PubMed Health⌕ Search

Biomedical subjects

A Larson

Publications and source records attributed to A Larson.

At least 55 records · Page 3Linked to original sources
PubMed1996

A molecular and morphological perspective on the phylogenetic relationships of the otophysan fishes.

We examined the phylogenetic relationships among the major lineages of otophysan fishes (Cypriniformes, Characiformes, Siluroidei, and Gymnotoidei) using a combined analysis of molecular and morphological characters. The molecular characters comprised 160 phylogenetically informative sites from nuclear-encoded ribosomal RNA and 208 phylogenetically informative sites from the mitochondrial genes encoding ribosomal RNA and the valine transfer RNA for nine otophysan taxa and a gonorynchiform outgroup. The morphological data comprised 85 characters that were obtained from an earlier cladistic study. Congruence among molecular and morphological characters is generally high. The combined analysis supports a sister group relationship between the Gymnotoidei and Siluroidei, which together form a sister group to the Characiformes. The separation of the Cypriniformes from all other otophysans represents the earliest phylogenetic split within the Otophysi. Despire the generally high congruence among molecular and morphological characters, the molecular data analyzed separately produce a topology that differs from the analysis of the combined data. Sources of the taxonomic incongruence between the molecular and morphological data are examined.

Animals↗
PubMed1996

Why? Who? How? Estimating numbers of illicit drug users: lessons from a case study from the Australian Capital Territory.

There is currently a resurgence of interest in estimating numbers of illicit drug users in Australia. Defining why numbers are needed, who is to be counted and how estimates should be derived are vital steps in the production of useful, valid estimates. We present a range of estimates of heroin users in the Australian Capital Territory which were developed as part of an investigation of the feasibility of prescribing heroin to dependent users. These produced estimates ranging from 433 to 1251 users. We conclude that household surveys, capture-recapture, and multipliers derived from nomination techniques have serious and often unrecognised limitations. Capture-recapture estimates, in particular, are unlikely to be useful, except at a local level. The best way forward for the derivation of national estimates for the National Drug Strategy is a three-pronged approach; national surveys, validated multipliers and monitoring of key indicators by drug-related services and agencies.

Australia↗
PubMed1996

Drowning fatalities of children in Tasmania: differences from national data.

All drownings of people under 15 years of age in Tasmania from 1981 to 1993 were identified from the Tasmanian coroner's case files. Age- and sex-specific mortality rates were calculated and found to be similar to Australian drowning mortality rates. An exception was the lower drowning rate for Tasmanian females aged 0 to 4 years. Only 9 per cent of drowning deaths were caused by immersion in a swimming pool, 32 per cent of deaths occurred in dams and ponds and 21 per cent occurred in a river. Most drownings (88 per cent) associated with dams, ponds, swimming pools and baths were in the 0-to-4-year age group. Compared with Australia as a whole, toddlers drowning in swimming pools is uncommon in Tasmania; however, there are relatively more drownings in dams and ponds. Strategies for the prevention of drowning in childhood in Tasmania should consider the hazards associated with rural living.

Adolescent↗
PubMed1995

A defined region of loss of heterozygosity at 11q23 in cutaneous malignant melanoma.

Karyotypic and molecular data indicate that genetic alterations of the long arm of chromosome 11 (11q) may be involved in malignant melanoma. To test this we analyzed 5 polymorphic microsatellite repeats on 11q using a PCR-based assay for loss of heterozygosity in normal and tumor tissues from 24 individuals with cutaneous malignant melanoma of various stages. Our findings indicate that a tumor suppressor gene that plays a role in malignant melanoma is located on the long arm of chromosome 11, likely within a 51 cM region at 11q23. Its loss appears to be a late event in tumor progression and may serve as an indicator for a less favorable clinical outcome.

Adult↗
PubMed1994

Loss of heterozygosity in cervical carcinoma: subchromosomal localization of a putative tumor-suppressor gene to chromosome 11q22-q24.

