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Biomedical subjects

C O'Neill

Publications and source records attributed to C O'Neill.

At least 109 records · Page 6Linked to original sources
PubMed1995

Induction of spermatogenesis by androgens in gonadotropin-deficient (hpg) mice.

Using a new experimental model for studying the hormonal induction of spermatogenesis, the hpg mouse, which has congenital functional gonadotropin deficiency due to a major deletion in the GnRH gene, we investigated the roles of testosterone (T) and dihydrotestosterone (DHT) in the initiation of spermatogenesis. Weanling homozygous hpg male mice were implanted subdermally with SILASTIC brand implants of varying lengths (0-2 cm) filled with T or DHT, using phenotypically normal (N/N or N/hpg) and untreated hpg/hpg mice as positive and negative controls. After 8 weeks, both T and DHT equally stimulated (approximately 14-fold) testis size and induced qualitatively complete spermatogenesis despite low intratesticular androgen levels and undetectable circulating FSH. Stereological quantitation of Sertoli and germ cells demonstrated a dose-dependent rise in the absolute numbers of all germ cell types induced by both T and DHT. At maximal androgen doses, germ cell numbers expressed per Sertoli cell and homogenization-resistant elongated spermatids expressed per mg testis were increased to more than 80% of non-hpg control values. An in vitro fertilization assay confirmed that both T and DHT induced quantitatively normal fertilizing capacity of the sperm in hpg males. We conclude that androgens, acting through the androgen receptor without need for aromatization, initiate qualitatively complete spermatogenesis in the mouse, including fertile sperm despite low intratesticular androgen levels and the absence of blood FSH levels. The hpg mouse model is a useful new paradigm to study the molecular basis of the hormonal induction of spermatogenesis.

Androgens↗
PubMed1995

Recurrence of the R408W mutation in the phenylalanine hydroxylase locus in Europeans.

The relative frequency of the common phenylalanine hydroxylase (PAH) mutation R408W and its associations with polymorphic RFLP, VNTR, and short-tandem-repeat (STR) sites in the PAH gene were examined in many European populations and one representative North American population of defined European descent. This mutation was found to cluster in two regions: in northwest Europe among Irish and Scottish peoples, and in eastern Europe, including the Commonwealth of Independent States. This allele was significantly less frequent in intervening populations. In eastern European populations, the R408W mutation is strongly associated with RFLP haplotype 2, the three-copy VNTR allele (VNTR 3), and the 240-bp STR allele. In northwestern European populations, it is strongly associated with RFLP haplotype 1, the VNTR allele containing eight repeats (VNTR 8), and the 244-bp STR allele. An examination of the linkage between the R408W mutation and highly polymorphic RFLP, VNTR, and STR haplotypes suggests that recurrence is the most likely mechanism to account for the two different major haplotype associations of R408W in Europe.

Alleles↗
PubMed1994

Increased beta-amyloid release and levels of amyloid precursor protein (APP) in fibroblast cell lines from family members with the Swedish Alzheimer's disease APP670/671 mutation.

Cell lines transfected with the Swedish Alzheimer's disease amyloid precursor protein APP670/671 mutation release significantly more beta-amyloid than wild-type cells. Citron et al. [Proc. Natl. Acad. Sci. USA (1994) in press] have recently shown that fibroblasts carrying the APP670/671 mutation also release more beta-amyloid than control cells [1]. The present study confirms a ca. threefold increase in beta-amyloid release from mutation-bearing fibroblasts. APP mRNA levels did not differ between mutation-bearing and control cells, although mutation-bearing fibroblasts contained significantly more APP751/770 than controls. Mild stress decreased beta-amyloid secretion and increased APP751/770 levels in all cell lines. In conclusion, the proportion of APP committed to amyloidogenic processing is increased in fibroblasts from family members with the APP670/671 mutation, and this mutation may also compromise the APP stress response.

Alzheimer Disease↗
PubMed1994

Regionally selective alterations in G protein subunit levels in the Alzheimer's disease brain.

