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Biomedical subjects

D Harris

Publications and source records attributed to D Harris.

At least 109 records · Page 6Linked to original sources
PubMed1998

Thrombopoietin stimulates myelodysplastic syndrome granulocyte-macrophage and erythroid progenitor proliferation.

Thrombopoietin (TPO) has been successfully used to stimulate megakaryocyte progenitor proliferation and platelet production both in vitro and in vivo. We and other investigators have found that TPO also stimulates normal marrow colony-forming unit granulocyte-macrophage (CFU-GM) and burst-forming unit-erythroid (BFU-E) growth. In contrast to its effect on normal marrow precursors, TPO stimulates acute myelogenous leukemia (AML) progenitor proliferation in only 25% of the cases. Because the hematopoietic cells in Myelodysplastic syndrome (MDS) originate from both the normal and leukemic clones, we hypothesized that TPO may be a useful therapeutic agent for MDS. To test this hypothesis, we used fresh marrow samples taken from 14 MDS patients. We found that in the presence of fetal calf serum (FCS) and erythropoietin (EPO) TPO (5 to 40 ng/ml) MDS CFU-GM and BFU-E colony-forming cell proliferation were stimulated in a dose-dependent fashion by up to 103% and 93% respectively. This effect was similar to the stimulation obtained with optimal concentrations of granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage CSF (GM-CSF), or interleukin-3 (IL-3). Furthermore, TPO increased the colony-stimulatory effects of G-CSF, GM-CSF, IL-3, and stem cell factor (SCF) on MDS marrow cells. However, depletion of either T lymphocytes or adherent cells abrogated the effect of TPO, suggesting that the effect is not a direct one but is mediated through interaction with cytokines produced by accessory cells. Taken together, our data suggest that the therapeutic role of TPO in the management of MDS warrants further investigation.

Aged↗
PubMed1997

Role of glutamine-151 of human immunodeficiency virus type-1 reverse transcriptase in RNA-directed DNA synthesis.

Glutamine-151 of HIV-1 RT has been shown to be a catalytically important residue through the characterization of its mutant phenotype Glu151Ala (Sarafianos et al., 1995a). To further understand the role of this residue, we have extended this analysis to include polymerization on natural RNA template in addition to DNA template. We find that Q151A mutant exhibited a severe reduction in the polymerase activity without any significant effect on the affinity for dNTP substrate. Unlike DNA-directed reactions, the rate-limiting step for RNA-directed reactions does not appear to be either at the dNTP binding step or the chemical step. Analysis of the products formed on natural heteromeric HIV-genomic RNA template annealed with an 18-mer DNA primer with a sequence complementary to the primer binding site (PBS) has shown that addition of nucleotides is nonlinear with time since the enzyme appears to stall on the RNA template following the incorporation of the first nucleotide. The Q151A mutant was found to be nearly devoid of pyrophosphorolytic activity on a RNA-PBS template-primer. Similar properties have been previously reported for a mutant of R72 (R72A) of HIV-1 RT (Sarafianos et al., 1995b). However, R72 was implicated in stabilizing the transition state ternary complex before and after the phosphodiester bond formation (Kaushik et al., 1996; Sarafianos et al., 1995b). Our results with Q151A suggest that the side chain of Q151 may help stabilize the side chain of R72, and the loss of pyrophosphorolysis activity observed with the Q151 mutant may be the indirect manifestation of this stabilizing effect on R72. These observations point to the functional interdependence of residues Q151 and R72 in the polymerase function of the enzyme. An analysis of the 3D model structure of HIV-1 RT bound to DNA-DNA and RNA-DNA template-primer reveals that the guanidine hydrogen of R72 seems to stabilize Q151 by hydrogen bonding with its amide oxygen. A systematic conformational search of the side chain of Q151 also suggests a stable orientation where its specific interaction with the base of the RNA template may aid in stabilizing it.

Amino Acid Sequence↗
PubMed1997

1,25-Dihydroxyvitamin D3 and its analogues inhibit acute myelogenous leukemia progenitor proliferation by suppressing interleukin-1beta production.

