult cases, where the tumor margins are not well delineated. The inter-observer variation for the measurement of the visual metric was only 16%, i.e., observers generally agreed on the lengths of the diameters. However, in 30% of the studied cases no consensus was found for the categorical tumor response measurement, indicating that the categories are very sensitive to variations in the diameter measurements. Moreover, the method failed to correctly identify the response in half of the cases. The data demonstrate that automatic 3D methods are clearly necessary for objective and clinically meaningful assessment of tumor volume in single or multicenter clinical trials.

Adult↗

PubMed1998

Mentoring relationships of New Zealand nurses: results of an empirical study (Part 2).

The first national study of mentoring relationships of New Zealand nurses used three issues from the descriptive literature as its conceptual framework. The results and discussion of the study are reported in part two. Results demonstrated that moderate levels of mentoring according to Kram's (1985) typology occurred amongst nurses and that they had many supportive relationships, mainly with women who were peers. The characteristics of nurses' mentoring relationships did not differ significantly from mainstream empirical data when factors such as gender, organisational status, age differences and duration of relationships were considered. Concerns about the future direction of mentoring research and in particular about recent international literature calling for the development of a separate mentoring theory for women conclude the article.

Adult↗

PubMed1998

High level multiplex genotyping by MALDI-TOF mass spectrometry.

A primer extension assay is used to perform highly multiplexed genotyping of single nucleotide polymorphisms (SNPs) present in genomic DNA amplified by a multiplex PCR. The assay uses matrix-assisted laser desorption ionization time-of-flight mass spectrometry to accurately measure the masses of short oligonucleotide primers extended by a single dideoxynucleotide. The multiplexed genotyping assays rely on the natural molecular weight differences of DNA bases. By careful analysis of primer composition complementary to the target, or by judicious addition of one or more noncomplementary 5' bases to the genotyping primers, mass spectra of interleaved genotyping products can be generated with no ambiguity in allele assignment. Using a model multiplex PCR system, we demonstrate the ability to perform 12-fold multiplex SNP analysis.

Base Sequence↗

PubMed1998

Concurrent and predictive validity of an early language screening program.

The efficacy of screening 2-year-old children for language delay using a parent-report questionnaire was investigated in three studies. The Language Development Survey (Rescorla, 1989) was mailed to 650 families at the time of their child's second birthday. Fifty-three percent of the surveys received by parents were completed and returned. Screening outcomes were then compared, in double-blind fashion, with the results of comprehensive clinical evaluations at ages 2 (N = 64) and 3 (N = 36). Parents' report of the size of their children's expressive vocabularies was highly correlated with clinical language measures at age 2. Children who screened positive performed significantly poorer than children who screened negative on standardized language tests and on measures taken from spontaneous conversation. The screening program demonstrated excellent sensitivity and specificity for identifying language delay at age 2 but somewhat lower levels for predicting developmental status one year later.

Age Factors↗

PubMed1998

Expression of extracellular superoxide dismutase in the human male reproductive tract, detected using antisera raised against a recombinant protein.

Mammalian spermatozoa are particularly susceptible to the deleterious effects of reactive oxygen species and lipid peroxidation, which ultimately lead to impaired fertility. A number of enzymes are present in the male reproductive tract which may play a role in preventing oxidative damage; in particular, the epididymis is the site of synthesis and secretion of large amounts of extracellular superoxide dismutase (eSOD). In order to study the distribution of eSOD in the male reproductive tract, and distinguish it from other related superoxide dismutase isoenzymes (e.g. cytosolic SOD), polyclonal antisera have been raised against a recombinant human eSOD fusion protein, expressed in bacterial cells. This protein was expressed from a synthetic gene fragment, using preferred Escherichia coli codons, designed to overcome the problems associated with the high guanine+cytosine content of the natural human eSOD transcript. Using this antiserum, eSOD can be readily detected in a range of human reproductive tissues as well as in human seminal plasma. However, the presence of similar levels of eSOD in the seminal plasma of vasectomized men (probably of prostatic origin) precludes its use as a simple diagnostic indicator of eSOD activity levels in the epididymis.