In the present study the relative densities of a number of G protein subunits were quantified in membranes prepared from the hippocampus, temporal cortex and angular gyrus of Alzheimer's disease and control post-mortem brain by immunoblotting with specific polyclonal antisera against Gs alpha, Gi alpha, Gi alpha-1, G(o) alpha and G beta protein subunits. In addition, basal, Gs-stimulated and Gi-inhibited adenylyl cyclase activities were measured in the same hippocampal membrane samples. Densitometric analysis of the immunoblot data revealed a 58% reduction in the levels of Gi alpha, and a 75% reduction in the levels of Gi alpha-1, in the Alzheimer's disease temporal cortex. Gi alpha levels were reduced, by 37% in the angular gyrus of the Alzheimer's disease cases. The ratio of large to small molecular weight isoforms of the Gs alpha subunit was significantly increased in both the hippocampus and the angular gyrus of the Alzheimer's disease samples when compared to control values, although the difference in individual Gs alpha isoform levels did not attain statistical significance when comparing groups. No statistically significant differences were observed in G(o) alpha or G beta levels when comparing control and Alzheimer's disease cases. Gs-stimulated adenylyl cyclase activity was significantly reduced in the Alzheimer's disease samples compared to controls, whereas Gi-inhibited adenylyl cyclase activity was unchanged. No significant differences were observed between the control and Alzheimer's disease samples for either basal or forskolin stimulated adenylyl cyclase activity. The ratio of hippocampal Gs-stimulated to basal adenylyl cyclase activity correlated significantly with the large to small Gs alpha subunit ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1994

Adenylyl cyclase activity and G-protein subunit levels in postmortem frontal cortex of suicide victims.

Basal and stimulated adenylyl cyclase activities and Gs and Gi protein alpha-subunit levels (Gs alpha and Gi alpha) were compared in postmortem frontal cortex from 18 suicide cases and 22 matched controls. Basal, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) stimulated and forskolin stimulated enzyme activities were significantly lower in the suicide cases, compared to controls. These effects were most apparent in those suicides that had died from violent means or that had had a history of depression and appeared to reflect the lowered basal activity rather than a reduced ability of either GTP gamma S or forskolin to activate the enzyme. No significant correlations were found between adenylyl cyclase activity and either subject age or postmortem delay. Western blotting revealed no significant differences in Gs alpha and Gi alpha levels between control and suicide cases. However, levels of the smaller Gs alpha isoform (Gs alpha-S) showed a tendency to be increased in the violent death suicide and depressed suicide subgroups, compared to controls. Levels of the larger Gs alpha isoform (Gs alpha-L) showed a significant positive correlation with subject age. Gi alpha levels showed a significant negative correlation with subject age and a positive correlation with postmortem delay. These results support the hypothesis that suicidal behaviour and depressive illness may be associated with an altered regulation of adenylyl cyclase.

Adenylyl Cyclases↗
PubMed1994

The significance of the Swedish APP670/671 mutation for the development of Alzheimer's disease amyloidosis.

Alzheimer's disease is characterized histopathologically by the detection of amyloid plaques and tangles in the brains of its victims. A major component of the amyloid plaques, the beta-amyloid peptide, is a metabolite of a larger transmembrane protein termed the amyloid precursor protein (APP). Several pathogenic mutations causing Alzheimer's disease have been identified in the APP gene, situated on chromosome 21. One of these is a double missense mutation in exon 16 of the APP gene which occurs in a large Swedish pedigree. Studies with transfected cell cultures have shown that cells expressing this double mutation release approximately 7 times more beta-amyloid than their wild type counterparts. Possible mechanisms whereby the APP mutations cause Alzheimer's disease are considered here against the background of current understanding of the physiological role and processing of APP.

Alzheimer Disease↗
PubMed1994

Subzonal insertion of multiple sperm is a treatment for male factor infertility.