We hypothesized that 1,25-dihydroxyvitamin D3 (1,25D3) and its analogues may inhibit acute myelogenous leukemia (AML) proliferation by interrupting IL-1beta-mediated growth-stimulatory signals. The incubation of the IL-1beta- responsive AML cell line OCIM2 with 10 nM 1,25D3 reduced growth 80% in liquid culture, and a 100-1000-fold lower concentration of 20-epi analogues (MC1288 and MC1301) was sufficient to achieve similar growth inhibition. The growth inhibition was associated with a rapid but transient downregulation of IL-1beta and IL-1beta-converting enzyme (ICE) mRNAs in 1,25D3- and 20-epi analogue- treated cells, and the 20-epi analogue was more effective than 1,25D3 in repressing ICE expression. An examination of long-term changes in the levels of mature IL-1beta and its precursor revealed that 24-h incubation of OCIM2 with either 1,25D3 or its 20-epi analogues abolished the production of mature IL-1beta. The effect of 1,25D3 and its analogues on growth of fresh bone marrow cells from seven AML patients was tested by a clonogenic assay. Growth inhibition of 60% was reached in only one of seven 1,25D3-treated samples, but all seven samples were inhibited 60-90% by the 20-epi analogue MC1301. Growth inhibition by 1,25D3 and the analogue was reversible by addition of IL-1beta. These results suggest that 1,25D3 and its 20-epi analogues interrupt IL-1beta autocrine growth regulation by inhibiting IL-1beta production and processing but not the response to IL-1beta.

Antineoplastic Agents↗
PubMed1997

Structural analysis of the Trichodesmium nitrogenase iron protein: implications for aerobic nitrogen fixation activity.

Trichodesmium spp. are marine filamentous nitrogen-fixing cyanobacteria which play an important role in the nitrogen budget of the open ocean. Trichodesmium is unique in that it is nonheterocystous and fixes nitrogen during the day, while evolving oxygen through photosynthesis, even though nitrogenase is sensitive to oxygen inactivation. The sequence of the gene encoding the Fe protein component of nitrogenase from the recently cultivated isolate Trichodesmium sp. IMS 101 was used to construct a 3-dimensional model of the Fe protein, by comparison to the X-ray crystallographic structure of the Fe protein of the gamma-proteobacterium Azotobacter vinelandii. The primary differences in amino acid sequences of the Fe protein from diverse organisms do not impact the critical structural features of the Fe protein. It can be concluded that aerobic nitrogen fixation in Trichodesmium spp. is not facilitated by unique structural features of Trichodesmium Fe protein.

Aerobiosis↗
PubMed1997

The nucleotide sequence of Saccharomyces cerevisiae chromosome IX.

Large-scale systematic sequencing has generally depended on the availability of an ordered library of large-insert bacterial or viral genomic clones for the organism under study. The generation of these large insert libraries, and the location of each clone on a genome map, is a laborious and time-consuming process. In an effort to overcome these problems, several groups have successfully demonstrated the viability of the whole-genome random 'shotgun' method in large-scale sequencing of both viruses and prokaryotes. Here we report the sequence of Saccharomyces cerevisiae chromosome IX, determined in part by a whole-chromosome 'shotgun', and describe the particular difficulties encountered in the random 'shotgun' sequencing of an entire eukaryotic chromosome. Analysis of this sequence shows that chromosome IX contains 221 open reading frames (ORFs), of which approximately 30% have been sequenced previously. This chromosome shows features typical of a small Saccharomyces cerevisiae chromosome.

Base Composition↗
PubMed1997

Differential activation of protein kinase C delta and epsilon gene expression by gonadotropin-releasing hormone in alphaT3-1 cells. Autoregulation by protein kinase C.

