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Biomedical subjects

J Baker

Publications and source records attributed to J Baker.

At least 91 records · Page 5Linked to original sources
PubMed1998

A novel class of evolutionarily conserved genes defined by piwi are essential for stem cell self-renewal.

Germ-line stem cells (GSCs) serve as the source for gametogenesis in diverse organisms. We cloned and characterized the Drosophila piwi gene and showed that it is required for the asymmetric division of GSCs to produce and maintain a daughter GSC but is not essential for the further differentiation of the committed daughter cell. Genetic mosaic and RNA in situ analyses suggest that piwi expression in adjacent somatic cells regulates GSC division. piwi encodes a highly basic novel protein, well conserved during evolution. We isolated piwi homologs in Caenorhabditis elegans and humans and also identified Arabidopsis piwi-like genes known to be required for meristem cell maintenance. Decreasing C. elegans piwi expression reduces the proliferation of GSC-equivalent cells. Thus, piwi represents a novel class of genes required for GSC division in diverse organisms.

Amino Acid Sequence↗
PubMed1998

Report of the Second Equine Leucocyte Antigen Workshop, Squaw valley, California, July 1995.

The final assignment of antibody clusters for leucocyte antigens and immunoglobulins, as described in detail in Sections 3 and 4, is summarized in Table 4. Together with other mAbs developed outside of ELAW II (Table 9) this pool of reagents represent a powerful array of tools for the study of equine immunity. The Second Equine Leucocyte Antigen Workshop made considerable advances in pursuing the objectives of establishing the specificities of mAbs and achieving consensus on the nomenclature for equine leucocyte and immunoglobulin molecules. Of equal importance, several productive collaborations were fostered among the participating laboratories and observers. Overall, enormous advances have been made in the past decade since mAbs specific for equine leucocyte antigens and immunoglobulins were first reported. There remains enormous scope and need for further studies of equine leucocyte antigens and immunoglobulins, both for the purposes of comparative immunology and for the good of the horse. In the future novel techniques will be required to develop reagents for specific target antigens such as the orthologues of the CD25 or CD45 isoforms. In studies of equine immunoglobulins the functional role of the IgG isotypes must be better established, reagents for IgE must be developed, and cloning of the immunoglobulin heavy chain genes will be essential if the complexities of the IgG sub-isotypes are to be elucidated. The tasks still facing the currently small group of equine immunologists throughout the world remain formidable, and will only be tackled successfully in a spirit of collaboration.

Animals↗
PubMed1998

Interferon-beta-1-b (IFN-B) decreases induced nitric oxide (NO) production by a human astrocytoma cell line.

Inducible nitric oxide synthase (iNOS) is expressed by astrocytes in demyelinating regions of multiple sclerosis (MS) brain plaques, suggesting that NO contributes to MS pathology. Since the immunosuppressive cytokine IFN-B ameliorates MS disease activity, it is of interest to assess the modulatory role of IFN-B on NO production. We studied the effects of IFN-B, as well as dexamethasone, IL-10, and transforming growth factor-beta (TGF-B), on cytokine-induced NO production by the human astrocytoma cell line, A172. L-NMMA and aminoguanidine, competitive inhibitors of iNOS suppressed NO production as measured by the NO byproduct, nitrite, as did IFN-B. Dexamethasone enhanced NO production, and IFN-B decreased the amount of the enhancement. Neither IL-10 nor TGF-B inhibited nitrite production. The therapeutic effect of IFN-B in MS may be partly due to suppression of pathogenic NO production.

Astrocytoma↗
PubMed1998

Histological, chemical, and crystallographic analysis of four calcium phosphate cements in different rabbit osseous sites.

Four calcium phosphate cement formulations were implanted in the rabbit distal femoral metaphysis and middiaphysis. Chemical, crystallographic, and histological analyses were made at 2, 4, and 8 weeks after implantation. When implanted into the metaphysis, part of the brushite cement was converted into carbonated apatite by 2 weeks. Some of the brushite cement was removed by mononuclear macrophages prior to its conversion into apatite. Osteoclastlike cell mediated remodeling was predominant at 8 weeks after brushite had converted to apatite. The same histological results were seen for brushite plus calcite aggregate cement, except with calcite aggregates still present at 8 weeks. However, when implanted in the diaphysis, brushite and brushite plus calcite aggregate did not convert to another calcium phosphate phase by 4 weeks. Carbonated apatite cement implanted in the metaphysis did not transform to another calcium phosphate phase. There was no evidence of adverse foreign body reaction. Osteoclastlike cell mediated remodeling was predominant at 8 weeks. The apatite plus calcite aggregate cement implanted in the metaphysis that was not remodeled remained as poorly crystalline apatite. Calcite aggregates were still present at 8 weeks. There was no evidence of foreign body reaction. Osteoclastlike cell remodeling was predominant at 8 weeks. Response to brushite cements prior to conversion to apatite was macrophage dominated, and response to apatite cements was osteoclast dominated. Mineralogy, chemical composition, and osseous implantation site of these calcium phosphates significantly affected their in vivo host response.

