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Biomedical subjects

A R Jones

Publications and source records attributed to A R Jones.

At least 37 records · Page 2Linked to original sources
PubMed2000

Fructose metabolism by mature boar spermatozoa.

In 1945, Mann showed fructose to be the principal sugar in semen. For over half a century the means by which fructose is metabolized by sperm has been assumed to be by an initial phosphorylation catalysed by hexokinase, but this has never been substantiated. In the present study, by comparing the metabolism of glucose and fructose by both whole boar sperm and hypotonically treated cells, it is confirmed that fructose is phosphorylated by hexokinase to produce fructose 6-phosphate.

Animals↗
PubMed2000

Influence of a rural primary care clerkship on medical students' intentions to practice in a rural community.

The purpose of this study is to examine the relationship of a rural clerkship to medical students' interest in establishing careers in rural communities. The Association of American Medical Colleges Medical School Graduation Questionnaire (GQ) for years 1988 through 1997 was examined to compare the career plans of students graduating from Morehouse School of Medicine (MSM) with those of all students graduating from United States medical schools before the period 1988 through 1992 and after the period 1993 through 1997, after the inception of the rural clerkship at MSM. Select GQ data items examined include student demographics, medical school experiences, and career plans. Statistical analyses were used to compare pre- and post-clerkship responses for MSM students and to compare their responses with the national trends. Results indicate that, following a transition period, MSM students showed an increased preference for a future career in a rural community. A smaller upward trend in the national data was observed. There appears to be an association between the rural clerkship experience at MSM and the stated preferred career choices of the students.

Adult↗
PubMed2000

Substrates for endogenous metabolism by mature boar spermatozoa.

Washed boar spermatozoa incubated in the absence of exogenous substrates maintained a high energy charge potential (ECP) for at least 10 h. Addition of bromopyruvate, an inhibitor of stage 2 of the glycolytic pathway, at any time during the incubation caused an immediate decrease in the ECP, indicating that the mobilization of endogenous compounds requires this section of the pathway for the production of lactate, the major mitochondrial substrate for ATP production. Some of the sources of the metabolic substrates have been identified, by NMR and metabolic studies, as di- or triglycerides, to produce glycerol, and membrane phospholipids for the production of glycerol 3-phosphate. Acetylcarnitine contributes acetyl groups early in the incubation; glycerylphosphorylcholine is degraded to glycerol 3-phosphate and choline after about 5 h, and acetate also accumulates after about 5 h. The presence of phosphorylcholine and phosphorylethanolamine later in the incubation indicates that phospholipids are also degraded to glycerol.

Acetates↗
PubMed1999

Superior autologous blood stem cell mobilization from dose-intensive cyclophosphamide, etoposide, cisplatin plus G-CSF than from less intensive chemotherapy regimens.

The study purpose was to determine if G-CSF plus dose-intensive cyclophosphamide 5.25 g/m2, etoposide 1.05 g/m2 and cisplatin 105 mg/m2 (DICEP) results in superior autologous blood stem cell mobilization (BSCM) than less intensive chemotherapy. From January 1993 until May 1997, 152 consecutive patients with non-Hodgkin's lymphoma (n = 55), breast cancer (n = 47), Hodgkin's disease (n = 14), multiple myeloma (n = 9), AML (n = 9), or other cancers (n = 18) initially underwent BSCM by one of three methods: Group 1: G-CSF alone x 4 days (n = 30). Group 2: disease-oriented chemotherapy, dosed to avoid blood transfusions, followed by G-CSF starting day 7 or 8, and apheresis day 13 or 14 (n = 82). Group 3: DICEP days 1-3, G-CSF starting day 14, and apheresis planned day 19, 20 or 21 (n = 40). A multivariate analysis was performed to determine which factors independently predicted BSCM. The median peripheral blood CD34+ (PB CD34+) cell count the morning of apheresis linearly correlated with the number of CD34+ cells removed per litre of apheresis that day. The median PB CD34+ cell count and median CD34+ cells x 10(6) removed per litre of apheresis were highest for Group 3, intermediate for Group 2, and lowest for Group 1. By multivariate analysis, mobilization group (3 > 2 > 1), disease other than AML, no prior melphalan or mitomycin-C, and less than two prior chemotherapy regimens predicted better BSCM. Out of 15 Group 3 patients who had infiltrated marrows, 11 had no detectable cancer in marrow and apheresis products after DICEP. These data suggest that DICEP results in superior BSCM than less intensive chemotherapy regimens.

Adolescent↗
PubMed1999

Allogeneic blood stem cell and bone marrow transplantation for acute myelogenous leukemia and myelodysplasia: influence of stem cell source on outcome.