The effect of gonadotropin-releasing hormone (GnRH) upon protein kinase C (PKC) delta and PKCepsilon gene expression was investigated in the gonadotroph-derived alphaT3-1 cell line. Stimulation of the cells with a stable analog [D-Trp6]GnRH (GnRH-A) resulted in a rapid elevation of PKCepsilon mRNA levels (1 h), while PKCdelta mRNA levels were elevated only after 24 h of incubation. The rapid elevation of PKCepsilon mRNA by GnRH-A was blocked by pretreatment with a GnRH antagonist or actinomycin D. The PKC activator 12-O-tetradecanoylphorbol-13-acetate (TPA), but not the Ca2+ ionophore ionomycin, mimicked the rapid effect of GnRH-A upon PKCepsilon mRNA elevation. Additionally, the rapid stimulatory effect of GnRH-A was blocked by the selective PKC inhibitor GF109203X, by TPA-mediated down-regulation of endogenous PKC, or by Ca2+ removal. Interestingly, serum-starvation (24 h) advanced the stimulation of PKCdelta mRNA levels by GnRH-A and the effect could be detected at 1 h of incubation. The rapid effect of GnRH-A upon PKCdelta mRNA levels in serum-starved cells was mimicked by TPA, but not by ionomycin, and was abolished by down-regulation of PKC or by Ca2+ removal. Preactivation of alphaT3-1 cells with GnRH-A for 1 h followed by removal of ligand and serum resulted in elevation of PKCdelta mRNA levels after 24 h of incubation. Western blot analysis revealed that GnRH-A and TPA stimulated (within 5 min) the activation and some degradation of PKCdelta and PKCepsilon. We conclude that Ca2+ and PKC are involved in GnRH-A elevation of PKCdelta and PKCepsilon mRNA levels, with Ca2+ being necessary but not sufficient, while PKC is both necessary and sufficient to mediate the GnRH-A response. A serum factor masks PKCdelta but not PKCepsilon mRNA elevation by GnRH-A, and its removal exposes preactivation of PKCdelta mRNA by GnRH-A which can be memorized for 24 h. PKCdelta and PKCepsilon gene expression evoked by GnRH-A is autoregulated by PKC, and both isotypes might participate in the neurohormone action.

Animals↗
PubMed1997

Structural magnetic resonance imaging abnormalities in men with severe chronic schizophrenia and an early age at clinical onset.

BACKGROUND: Early age at onset of schizophrenia often signifies a more severe form of the illness. However, the relationship between age at onset and brain abnormalities has not been established. We assessed temporal-limbic morphometry in severely ill men with chronic schizophrenia who had a relatively early onset of illness and examined the relationships among regional brain volumes, clinical symptoms, and age at illness onset. METHOD: Temporal lobe, superior temporal gyrus, hippocampus, temporal horn, lateral ventricles, third ventricle, and frontoparietal volumes were measured on magnetic resonance imaging data from 56 schizophrenic men (mean [SD] age at illness onset, 16.6 [4.2] years) recruited from a state hospital and 52 age- and range-matched healthy control men. RESULTS: Patients had significantly smaller gray matter volumes in the temporal lobe, superior temporal gyrus, and frontoparietal regions; smaller temporal lobe white matter volumes; and larger cerebrospinal fluid volumes for temporal lobe sulci and the 3 ventricular measures. There were no group differences in hippocampal volumes. Psychotic symptom subscores from the Brief Psychiatric Rating Scale were selectively correlated with smaller left posterior superior temporal gyrus gray matter volumes. None of the brain measurements were significantly correlated with age at illness onset. CONCLUSIONS: Data from this unique sample of severely ill schizophrenic men emphasize a pattern of structural abnormalities involving the cortex, but not the hippocampus, in schizophrenia. Furthermore, these data support theories suggesting that superior temporal gyrus abnormalities contribute selectively to psychotic symptoms and that the extent of structural abnormalities is unrelated to age of clinical symptom onset.

Adolescent↗
PubMed1997

Presence of mature sperm in testicular parenchyma of men with nonobstructive azoospermia: prevalence and predictive factors.

