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Biomedical subjects

T G Cooper

Publications and source records attributed to T G Cooper.

At least 109 records · Page 6Linked to original sources
PubMed1996

Changes in the motility patterns of spermatozoa from the rabbit epididymis as assessed by computer-aided sperm motion analysis.

Sperm maturation in the epididymis includes changes in their potential for motility that enables spermatozoa to reach the egg and penetrate its investments. The motility characteristics of spermatozoa from the testis, the epididymis, and vas deferens of the rabbit were investigated by computer-assisted sperm analysis (CASA). Various forms of motility were displayed by sperm from different regions of the epididymis released into incubation medium. Testicular sperm were motile, although nonprogressive. The maximum percentage motility was expressed by sperm in the proximal cauda epididymidis, and forward progression was developed by spermatozoa from the distal caput. Once forward progression was established, the curvilinear velocity was about the same for sperm from all regions of the tract, whereas straight-line velocity increased between the mid-corpus and cauda and paralleled the decline in lateral displacement of the head. The maintenance of motility in vitro was best maintained by sperm from the distal regions of the tract although sperm from the distal caput maintained motility better than sperm from the proximal and midcorpus regions. Analysis of the motile sperm cells revealed several types of trajectories ("irregular," "small circular," "large circular and arcs," "jagged" and "straight-line") that were analyzed by discriminant analysis using the variables generated by CASA. Accuracy of classification varied from 70% to 96%, depending on the type of track. The classification function was then applied to the changes that occurred during incubation and showed that irregular trajectories gave way to small and then large circular tracks and progressive forms as sperm matured.

Animals↗
PubMed1996

Force of voluntary exercise does not affect sensorimotor cortex activation as detected by functional MRI at 1.5 T.

Echo-planar brain images (1.5 T, 1-shot GRE, TR/TE = 3000/45) were acquired during 30-60 s cycles of repetitive (1.3-1.7 Hz) finger flexion exercise against light (0.24) vs heavy (1.40 kg) weights. In protocols during which exercise was alternated with periods of rest, active voxels were identified in the contralateral motor and somatosensory areas by cross-correlation against an on-off waveform. However, there was no significant difference between the responses to light vs heavy weights. In a continuous repetitive exercise protocol, in which only the weights were cycled, no force-correlated voxels were identified. Inasmuch as force-correlated neurons are known to be present in the primate cortex, the results illustrate a potential limitation of functional MRI studies based on the BOLD effect.

Adult↗
PubMed1996

The role of phosphocreatine kinase in the motility of human spermatozoa supported by different metabolic substrates.

In the spermatozoa of some species creatine kinase (CK: E.C. 2.7.3.2) is involved in shuttling energy, in the form of creatine phosphate, between the mid-piece mitochondria and flagellum. In this study, the effects of the CK inhibitor dinitrofluorobenzene (DNFB) on human sperm CK activity, motility and ATP concentrations were assessed with different energy substrates. There was a dose-dependent inhibition of CK activity by DNFB but inhibition was incomplete and there was no effect on the percentage of flagellating cells, irrespective of substrate. However, when lactate alone supported the cells DNFB decreased velocities and increased amplitude of head displacement (fewer progressively motile forms were observed), whereas ATP concentrations in spermatozoa were unaltered. Demembranated sperm models could be reactivated by ADP plus creatine phosphate, but not to the extent caused by ATP, and were able to be inhibited by myokinase inhibitors. Increased velocities, linearity (LIN) and beat cross frequency (BCF) were demonstrated for spermatozoa incubated with lactate, in contrast to glucose as sole energy source, and higher velocities and BCF were generated in the presence of both substrates. This suggests that the production of ATP by glycolysis and respiration are independent and complementary. CK is not obligatory for sperm motility but supplements energy provision under certain conditions.

Adenosine Triphosphate↗
PubMed1996

Changes in chromatin condensation of human spermatozoa during epididymal transit as determined by flow cytometry.

Inasmuch as caput epididymal and even testicular spermatozoa are now being used to generate pregnancies by direct injection into the oocyte, differences in the chromatin of spermatozoa from proximal and distal locations in the epididymis were studied. Acridine Orange staining was used to investigate chromatin structure in human spermatozoa which had left the testis and were undergoing maturation in the epididymis. Measurement of green and red fluorescence intensities of human spermatozoa by flow cytometry demonstrated a decrease in binding of Acridine Orange to DNA as the spermatozoa traversed the epididymis. Using spermatozoa from the cauda epididymis as the standard, the percentages of spermatozoa from the efferent duct, proximal corpus epididymis, midcorpus epididymis, distal corpus epididymis, proximal cauda epididymis and distal cauda epididymis that had matured with regard to chromatin condensation were 28 +/- 5, 39 +/- 3, 49 +/- 5, 64 +/- 5, 69 +/- 6 and 74 +/- 4% respectively. It may be concluded that eggs fertilized by ejaculated spermatozoa receive a more highly condensed form of chromatin than that received by eggs inseminated with proximal epididymal or testicular spermatozoa.