We have compared the outcomes of 87 patients with acute myelogenous leukemia (AML) and myelodysplasia (MDS) receiving matched sibling transplants with stem cells from peripheral blood (blood cell transplant, BCT) or bone marrow (BMT). In good risk patients (AML in CR1) granulocytes recovered to 0.5 x 10(9)/l a median of 14 days after BCT compared with 19 days after BMT (P < 0.0001). For patients with poor risk disease (AML beyond CR1 and MDS) corresponding figures were 16 vs 26 days (P < 0.0001). Platelet recovery to 20 x 10(9)/l was also faster after BCT (good risk 12 vs 20 days, P < 0.0001; poor risk 17 vs 22 days, P = 0.04). Red cell transfusions were unaffected by cell source, but BCT recipients required less platelet transfusions (good risk 1 vs 5, P = 0.002; poor risk 5 vs 11, P = 0.004). Blood cell transplants resulted in more chronic GVHD (86% vs 48%, P = 0.005) and a significantly higher proportion of recipients with KPS of 80% or less (48% vs 5%, P = 0.004). Disease-free survival at 4 years was 23% for both groups of poor risk patients but outcome in good risk patients was better after BCT (93% vs 62%, P = 0.047) related mainly to less relapse. While disease-free survival may be better after BCT than BMT for AML in CR1, quality of life may be relatively impaired.

Adolescent↗
PubMed1999

A re-appraisal of the post-testicular action and toxicity of chlorinated antifertility compounds.

Some 30 years ago, alpha-chlorohydrin and some analogues were considered as close to the ideal contraceptive which acted rapidly and reversibly on the post-testicular maturation of spermatozoa. Despite their early promise, research funding was withdrawn only 5 years later because of what were considered to be unacceptable side-effects in primates. The literature on the toxic effects of these contraceptive agents was reviewed and was found to be wanting in respect to the rigour of scientific methods applied (impure compounds were used, inappropriate target populations were studied, excessive doses were employed, abstracts were cited from which no full publications subsequently arose). These compounds remain the closest approach yet to non-hormonal contraceptives for males and have led to the synthesis of related compounds which have a similar antifertility action but with much diminished toxicity. If toxicity remains a problem, a range of other compounds now known to have a similar antifertility action, should be investigated.

Animals↗
PubMed1999

Glycolytic enzyme activity in hypotonically treated boar spermatozoa.

Treatment of washed boar sperm with hypotonic phosphate buffer disrupted the cytoplasmic membrane and released the soluble contents and phosphofructokinase, but the other glycolytic enzymes and lactate dehydrogenase were retained. Addition of the appropriate substrates and co-factor(s) to preparations of treated cells in phosphate-buffered saline showed that enzyme activity could be re-instated. This simple preparation should be of assistance in the investigation of specific sections of the glycolytic pathway without the use of chemical inhibitors.

Adenosine Diphosphate↗
PubMed1998

Guidelines for organisation and management of external quality assessment using proficiency testing. Expert Panel on Cytometry of the International Council for Standardization in Haematology.

This document is intended to assist towards the WHO objective that external quality assessment (EQA) schemes be established at national and/or regional levels world-wide. Quality assurance is defined as all steps taken by the director of a laboratory to ensure reliability of laboratory results and to increase accuracy, reproducibility and between-laboratory comparability. This includes the use of internal quality control procedures and participation in external quality assessment. Internal quality control provides the means for evaluation of analytic test results at the time of testing in order to decide whether they are reliable enough to be released to the requesting clinicians. EQA, on the other hand, refers to a system of retrospective and objective comparison of results from different laboratories by means of proficiency testing (PT) organised by an external agency. The main purpose is to establish between-laboratory and between-method (including between-instrument) comparability, and agreement with a reference standard where one exists. Internal quality control and EQA complement each other and must never be considered as alternatives.

Animals↗
PubMed1998

Chemical interference with sperm metabolic pathways.

During the 1960s, the quest for a simple non-steroidal chemical possessing male antifertility activity culminated with the discovery of the activity of alpha-chlorohydrin in 1970. Investigations into the mechanism of action of this compound revealed that it was affecting the glycolytic pathway within mature spermatozoa through its conversion to an inhibitory metabolite. Use of these and other simple chemical inhibitors has subsequently led to a clearer understanding of the metabolic pathways involved in the generation of ATP, which is necessary for sperm motility. Mature boar spermatozoa from the cauda epididymidis are almost totally reliant on the glycolytic pathway, not necessarily for the immediate generation of ATP, but for the ultimate production of lactate, which appears to be the sole substrate used for the mitochondrial production of ATP. The only exogenous substrates that support lactate production in vitro are fructose, glucose, glycerol and glycerol 3-phosphate and when these substrates are plentiful, there is evidence that compounds can be retained as such or as intermediates of the glycolytic pathway. When exogenous substrates are limited, the cells have the capability to mobilize endogenous compounds and to maintain the continuous synthesis of ATP.

Adenosine Triphosphate↗
PubMed1998

Stimulant use in sports.