OBJECTIVES: Hitherto, patients with testicular dysfunction and azoospermia had to resort to adoption, donor sperm insemination, or child-free living. The realization that a proportion of such men harbor spermatozoa in their testicular parenchyma, combined with the ability of intracytoplasmic sperm injection (ICSI) to effect pregnancy with single sperm, has prompted male infertility clinicians to explore testicular sperm extraction (TESE) in this patient population. We sought to investigate the likelihood of finding spermatozoa during TESE from men presenting with nonobstructive azoospermia and to define if any factors existed that were predictive of eventual sperm presence or absence. METHODS: Thirty patients with nonobstructive azoospermia underwent TESE and simultaneous formal testis biopsy, cytologic analysis, and wet preparation analysis. Tissue obtained from TESE was analyzed according to a rigorous protocol, followed by exhaustive searching by trained embryologists. RESULTS: Twenty-one patients (70%) had spermatozoa found on testicular tissue analysis. Neither patient age nor follicle-stimulating hormone (FSH) level was predictive of the ability to find sperm. With regard to histologic pattern, 50% of men with Sertoli cell-only, 75% of patients with maturation arrest, and 100% of patients with spermatids seen on histologic analysis had sperm retrieved from their testicular tissue during TESE. Absence of sperm on cytologic smear and wet preparation analysis failed to predict the presence of sperm on formal testicular tissue analysis in 40% of patients. CONCLUSIONS: Men with nonobstructive azoospermia may have mature spermatozoa present within their testicular parenchyma. Relying on these data, patients should not be excluded from TESE based on serum FSH level, age, prior histopathologic pattern, or cytology/wet preparation results. These figures will allow clinicians to counsel patients with nonobstructive azoospermia informatively regarding TESE and their chances of having testicular sperm retrieved.

Adult↗
PubMed1997

Radiation therapy toxicities.

Since the infancy of radiology and radiation therapy, reactions to radiation have been noted and followed, and attempts have been made to minimize these reactions. We have turned to radiobiologists to explain these reactions and to radiation oncologists to prevent or decrease the normal tissue effects of radiation therapy. Radiation toxicities are divided into early (acute) and late (chronic) reactions; however, it is important to note that severe toxicities are rare and occur typically in less than 5% of veterinary radiation therapy patients.

Animals↗
PubMed1997

Radioresistance, chemoresistance, and apoptosis resistance. The past, present, and future.

A wide variety of cancer therapy resistance mechanisms are available, with perhaps surprising overlap between causes of chemotherapy and radiation resistance. As previously discussed, most of the widely used chemotherapeutic agents and gamma-radiation utilize apoptosis as the common death pathway, thereby making apoptosis and the ability to manipulate apoptosis of integral importance to the future of cancer therapy. This is evidenced by the information explosion on this topic in the last 5 years. Obviously much remains to be learned. However, with the aforementioned cooperation of the oncology team and a greater understanding of the molecular mechanisms behind cancer and cancer therapy resistance, response rates, survival times, the quality of life of patients enduring antineoplastic therapies, and the importance of comparative oncology can only increase. We look forward to the findings in the coming years on this incredibly clinically relevant topic with great fondness and uncertainty.

Animals↗
PubMed1997

Radiation oncology of head and neck tumors.

Malignant tumors of the head and neck region occur commonly in veterinary medicine. Unfortunately, tumors in the head and neck can cause treatment dilemmas because many neoplastic entities at this site are locally aggressive. Additional local therapies such as radiation therapy are becoming commonplace as standardized therapies for many head and neck tumors in veterinary medicine.

Animals↗
PubMed1997

Computer-controlled infusion of ORG 21465, a water soluble steroid i.v. anaesthetic agent, into human volunteers.