Acridine Orange↗
PubMed1996

Maturation of sperm motility in the epididymis of the common marmoset (Callithrix jacchus) and the cynomolgus monkey (Macaca fascicularis).

The acquisition by spermatozoa of the capacity for movement upon liberation from the epididymal duct into buffer is one of the obvious changes associated with sperm maturation and, hence, studies of sperm kinematics might provide good indices for sperm maturation. Profiles of development in the movement pattern of spermatozoa taken from six regions of the epididymis were established in marmoset and cynomolgus monkeys using computer-assisted sperm analysis. Motion of spermatozoa from initial regions was sluggish and irregular, then developed in the more distal region into erratic movement effected by an increase in the vigour of flagellation as reflected by curvilinear velocity. The tendency of immature spermatozoa to display circular motion was more common in the marmoset than in the cynomolgus monkey. In the marmoset the most drastic changes in percentage motility and kinematic parameters of spermatozoa occurred between the distal caput and the proximal corpus; maximal values for these parameters were found around the distal corpus epididymis. For the cynomolgus spermatozoa the sharpest gain in percentage motility was also achieved between the caput and proximal corpus epididymis, but with full kinematic development in the proximal cauda epididymis. These maturational changes were not synchronous among spermatozoa from the same site as they moved along the epididymis, as reflected in the heterogeneity of each sample in the kinematic properties of individual spermatozoa, especially those from the proximal corpus epididymis. The maturational profiles in the monkeys are comparable to the situation in the human, for which they may provide a useful model.

Animals↗
PubMed1996

The effect of bradykinin and the bradykinin antagonist Hoe 140 on kinematic parameters of human spermatozoa.

Bradykinin (BK) has been suggested to be an active substance in the disputed therapeutic use of kallikrein to improve semen quality. The effects of exogenous BK and its antagonist Hoe 140, which acts on one of the bradykinin receptors (BK2), were examined in two groups of patients attending the fertility clinic: those with asthenozoospermia (group I) and normozoospermia (group II). Bradykinin (10nM-1 microM) added to washed human spermatozoa had no effect on most kinematic parameters and caused only a marginal increase (7%) in curvilinear velocity at 50 nM in group I patients; however, this increase was not suppressed by concomitant addition of the BK antagonist. The bradykinin antagonist itself had no effect on the percentage motility or kinematic motility parameters of washed human spermatozoa in either group of patients. The motility of spermatozoa in semen was also unaffected by the presence of the bradykinin antagonist. It is concluded that bradykinin does not act exogenously on washed spermatozoa nor endogenously on spermatozoa in semen to stimulate motility via BK2 receptors, regardless of the initial quality of the sperm motility.

Bradykinin↗
PubMed1996

G1n3p is capable of binding to UAS(NTR) elements and activating transcription in Saccharomyces cerevisiae.

When readily used nitrogen sources are available, the expression of genes encoding proteins needed to transport and metabolize poorly used nitrogen sources is repressed to low levels; this physiological response has been designated nitrogen catabolite repression (NCR). The cis-acting upstream activation sequence (UAS) element UAS(NTR) mediates Gln3p-dependent, NCR-sensitive transcription and consists of two separated dodecanucleotides, each containing the core sequence GATAA. Gln3p, produced in Escherichia coli and hence free of all other yeast proteins, specifically binds to wild-type UAS(NTR) sequences and DNA fragments derived from a variety of NCR-sensitive promoters (GDH2, CAR11 DAL3, PUT1, UGA4, and GLN1). A LexA-Gln3 fusion protein supported transcriptional activation when bound to one or more LexAp binding sites upstream of a minimal CYC1-derived promoter devoid of UAS elements. LexAp-Gln3p activation of transcription was largely independent of the nitrogen source used for growth. These data argue that Gln3p is capable of direct UAS(NTR) binding and participates in transcriptional activation of NCR-sensitive genes.

Base Sequence↗
PubMed1996

Combinatorial regulation of the Saccharomyces cerevisiae CAR1 (arginase) promoter in response to multiple environmental signals.