The authors provide an overview of the topic of stimulant use in psychiatric sports medicine. They address the following areas: 1) the history of stimulant use in sports; 2) recent events related to the use of stimulants in sports, including a new stimulant used at the 1996 Olympic competition in Atlanta, GA; 3) ergogenic or ergolytic (i.e., performance-impairing) potential of several major categories of stimulants, including amphetamines, beta2 agonists, caffeine, and cocaine; 4) review of how the brain reward circuit is affected by stimulants; 5) individual factors that induce athletes to utilize stimulants; and 6) sports organizational factors that induce athletes to use stimulants.

Brain↗
PubMed1997

Single-agent high-dose melphalan salvage therapy for Hodgkin's disease: cost, safety, and long-term efficacy.

BACKGROUND: Few data are available on the cost, safety, and long-term efficacy of single-agent high-dose melphalan (HDM) followed by autologous bone marrow (ABMT) or blood stem cell (ABSCT) transplantation in the salvage therapy of Hodgkin's disease (HD). PATIENTS AND METHODS: From February 1981 to September 1996, 23 patients with relapsed (n = 15) or refractory (n = 8) HD received salvage therapy with HDM 140-200 mg/m2 followed by non-cryopreserved ABMT (n = 18) or cryopreserved ABSCT (n = 5). The cost of HDM/ABSCT in 1996, from initial consultation until transfer back to referring physician, was determined and compared to the estimate costs of two multi-agent regimens commonly used for HD. RESULTS: HDM was well tolerated with no early transplant-related mortality. The five-year overall and progression-free survival rates were 52% and 50%, respectively. The average total cost in Canadian funds of HDM/ABSCT in 1996 was $34,400/patient. This cost was estimated to be $4,700-6,800 cheaper per patient than the multi-agent high-dose regimens. CONCLUSION: These data suggest that HDM is safe, feasible, active, and reasonably inexpensive salvage therapy for patients with relapsed/refractory HD.

Adolescent↗
PubMed1997

Metabolism of lactate by mature boar spermatozoa.

Boar sperm oxidatively metabolized fructose, glucose, glycerol, glycerol 3-phosphate and lactate to CO2 but pyruvate produced only small amounts of CO2 and this was almost completely prevented when endogenous glycolytic metabolism was inhibited. Lactate was the preferred substrate over fructose, glycerol and glycerol 3-phosphate and when lactate was offered in the presence of pyruvate, lactate was preferentially oxidized to CO2. The rate of oxidation of fructose, glycerol and glycerol 3-phosphate was approximately halved in the presence of equi-molar concentrations of lactate and the metabolism of lactate was progressively decreased in the presence of increasing concentrations of mersalyl, an inhibitor of lactate transport. Sperm maintained a high energy charge potential when incubated with lactate as substrate in the presence or absence of bromopyruvate, an inhibitor of endogenous glycolytic metabolism. This evidence confirms that it is lactate, rather than pyruvate, that enters the mitochondria thereby constituting a lactate-pyruvate transport system in these cells for regenerating cytoplasmic nicotinamide adenine dinucleotide (NAD+). Electrophoretic examination of the lactate dehydrogenase isozymes from sperm and several other tissues of the boar showed that sperm contained almost entirely an isozyme which was not present in the other tissues.

Animals↗
PubMed1997

Triosephosphate metabolism by mature boar spermatozoa.

Boar sperm rapidly interconverted dihydroxyacetone phosphate and glyceraldehyde 3-phosphate, produced fructose-1,6-bisphosphate, approximately equilibrium concentrations of fructose 6-phosphate and glucose 6-phosphate but not glycerol or glycerol 3-phosphate. In the presence of 3-chloro-1-hydroxypropanone, an inhibitor of stage 2 of the glycolytic pathway, the triosephosphates were metabolized faster, produced less fructose-1,6-bisphosphate, fructose 6-phosphate and glucose 6-phosphate, but not glycerol or glycerol 3-phosphate. This suggests that these cells may have the capacity to convert glycolytic intermediates into a storage metabolite to conserve carbon atoms for the eventual synthesis of lactate.

Acetone↗
PubMed1997

Metabolic activity of hypotonically treated mature boar spermatozoa.

Treatment of washed boar sperm with hypotonic phosphate buffer removed the acrosome, disrupted the cytoplasmic membrane and almost completely separated the heads from the mid piece-tail segment. As assessed by oxygen uptake studies and their ability to oxidize 14C-labelled substrates to 14CO2, hypotonically-treated cells exhibit low glycolytic activity yet mitochondrial activity remains high. Both lactate and glycerol 3-phosphate underwent oxidation and these substrates continued to be metabolized by this preparation which had been stored for up to 10 days at 4 degrees C. Such preparations may be of assistance in the investigation of the biochemistry of boar sperm mitochondria.

Acrosome↗