Biomedical subjects

M R Shen

Publications and source records attributed to M R Shen.

31 records · Page 2Linked to original sources

PubMed1994

Rodent BC1 RNA gene as a master gene for ID element amplification.

ID elements are short interspersed repetitive DNA elements (SINEs) which have amplified in rodent genomes via retroposition, a process involving an RNA intermediate. BC1, an abundant ID-related transcript, is transcribed from a conserved, single-copy gene in rodents. The gene encoding BC1 RNA represents one of the earliest and possibly the first ID-containing sequence. Comparison of consensus sequences of each rodent ID with its corresponding BC1 RNA gene showed that the variations of BC1 RNA within rodents corresponded to specific changes within the ID consensus sequence for each rodent species. This supports the hypothesis that the BC1 gene is a master gene responsible for the amplification and evolution of ID elements. The rat ID family consists of at least four subfamilies, with the oldest subfamily having been derived from the BC1 RNA. The other three subfamilies appear to have been derived from a new master gene(s), which has been responsible for the large increase in ID element copy number within the rat genome. We have found that the guinea pig genome contains two copies of the BC1 gene, apparently the result of a DNA-mediated duplication event. Both of these guinea pig BC1 genes have a conserved TATA-like element in the 5' flanking region and have contributed to guinea pig ID amplifications.

Animals↗

PubMed1994

Adenosine modulation of neurotransmission in penile erection.

1. Adenosine inhibited the noradrenaline-induced contraction of rabbit corpus cavernosum in a dose-dependent manner. The effect of adenosine was greater in intact corpus cavernosa than in endothelium-denuded preparations. This finding indicates that the relaxing effect of adenosine is partially endothelium-dependent and involved in the release of endothelium-derived relaxing factors. 2. Adenosine and its analogues relaxed the noradrenaline-induced contractile response as well as inhibited the transmural nerve induced contraction with the potency order: NECA > R-PIA > adenosine. These data indicate that adenosine can modulate both the non-adrenergic non-cholinergic and adrenergic neurotransmission. DMPX, an adenosine antagonist selective for the A2 receptors, abolished the electrically elicited relaxation. However, CGS 21680, selective for A2a receptor, had no effect on relaxation. Therefore, adenosine receptors involved in the modulation of neurotransmission in rabbit corpus cavernosum appear to be A2b subtype. 3. Adenosine also induced an increase in human cavernosal arterial velocity and resistive index measured by colour duplex sonography. The combination of adenosine and 10 micrograms prostaglandin E1 was more effective in resistive index and erection grade than 20 micrograms prostaglandin E1 alone. Our results suggest that adenosine seems to be an important neuromodulator for penile erection and can be an effective and alternative combination in the treatment of impotence.

Adenosine↗

PubMed1993

Adenosine stimulates human sperm motility via A2 receptors.

The effects of adenosine and its analogues on human sperm motility were studied using a transmembrane migration method. Specific binding sites for adenosine in human sperm were also investigated. Adenosine and 5'-N-ethylcarboxamidoadenosine (NECA) stimulated human sperm motility with similar efficacies and the maximal amplitudes of motility increases were both about 70%. 3,7-Dimethyl-1-propargylxanthine (DMPX), a potent A2 antagonist, competitively antagonized NECA-induced motility stimulation. Successively higher concentrations of DMPX shifted the dose-response curve of NECA to the right in a nearly parallel fashion. Dipyridamole, an inhibitor of adenosine uptake, does not reduce the ability of adenosine to stimulate human sperm motility. In radioligand-binding studies, adenosine A1 selective analogues, cyclopentyl-1,3-dipropylxanthine and 1-methyl-2-phenylethyl adenosine, have little competitive effect on [3H]NECA binding in human sperm membrane. These results provide evidence that adenosine enhances human sperm motility via adenosine A2 receptors on the surface of sperm membranes.

Adenosine↗

PubMed1992

An in vivo assay for measuring the recombination potential between DNA sequences in mammalian cells.

Mammalian intermolecular recombination vectors that place the recombination junction within the intron of a selectable marker gene are presented. Many of the previously reported recombination assays require that recombination occur homologously and that they occur within the coding region of the selectable marker. This vector system involves the use of a human thymidine kinase (tk) minigene and measures the recombination frequency between any chosen DNA sequences, in mammalian thymidine kinase negative cells. The tk minigene is divided into a 5' vector and a 3' vector. In the 5' vector, the DNA sequence of interest is inserted in the proximal portion of tk intron 2. In the 3' vector, the DNA sequence of interest is inserted in the intron sequence between the proteolipid protein exon 2 and tk exons 3-7. Recombination through the DNA sequences of interest, either homologous or illegitimate, will reconstruct a functional tk minigene. The recombination junction is spliced out of the transcribed mRNA and thymidine kinase positive cells can be selected in hypoxanthine-aminopterin-thymidine medium. We have tested these vectors to measure the recombination potential of two Alu repetitive sequences (BLUR 8 and BLUR 11) against a control DNA sequence. BLUR 8 and BLUR 11 do not seem to recombine at a significantly higher frequency over that of the control DNA sequence. These recombination vectors display similar sensitivity to previous recombination systems, but allow tremendous flexibility in the choice of potentially recombinogenic sequences.