Infection of cervical epithelial cells with so-called "aggressive" subtypes of human papilloma virus (HPV) appears to be an important factor in the etiology of cervical carcinoma. However, mounting evidence suggests that additional genetic changes are required for progression to an invasive carcinoma. Functional studies have shown that human chromosome 11 contains a gene or genes capable of suppressing tumorigenicity in cell lines derived from different histopathological types of cervical carcinoma, suggesting that aberration of this gene(s) may represent at least one of the additional changes required for tumorigenic progression. To identify the likely chromosomal position of this gene(s), we have carried out a systematic genetic analysis of chromosome 11 in the primary tumors of 32 patients with cervical carcinoma. Sixteen highly polymorphic markers, 10 of which were based on simple sequence repeats typed by PCR, were used to compare matched DNA samples from noninvolved tissue and portions of tumor tissue highly enriched for neoplastic cells by the cryostat-sectioning technique. Of the 32 patients examined, 14 (44%) demonstrated clonal genetic alterations resulting in loss of heterozygosity for one or more markers. Seven of the clonal genetic alterations on chromosome 11 were specific to the long arm, and the overlap between these and other allelic deletions suggests that a suppressor gene(s) relevant to cervical carcinoma maps to chromosome 11q22-q24.

Alleles↗
PubMed1994

The comparison of morphological and molecular data in phylogenetic systematics.

Analytical methods facilitating the use of molecular and morphological characters as complementary sources of phylogenetic information are explored. Separation of phylogenetically useful information from misleading patterns of character variation is most effective when the methods of "taxonomic congruence" and "character congruence" are used together. Statistical approaches for implementing both methods are described and illustrated with an example from the phylogeny of salamanders.

Animals↗
PubMed1994

Indirect estimates of 'hidden' populations: capture-recapture methods to estimate the numbers of heroin users in the Australian Capital Territory.

This paper describes a method of estimating the size of a population based on matching the individuals from the population appearing in two or more nonrandom samples. The method has been developed by population biologists and demographers who have shown that the simple estimates based on only two samples are very sensitive to the assumption that the two samples are independent. This assumption is rarely met with human populations. However, estimates based on three or more samples can be derived by fitting a log-linear model to a 2k contingency table. The method is applied to a data set of heroin users seeking treatment or counselling or arrested on drug charges in 1988 or 1989 in a small Australian city. The method produced a stable estimate of 1250 heroin users. This includes only users who are vulnerable to arrest and/or interested in seeking treatment. Although estimates produced by this method should be validated with other techniques it provides a simple, quick method to estimate the numbers of people in other hidden populations which are difficult to access.

Australia↗
PubMed1992

Evidence for a non-estrogenic cytostatic effect of estramustine on human prostatic carcinoma cells in vivo.

Estramustine is one of the main metabolites of estramustine phosphate (EstracytR), a drug used in the treatment of advanced prostatic cancer. In the present study the hormone independent human prostatic carcinoma cell line DU 145 implanted subcutaneously in nude mice (NMRI) was used to investigate the mode of action of estramustine in vivo. Metaphase arrest was found in mice treated with estramustine intraperitoneally, 200 and 400 micrograms daily for 2 weeks, 5 days a week. A significant dose dependent decrease in the number of anaphase figures was found. A 7 to 8 fold increase in the number of abnormal metaphases, i.e., highly contracted and unaligned chromosomes, was found. Uptake and retention of 3H-estramustine was found in tumour tissue. No increase in the mitotic index or the number of abnormal metaphases was found in animals treated with polyestradiol phosphate (EstradurinR). This is the first time evidence has been presented demonstrating the anti-mitotic effect of estramustine in vivo.

Animals↗
PubMed1992

The expression of estramustine-binding protein in the human prostatic cancer cell line DU 145 is not androgen dependent.

