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Biomedical subjects

P Perry

Publications and source records attributed to P Perry.

At least 37 records · Page 2Linked to original sources
PubMed1994

Unusual chromosome structure of fission yeast DNA in mouse cells.

Chromosomes from the fission yeast Schizosaccharomyces pombe have been introduced into mouse cells by protoplast fusion. In most cell lines the yeast DNA integrates into a single site within a mouse chromosome and results in striking chromosome morphology at metaphase. Both light and electron microscopy show that the yeast chromosome region is narrower than the flanking mouse DNA. Regions of the yeast insert stain less intensely with propidium iodide than surrounding DNA and bear a morphological resemblance to fragile sites. We investigate the composition of the yeast transgenomes and the modification and chromatin structure of this yeast DNA in mouse cells. We suggest that the underlying basis for the structure we see lies above the level of DNA modification and nucleosome assembly, and may reflect the attachment of the yeast DNA to the rodent cell nucleoskeleton. The yeast integrant replicates late in S phase at a time when G bands of the mouse chromosomes are being replicated, and participates in sister chromatid exchanges at a high frequency. We discuss the implications of these studies to the understanding of how chromatin folding relates to metaphase chromosome morphology and how large stretches of foreign DNA behave when introduced into mammalian cells.

Anaphase↗
PubMed1993

The frequency of micronuclei in bone-marrow erythroblasts during the treatment of childhood acute lymphoblastic leukaemia.

We scored the frequency of micronuclei in bone-marrow erythroblasts from 41 patients with childhood acute lymphoblastic leukaemia (childhood ALL) at diagnosis and during their 2-year treatment cycle in order to see whether there would be any variation in the cytogenetic damage induced by chemotherapy. We found that most patients showed the same trend in micronucleus frequency, with a progressive rise from the diagnostic slide through induction to pre-intensification and completion of treatment. The rise was attributed to damage to the erythroblasts occurring as a result of chemotherapy, and was judged not prognostically significant in this study.

Adolescent↗
PubMed1992

ELISA test, a new method to detect and quantify isoproturon in soil.

An indirect competitive Enzyme-Linked ImmunoSorbent Assay (ELISA) has been developed to quantify isoproturon (a commonly used phenylurea herbicide) in soil samples. To produce the specific antibodies needed for detection of isoproturon, an isopropylanilin analogue was covalently linked to a proteic carrier and the resulting conjugate used as immunogen. Hybridomas were obtained from spleen cells of mice immunized with this conjugate. One specific monoclonal antibody (MAb) was selected and used to the ELISA allowing the detection of small amounts of herbicide (20-250 micrograms l-1). Cross-reactivities with other current phenylureas appear to be insignificant. Samples of six soils were mixed with several quantities of herbicide (to reach final concentrations ranging between 0.15 and 1 microgram g-1) and extracted either with methanol to determine the total residue or with a solution of CaCl2, to establish the herbicide available from the soil solution. The extracts were analyzed simultaneously by gas chromatography and ELISA in these conditions, correlation coefficients between both methods were never lower than 93.5%. Organic matter and ionic strength appeared to be the most important parameters interfering the ELISA test. To avoid these drawbacks, standard curves were established for the ELISA by spiking isoproturonless soils extracts. In these conditions, correlations between both methods were considered as sufficient. ELISA of untreated samples were carried out to verify the isoproturon availability curves established previously.

Antibodies, Monoclonal↗
PubMed1992

Antibodies to defined histone epitopes reveal variations in chromatin conformation and underacetylation of centric heterochromatin in human metaphase chromosomes.

Unfixed metaphase chromosome preparations from human lymphocyte cultures were immunofluorescently labelled using antibodies to defined histone epitopes. Both mouse monoclonal antibody HBC-7, raised against the N-terminal region of H2B, and rabbit serum R5/12, which recognizes H4 acetylated at Lys-12, gave non-uniform labelling patterns, whereas control antibodies against total histone fractions H4 and H1 produced homogeneous fluorescence. HBC-7 bound approximately uniformly to the bulk of the chromosomes, but the major heterochromatic domains of chromosomes 1, 9, 15, 16 and the Y showed significantly brighter fluorescence. Serum R5/12 indicated an overall reduction in acetylation of H4 in metaphase chromosomes compared with interphase nuclei, although some specific chromosomal locations had considerably elevated acetylation levels. Acetylation levels in the major heterochromatic domains appeared extremely low. To investigate further the differences noted in heterochromatin labelling, metaphases from cultures grown in the presence of various agents known to induce undercondensation of the major heterochromatic domains were similarly immunolabelled. Decondensed heterochromatin no longer exhibited higher than normal immunofluorescence levels with HBC-7. The higher resolution afforded by "stretching" the centromeric heterochromatin of chromosomes 1, 9 and 16 confirmed the low level of H4 acetylation in these domains. We consider the implications of these observations in relation to chromatin conformation and activity.