Amino Acid Sequence↗

PubMed1998

Macaque MDC family of proteins: sequence analysis, tissue distribution and processing in the male reproductive tract.

A large number of sequence-related, cysteine-rich membrane proteins containing metalloproteinase-like and disintegrin-like domains (the MDC protein family) have been identified in mammalian tissues from a variety of species. Previous studies in the macaque (Macaca fascicularis) have led to the cDNA cloning and sequence analysis of a number of MDC proteins which are abundantly expressed in the male reproductive tract. We now describe the distribution of seven of these macaque MDC transcripts in a range of different tissues. This description includes a novel macaque testis-derived MDC, tMDC III, whose full-length sequence is reported for the first time. In addition, polyclonal antisera have been used to localize a number of these MDC proteins to spermatogenic cells in testis sections, and to demonstrate their processing on the sperm surface during epididymal transit.

ADAM Proteins↗

PubMed1998

Expression of extracellular glutathione peroxidase type 5 (GPX5) in the rat male reproductive tract.

The mammalian epididymis is the site of expression and secretion of an abundant, tissue-specific, androgen-regulated, selenium-independent, glutathione peroxidase isoenzyme (GPX5), which has been proposed to play a role in protecting the membranes of spermatozoa from the damaging effects of lipid peroxidation and/or preventing premature acrosome reaction. Using a combination of reverse transcription-polymerase chain reaction, Northern blot analysis and Western blotting, we now describe in detail the developmental expression of GPX5 transcripts and protein in the rat epididymis and characterize the association of rat GPX5 with the sperm plasma membrane.

Animals↗

PubMed1998

Fungal beta-tubulin, expressed as a fusion protein, binds benzimidazole and phenylcarbamate fungicides.

Benzimidazoles are important antitubulin agents used in veterinary medicine and plant disease control. Resistance is a practical problem correlated with single amino acid changes in beta-tubulin and is often linked to greater sensitivity to phenylcarbamates. This negative cross-resistance creates opportunities for durable antiresistance strategies. Attempts to understand the molecular basis of benzimidazole resistance have been hampered by the inability to purify tubulin from filamentous fungi. We have overcome some of these problems by expressing beta-tubulin as a fusion with a maltose binding protein. This fusion protein is soluble, and we confirm for the first time using a gel filtration assay that benzimidazoles indeed bind to beta-tubulin. This binding is reduced by the mutation Glu198-->Gly198, which also confers resistance. Binding of phenylcarbamates is the complete opposite, reflecting their biological activity and the negative cross-resistance. This suggests that the fungicide binding sites fold correctly in the fusion protein.

Base Sequence↗

PubMed1998

Infectious dermatitis in a ball python (Python regius) colony.

Seven wild-caught ball pythons (Python regius), including six gravid females and one male, were obtained from Africa and were housed in a government animal facility in Research Triangle Park, North Carolina. Upon arrival, the snakes were found to be infested with ticks (Aponomma latus), which were manually removed. Four weeks following arrival, vesicular skin lesions began to appear on the snakes. Despite treatment of all affected female snakes with amikacin (5 mg/kg i.m., every 3 days) and cefotaxime (25 mg/kg i.m., every 3 days), the condition progressed and five of the female snakes died 7 wk after arrival. The remaining male and one female improved after an increase in environmental temperature, with ecdysis followed by healing. Physiologic stress, ectoparasites, and shipping may have predisposed the snakes to sepsis.

Amikacin↗

PubMed1998

The MDC family of proteins and their processing during epididymal transit.