CAR1 (arginase) gene expression responds to multiple environmental signals; expression is induced in response to the intracellular accumulation of arginine and repressed when readily transported and catabolized nitrogen sources are available in the environment. Up to 14 cis-acting sites and 9 trans-acting factors have been implicated in regulated CAR1 transcription. In all but one case, the sites are redundant. To test whether these sites actually participate in CAR1 expression, each class of sites was inactivated by substitution mutations that retained the native spacing of the CAR1 cis-acting elements. Three types of sites function independently of the nitrogen source: two clusters of Abflp- and Rap1p-binding sites, and a GC-rich sequence. Two different sets of nitrogen source-dependent sites are also required: the first consists of two GATAA-containing UASNTR sites that mediate nitrogen catabolite repression-sensitive transcription, and the second is arginine dependent and consists of three UAS1 elements that activate transcription only when arginine is present. A single URS1 site mediates repression of CAR1 arginine-independent upstream activator site (UAS) activity in the absence of arginine and the presence of a poor nitrogen source (a condition under which the inducer-independent Gln3p can function in association with the UASNTR sites). When arginine is present, the combined activity of the UAS elements overcomes the negative effects mediated by URS1. Mutation of the classes of sites either singly or in combination markedly alters CAR1 promoter operation and control, supporting the idea that they function synergistically to regulate expression of the gene.

Arginase↗
PubMed1996

Gat1p, a GATA family protein whose production is sensitive to nitrogen catabolite repression, participates in transcriptional activation of nitrogen-catabolic genes in Saccharomyces cerevisiae.

Saccharomyces cerevisiae cells selectively use nitrogen sources in their environment. Nitrogen catabolite repression (NCR) is the basis of this selectivity. Until recently NCR was thought to be accomplished exclusively through the negative regulation of Gln3p function by Ure2p. The demonstration that NCR-sensitive expression of multiple nitrogen-catabolic genes occurs in a gln3 delta ure2 delta dal80::hisG triple mutant indicated that the prevailing view of the nitrogen regulatory circuit was in need of revision; additional components clearly existed. Here we demonstrate that another positive regulator, designated Gat1p, participates in the transcription of NCR-sensitive genes and is able to weakly activate transcription when tethered upstream of a reporter gene devoid of upstream activation sequence elements. Expression of GAT1 is shown to be NCR sensitive, partially Gln3p dependent, and Dal80p regulated. In agreement with this pattern of regulation, we also demonstrate the existence of Gln3p and Dal80p binding sites upstream of GAT1.

Amino Acid Sequence↗
PubMed1996

Influence of oral administration of ornidazole on capacitation and the activity of some glycolytic enzymes of rat spermatozoa.

The chlortetracycline fluorescence assay was used to study the status of capacitation and the extent of induced acrosome reactions in cauda epididymidal spermatozoa from fertile and infertile rats fed, respectively, with vehicle or ornidazole (400 mg kg-1 day-1) for 10 days. Uniform bright fluorescence over the whole head was classified as the uncapacitated pattern, whereas a postacrosomal dark band, and a uniformly weaker fluorescence over the acrosome, reflected patterns intermediate between the uncapacitated and acrosome-reacted states. Acrosome-reacted spermatozoa displayed a dark head but always retained fluorescence at their tip. There was no difference between experimental and control groups of rats with regard to the development of the chlortetracycline fluorescence patterns during incubation. Under basal incubation conditions, the acrosome reaction was slightly delayed in spermatozoa from ornidazole-treated animals. In contrast, more spermatozoa were acrosome reacted in this group after incubation for 5 h when the concentration of BSA was increased from 4 to 20 mg ml-1. The Ca(2+)-ionophore A23187 induced a similar stimulation of capacitation and acrosome reactions in spermatozoa from control and ornidazole-fed animals, but in the latter group A23187 caused strong immobilization of spermatozoa. In the capacitation medium containing 5 mmol lactate l-1 and 5 mmol glucose l-1, the straight-line velocity of spermatozoa from ornidazole-treated rats was reduced by 50% compared with controls, irrespective of the concentration of BSA. Two glycolytic enzymes, triose phosphate isomerase and glyceraldehyde 3-phosphate dehydrogenase, displayed reduced activity (48% and 68% of controls, respectively) in cauda epididymidal spermatozoa from ornidazole-fed rats, whereas the activities of hexokinase and lactate dehydrogenase remained unchanged. This finding suggests that the fertility-compromising action of ornidazole is due to a disturbed glycolytic pathway.

Acrosome↗
PubMed1995

UASNTR functioning in combination with other UAS elements underlies exceptional patterns of nitrogen regulation in Saccharomyces cerevisiae.