Acetylation↗
PubMed1992

Transactivation of the major capsid protein gene of herpes simplex virus type 1 requires a cellular transcription factor.

The purpose of this investigation was to identify and characterize the regulatory elements involved in the transcriptional activation of the beta gamma (leaky-late or gamma 1) genes of herpes simplex virus type 1 (HSV-1) by using the major capsid protein (VP5 or ICP5) gene as model. Gel mobility shift assays with nuclear extracts from uninfected and infected HeLa cells enabled us to identify two major protein-DNA complexes involving the VP5 promoter. The mobilities of these two complexes remained unaltered, and no unique complexes were observed when infected cell nuclear extracts were used. DNase I and orthophenanthroline-Cu+ footprint analyses revealed that the two complexes involve a single binding site, GGCCATCTTGAA, located between -64 and -75 bp relative to the VP5 cap site. To determine the function of this leaky-late binding site (LBS) in VP5 gene activation, we tested the effect of mutations in this region by using transient expression of a cis-linked chloramphenicol acetyltransferase gene. Deletion of the above sequence resulted in a seven- to eightfold reduction in the level of transactivation of the chloramphenicol acetyltransferase gene by superinfection with HSV-1 or by cotransfection of HSV-1 immediate-early genes. From these results, we conclude that the LBS sequence and a cellular factor(s) are involved in the transactivation of the VP5 gene. A search of published gene sequences revealed that sequences related to the LBS exist in a number of other HSV-1, cytomegalovirus, retrovirus, and cellular promoters. Sequence homologies of binding sites and results of unpublished competition binding studies suggest that this leaky-late binding factor may be related to, or the same as, a ubiquitous cellular transcriptional factor called YY1 or common factor-1 (also known as NF-E1, delta, and UCRBP).

Base Sequence↗
PubMed1992

Infantile hypertrophic pyloric stenosis.

This is a world-wide disease, more common in Caucasians and probably on the increase. The aetiology remains very poorly understood. Presentation is between 2 and 8 weeks with vomiting, classically projectile, in an otherwise well hungry child. The diagnosis can confidently be made in most cases by a careful test feed; ultrasound and barium meal examinations are only required for difficult cases. Intravenous fluid replacement is essential prior to surgery and 24 h or longer may be required to correct acid base disturbances and enable safe general anaesthesia. Pyloromyotomy (Ramstedt's operation) remains the only satisfactory treatment, our mortality rate for this is 0.4%. Occasional vomits occur postoperatively in over half of patients but we are sceptical of the value of graded postoperative feeding regimens. There are no known long-term sequelae to surgery and this remains a most rewarding paediatric surgical condition to treat.

Age Factors↗
PubMed1990

Human keratinocytes are a source for tumor necrosis factor alpha: evidence for synthesis and release upon stimulation with endotoxin or ultraviolet light.

Tumor necrosis factor alpha (TNF-alpha), in addition to being cytotoxic for certain tumor cells, has turned out as a multifunctional cytokine that is involved in the regulation of immunity and inflammation. Since human keratinocytes have been demonstrated to be a potent source of various cytokines, it was investigated whether epidermal cells synthesize and release TNF-alpha. Supernatants derived from normal human keratinocytes (HNK) and human epidermoid carcinoma cell lines (KB, A431) were tested both in a TNF-alpha-specific ELISA and a bioassay. In supernatants of untreated epidermal cells, no or minimal TNF-alpha activity was found, while after stimulation with lipopolysaccharide (LPS) or ultraviolet (UV) light, significant amounts were detected. Western blot analysis using an antibody directed against human TNF-alpha revealed a molecular mass of 17 kD for keratinocyte-derived TNF-alpha. These biological and biochemical data were also confirmed by Northern blot analysis revealing mRNA specific for TNF-alpha in LPS- or ultraviolet B (UVB)-treated HNK and KB cells. In addition, increased TNF-alpha levels were detected in the serum obtained from human volunteers 12 and 24 h after a single total body UVB exposure, which caused a severe sunburn reaction. These findings indicate that keratinocytes upon stimulation are able to synthesize and release TNF-alpha, which may gain access to the circulation. Thus, TNF-alpha in concert with other epidermal cell-derived cytokines may mediate local and systemic inflammatory reactions during host defense against injurious events caused by microbial agents or UV irradiation.