All members of the MDC family of integral membrane proteins contain a metalloproteinase-like domain, a disintegrin-like domain and a cysteine-rich domain. They have been identified in a wide range of mammalian tissues and many are abundantly expressed in the male reproductive tract. We have previously cloned and sequenced several MDC transcripts expressed in the testes of the macaque (Macaca fascicularis). Using polyclonal antisera we have localized a number of these MDC proteins (fertilin alpha, fertilin beta, tMDC I, tMDC II and tMDC III) to spermatogenic cells and demonstrated that they are processed as spermatozoa pass through the epididymis, yielding proteins that retain their disintegrin domain on mature, fertilization-competent cauda spermatozoa. In rodents, two of these MDC proteins (fertilin beta and tMDC I) have been implicated in egg recognition, mediated by a disintegrin-integrin interaction. It is possible that the additional MDC proteins expressed on macaque spermatozoa may also be involved in this process.

Animals↗

PubMed1998

Interleukin-12-induced adhesion molecule expression in murine liver.

Systemically administered interleukin (IL)-12 causes liver inflammation in mice characterized by Kupffer cell proliferation and hypertrophy, hepatocyte necrosis, and multifocal accumulations of leukocytes in the hepatic parenchyma and around portal tracts and central veins. We have used both immunohistochemical staining and radiolabeled antibody quantitation to examine adhesion molecule expression in the livers of mice dosed daily with murine IL-12. Cells infiltrating livers of IL-12-treated mice were primarily mononuclear leukocytes expressing LFA-1, VLA-4, MAC-1, and CD18 adhesion molecules but little L-selectin. Kupffer cells constitutively expressed LFA-1 and smaller amounts of MAC-1, and high levels of ICAM-1 were constitutively expressed by liver sinusoidal lining cells, portal tract, and central vein endothelia. With IL-12 treatment, existing ICAM-1 expression was up-regulated and de novo expression occurred along bile duct epithelia. VCAM-1 levels were dramatically increased, with induced expression occurring along portal tract and central vein endothelia and scattered bile duct epithelial cells and in aggregations of cells in perivascular areas and the liver parenchyma. Although constitutive expression of E- and P-selectin was negligible, Il-12 induced a moderate rise in E-selectin levels. These increases in adhesion molecule expression may have implications for the therapeutic use of IL-12, especially in patients with liver disease or autoimmune conditions where augmented adhesion molecule expression may be critical to disease pathogenesis.

Animals↗

PubMed1997

Isolation and characterization of basal cells from human upper respiratory epithelium.

Cellular pathways of normal and reparative differentiation of upper airway epithelium are not well understood. Of the three main cell types, basal and secretory cells are known to divide, while ciliated cells are considered terminally differentiated. Several investigations support the role of the basal cell as a progenitor cell type, but others suggest that the secretory cell can regenerate a complete mucocilliary epithelium. Thus, lineage relationships within renewing adult epithelia are still unclear. Understanding the pathways involved in upper airway epithelial cell differentiation is critical for studying injury and repair mechanisms and for developing clinical strategies for tracheal reconstruction. We undertook the current studies to determine the integrin profile of isolated human upper airway basal cells. Respiratory epithelial cells (REC) were isolated by elastase digestion, stained with FITC-labeled Griffonia simplicifolia isolectin B4 (GSI-B4), and sorted by flow cytometry. Approximately 80% of the lectin-positive cells were basal cells, as determined by morphology and cytokeratin staining. These cells expressed integrins alpha 1, alpha 2, alpha 3, alpha 5, alpha v beta 5, beta 1, beta 3, and alpha 6 beta 4, by immunohistochemistry. This is the first report to identify the integrin profile of isolated human upper airway basal cells. These basal cells could be maintained on type I collagen for at least 7 days, where they became partially confluent and retained expression of cytokeratins 5 and 14. Availability of pure populations of basal cells should permit investigations of their role in both normal and maladaptive repair of adult upper airway epithelium.

Adult↗

PubMed1997

Contemporary cardiac rehabilitation services.

Major changes will be required in the components and delivery of cardiac rehabilitation services in the era of managed care. These include restructuring and amplifying the coronary risk reduction services that are currently provided, and offering group and home-based cardiac rehabilitation services to increase their availability.