Animals↗

PubMed1992

Effects of lithium and haloperidol on human sperm motility in-vitro.

Two psychotropic drugs, lithium and haloperidol, were evaluated for their in-vitro effects on sperm motility using a transmembrane migration method. Sperm motility was measured either immediately after semen had been mixed with the drug or after a 2 h incubation period at 37 degrees C. Lithium inhibited human sperm motility in a dose-dependent manner with an EC50 of 10 mM when the semen-lithium mixture had been incubated. Sperm motility was increased to 127% of control when semen had been incubated with 0.027 microM haloperidol; this concentration was within the therapeutic range.

Dose-Response Relationship, Drug↗

PubMed1992

Study of the changes in collagen of the tunica albuginea in venogenic impotence and Peyronie's disease.

We identified the collagen type and content of the tunica albuginea in Peyronie's disease and venogenic impotence compared with the tunica albuginea from the donor of the renal transplant and patients with penile injury. Type III collagen was detected obviously in Peyronie's plaque and was also present in venogenic impotence. It can be hardly found in normal controls. The ratios of type III to type I collagen were significantly higher in Peyronie's plaque while there was a moderate increase in venogenic impotence. The scarcity of type V collagen was noted in human tunica albuginea. The decreased percentage of glycine and alanine in Peyronie's disease and venogenic impotence implied the abnormal composition of collagen or presence of noncollagen protein. The results suggest the biochemical aberration of the tunica albuginea might interfere with the normal function of the penile drainage system.

Amino Acids↗

PubMed1992

Effects of pentoxifylline in the hamster zona-free oocyte spermatozoa penetration assay and on spermatozoa transmembrane migration motility.

The effects of pentoxifylline on capacitation, acrosome reaction and motility of spermatozoa in vitro were evaluated by the hamster zona-free oocyte penetration assay and the transmembrane migration method, respectively. The improvement in penetration capacity by the addition of pentoxifylline 40 min before coincubation had a trend toward statistical significance (0.05 less than less than 0.1) in normal fertile men and had statistical significance (p less than 0.05) in asthenospermic patients. There was no improvement by the addition of pentoxifylline 16 h before coincubation. Pentoxifylline significantly increased sperm motility in both normal (p less than 0.001) and asthenospermic patients (p less than 0.05) in the transmembrane migration method. This study showed that pentoxifylline could be used as a stimulant of in vitro sperm motility in male infertility.

Animals↗

PubMed1992

A possible role of heat shock proteins in human sperm motility.

The testicular spermatogenic stem and seminiferous tubular cells selectively synthesize heat shock proteins (Hsps) during heat stress. Hsps, synthesized from testicular cells and leukocytes, are identical in molecular masses as well as chemical properties. In this study, we induced the Hsps from leukocytes and investigated their in vitro effects on human sperm motility. Semen samples were divided into two parts, washed and unwashed. The whole blood was heated in 43 degrees C for 15 minutes for induction of Hsps. A trans-membrane migration method was used to examine the effect of heated blood plasma on human sperm motility. The main heat-induced proteins of leukocytes were detected by 2-D electrophoresis and Coomassie blue stain. Leukocytes treated by heat produced a large amount of Hsp72 and Hsp80, while only a small amount was observed in that of non-heated leukocytes. The heated blood plasma inhibited motility of washed sperm in a manner that was dose-dependent. In the presence of seminal plasma fluid, however, the inhibitory effects of heated plasma on human sperm motility could not be observed. It was concluded that the heat-induced substance(s) from leukocytes, which being highly possible the Hsps, interfered the mobility of wash human sperm and the inhibition might be antagonized by seminal plasma.

Heat-Shock Proteins↗

PubMed1991

Evolution of the master Alu gene(s).

A comparison of Alu sequences that comprise more recently amplified Alu subfamilies was made. There are 18 individual diagnostic mutations associated with the different subfamilies. This analysis confirmed that the formation of each subfamily can be explained by the sequential accumulation of mutations relative to the previous subfamily. Polymerase chain reaction amplification of orthologous loci in several primate species allowed us to determine the time of insertion of Alu sequences in individual loci. These data suggest that the vast majority of Alu elements amplified at any given time comprised a single Alu subfamily. We find that, although the individual divergence relative to a consensus sequence correlate reasonably well with sequence age, the diagnostic mutations are a more accurate measure of the age of any individual Alu family member. Our data are consistent with a model in which all Alu family members have been made from a single master gene or from a series of sequential master genes. This master gene(s) accumulated diagnostic base changes, resulting in the amplification of different subfamilies from the master gene at different times in primate evolution. The changes in the master gene(s) probably occurred individually, but their appearance is clearly punctuated. Ten of them have occurred within an approximately 15-million-year time span, 40-25 million years ago, and 8 changes have occurred within the last 5 million years. Surprisingly, no changes appeared in the 20 million years separating these periods.