ORG 21465 has been found to possess anaesthetic properties in humans and its pharmacokinetics are known. We performed this study to confirm the characteristics associated with its administration and to define its pharmacodynamic profile, in particular to explore the relationship between sedation, anaesthesia, excitation and plasma drug concentrations. A water soluble preparation of ORG 21465 was administered to six male volunteers as a series of three 15-min computer-controlled, pharmacokinetic model-driven infusions targeting three exponentially increasing plasma concentrations: 0.5, 1 and 2 micrograms ml-1. The clinical characteristics of the resultant sedation and anaesthesia were observed. Plasma concentrations of ORG 21465 were measured during and for 500 min after the infusions and the EEG recorded. A sigmoid e-max effect compartment pharmacodynamic model was fitted to the plasma concentrations and an EEG derivative (spectral edge frequency (SEF)). Anaesthesia with ORG 21465 was associated with involuntary movements in all subjects. A steady state concentration of 1180 ng ml-1 depressed SEF by 50%, the Hill factor describing the sigmoid nature of the concentration-response curve was 1.42 and the equilibration rate constant of the biophase was 0.112 min-1. Anaesthesia with ORG 21465 was found to be unsatisfactory because of involuntary movements and slow equilibration with the biophase.

Adult↗
PubMed1997

Audit of ascertainment of deaths to children born in Cumbria, UK, 1950-89 through the NHS central register.

STUDY OBJECTIVE: To evaluate the completeness of notification of deaths by the National Health Service Central Register (NHSCR) for England and Wales. DESIGN: Deaths for a birth cohort were ascertained through scanning the relevant volumes of NHSCR. Attempts were made to confirm these deaths and additional deaths were ascertained through searching local records. Logistic regression was used to investigate how the probability of a death being missed by NHSCR varied with the year of birth, age at death, sex, and social class. SETTING: Deaths up to the end of 1989 in the CA postal area among 264,046 children born between 1950 and 1989 to mothers living in Cumbria. RESULTS: NHSCR originally ascertained 4139 deaths; local searches confirmed 3338 (81%) of these and found an additional 342. Most deaths missed by the NHSCR were neonatal deaths in the 1950s and 1960s. In the 1950s, 31% of children who died in the neonatal period either were not entered on NHSCR or, if they were entered, there was no record of their death. For children born from 1970 onwards, ascertainment of deaths through NHSCR was over 99% complete. CONCLUSIONS: The NHSCR was started in 1948 for the administration of records of National Health Service patients. It seems that many babies who died soon after birth were not therefore recorded. In parallel with the increasing use of NHSCR for epidemiological purposes, there has been a substantial and continuing improvement in its clerical procedures since the mid 1960's.

Cause of Death↗
PubMed1997

Mechanism of mitogen-activated protein kinase activation by gonadotropin-releasing hormone in the pituitary of alphaT3-1 cell line: differential roles of calcium and protein kinase C.

The mechanism of mitogen-activated protein kinase (MAPK, ERK) stimulation by the GnRH analog [D-Trp6]GnRH (GnRH-a) was investigated in the gonadotroph-derived alphaT3-1 cell line. GnRH-a as well as the protein kinase C (PKC) activator 12-O-tetradecanoyl phorbol-13-acetate (TPA) stimulated a sustained response of MAPK activity, whereas epidermal growth factor (EGF) stimulated a transient response. MAPK kinase (MEK) is also activated by GnRH-a, but in a transient manner. GnRH-a and TPA apparently activated mainly the MAPK isoform ERK1, as revealed by Mono-Q fast protein liquid chromatography followed by Western blotting as well as by gel kinase assay. GnRH-a and TPA stimulated the tyrosine phosphorylation of several proteins, and this effect as well as the stimulation of MAPK activity were inhibited by the PKC inhibitor GF 109203X. Similarly, down-regulation of TPA-sensitive PKC subspecies nearly abolished the effect of GnRH-a and TPA on MAPK activity. Furthermore, the protein tyrosine kinase (PTK) inhibitor genistein inhibited protein tyrosine phosphorylation and reduced GnRH-a-stimulated MAPK activity by 50%, suggesting the participation of genistein-sensitive and insensitive pathways in GnRH-a action. Although Ca2+ ionophores have only a marginal stimulatory effect, the removal of Ca2+ markedly reduced MAPK activation by GnRH-a and TPA, but had no effect on GnRH-a and TPA stimulation of protein tyrosine phosphorylation. Interestingly, the removal of Ca2+ also partly inhibited the activation of MAPK by EGF and vanadate/H2O2. Thus, a calcium-dependent component(s) downstream of PKC and PTK might also participate in MAPK activation. Elevation of cAMP by forskolin exerted partial inhibition on EGF, but not on TPA or GnRH-a action, suggesting that MEK activators other than Raf-1 might be involved in GnRH action. We conclude that Ca2+, PTK, and PKC participate in the activation of MAPK by GnRH-a, with Ca2+ being necessary downstream to PKC and PTK.

