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S A Hill

Publications and source records attributed to S A Hill.

At least 19 recordsLinked to original sources
PubMed2000

The 4-pregnene and 5alpha-pregnane progesterone metabolites formed in nontumorous and tumorous breast tissue have opposite effects on breast cell proliferation and adhesion.

Progesterone is required for the full proliferative activity of the breasts and may be directly or indirectly involved in either stimulating or inhibiting breast cancer. To determine whether the effects on breast cancer are attributable to progesterone metabolites, we compared the capacity of nontumorous and tumorous breast tissue to convert progesterone and then tested the effects of these metabolites on breast cell proliferation and anchorage. Tissues from the operated breasts of six patients with infiltrating duct carcinomas were incubated with [14C]progesterone for 2, 4, and 8 h, and the metabolites were identified and quantified. The identified metabolites (equal to >95% of recovered radioactivity) can be divided into those that retain the double bond of progesterone in the carbon-4 position of ring A (4-pregnenes) and those that are 5alpha-reduced (5alpha-pregnanes). The results show that tumorous breast tissue has elevated 5alpha-reductase activity, which results in significantly higher total levels of 5alpha-pregnanes, especially 5alpha-pregnane-3,20-dione (5alphaP), whereas normal (nontumorous) breast tissue produces more 4-pregnenes, especially 3alpha-hydroxy-4-pregnen-20-one (3alphaHP). 5alphaP and 3alphaHP are each one enzymatic step removed from progesterone, resulting from the action of either 5alpha-reductase or 3alpha-hydroxysteroid oxidoreductase (3alpha-HSO), respectively. The ratio of 5alpha-pregnanes:4-pregnenes is >5-fold greater and the ratio of 5alphaP:3alphaHP is nearly 30-fold greater in tumorous than nontumorous breast tissue incubates. In vitro studies with three breast cell lines (MCF-7, MCF-10A, and ZR-75-1) show that 3alphaHP dose dependently inhibits, whereas 5alphaP significantly stimulates, proliferation. Additional studies with MCF-7 and MCF-10A cells indicate that each of the 4-pregnenes isolated from breast tissue suppresses, whereas each respective 5alpha-reduced product stimulates, cell proliferation. Studies of cell anchorage were conducted using MCF-7 cells and various concentrations of 5alphaP or 3alphaHP. The number of cells attached to the substrate was significantly (P<0.05) decreased by treatment with > or =30 nM 5alphaP and increased by treatment with > or =50 nM 3alphaHP. Conversely, the number of cells detached from the substrate after partial trypsin exposure was significantly increased by treatment with > or =40 nM 5alphaP and decreased by treatment with > or =30 nM 3alphaHP. The results suggest that a change in in situ progesterone metabolism, resulting in an increased 5alpha-pregnane:4-pregnene (especially 5alphaP:3alphaHP) ratio, may promote breast cancer by promoting increased cell proliferation and detachment, whereas increases in 4-pregnenes may retard these tumorigenic processes. These studies suggest that endogenous progesterone metabolites may provide a new hormonal basis for breast cancer.

Adult↗
PubMed2000

Neisseria gonorrhoeae recJ mutants show defects in recombinational repair of alkylated bases and UV-induced pyrimidine dimers.

Neisseria gonorrhoeae lacks several common DNA repair pathways found in other organisms. As recent evidence had indicated that gonococci use recombinational repair to repair UV-induced DNA lesions, this study examined whether the gonococcal RecJ homologue contributes in this repair capacity. The recJ gene from strain MS11 was cloned and sequenced and was found to show a considerable degree of identity to its Escherichia coli homologue. A N. gonorrhoeae delta recJ mutant was constructed and tested for recombinational proficiency as well as for defects in DNA repair. In the absence of the RecJ exonuclease, DNA transformation and pilin switching occurred at wild type levels, indicating that the efficiency of recombination remained unimpaired. In contrast, N. gonorrhoeae delta recJ mutants showed extreme sensitivity to low levels of UV irradiation and to exposure to DNA-alkylating reagents [e.g. ethyl methanesulfonate (EMS) and methyl methanesulfonate (MMS)]. Complementation of the gonococcal recJ mutant in cis restored resistance to low-level UV, indicating that the gonococcal RecJ protein is involved in recombinational repair, and can act independently of other single-strand-specific exonucleases. Furthermore, transformation competence was not required for RecJ-dependent DNA repair. Overall, the data show that N. gonorrhoeae recJ mutants present a unique phenotype when compared to their E. coli recJ counterparts, and further support the contention that RecORJ-dependent recombinational repair is a major DNA repair pathway in the genus Neisseria.