Estramustine-binding protein (EMBP) constitutes one of the major proteins in the prostatic gland, it binds estramustine and estromustine, the active metabolites of estramustine phosphate (Estracyt). Previous studies in rats have indicated that the expression of EMBP is androgen dependent, with diminishing quantities following castration and estrogen treatment as well as restored pre-castration production upon administration of androgens. In this study, we have used the human prostatic cancer cell line DU 145 transplanted in female and male nude mice. This cell line, which is sex hormone independent, gave rise to subcutaneous tumors in the rats with no difference in growth characteristics between the males and females. The expression of EMBP was analysed by radioimmunoassay, immunohistochemical and Western blot techniques. No difference was seen between the two sexes with respect to EMBP content, demonstrating that the expression of EMBP, in contrast to that reported for the normal prostate, is neither androgen- nor estrogen-dependent in tumor tissues.

Animals↗
PubMed1992

Molecular phylogeny of the volvocine flagellates.

Phylogenetic studies of approximately 2,000 bases of sequence from the large and small nuclear-encoded ribosomal RNAs are used to investigate the origins of the genus Volvox. The colonial and multicellular genera currently placed in the family Volvocaceae form a monophyletic group that is significantly closer phylogenetically to Chlamydomonas reinhardtii than it is to the other unicellular green flagellates that were tested, including Chlamydomonas eugametos, Chlorella pyrenoidosa, and Haematococcus lacustris. Statistical analysis of 251 phylogenetically informative nucleotide positions rejects the "volvocine lineage" hypothesis, which postulates a monophyletic evolutionary progression from unicellular organisms (such as Chlamydomonas), through colonial organisms (e.g., Gonium, Pandorina, Eudorina, and Pleodorina) demonstrating increasing size, cell number, and tendency toward cellular differentiation, to multicellular organisms having fully differentiated somatic and reproductive cells (in the genus Volvox). The genus Volvox appears not to be monophyletic. Volvox capensis falls outside a lineage containing other representatives of Volvox (V. aureus, V. carteri, and V. obversus), and both of these Volvox lineages are more closely related to certain colonial genera than they are to each other. This implies either a diphyletic origin of Volvox from different colonial volvocacean ancestors, a phylogenetic derivation of some of the colonial genera from a multicellular (i.e., Volvox) ancestor, or both. Considered together with previously published observations, these results suggest that the different levels of organizational and developmental complexity found in the Volvocaceae represent alternative stable states, among which evolutionary transitions have occurred several times during the phylogenetic history of this group.

Animals↗
PubMed1991

Cost analysis of two implantable narcotic delivery systems.

This survey compares costs of two commonly utilized implantable narcotic delivery systems. The systems are classified into type-I (exteriorized system using the DuPen epidural catheter) and type-II (implanted system using the Synchromed pump). Costs were analyzed by reviewing actual patient hospital financial service records and Homecare vendor quotations. From the perspective of cost analysis alone, we conclude that savings accrue when patients requiring treatment beyond 3 months duration are managed with a type-II implanted system compared with a type-I system with an external pump.

Adult↗
PubMed1990

Nucleotide sequence analysis of a provirus derived from an individual with tropical spastic paraparesis.

Human T-cell lymphotropic virus type 1 (HTLV-1), the cause of inapparent infections and T-cell leukemias and lymphomas, has also been implicated in two chronic neurological diseases, tropical spastic paraparesis (TSP) and HTLV-1 associated myelopathy (HAM). We initiated a search for a neurotropic variant of HTLV-1 that might be responsible for these chronic progressive myelopathies by cloning and sequencing a provirus from a T-cell line from an individual with TSP. The LTRs and genes of the TSP provirus differ from HTLV-1 by 20-30 nucleotides in each region, but none of the substitutions ostensibly affect functional sites with the exception of the env gene. We document one substitution in the region encoding gp46 common to TSP and HAM proviruses and a mutation that introduces two stop codons in the region encoding gp21. The latter should delete about 100 amino acids from the transmembrane anchor, and, for this reason, the progeny of the sequenced provirus are likely to be defective viruses, maintained in the culture through coinfection of cells with wild-type non-defective HTLV-1. While defective viruses could be responsible for persistent infection of the nervous system in TSP, this cannot be generally the case as we show that HTLV-1 DNA amplified from cell lines from two other individuals with TSP lacked the stop codons. Similarly, comparisons of DNA amplified from HTLV-1 DNA in cases of ATL, HAM, and TSP did not establish a correlation between the mutation in gp46 and neurological disease. The issue of neurotropic variants in HTLV-1 associated neurological disease thus remains an open one which may be resolved in the future by examining proviruses in cells in the lesions in the nervous system; or proviruses in ATL and HAM/TSP which differ in their ability to replicate in glial or neuronal cells.