Animals↗
PubMed1997

Human gene therapy for melanoma: CT-guided interstitial injection.

OBJECTIVE: Our intent is to describe the role of CT in the intratumoral injection of Allovectin-7 (Vical, San Diego, CA), an allogeneic class I major histocompatibility complex antigen, HLA-B7, formulated with cationic lipid, in the treatment of metastatic malignant melanoma. MATERIALS AND METHODS: Ten patients with metastatic malignant melanoma were treated with gene therapy in which we used CT-guided intratumoral injection of plasmid DNA containing the HLA-B7 gene. This therapy was part of a phase I gene therapy trial in patients with metastatic melanoma. CT guidance was chosen as an accurate way to direct gene delivery in patients with deep, impalpable lesions. Tumor locations included pulmonary, mediastinal, hepatic, adrenal, and paracaval sites. Patients in the CT protocol underwent baseline CT studies. Examinations were repeated 2, 4, and 8 weeks after gene therapy and thereafter at 3-month intervals. Both injected and noninjected tumors were measured. CT-guided injections of 10, 50, or 250 micrograms of plasmid DNA were performed with 22-gauge spinal needles. Injection volumes were between 1.0 and 4.0 ml, depending on tumor size. CT-guided core biopsy specimens were obtained (with 18- or 20-gauge needles) from the selected tumor before therapy and 2, 4, and 8 weeks after therapy to assess HLA-B7 plasmid DNA and gene expression. Peripheral blood was analyzed for cytotoxic T lymphocytes directed against HLA-B7. RESULTS: CT-guided intratumoral injections were successful in delivering genetic material to all patients with impalpable tumors. Significant responses (as defined by a decrease of 25% or more in the product of the length and width of the injected tumor) were observed in six of the 10 patients. One of these six patients who had a solitary lesion remains free of disease 19 months after gene therapy. HLA-B7 protein expression was detected in 89% of biopsy specimens, and plasmid DNA and messenger RNA were detected in 56% and 22% of biopsy specimens, respectively. CONCLUSION: CT provides a safe, accurate, and efficacious way to monitor and assess tumor progression and response, and it provides guidance for biopsies and intratumoral injections during gene therapy. Significant responses in injected tumors of six of the 10 patients in our study suggest that further clinical trials of this gene therapy are warranted.

Adult↗
PubMed1997

Stöckert roller pump generated pulsatile flow: cerebral metabolic changes in adult cardiopulmonary bypass.

There is evidence that during cardiopulmonary bypass (CPB), pulsatile pump flow improves cerebral metabolism. This was a study to explore the effect of pulsatile versus nonpulsatile perfusion on cerebral lactate, pyruvate, glucose and beta-hydroxybutyrate using a Stöckert roller pump. We found no significant differences between the arterial-venous (A-V) differences of lactate, glucose and beta-hydroxybutyrate (p > 0.05). When the upward trend of A-V pyruvate was accounted for, there was again no difference (p = 0.2). Arterial lactate:pyruvate ratios were not significantly different between pulsatile and nonpulsatile pump flow (p > 0.05). Venous lactate:pyruvate ratios were significantly higher during pulsatile bypass, but when the downward trend was accounted for, the differences between pulsatile and nonpulsatile values were no longer significant (p = 0.4). Therefore, the metabolic changes were not significant. There was no significant difference in systemic vascular resistance (SVR) during pulsatile and nonpulsatile flow (p = 0.4). Pulsatile flow delivered by the Stöckert roller pump appears to have no metabolic or SVR advantages in adults undergoing CPB.

3-Hydroxybutyric Acid↗