Alkylation↗
PubMed2000

Determinants of anti-vascular action by combretastatin A-4 phosphate: role of nitric oxide.

The anti-vascular action of the tubulin binding agent combretastatin A-4 phosphate (CA-4-P) has been quantified in two types of murine tumour, the breast adenocarcinoma CaNT and the round cell sarcoma SaS. The functional vascular volume, assessed using a fluorescent carbocyanine dye, was significantly reduced at 18 h after CA-4-P treatment in both tumour types, although the degree of reduction was very different in the two tumours. The SaS tumour, which has a higher nitric oxide synthase (NOS) activity than the CaNT tumour, showed approximately 10-fold greater resistance to vascular damage by CA-4-P. This is consistent with our previous findings, which showed that NO exerts a protective action against this drug. Simultaneous administration of CA-4-P with a NOS inhibitor, N(omega)-nitro-L-arginine (L-NNA), resulted in enhanced vascular damage and cytotoxicity in both tumour types. Administration of diethylamine NO, an NO donor, conferred protection against the vascular damaging effects. Following treatment with CA-4-P, neutrophil infiltration into the tumours, measured by myeloperoxidase (MPO) activity, was significantly increased. Levels of MPO activity also correlated with the levels of vascular injury and cytotoxicity measured in both tumour types. Neutrophilic MPO generates free radicals and may therefore contribute to the vascular damage associated with CA-4-P treatment. MPO activity was significantly increased in the presence of L-NNA, suggesting that the protective effect of NO against CA-4-P-induced vascular injury may be, at least partially, mediated by limiting neutrophil infiltration. The data are consistent with the hypothesis that neutrophil action contributes to vascular injury by CA-4-P and that NO generation acts to protect the tumour vasculature against CA4-P-induced injury. The protective effect of NO is probably associated with an anti-neutrophil action.

Angiogenesis Inhibitors↗
PubMed2000

Positive and negative selection of antigen-specific B cells in transgenic mice expressing variant forms of the V(H)1 (T15) heavy chain.

Four variant forms of the V1 (T15-H chain) gene are synthesized in mice. Each V1 variant pairs with a distinct L chain to produce a binding site having specificity for phosphocholine (PC). Transgenic mice expressing variant forms of the V1 gene were analyzed to elucidate the factors driving B cell selection into the peripheral repertoire. In all four lines of H chain transgenic mice analyzed, transgene expression caused complete allelic exclusion of endogenous H chains in the bone marrow (BM), whereas most splenic B cells expressed endogenous H chains. The number of sIgM(+) BM B cells and their sIg receptor number was reduced compared to that of normal transgene-negative controls, suggesting that B cells expressing transgene-encoded H chains were being negatively selected in the BM. Mice expressing autoreactive forms of the V1 transgene with lower affinity for PC (M603H and M167H) exhibit positive selection of PC-specific B cells into the spleen, whereas mice expressing the higher affinity T15H variant exhibited elevated PC-specific B cells in the peritoneal cavity but few V(H)1(+) splenic B cells. These data suggest that the higher affinity T15-id(+) B cells preferentially survive in the peritoneal cavity. When these H chain transgenes were crossed into the mu MT knockout mouse in which surface expression of endogenous H chains is blocked, the percent of splenic V(H)1(+) PC-specific B cells increased up to 5-fold and T15-id(+) B cells were detectable in the spleen of T15H mice. This implies that T15-id(+) PC-specific B cells can be selected into the periphery, but they compete poorly with follicular B cells expressing endogenous Ig.

Animals↗
PubMed2000

Reappraisal of filter effects on P300 voltage and latency.

The selection of which high-pass filter cutoff to use in P300 studies continues to be a serious methodological consideration. To determine whether there was an optimal range of bandpass widths-a range in which P300 voltage and latency would not show statistically significant differences-the authors recorded P300 responses to the auditory "oddball" paradigm from Cz and Pz electrodes in a group of eight healthy males. The authors used high-pass filter cutoffs of 0.01, 0.1, 0.3, and 1.0 Hz with low-pass filter cutoffs of 30 and 100 Hz and measured both P300 peak voltages and P300 integrated mean voltages at 12 bandpass settings. There were statistically significant differences in 7 out of 12 bandpass comparisons for P300 peak voltages and in 7 out of 12 bandwidth comparisons for P300 integrated mean voltages. For P300 latencies, there were statistically significant differences in 9 out of 12 bandwidth comparisons. Based on these results, the best recommendation, therefore, is that the high-pass filter be set no higher than 0.3 Hz.