Animals↗

PubMed1991

Pentoxifylline stimulates human sperm motility both in vitro and after oral therapy.

Pentoxifylline is a haemorrheologic agent often used in the treatment of peripheral vascular disorders. In this study, we measured sperm motility with a trans-membrane migration method and investigated the effect of this drug in the treatment of male infertility. We found that pentoxifylline increased motility of ejaculated spermatozoa in vitro from both normal and asthenozoospermic samples. After giving pentoxifylline to patients with asthenozoospermia for 3 months, sperm motility significantly increased, but sperm concentration did not increase. From the above results, it can be concluded that pentoxifylline is a useful drug in the treatment of normogonadotropic asthenozoospermia.

Administration, Oral↗

PubMed1990

The inhibitory effect of anticonvulsants on human sperm motility: measured with a trans-membrane migration method.

The in-vitro effects of four anticonvulsant drugs (phenytoin, phenobarbitone, carbamazepine and valproate) on human sperm motility were studied with a trans-membrane migration method. Sperm motility was measured either immediately after semen had been mixed with the drug or after a 2-hour pre-incubation at 37 degrees C. When the drug effect was evaluated after the semen-drug mixture had been pre-incubated for 2 hours, the concentration of phenytoin, carbamazepine and valproate that inhibited sperm motility to 50% of control (EC50) was 1.59, 4.23, and 5.00 mM, respectively. If sperm motility was immediately measured without preincubation, the EC50 was increased to 8.47 and 100.00 mM for carbamazepine and valproate, respectively, whereas phenytoin could not inhibit sperm motility to less than 50% of the control at the tested concentrations. Both with and without pre-incubation, phenobarbitone, even up to 12.92 mM, could not inhibit sperm motility to less than 50% of the control. The result was compatible with previous findings that drugs with a membrane stabilizing effect may inhibit human sperm motility. This study provided further information regarding the application of human sperm motility as a cellular model for future pharmacological research.

Adult↗

PubMedDate not supplied

Identification of adenosine receptors in human spermatozoa.

1. The effects of adenosine receptor agonists and antagonists on human sperm motility have been studied. Specific binding sites for adenosine and its analogues on human sperm were also investigated. 2. Agonists stimulated human sperm motility in a dose-dependent manner with a potency order of 5'-N-ethylcarboxamidoadenosine (NECA, EC50 = 0.3 mumol/L) > 2-[p-(carboxyethyl)phenylethylamino]-5'-N- ethylcarboxamidoadenosine (CGS-21680, EC50 = 10 mumol/L) > adenosine (EC50 = 100 mumol/L). 3. NECA-stimulated motility was competitively inhibited by various adenosine receptor antagonists. The potency order was 3,7-dimethyl-1-propargylxanthine > 8-(p-sulfophenyl) theophylline > xanthine amino congener. 4. The radioligand [3H]-NECA bound to sperm membrane in a saturable manner with a Bmax of 21.3 pmol/mg protein and equilibrium Kd of 4 mumol/L. Adenosine agonists and antagonists competed for [3H]-NECA binding with the same rank order of potency as for the stimulation of human sperm motility. 5. GTP gamma s inhibited 63% of specific [3H]-NECA binding with IC50 value of 11 nmol/L. This suggests that the [3H]-NECA binding sites may be coupled to one or more G proteins. 6. These results indicate the presence of adenosine A2 receptors on human sperm which are responsible for adenosine-mediated enhancement of sperm motility.

Adenosine↗

PubMedDate not supplied

Effects of antiepileptic drugs on sperm motility of normal controls and epileptic patients with long-term therapy.

The in vitro effects of four antiepileptic drugs (AEDs) on human sperm motility were studied with a transmembrane migration method. Sperm motility of epileptic patients receiving chronic AED therapy was also investigated. Sperm motility was measured immediately after semen had been mixed with AED and after a 2-h preincubation at 37 degrees C. Both in vitro and in vivo studies demonstrated that AEDs inhibited sperm motility. When the drug effect was evaluated after the semen-AED mixture had been preincubated for 2 h, sperm motility was inhibited to 50% of control at concentrations of 1.59, 4.23, and 5.00 mM for phenytoin, carbamazepine, and valproate, respectively. Both with and without preincubation, phenobarbital, even up to 12.92 mM, did not inhibit the motility to less than 50% of the control. In the in vivo study, poor sperm motility was noted in epileptic patients with long-term AED therapy despite serum levels within the therapeutic range. Shorter duration of activity of spermatozoa was also observed in these patients. Interference with sperm membrane function by AEDs may be the underlying mechanism.

Adult↗