UASNTR, the UAS responsible for nitrogen catabolite repression-sensitive transcriptional activation of many nitrogen catabolic genes in Saccharomyces cerevisiae, has been previously thought to operate only as a pair of closely related dodecanucleotide sites each containing the sequence GATAA at its core. Here we show that a single UASNTR the unrelated cis-acting element was TTTGTTTAC situated upstream of GLN1, while in another the cis-acting element was the one previously shown to bind the PUT3 protein. When a UASNTR site functions in combination with an unrelated site, the regulatory responses observed are a hybrid consisting of characteristics derived from both the UASNTR site and the unrelated site as well. These observations resolve several significant inconsistencies that have plagued studies focused on elucidation of the mechanisms involved in the global regulation of nitrogen catabolism.

Base Sequence↗
PubMed1995

Role of the epididymis in mediating changes in the male gamete during maturation.

This article reviews recent knowledge about events occurring in the epididymis that are important for sperm to fertilise eggs. Well established concepts are stated without references (see Cooper, 1986 for older literature) but recent references are included where they throw light on mechanisms of epididymal function. During their sojourn in the epididymis spermatozoa acquire the capacity to move and to fertilise eggs; they are then stored in a quiescent state prior to ejaculation. The ability of sperm to undergo the events of fertilisation are developed as a result of interactions with certain epididymal secretions. Increases in our knowledge about the genes coding for epididymal secretions has not yet been matched by similar insight into the role that these secretions play in the maturation process. However, information about the changes that occur to the sperm cells during maturation permit certain scenarios to be sketched that may reflect reality. This review is one such attempt to bring the epididymal sperm-epithelial secretion into focus.

Animals↗
PubMed1995

Immunocytochemical localisation of some lysosomal hydrolases, their presence in luminal fluid and their directional secretion by human epididymal cells in culture.

The way in which the human epididymis modifies spermatozoa during their sojourn in this structure might be clarified by knowledge of the nature of its secretions. We have examined the presence of several lysosomal hydrolases in human epididymal tissue and fluids, and their synthesis and secretion by monolayer cultures. Tissues were obtained from men undergoing orchidectomy for prostatic carcinoma. The enzymes cathepsin D and acid alpha-glucosidase were localised in the lysosomes of epithelial cells from the corpus epididymidis, by an immunocytochemical technique. Cathepsin D was also found in epithelial cells of the efferent ducts within lysosomes, apical vesicles and multivesicular bodies. No immunolocalisation of acid glucosidase in the efferent ducts or on the microvilli of the corpus was demonstrable. Cathepsin D, beta-hexosaminidase (N-acetylglucosaminidase) and alpha-glucosidase were measurable in the luminal fluid from the human corpus epididymidis; beta-hexosaminidase was secreted into the culture medium by confluent monolayers of epididymal and efferent duct cells. Immunoprecipitation of cell extracts and culture medium of these cultures incubated with 35S-methionine revealed that the precursors of cathepsin D and beta-hexosaminidase were synthesized and secreted by such monolayers. Thus, active lytic enzymes are secreted by the human epididymis and could modify sperm membranes.

Adult↗
PubMed1995

Vascular permeability to effectors of the immune system in the male rat reproductive tract at puberty.

The net movements and distribution volumes of IgG in the pubertal rat testis and epididymis were measured using physiological techniques. A new method to calculate vascular permeabilities was developed. The volume of testicular extracellular fluid accessible to IgG (Veq, microliters/g) increased between 20 and 30 days of age and remained above 20-day-old levels. Estimates of the surface areas of the exchange vessels (S, cm2) increased with age, most between 20 and 30 days of age. The speed at which equilibrium between tissue extracellular fluid and serum was reached (K, min-1) increased between 20 and 30 days and decreased between 44 and 60 days of age. The lymph flow (QL) and estimates of permeabilities (P) to IgG increased between 20 and 30 days of age and remained high. In the caput epididymidis Veq increased between 30 and 60 days and S between 44 and 60 days of age, but K increased between 30 and 44 days and decreased between 44 and 60 days of age. QL and the estimates of P increased between 20 and 44 days of age and remained at that level. In the corpus epididymidis, Veq did not change with age, but S increased between 30 and 60 days and K, QL and P between 20 and 44 days of age. In the cauda epididymidis, there were no obvious changes in Veq with age, but the estimates of S increased and K values decreased between 44 and 60 days of age. QL and P increased between 30 and 44 days and then decreased. After 30 days of age the values for Veq, K, QL and S were larger in the testis than in the cauda, whereas P at 44 days of age was not different. The number of perivascular mononuclear cell infiltrate profiles per 1000 epididymal tubule cross-sections increased with age in the caput epididymidis, but no infiltrates were observed in the corpus or cauda before 60 days of age. It is concluded that the observed increases in vascular permeability to IgG with age in the testis, caput and corpus reflect the function of the microvessels rather than an increase in the size of the vascular bed.

Animals↗