Adult↗
PubMed2000

Age-related mitochondrial DNA mutations in the human larynx.

OBJECTIVE: To determine whether age-related mitochondrial DNA mutations occur in the human larynx. STUDY DESIGN: Genetic study of cadaveric larynx specimens. METHODS: Vocal fold mucosa, thyroarytenoid muscle, and cricoarytenoidjoint tissue were harvested from 13 fresh postmortem larynges (age range, 2 d-82 y). DNA was extracted from each sample, and the polymerase chain reaction (PCR) was used to amplify a target DNA sequence resulting from the common age-associated, 4977-base-pair (bp) mitochondrial DNA deletion. PCR products were visualized by agarose gel electrophoresis. Automated sequencing determined the sequence of identified PCR products. SUBJECTS: Thirteen cadaveric larynges were obtained through the University of Kentucky Medical Center (Lexington, KY). Specimens from patients with a history of head and neck cancer, previous laryngeal trauma, or surgery were excluded. RESULTS: Strongly positive bands were identified in samples from three individuals. Weaker bands were seen in samples from four other samples. No band was noted from the two pediatric larynges. Different band patterns were seen among the three different tissue sites in the larynges with positive PCR products, but no consistent pattern was seen. Sequencing of the identified PCR products from selected samples confirmed that they were products of the age-associated, 4977-bp mitochondrial DNA deletion. CONCLUSIONS: An age-associated mitochondrial DNA deletion was detected in several post-mortem human larynges. Its presence seemed to increase in appearance with age. In the larynges in which the deletion occurred, there were individual regional differences in the occurrence of the deletion, but no consistent pattern was noted across all individuals who carried the deletion.

Adult↗
PubMed2000

Opa expression correlates with elevated transformation rates in Neisseria gonorrhoeae.

Neisseria gonorrhoeae is naturally competent for DNA transformation. Under most conditions encountered in vivo, gonococci express one or more opacity (Opa) proteins on their surfaces. Recently, it was shown that DNA preferentially binds to the surfaces of Opa-expressing organisms compared to those of isogenic Opa-negative strains, presumably due to the numerous cationic residues in the predicted surface-exposed loops of the Opa protein. This study examined whether Opa-DNA interactions actually influence DNA transformation of the gonococcus. The data show that Opa-expressing gonococci are more efficient recipients of DNA for transformation and are more susceptible to exogenous DNase I treatment at early stages during the DNA transformation process than non-Opa expressors. Furthermore, inhibition of the transformation process was demonstrable for Opa(+) populations when either nonspecific DNA or the polyanion heparin was used. Overall, the data suggest that Opa expression, with its presumptive positive surface charge contribution, promotes DNA transformation by causing a more prolonged sequestration of donor DNA at the cell surface, which translates into more efficient transformation over time.

Antigens, Bacterial↗
PubMed2000

The man who claimed to be a paedophile.

A psychiatrist recounts a case of a man presenting with severe depression who claimed to have abused children and his pet dog. Clinical management of the case hinged on whether this claim was true, a lie or delusional. The uncertainty over this raised complex ethical dilemmas regarding confidentiality and protection of the public (and animals).

Affective Disorders, Psychotic↗
PubMed2000

Reforming gendered health care: an assessment of change.

Health policy in the United States has changed dramatically over the past three decades, with the main concern shifting from expanded health care coverage to containment of health care costs. The current focus on providing cost-effective health services, reflected in the growth of managed care initiatives, has elevated concern about the quality of health care. The authors contend that quality of health care has always been the key focus in the women's health movement, which evolved in the late 1960s as the first significant challenge to modern medicine. In this article, they apply the analytic lens of gender to develop a fresh perspective on U.S. health care organizations and policies, examining the six broad demands of the feminist consumer model of health care, all of which hinge on the issue of quality care for women, to determine whether women's health needs are now being better addressed. The authors conclude that, despite some notable gains in the roles of women as consumers and providers of health care, many of the new health reforms have replicated and solidified the historical inequities in the health care system.

Community Participation↗
PubMed1999

Cell to cell transmission of donor DNA overcomes differential incorporation of non-homologous and homologous markers in Neisseria gonorrhoeae.