Amino Acid Sequence↗
PubMed1989

Patterns of ribosomal RNA evolution in salamanders.

Sequence comparisons are presented for four segments of the large subunit of ribosomal RNA, including divergent domains D7a and D7b, portions of the large divergent domains D2, D3, and D8, and evolutionarily conservative sequences flanking divergent domains. These results resolve phylogenetic relationships among exemplars of seven families of salamanders and the three amphibian orders. Phylogenetic analysis confirms the prediction that divergent domains feature the highest relative rates of base substitution and length variation within the ribosome, but the divergent domains evolve more slowly than nuclear noncoding DNA and the silent sites of structural genes. Base substitutions demonstrate approximately twice as many transitions as transversions and an uneven distribution among sites within the divergent domains but no apparent bias in base composition. Length mutations are primarily small insertions and deletions, with deletions predominating. The divergent domains appear to be a good source of phylogenetic information for evolutionary events occurring approximately 100-200 million years ago.

Animals↗
PubMed1989

Changing population rates, policies and attitudes in Africa, the Middle East and South Asia.

This paper explores the relationship between population growth rates, government policies, and social attitudes in 3 regions: Africa, the Middle East, and South Asia. The comparative success of family planning programs in certain countries of South Asia (most notably India and Sri Lanka) can be partly ascribed to their long tradition of government leadership. In addition, families in those countries have strong incentives to educate their children. On the other hand, in North Africa and the Middle East, high levels of urbanization have had antinatalist effects, which are offset by very low levels of girls' schooling and of female employment outside the home. In Sub-Saharan Africa, high fertility is sustained by the structure of the family, with its tendency to separate reproductive decision-making from responsibility for child-rearing. In addition, governments there have had a comparatively weaker tradition in areas such as family behavior.

Africa↗
PubMed1988

Marriage in late nineteenth-century Melbourne.

"This article uses Melbourne [Australia] marriage certificates from 1866 to 1896 to compare urban and rural marriage trends and study the individual determinants of the timing of first marriage; on the whole, urban brides and grooms were likely to be younger than rural ones. Economic conditions, as measured by occupation, played a more important role in men's timing of marriage than in women's. The fact that prenuptial pregnancy led couples to marry several years before their peers suggests that family commitments and other personal, unmeasured, factors affected marriage age."

Age Factors↗
PubMed1988

Radioimmunodetection of prostatic cancer with 125I-labelled antibody against prostatic specific antigen.

A murine monoclonal antibody directed against human prostatic specific antigen was labelled with 125I and used in immunoscintigraphy studies of nude mice bearing xenografts of a human prostatic carcinoma cell line (DU-145). The antibody was injected intraperitoneally and the distribution was followed daily with the use of a gamma scintillation camera. Specific uptake was seen in the tumor, with optimal imaging 7-9 days after the injection of the radio-labelled antibody. Fab fragments of the radio labelled antibody were also investigated. These exhibited a strikingly shorter bio-distribution time, with optimal visualization of the tumor after 14-28 hours. Normal murine IgG and Fab fragments used in control experiments exhibited radioactivity that was comparable to that of normal tissue.

Animals↗