Animals↗
PubMed1998

Electrical cardioversion of atrial fibrillation or flutter with conscious sedation in the age of cost containment.

BACKGROUND: The purpose of this study was to compare the safety, efficacy, and cost of conscious sedation administered by electrophysiologists certified in the use of conscious sedation with sedation administered by anesthesiologists during cardioversion of atrial fibrillation or atrial flutter to sinus rhythm. METHODS AND RESULTS: Patients with hemodynamically stable persistent atrial fibrillation and flutter were included in this study. Group 1 patients (n = 33) were sedated by an anesthesiologist and group 2 patients (n = 26) were sedated by an electrophysiologist. Anesthesiologists used propofol and electrophysiologists used midazolam and morphine for sedation. A cost analysis based on professional charges and cost of medications was performed for both groups and compared. Hospital charges were similar for both groups and were excluded from the cost analysis. Although time to sedation in group 1 was shorter than that in group 2, sedation was adequate in both groups such that no patient in group 1 and only 1 patient in group 2 recalled being shocked. There were no complications in either group. The cost incurred in group 2 was less than that in group 1. CONCLUSIONS: Sedation administered by electrophysiologists for cardioversion of atrial arrhythmias is safe and cost effective. Midazolam and morphine, the sedative agents administered by electrophysiologists, were effective and well tolerated by patients.

Aged↗
PubMed1998

Psychogenic dysphonia: peeling back the layers.

Resolution of psychogenic dysphonia is often quick and effortless for client and therapist alike. In such instances, the therapeutic interventions are simple and straightforward, insights are reached without difficulty, and once normal voice has been established, resumption of dysphonia or other psychosomatic symptoms rarely occurs. Sometimes, however, psychogenic dysphonia is extremely difficult to overcome, requiring considerable time, effort, and determination on the part of the client, coupled with confident, skilled persistence and psychotherapeutic insight from the therapist. In such cases one feels a sense of working through many complex layers before obtaining satisfactory voice or reaching an understanding of the psychogenic factors that precipitated onset and/or maintenance of the dysphonia. Two cases that illustrate this involved process of peeling back the layers are presented. For resolution of severe psychogenic dysphonia, the therapist must be able to recognize and establish the complex relationship between the neurophysiological, intrapsychic, and interpersonal levels of function as they affect the client's voice and person, as a whole. This work requires considerable courage and skill on the part of the therapist to question, explore, change direction, and select alternative approaches. It is important that the problem can be resolved with a depth of understanding which is relevant for the client, and with due attention to the social context and wider systems of which he or she is a part.

Female↗
PubMed1998

Pharmacokinetics of phenylbutazone in plasma and milk of lactating dairy cows.

Phenylbutazone was administered intravenously (i.v.) to a group of four lactating cows at a dosage of 6 mg/kg body weight. Whole plasma, protein-free plasma and milk were analysed for phenylbutazone residues. Pharmacokinetic parameters of total and free phenylbutazone in plasma were calculated using a non compartmental method. In regards to whole plasma data, the mean volume of distribution at steady state (Vss), was 147 mL/kg body weight, with a mean (+/-SEM) terminal elimination half-life (t1/2) of 40+/-6 h. The mean clearance (Cl) was 3 mL/h/kg body weight. The Vss as determined from the protein-free plasma fraction was 50021 mL/kg body weight. This larger Vss of free phenylbutazone compared to total plasma phenylbutazone was attributed to a high degree of plasma protein binding, as well as the greater penetration of free phenylbutazone into tissues. The mean t1/2 of free phenylbutazone was 39+/-5 h. This similarity to the t1/2 estimated from total plasma phenylbutazone data is attributed to an equilibrium between free and plasma phenylbutazone during the terminal elimination phase. Mean t1/2 as determined from milk, applying a urinary excretion rate model, was 47+/-4 h. Milk clearance of phenylbutazone was 0.009 mL/h/kg body weight, or about 0.34% of total body clearance. Furthermore, evidence suggests that phenylbutazone either binds to milk proteins, or is actively transported into milk, as its concentration in milk was greater than that predicted due to a simple partitioning from plasma into milk.

Animals↗
PubMed1998

Mutations in the potyvirus helper component protein: effects on interactions with virions and aphid stylets.

Mutations of K --> E in the highly conserved 'KITC' motif of the potyvirus helper component (HC) protein result in loss of HC function in aphid transmission, presumably because of inability to interact with virions, stylets or both. In this study we show that HC of potato virus C (PVC), a naturally occurring variant of potato virus Y (PVY) that has the K --> E mutation, lacks the ability to be retained in stylets, whereas PVY HC is retained. The K --> E mutation in either PVC or a site-directed mutant of tobacco etch virus (TEV) did not hinder binding to capsid protein, nor did deletion of the N-terminal 107 aa of TEV HC. An additional mutation, F -->, L at aa 10 of TEV HC, which renders HC non-functional but does not affect binding to capsid protein, is reported. Collectively, the results suggest that the N-terminal domain is required for interaction of HC with stylets rather than for binding to virions.