The neisseriae are naturally competent for DNA transformation. This genetic study examines whether the modification status of chromosomal donor DNA affects transformation of Neisseria gonorrhoeae to drug resistance. When a single modification system was inactivated, unmodified chromosomal donor DNA was not restricted when used to transform the cognate restriction+ host, irrespective of whether the donor DNA carried a point mutation (homologous marker) or a drug-resistance gene cassette (non-homologous marker). These observations contrasted transformations performed with unmodified plasmid donor DNAs, where the incoming DNA was excluded. However, during the study, it became apparent that certain strains of gonococci showed differential incorporation of non-homologous markers when compared with the incorporation of the homologous marker, even when the donor DNAs were prepared from parental strains. Differential incorporation of markers could be rescued either through cell to cell transmission of donor DNA, or by performing in vitro transformations with donor DNA preparations that were obtained from spent culture supernatants. Overall, the data indicate that, in addition to the exclusion of foreign DNA through the requirement for a genus-specific uptake sequence, gonococci appear capable of excluding DNA on the basis of homology.

Conjugation, Genetic↗
PubMed1999

Comparisons of defective HTLV-I proviruses predict the mode of origin and coding potential of internally deleted genomes.

Cell lines infected with a variety of HTLV-I isolates were examined for the presence of defective proviruses that contain deletions spanning the gag, pol, and env genes. Internally deleted proviruses were identified by Southern blotting and by PCR amplification with 5' and 3' primers complementary to gag and tax sequences, respectively. PCR products representing eight defective proviruses from seven different cell lines were subsequently cloned and sequenced. The objectives of this study were twofold: first, we sought to determine whether nucleotide sequences surrounding sites of deletion shared common features that might reveal the mechanisms by which the defective genomes originated. Second, we asked whether deleted proviruses encode Gag fusion proteins with related C-terminal residues derived from open reading frames in the pX region. While most of the defective proviruses had incurred a single, large deletion, two of them displayed a more complex pattern of multiple rearrangements. Alignments of bases flanking the 5' and 3' deletion endpoints within each provirus showed tracts of sequence identity consistent with a mechanism involving aberrant intramolecular strand-transfer events during replication. We suggest that the amount or activity of HTLV-I polymerase in virions may contribute both to the poor infectivity of the virus and to the high deletion frequency. Two of the eight proviruses that were examined encoded a gag gene joined to an extended open reading frame; the other six had very short open reading frames (one to six amino acids) derived from pX or env regions joined to gag that showed no apparent amino acid sequence similarity.

Amino Acid Sequence↗
PubMed1999

Plant mitochondrial 2-oxoglutarate dehydrogenase complex: purification and characterization in potato.

The 2-oxoglutarate dehydrogenase complex (OGDC) in potato (Solanum tuberosum cv. Romano) tuber mitochondria is largely associated with the membrane fraction of osmotically ruptured organelles, whereas most of the other tricarboxylic acid cycle enzymes are found in the soluble matrix fraction. The purification of OGDC from either membrane or soluble matrix fractions resulted in the increasing dependence of its activity on the addition of dihydrolipoamide dehydrogenase (E3). A 30-fold purification of OGDC to apparent homogeneity and with a specific activity of 4.6 micromol/min per mg of protein in the presence of exogenously added E3 was obtained. SDS/PAGE revealed that the purified complex consisted of three major polypeptides with apparent molecular masses of 48, 50 and 105 kDa. Before the gel-filtration purification step, E3 polypeptides of 57 and 58 kDa were identified by immunoreaction as minor proteins associated with OGDC. The N-terminal sequence of the 57 kDa protein was identical with that previously purified as the E3 component of the pyruvate dehydrogenase complex from potato. The 105 kDa protein was identified as the 2-oxoglutarate dehydrogenase subunit of OGDC by N-terminal sequencing. The N-terminal sequences of the 50 and 48 kDa proteins shared 90-95% identity over 20 residues and were identified by sequence similarity as dihydrolipoamide succinyltransferases (OGDC-E2). The incubation of OGDC with [U-(14)C]2-oxoglutarate resulted in the reversible succinylation of both the 48 and the 50 kDa protein bands. Proteins previously reported as subunits of complex I of the respiratory chain from Vicia faba and Solanum tuberosum are proposed to be OGDC-E2 and the possible basis of this association is discussed.

Acyltransferases↗
PubMed1999

Defective and wild-type human T-cell leukemia virus type I proviruses: characterization of gene products and trans-interactions between proviruses.

