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Biomedical subjects

R Jones

Publications and source records attributed to R Jones.

At least 649 records · Page 36Linked to original sources
PubMed1991

Interaction of zona pellucida glycoproteins, sulphated carbohydrates and synthetic polymers with proacrosin, the putative egg-binding protein from mammalian spermatozoa.

Fertilization in mammals is a unique cell-cell recognition event that involves specific receptors on the surface of each gamete. Previous work has shown that proacrosin, a protein found within the acrosome of mammalian spermatozoa, binds non-enzymatically to zona pellucida glycoproteins (ZPGPs) that surround the egg and that this binding can be inhibited by sulphated polysaccharides such as fucoidan. The mechanism of this interaction has been investigated using 125I-ZPGPs and 125I-fucoidan as probes. Results show that it involves poly(sulphate) groups on zona glycoproteins that bind with high affinity (Kd = 1.2 to 5.0 x 10(-8)M) to complementary 'docking' sites on proacrosin. The spatial orientation of these sulphates, together with the tertiary structure of the target protein, determines the selectivity of polymer binding. Thus, dextran sulphate and poly(vinyl sulphate) are strong inhibitors of the above probes whereas dextran, chondroitin sulphates A and C and poly(vinyl phosphate) are ineffective. Proacrosin, therefore, has properties analogous to those described for 'bindin', the egg adhesion protein found within the acrosomal vesicle of sea urchin spermatozoa.

Acrosin↗
PubMed1991

Effect of moisture in total mixed rations on feed consumption and milk production and composition in Holstein cows.

The DM levels in total mixed rations were maintained at 62.7, 52.8, and 45.8% by incorporating 38% of the DM from alfalfa silages of twi different DM contents into the ration to determine the effect on milk production and composition when fed to lactating Holstein cows. The alfalfa silages were stored at approximately 25 and 50% DM and harvested from the same field on consecutive days either direct-cut and bagged or wilted overnight before bagging. Silages were used (minimum of 8.5 kg of Dm/d) in a total mixed ration formulated to be isonitrogenous (using cottonseed meal) and isocaloric and fed to 144 lactating cows randomly allotted into three equal groups based on days in milk (initially 33 d), lactation number, and pretrial 3.5% FCM production. Yields of 3.5% FCM were 35.3, 35.7 and 35.4 kg, respectively, for the dry, intermediate, and wet rations and were not significantly different. Consumption of DM tended to decline as DM content of the ration decreased, but the decrease was not significant. Results showed that total mixed ration moisture levels evaluated in this trial had no significant effects on consumption of DM of isonitrogenous rations or milk yield and composition.

Animals↗
PubMed1991

The General Practice Research Club.

The General Practice Research Club was established in 1969, and now has 120 members. A meeting of the club is held twice a year, at which various papers, from research ideas through to completed, published studies are presented. A survey of 40 individuals who had presented papers at meetings during the period 1984-89 showed that almost half (18) had presented papers on clinical topics. As a result of the presentation, 29 individuals had modified their research, with 11 undertaking major alterations. The meeting was rated most highly by those offering ideas and plans for research. Most individuals responded positively to the meetings, commenting that they valued peer review, found the meetings encouraging, and useful for focusing ideas. Lack of criticism and feedback was commented upon. The club has an important role to play in encouraging research by service general practitioners.

England↗
PubMed1991

Preconditioning the heart by repeated stunning improves myocardial salvage.