Animals↗
PubMed1998

Comparative analyses of intracellularly expressed antisense RNAs as inhibitors of human immunodeficiency virus type 1 replication.

The antiviral activities of intracellularly expressed antisense RNAs complementary to the human immunodeficiency virus type 1 (HIV-1) pol, vif, and env genes and the 3' long terminal repeat (LTR) sequence were evaluated in this comparative study. Retroviral vectors expressing the antisense RNAs as part of the Moloney murine leukemia virus LTR promoter-directed retroviral transcript were constructed. The CD4+ T-cell line CEM-SS was transduced with retroviral constructs, and Northern blot analyses showed high steady-state antisense RNA expression levels. The most efficient inhibition of HIV-1 replication was observed with the env antisense RNA, followed by the pol complementary sequence, leading to 2- to 3-log10 reductions in p24 antigen production even at high inoculation doses (4 x 10(4) 50% tissue culture infective doses) of the HIV-1 strain HXB3. The strong antiviral effect correlated with a reduction of HIV-1 steady-state RNA levels, and with intracellular Tat protein production, suggesting that antisense transcripts act at an early step of HIV-1 replication. A lower steady-state antisense RNA level was detected in transduced primary CD4+ lymphocytes than in CEM-SS cells. Nevertheless, replication of the HIV-1 JR-CSF isolate was reduced with both the pol and env antisense RNA. Intracellularly expressed antisense sequences demonstrated more pronounced antiviral efficacy than the transdominant RevM10 protein, making these antisense RNAs a promising gene therapy strategy for HIV-1.

3T3 Cells↗
PubMed1998

Relation between Heberden's nodes and distal interphalangeal joint osteophytes and their role as markers of generalised disease.

OBJECTIVE: Heberden's nodes are often used as a marker for osteoarthritis (OA). This study examined how often Heberden's nodes and radiological distal interphalangeal (DIP) osteophytes coexist in the same digit and the sensitivity, specificity, and positive predicative value of each for OA at different sites or generalised disease. METHODS: This was a population-based study of 660 middle ages women taking part in a twin study of OA. Distal interphalangeal osteophytes were defined radiologically and graded on a four point scale (0-3) using a published atlas of individual features. Heberden's nodes were defined by standardised clinical examination. OA in other joint (knees, proximal interphalangeal (PIP) joints and carpometacarpal (CMC) joints) was defined radiologically using a published atlas. RESULTS: Poor agreement was observed between a Heberden's node (HN) and a radiological distal interphalangeal osteophyte in the same finger of the same hand (K statistic (95% CI) = 0.36 (0.33, 0.39)). Although HN and radiological DIP osteophytes had similar sensitivity, the specificity and positive predicative value of DIP osteophytes was considerably higher for detecting knee, CMC, PID OA, and OA in more than two groups of joint (knee, CMC, and DIP joints). CONCLUSION: HN are not synonymous with DIP osteophytes. Radiological DIP osteophytes are a better marker of knee and multiple joint OA than HN. HN may still be an imperfect surrogate for hand OA when radiology is impractical, but are not an accurate marker of generalised disease.

Female↗
PubMed1998

Characterization of corticotropin-releasing hormone (CRH) in human skin.

We have confirmed the expression of CRH and CRH receptor type 1 genes in human skin, cultured HaCaT keratinocytes, squamous cell carcinoma, and melanoma cells. The size of CRH messenger ribonucleic acid (mRNA), estimated by Northern blot hybridization, was 1.5 kilobases. CRH peptide was identified by reverse phase high pressure liquid chromatography separation in both whole skin and cultured cells. Forskolin and dexamethasone at concentrations of 10 micromol/L stimulated and inhibited, respectively, CRH peptide production in squamous cell carcinoma and melanoma cells, but had no significant effect on the CRH mRNA level. In melanoma cells, stimulation of melanogenesis down-regulated CRH receptor type 1 mRNA expression, but was without effect on CRH mRNA production. We suggest that in human skin the CRH signaling system is both operative and under regulatory control.

Blotting, Northern↗
PubMed1998

Out of plan. Certain HMO characteristics affect physicians' satisfaction and influence their decision to reenroll.

The authors examine the issue of continuity, which is directly associated with patient satisfaction, from the perspective of the physician. They attempt to determine which factors are most important in determining physician satisfaction with an HMO and the link between satisfaction with an HMO and intent to remain affiliated with that HMO. Their study reveals that 11 factors explain 71% of the variation in overall physician satisfaction and that a physician's satisfaction with a plan is closely linked to intentions to reenroll. Implications for HMOs, physicians, employers, and public policy makers are explored.

Attitude of Health Personnel↗