Defective provirus genomes of human T-cell leukemia virus type I are frequently detected in lymphocytes from infected individuals and in infected cell lines. One type of defective provirus contains internal deletions spanning gag, pol, and env genes but retains portions of open reading frames for trans-regulatory proteins. The deleted proviruses could potentially contribute to viral pathology by producing novel gene products that directly affect cell metabolism or that modulate expression of resident, wild-type proviruses. Virus gene products and the control of their expression were examined in cells transfected with defined molecular clones of wild-type and defective proviruses. Internally deleted provirus clones, which are unable to produce functional Tax and Rex proteins, were transcriptionally inactive in transfected cells. Ectopic expression of p40Tax activated transcription of the deleted provirus, resulting in the accumulation of a two-exon mRNA that yields a truncated form of Rex (p21Rex). Although this two-exon mRNA also has a potential initiation codon in the tax frame, a truncated form of Tax was not detected by immunoblotting or in transactivation assays. When complemented with p40Tax and p27Rex, cells transfected with deleted proviruses accumulated an unspliced mRNA that could potentially encode gag-pX fusion proteins. Although expression of deleted proviruses was dependent on trans-acting factors produced from intact proviruses, gene products from defective proviruses did not significantly affect expression of a cotransfected, full-length provirus.

Cell Line↗
PubMed1999

Monthly intra-individual variation in lipids over a 1-year period in 22 normal subjects.

OBJECTIVES: Previous reports on biological variation in lipids differ widely in the time interval between sampling, the number of samples analyzed per patient and the total study period. The present investigation was carried out to determine monthly intra-individual variation in lipids over 1 year and to establish whether there was a consistent change in lipid values over the summer months. The importance of taking this variation into consideration during the assessment of risk of coronary heart disease (CHD) was also examined. DESIGN AND METHODS: Cholesterol, triglycerides, HDL, apo A1, and apo B were measured at monthly intervals for 12 months in 22 healthy, free-living volunteers (11 females, 11 males) by standardized methods. RESULTS: When compared to analytical variation, biological variation was the dominant component of the intra-individual changes observed during the 1-year study period. As expected, triglycerides showed the greatest biological variation; the ratio of biological/analytical variation was 33.1. Much smaller ratios were observed for the other lipids measured in this study with values ranging from 4.2 to 6.8. Different subjects attained their maximum and minimum values in virtually every month of the year. There were significant reductions in cholesterol, HDL, LDL, and apo A1 in the summer months while triglycerides showed a non-significant increase and apo B a non-significant decrease during this period. CONCLUSIONS: All the analytes showed considerable intra-individual variation. It is, therefore, important to measure lipids sequentially over several weeks to arrive at an average value for risk stratification for CHD.

Adult↗
PubMed1999

Improvement in human tumour oxygenation with carbogen of varying carbon dioxide concentrations.

BACKGROUND AND PURPOSE: Carbogen (95%O2, 5%CO2) is being used in clinical trials as a hypoxic radiosensitiser. Tolerance to carbogen can be a problem, this study compares tumour oxygenation during inhalation of hyperoxic gas containing either 2% or 5% CO2. MATERIALS AND METHODS: Tumour pO2 was measured in 16 patients using the Eppendorf pO2 histograph. RESULTS: After breathing gas containing either 5% or 2% CO2 an increase in median pO2 was measured in every tumour, the frequency of low pO2 values ( < or = 10 mmHg) fell from 47% to 29% in the 5% group and from 55% to 17% in the 2% group. CONCLUSIONS: This study confirms that breathing 2% CO2 and 98% O2 is well tolerated and effective in increasing tumour oxygenation.

Administration, Inhalation↗
PubMed1999

Evidence for characteristic vascular patterns in solid tumours: quantitative studies using corrosion casts.

The vascular architecture of four different tumour cell lines (CaX, CaNT, SaS, HEC-1B) transplanted subcutaneously in mice was examined by means of microvascular corrosion casting in order to determine whether there is a characteristic vascular pattern for different tumour types and whether it differs significantly from two normal tissues, muscle and gut. Three-dimensional reconstructed scanning electron microscope images were used for quantitative measurements. Vessel diameters, intervessel and interbranch distances showed large differences between tumour types, whereas the branching angles were similar. In all tumours, the variability of the vessel diameters was significantly higher than in normal tissue. The quantitative data provide strong evidence for a characteristic vascular network determined by the tumour cells themselves.

Adenocarcinoma↗