Repeated regional ischemia of short duration followed by reperfusion leads to preconditioning of the myocardium. Left anterior descending coronary artery (LAD) occlusion was applied for 5 minutes and then released for 10 minutes. This was repeated four times by using an intact pig model. LAD occlusion was then continuously applied for 1 hour. Myocardial function, high energy phosphates, and membrane phospholipids were compared with a control (nonstunned) group over a 6-hour reperfusion period. Stunning itself produced no significant change in regional function, total phospholipids, or free fatty acids (FFA). However, regional function, adenosine triphosphate, and creatine phosphate were significantly (p less than 0.05) reduced over control. After 60 minutes of ischemia, regional function was significantly improved by preconditioning that persisted throughout reperfusion (p less than 0.01). This was associated with an 11% mean decrease in infarct size (p less than 0.05). Adenosine triphosphate was significantly preserved during ischemia in the preconditioned hearts, and this preservation persisted throughout reperfusion (p less than 0.05). Total phospholipids were not affected by ischemia in either group. However, during reperfusion both groups demonstrated a 15-20% decrease in phospholipid levels at 1 hour, with only the stunned group showing a progressive increase at 3 and 6 hours (p less than 0.05). Examination of FFA during reperfusion demonstrated a profound increase in only the unstunned animals (p less than 0.05), correlating with the decreased level of membrane phospholipids noted in this group. In conclusion, repeated stunning predisposes the heart to recovery after regional ischemia. This results in improved mechanical function, increased high-energy phosphate stores, and decreased infarct size.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1991

Chloroquine distribution in postmortem cases.

Chloroquine concentrations in blood and tissues were examined in overdose and non-overdose cases to determine appropriate ranges for interpretation. Twenty-nine literature overdose cases and 8 non-overdose literature cases were compared with this laboratory's findings. The results indicate significant postmortem redistribution of chloroquine. Combining this laboratory's results and the literature results indicates that using a liver concentration of 150 mg/kg as a cutoff between overdose and non-overdose concentrations properly identified 30 of the 34 published cases containing liver chloroquine and 19 of the 20 presented cases.

Accidents, Aviation↗
PubMed1990

Analysis of major androgen-regulated cDNA clones from the rat epididymis.

Four abundant cDNA clones have been isolated from a rat epididymal cDNA library. Northern blot analysis has shown that these clones partially encode 4.5 kb, 2.8 kb, 1.2 kb and 0.85 kb mRNAs and that their expression is not detectable in total RNA preparations from heart, kidney, liver or testis. Fourteen days after castration the levels of the 2.8 kb, 1.2 kb and 0.85 kb transcripts were greatly reduced whereas the 4.5 kb mRNA was undetectable. Subsequent treatment of castrated rats with testosterone for 1 day resulted in a complete restoration of the pre-castration steady-state levels of the 2.8 kb and 0.85 kb mRNAs, restoration of the 4.5 kb mRNA to 70% of pre-castration levels, and a slight over-induction of the 1.2 kb mRNA. Analyses of separate regions of the epididymal tract showed that expression of the 2.8 kb and 1.2 kb mRNAs increased towards the distal end of the epididymis, while the 4.5 kb and 0.85 kb transcripts were primarily synthesised in the caput region.

Amino Acid Sequence↗
PubMed1990

Specific binding of sulphated polymers to ram sperm proacrosin.

Sulphated polysaccharides and zona pellucida glycoproteins have been shown to bind non-enzymatically to proacrosin, the protein found within the acrosomal vesicle of mammalian spermatozoa. The mechanism of this interaction has been investigated using 125I-fucoidan to probe purified ram sperm proacrosin. Results show that (a) binding of 125I-fucoidan to proacrosin is inhibited only by sulphated polymers and (b) recognition is mediated by poly(sulphate) groups and is largely independent of the composition of the polymer chain. It is suggested that a similar mechanism is responsible for the interaction between proacrosin and zona pellucida glycoproteins during the early stages of fertilization in mammals and this process mediates firm binding of spermatozoa to the egg.

Acrosin↗
PubMed1990

Endogenous and exogenous polyamines in support of tumor growth.

The combination of inhibitors of ornithine decarboxylase and polyamine oxidase and of antibiotics suitable for the (partial) decontamination of the gastrointestinal tract with a polyamine-deficient diet reduced the growth rate of Lewis lung carcinoma by more than 80%. The formation of lung metastases was prevented by 70 to 100%, depending on the treatment. The reduction of tumor growth was accompanied by a decrease of tissue polyamine concentrations, a reduced rate of tumor cell proliferation, and protein synthesis. The comparison of the ornithine decarboxylase inhibitors Eflornithine [D,L-2-(difluoromethyl)ornithine] and (E)-2-(fluoromethyl)dehydroornithine ethylester confirmed the greater in vivo potency of the latter compound. Our method of growth inhibition by systematic polyamine deprivation is not tumor specific, but presumably generally applicable to rapid growth.