OBJECTIVE: To determine whether subzonal insemination of multiple sperm is an effective treatment for male factor infertility. DESIGN: Subzonal insemination by micromanipulation of sperm and oocytes for male factor patients. PATIENTS: Two hundred eight patients were selected on previous fertilization history and/or semen parameters. They could be assigned to one of three groups: group A had previous IVF failure, group B had a low fertilization rate with previous IVF, and group C had insufficient sperm for IVF. INTERVENTIONS: Oocytes were inseminated by subzonal insertion of multiple sperm. MAIN OUTCOME MEASURES: Fertilization and pregnancy rates. RESULTS: There have been 208 patients treated through 332 treatment cycles. Of 2,789 oocytes inseminated, 784 oocytes were fertilized (28%) and 516 of these (66%) were monospermic. This represents normal fertilization in 207 cycles (62% of total patient cycles). These 207 cycles produced an average of 2.6 +/- 1.8 embryos. The resultant 487 embryos were either transferred or cryopreserved for future transfer. A total of 42 pregnancies (21% per ET) resulted from 200 ET procedures with 397 embryos. Miscarriages or elective terminations have occurred (11/42 pregnancies, 26% to date) and 21 deliveries have resulted in 26 babies. There are nine ongoing pregnancies. Three of the pregnancies have been from cryopreserved embryos. Group B patients had the highest fertilization rate (23%) but the lowest pregnancy rate (7%). No other significant relationships between patient group and outcome were found. CONCLUSIONS: Subzonal insemination of multiple sperm is an effective treatment for some forms of male factor infertility.

Embryo Transfer↗
PubMed1994

Short-term corticosteroid treatment does not improve implantation for embryos derived from subzonal insertion of sperm.

A total of 111 patients undergoing treatment for male factor infertility using SUZI participated in the trial for one treatment cycle only. They were allocated to have either corticosteroid treatment to induce immunosuppression or placebo. An elevated beta-hCG was found in 25% (9 of 36) of patients having an ET and receiving treatment. The corresponding figure for the control group was 33% (10 of 30). On ultrasound examination, fetal hearts were found in 22% (8 of 36) and 20% (6 of 30), respectively, of patients having an ET. chi 2 analysis showed no difference in the results. When the results were analyzed on a per oocyte basis there was no significant difference in the implantation rate.

Embryo Implantation↗
PubMed1994

Injection of multiple sperm into the perivitelline space as a treatment of male infertility.

This paper reports the outcome of 274 treatment cycles using multiple injection of sperm into the perivitelline space as a treatment of male factor infertility. A total of 170 couples underwent this form of treatment; 59.1% of cycles had at least one oocyte normally fertilized with an overall normal fertilization rate of 17.2%. The development rate of normally fertilized embryos was high (98.5%) and resulted in a pregnancy rate (positive human chorionic gonadotrophin 18 days after embryo transfer) of 21.4% per embryo transfer procedure (a maximum of 3 embryos were transferred per procedure). The relationship between the number of sperm injected and the fertilization rate and other factors affecting the outcome are discussed.

Female↗
PubMed1994

The biochemistry of prostaglandins: a primer.

The membranes of cells serve to endow structural integrity, compartmentalize regions of the cell and allow the generation of a stable intracellular milieu. The lipid component of the membrane forms a matrix for structurally and functionally important proteins. It is also increasingly obvious that these lipids form substrates for the synthesis of a range of molecules which have a central role in cellular communication and regulation. The prostaglandins were the first class of such molecules described and to some extent may serve as an archetype for an understanding of the various classes of lipid mediators. The release of arachidonic acid from lipids (phospholipids in particular) is achieved by lipases (phospholipase A2). Arachidonic acid itself may act directly on cells to modify function. For instance, it may modulate ion channel function. However, it is more often a substrate for cyclooxygenase which produces prostaglandin H2, being the precursor for further prostaglandin and thromboxane synthesis, or for lipoxygenase, to produce the precursor for leukotrienes (a related class of mediators). The prostaglandins may act intracellularly, are readily released from cells to act in an autocrine or paracrine fashion, and may enter the blood vessels or lymphatics to exert endocrine effects. Target cells may contain receptors with relative specificity for various members of the prostaglandin family, thus eliciting some specificity of action by the mediators.

Arachidonic Acid↗
PubMed1994

Detection and preliminary characterization of two enzymes involved in biosynthesis of platelet-activating factor in mouse oocytes, zygotes and preimplantation embryos: dithiothreitol-insensitive cytidinediphosphocholine: 1-O-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase and acetyl-coenzyme A:1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyltransferase.