Blotting, Northern↗
PubMed1990

Cytokine modulation of keratinocyte cytokines.

There is increasing evidence that epidermal cytokines may have an important role in mediating inflammatory and immune responses in the skin. A number of cell types in the epidermis are capable of secreting cytokines including keratinocytes, Langerhans cells, melanocytic cells, and even Merkle cells. Keratinocytes are the major source of cytokines in the epidermis and have been reported to secrete IL-1, IL-3, IL-6, IL-8, CSF, TNF alpha, TGF alpha, TGF beta, and PDGF. Normally these cytokines are not actively secreted by keratinocytes; however, a number of agents are capable of mediating keratinocyte cytokine production, including cytokines themselves. We examined the effect of a number of cytokines on keratinocyte IL-1, IL-6, GM-CSF, and PDGF production. It was found that these keratinocyte cytokines are all modulated by one or more cytokines, including several that keratinocytes themselves secrete. These effects appear to be mediated by high-affinity cytokine receptors on keratinocytes. We are only beginning to understand the molecular mechanisms underlying the production, regulation, and precise role of keratinocyte cytokines in normal and diseased skin; however, recent studies suggest that cytokines secreted by epidermal cells and lymphoid cells may be important modulators of keratinocyte cytokine production.

Animals↗
PubMed1990

Maintenance treatment with antidepressants in panic disorder.

Because panic disorder is a chronic illness, patients may require long-term pharmacologic treatment. Unfortunately, the benefits and risks of such therapy have received little study. At least two classes of antidepressants, the tricyclic antidepressants and the monoamine oxidase inhibitors, are effective for the treatment of panic disorder, but because relapse is common when these drugs are discontinued, many patients require maintenance treatment. However, such long-term use of tricyclic antidepressants and monoamine oxidase inhibitors exposes patients to risks that include potentially fatal overdoses and hypertensive crises. Patients should be aware of the risks involved and should weigh them against the benefits of long-term use. They should reduce the dose to the lowest effective level, from time to time gradually taper medications to assess continuing need, and avail themselves of other therapies rather than rely solely on drug treatment. Above all, more research should be done on the long-term risks and benefits of antidepressant drugs.

Agoraphobia↗
PubMed1990

Instruction on Piagetian concepts for children with mental retardation.

Eighteen children with mild mental retardation were pretested on unidimensional classification (oddity), unidimensional seriation, number conservation, Slosson's Intelligence Test, and the Peabody Picture Vocabulary Test (PPVT). The children were instructed on the Piagetian concepts twice per week for 4 months via a learning-set technique. All 315 problems (except 20 verbal classification and 15 verbal seriation items) involved concrete items. When posttested at the semester's end, the children had, with few exceptions, mastered the Piagetian concepts and made significant gains on performance on the PPVT.

Adolescent↗
PubMed1989

Recombinant human erythropoietin treatment in pre-dialysis patients. A double-blind placebo-controlled trial.

STUDY OBJECTIVE: To determine the efficacy and safety of recombinant human erythropoietin (r-HuEPO) in predialysis renal patients. DESIGN: Randomized, double-blind, placebo-controlled trial for 8 weeks. SETTING: Inpatient and outpatient facility in the Clinical Research Center of a university-based hospital. PATIENTS: Fourteen adult subjects with renal insufficiency (mean serum creatinine, 473 mumol/L +/- 61 [6.2 +/- 0.8 mg/dL]) and anemia (mean hematocrit, 0.27 +/- 0.01). INTERVENTIONS: Recombinant human erythropoietin, 50, 100, or 150 IU/kg body weight or placebo given intravenously three times per week. MEASUREMENTS AND MAIN RESULTS: Subjects who received active r-HuEPO showed a dose-dependent rise in hematocrit; mean hematocrit increased 41% from 0.27 +/- 0.01 to 0.38 +/- 0.01. At the same time, erythrocyte mass rose 43% from 13.7 +/- 0.6 mL/kg in the baseline state to 19.6 +/- 1.0 mL/kg after treatment. Maximal oxygen consumption during exercise increased 9% from 16.0 mL/min.kg +/- 1.8 to 17.5 mL/min.kg +/- 1.9. CONCLUSIONS: Recombinant human erythropoietin is effective and safe in ameliorating the anemia of pre-dialysis patients.

Adult↗