Animals↗
PubMed1990

ADP-ribosylation of nuclear proteins in rat ventral prostate during ageing.

Poly(ADPR)polymerase activity and poly(ADP-ribosyl)ation of nuclear proteins have been investigated in ventral prostate nuclei of different aged rats (14, 28, 60, 180, 360 day old animals), by reverse-phase HPLC and acetic acid-urea polyacrylamide gel electrophoresis. The major ADP-ribose acceptor proteins were identified as histone H1 and H2b. It is concluded that concomitant with major changes to chromatin organization, poly(ADP-ribosyl)ation reaction is progressively inhibited during aging of rat ventral prostate. These results support the hypothesis that prostatic dysfunction in senescent animals is related to a failure of DNA repair mechanisms and deregulated template activity.

Aging↗
PubMed1990

Mind that child.

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Adolescent↗
PubMed1990

Antibodies specific for VB8 receptor peptide suppress experimental autoimmune encephalomyelitis.

Recent studies from our laboratory have shown, for the first time, that a synthetic peptide from that TCR VB chain used preferentially by encephalitogenic T cells induced the formation of protective, MHC class I-restricted T cells and prevented the development of EAE in Lewis rats. In this report we 1) demonstrate that immunization with the TCR-VB8-39-59 peptide generated peptide-specific antibodies that protect against experimental autoimmune encephalomyelitis induced by either of the two distinct encephalitogenic epitopes of basic protein, and 2) characterize the production and biologic functions of rat and rabbit antibody responses to the TCR peptide. The antibodies in both species increased in titer over time, were highly specific for the immunogen by direct reaction and inhibition assays, stained only VB8+ T cells, and suppressed clinical signs and to lesser extent the number of histologic lesions of experimental autoimmune encephalomyelitis mediated by VB8+ T cells. Coupled with our previous work, these results indicate that both humoral and cellular responses to the TCR-VB8-39-59 peptide can contribute independent immunoregulatory effects on encephalitogenic T lymphocytes that use common V region genes in response to epitopes of myelin basic protein.

Amino Acid Sequence↗
PubMed1990

Current opinion.

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Electroshock↗
PubMed1990

Unusual fucoidin-binding properties of chymotrypsinogen and trypsinogen.

Previous work (Jones, R. (1987) Cell Biol. Int. Reports 11, 833 and Jones et al. (1988) Development 102, 781-792) has shown that sperm proacrosin (the zymogen form of the acrosomal proteinase acrosin, EC 3.4.21.10) has the capacity to recognize and bind sulphated polysaccharides and that this property is important for the initial stages of fertilization in mammals. To investigate whether this behaviour is specific to proacrosin, a variety of other proteinases (chymotrypsinogen, trypsinogen, thrombin, elastase, plasminogen, pepsin, Streptomyces griseus proteinase and V8 proteinase from Staphylococcus aureus) were immobilized on nitrocellulose and probed with [125I]fucoidin. Only chymotrypsinogen and trypsinogen retained significant amounts of the probe with Kd values of 1.4.10(-6) M and 3.0.10(-5) M, respectively. Proteinase inhibitors were ineffective as blocking agents suggesting that enzymic activity is not involved in recognition. However, the tertiary structure of the proteins is important, since cleavage of intramolecular disulphide bonds with 2-mercaptoethanol reduced binding by 50-60%. Competition experiments with a variety of mono- and polysaccharides suggest that the number and disposition of sulphate groups is critical for interaction with basic residues on the protein. It is concluded that, like proacrosin, chymotrypsinogen and trypsinogen are bifunctional proteins.

Acrosin↗