The aim of this study was to determine whether the final enzymes in the two biosynthetic pathways for platelet-activating factor (PAF) (the 'de novo' and the 'membrane remodelling' pathways) are present in mouse embryos, zygotes and oocytes. The enzymes are dithiothreitol-insensitive cytidinediphosphocholine: 1-O-alkyl-2-acetyl-sn-glycerol cholinephosphotransferase (cholinephosphotransferase) in the de novo pathway and acetyl-coenzyme A:1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyltransferase (acetyltransferase) in the membrane remodelling pathway. Activity of both enzymes was detected in the unfertilized oocyte, the zygote and also in the preimplantation embryo (48, 72 and 96 h after the ovulatory injection of hCG). In both cases the activity was destroyed by boiling and increased linearly with incubation time and the concentration of embryo homogenate present, indicating that the reactions were catalysed by enzymes. The product of the reactions was confirmed as PAF using HPLC and structural analyses by enzymatic digestion. Cholinephosphotransferase required Mg2+ and was inhibited by Ca2+, while acetyltransferase required the presence of NaF (a phosphatase inhibitor). The activity of cholinephosphotransferase was similar in unfertilized oocytes and zygotes, and did not change significantly with advancing developmental stage in preimplantation embryos. Acetyltransferase had a significantly lower specific activity (0.078 +/- 0.044 fmol PAF per oocyte per min, mean +/- SEM) in unfertilized oocytes than in zygotes of corresponding age (0.358 +/- 0.097 fmol PAF per zygote per min) (P < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyltransferases↗
PubMed1994

Lipoic and dihydrolipoic acids as antioxidants. A critical evaluation.

A detailed evaluation of the antioxidant and pro-oxidant properties of lipoic acid (LA) and dihydrolipoic acid (DHLA) was performed. Both compounds are powerful scavengers of hypochlorous acid, able to protect alpha 1-antiproteinase against inactivation by HOCl. LA was a powerful scavenger of hydroxyl radicals (OH.) and could inhibit both iron-dependent OH. generation and peroxidation of ox-brain phospholipid liposomes in the presence of FeCl3-ascorbate, presumably by binding iron ions and rendering them redox-inactive. By contrast, DHLA accelerated iron-dependent OH. generation and lipid peroxidation, probably by reducing Fe3+ to Fe2+. LA inhibited this pro-oxidant action of DHLA. However, DHLA did not accelerate DNA degradation by a ferric bleomycin complex and slightly inhibited peroxidation of arachidonic acid by the myoglobin-H2O2 system. Under certain circumstances, DHLA accelerated the loss of activity of alpha-antiproteinase exposed to ionizing radiation under a N2O/O2 atmosphere and also the loss of creatine kinase activity in human plasma exposed to gas-phase cigarette smoke. Neither LA nor DHLA reacted with superoxide radical (O.2-) or H2O2 at significant rates, but both were good scavengers of trichloromethylperoxyl radical (CCl3O2.). We conclude that LA and DHLA have powerful antioxidant properties. However, DHLA can also exert pro-oxidant properties, both by its iron ion-reducing ability and probably by its ability to generate reactive sulphur-containing radicals that can damage certain proteins, such as alpha 1-antiproteinase and creatine kinase.

Animals↗
PubMed1994

The OXCHECK Study: a nursing perspective. Oxford and Collaborators Health Check.

The Oxford and Collaborators Health CHECK Trial (OXCHECK) was a randomized controlled trial of the effectiveness of nurse-administered health checks in the general practice setting. It was designed primarily to influence risk factors for cardiovascular disease and cancer. The fourth and final year has now been completed, and the data analysis on over 8,100 health checks is under way. The findings from Year I have not been very encouraging in terms of lifestyle changes in moderate risk groups. This article briefly describes the design and methodology of the project, but mainly focuses on the practical issues involved in performing the health checks and on how the nurses and patients have felt about participating in the project. Much has happened to general practice, health promotion and the economy since the inception of OXCHECK in 1988. The OXCHECK nurses have experienced a variety of responses and attitudes from patients. These are significant insomuch as they may provide a rationale for designing alternative methods of assessing lifestyle change and individuals' perception of risk. The importance of providing a strong link between the academic department involved in the project and the local clinical practices will be discussed in the context of other key facilitating roles. However, the appropriateness of promoting certain preventive measures in the general practice setting can also be questioned.