Community Health Services↗

PubMed1997

The human fertilin alpha gene is non-functional: implications for its proposed role in fertilization.

In the guinea-pig, the alpha subunit of the fertilin complex, a heterodimeric surface membrane glycoprotein found on the head region of spermatozoa, has previously been proposed to mediate membrane fusion with the oolemma plasma membrane during fertilization. Here we describe experiments which indicate that the only fertilin alpha-like gene in humans is an expressed, but nonfunctional, pseudogene, possibly derived by genetic recombination between the two fertilin alpha genes found in some primates. This finding clearly raises questions about the importance and/or role of fertilin alpha in mammalian fertilization.

ADAM Proteins↗

PubMed1997

Rat MDC family of proteins: sequence analysis, tissue distribution, and expression in prepubertal and adult rat testis.

Increasing number of sequence-related cysteine-rich membrane proteins containing metalloproteinase-like and disintegrin-like domains (the MDC protein family) have been identified in mammalian tissues. Here, we report the cloning and sequence analysis of cDNAs encoding several rat orthologues of this protein family, some of which are found to be expressed exclusively in the male reproductive tract, others exhibiting a broader tissue distribution. We also examine their expression in prepubertal an adult rat testis, which, in conjunction with the data on tissue distribution, form a necessary prelude to further studies aimed at establishing their individual functions.

ADAM Proteins↗

PubMed1997

Puberty influences expression of phospholipid hydroperoxide glutathione peroxidase (GPX4) in rat testis: probable hypophysis regulation of the enzyme in male reproductive tract.

Mammalian spermatozoa are unusually rich in polyunsaturated fatty acids, a property that predisposes them to the deleterious effects of oxygen free radicals. Mouse and human spermatozoa utilize glutathione peroxidase, (GPX), to inactivate oxygen free radicals. In the GPX super-family there is the enzyme phospholipid hydroperoxide glutathione peroxidase (GPX4) that specifically protects membrane phospholipids against peroxidation. GPX4 is present, primarily, in testis where its enzymatic activity seems to be present only after puberty. In order to clarify this question we utilized total RNA from rat testis, liver and lung to carry out cDNA synthesis and the following RT-PCR amplification of cDNA products by using specific primers of rat liver sequence. RT-PCR products of the expected size for GPX4 (525 bp) were obtained from the three tissues. At last, these fragments were submitted to sequencing analysis. Here we demonstrate that the sequence analysis of rat testis GPX4 coding region is identical to that of rat liver and lung; however puberty influences the expression pattern of rat testis GPX4. In fact Northern blot analysis of total RNA from normal and pre-puberal hypophysectomized rats demonstrates the absence of a specific GPX4 mRNA in total RNA from pre-puberal hypophysectomized rat testis; on the other hand this specific transcript is present in both normal rat testis and liver and in pre-puberal hypophysectomized rat liver. Expression pattern of GPX4 is very low in lung both in post-puberal and pre-puberal hypophysectomized rats. Therefore hypophysis could regulate GPX4 transcript in rat testis.

Amino Acid Sequence↗

PubMed1997

Mentoring relationships of New Zealand nurses: an empirical study (Part 1).

A national, random, postal survey (n = 298) of mentoring behaviour among New Zealand nurses was undertaken. The initial research problem was to seek an explanation for the apparent lack of mentoring in New Zealand nursing. However, as the study evolved the lack of agreement concerning the definition of mentoring became a major research obstacle. A new conceptual framework of mentoring grounded in the work of Kathy Kram (1985) was devised. A quantitative global measure of mentoring behaviour (the TMS score) was used to measure levels of mentoring behaviour. This score was used as the dependent variable in subsequent statistical tests of: the definitional hypothesis-the study's validity check; the peer mentoring hypothesis which explored selected dynamics of mentor protégé relationships, and four allied research questions. The conceptual framework and approach are discussed in part one.

Education, Nursing, Continuing↗