Adult↗
PubMed1994

Morphometric evidence of changes in the vasculature of the uterine tube of mice induced by the 2-cell embryo on the second day of pregnancy.

Some evidence suggests that the uterine tube plays an active role in supporting the development of the preimplantation embryo. To determine whether there were morphological and/or ultrastructural changes in the uterine tube as a consequence of pregnancy, the region of the uterine tube containing 2-cell embryos or oocytes was examined in untreated d 2 pregnant and pseudopregnant mice. The general morphology of the uterine tube was assessed by light and electron microscopy. Qualitative assessment of uterine tube morphology suggested that although the epithelium and muscular layers of the oviduct were similar in pregnancy and pseudopregnancy there were differences in the vasculature between the 2 groups. In transverse sections of the uterine tube, cross-sectional vascular surface area was assessed morphometrically. There was a statistically significant decrease (P < 0.001) in the cross-sectional vascular surface of the oviduct in pregnant mice compared with pseudopregnant mice. This reduction was apparently due to (1) a decrease in the median cross-sectional surface area of small intramural blood vessels, and (2) an apparent collapse of many subepithelial capillaries. Pregnant mice also had fewer fenestrated capillaries whereas such vessels were common in pseudopregnancy. Activated, aggregated platelets were only observed in the capillaries and venules of pregnant, untreated mice. Some animals were treated with 10 micrograms WEB 2086/day on d 1 and d 2, a platelet-activating factor receptor antagonist. This treatment reversed the reduced vascular surface cross-sectional area found in early pregnancy, but had no effect on vascular measurements in pseudopregnancy.

Animals↗
PubMed1993

Long-term follow-up of patients with invasive fungal disease who received adjunctive therapy with recombinant human macrophage colony-stimulating factor.

Mortality of bone marrow transplant (BMT) patients who develop invasive fungal infection is greater than 80%. Long-term follow-up of 46 consecutive BMT patients who received recombinant human macrophage colony-stimulating factor (rhM-CSF) as adjunctive therapy with standard antifungal treatment who were entered into phase I/II trials at The Fred Hutchinson Cancer Research Center is reported. rhM-CSF (100 micrograms/m2 to 2,000 micrograms/m2; Chiron/Cetus Corporation, Emeryville, CA) was administered from day 0 to 28 after determination of progressive fungal disease. Results of long-term follow-up of fungal infection, relapse, and survival were compared with 58 similar historical controls. Multivariable analysis of the patients who received rhM-CSF showed two factors that significantly correlated with poor survival: Karnofsky score < or = 20% and Aspergillus infection. Overall, survival of patients who received rhM-CSF was greater than that of historical patients (27% v 5%) and was entirely because of a 50% survival rate in patients with Candida infection and Karnofsky scores greater than 20%. Prospective, randomized, controlled trials to determine efficiency of rhM-CSF are indicated and should be directed at patients with invasive candidiasis.

Adult↗
PubMed1993

Disrupted beta 1-adrenoceptor-G protein coupling in the temporal cortex of patients with Alzheimer's disease.

The efficacy of beta 1-adrenoceptor-G protein coupling was studied in postmortem temporal cortex synaptic membranes from a series of control and Alzheimer's disease subjects. For the control cases, the non-hydrolysable GTP analogue 5'-guanylylimidodiphosphate (Gpp[NH]p) gave a significant reduction in the affinity of the agonist isoprenaline to displace binding of the radiolabelled antagonist (+/)-4-(3-t-butylamino-2-hydroxypropoxy)[5,7-3H]benzimidazol-2-one ([3H]CGP-12177). This effect was attributed to the conversion of high agonist-affinity sites to a lower-affinity state and was not found for the Alzheimer's disease cases. These data indicate that a disruption of beta 1-adrenoceptor-G protein coupling occurs in the temporal cortex of Alzheimer's disease patients.

Aged↗