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Biomedical subjects

G J Wishart

Publications and source records attributed to G J Wishart.

At least 19 recordsLinked to original sources
PubMed1992

Factors from fluid of the ovarian pocket that stimulate sperm motility in domestic hens.

Fluid was collected from the region of the peritoneum surrounding the ovarian pocket of domestic hens at about the time of ovulation. This fluid, diluted to 10%, increased the motility of chicken spermatozoa by a maximum of sixfold at 40 degrees C in vitro. Gel filtration revealed two peaks of motility-stimulating activity: one was identified as calcium and the other as a heat-labile substance of low M(r) (200). It is suggested that this motility-stimulating activity may facilitate fertilization, as spermatozoa are normally stored in a quiescent state within the oviduct and can be passively transported by cilia to the site of fertilization in the ovarian pocket.

Animals↗
PubMed1991

Temperature-mediated regulation of calcium flux and motility in fowl spermatozoa.

The motility of fowl spermatozoa at various temperatures was shown to be a function of their intracellular calcium content, measured after hypotonic lysis of the cells. Retention of calcium by spermatozoa, with consequent enhancement of motility, increased as the temperature was lowered from 40 degrees to 30 degrees C. Raising the temperature within this range subsequently reduced calcium retention and motility again. The temperature-dependent retention of calcium was a function of the rate of calcium efflux rather then influx. The temperature-sensitive efflux mechanism appeared to involve a Ca2+ ATPase which was relatively inactive at 30 degrees C, but active at 40 degrees C.

Animals↗
PubMed1989

Physiological changes in fowl and turkey spermatozoa during in vitro storage.

1. Although early work on semen storage has been rather empirical in approach, only basic research can provide a framework of biological mechanisms from which improvements in the techniques of cryopreservation and liquid semen storage can progress logically. 2. A major drawback in this work has been the lack of adequate tests for quantitating and differentiating aspects of 'fertility'. 3. Basic research has now provided techniques for assessing: sperm fertilising ability in terms of numbers of fertile eggs; the efficiency of hens' oviducts at accepting and retaining spermatozoa, and sperm 'quality' as motility, metabolism and plasma membrane patency. 4. These techniques may be used for a more critical assessment of the effects of both cryopreservation and liquid semen storage on sperm function, although the integrity of sperm surface proteins may be a more sensitive variable which has yet to be measured. 5. Further improvements in sperm cryopreservation technology are best approached through an understanding of the fundamental cellular and molecular changes which take place during freezing; thus far little is known of such changes in avian spermatozoa. 6. The ideal milieu for maintaining spermatozoa in liquid semen storage should mimic the environment of the oviducal sperm storage tubules; elucidation of the factors involved in progressing steadily.

Animals↗
PubMed1989

Elucidation of the mechanism responsible for the temperature-dependent reversible inactivation of the motility of fowl spermatozoa.

1. When washed fowl spermatozoa were held at 30 degrees C in a Ca++-free medium they retained internal Ca++, assimilated from the seminal plasma in vivo, which maintained their motility. 2. When this preparation was warmed to 40 degrees C, Ca++ was lost to the medium and the spermatozoa became immotile. 3. On subsequent cooling to 30 degrees C, the spermatozoa were capable of re-sequestering the Ca++, which restored their motility. 4. Removal of internal Ca++, with subsequent reduction of cellular activity, improved the survival of fowl spermatozoa held at 30 degrees C.

Animals↗
PubMed1988

Predicting the fertilising ability of avian semen: the development of an objective colourimetric method for assessing the metabolic activity of fowl spermatozoa.

1. A simple, objective colourimetric technique for estimating the capacity of fowl spermatozoa to reduce a tetrazolium dye is described. 2. The test is shown to give a quantitative measurement of the metabolic activity of spermatozoa, as judged by their rate of oxygen utilisation, and thus of the 'quality' of semen in poultry.

Animals↗
PubMed1988

Predicting the fertilising ability of avian semen: comparison of a simple colourimetric test with other methods for predicting the fertilising ability of fowl semen.

1. The rate of tetrazolium dye-reduction by fowl spermatozoa measured by an objective colourimetric assay was shown to correlate strongly with sperm motility, morphology, ATP content and fertilising ability. 2. Although dye-reduction appeared less well correlated with fertilising ability than the other variables, the method for its determination has many practical advantages for the assessment of semen quality in poultry.

Adenosine Triphosphate↗
PubMed1987

Regulation of the motility of fowl spermatozoa by calcium and cAMP.

Using an objective light-scattering technique, it was confirmed that washed fowl spermatozoa become immotile as the temperature is raised from 30 degrees C to the normal body temperature of 40-41 degrees C. Motility of washed spermatozoa was restored at 40 degrees C by the addition of caffeine or calcium, both stimulating motility to a maximum in a dose-dependent manner. Neither effector stimulated the motility of spermatozoa at 30 degrees C. Caffeine, but not calcium, caused an increase in sperm cAMP levels at 40 degrees C. The concentrations of calcium and cAMP in untreated spermatozoa were not significantly different in samples incubated at 30 degrees C or 40 degrees C.

Animals↗
PubMed1987

Resolution of the sperm motility-stimulating principle of fowl seminal plasma into Ca2+ and an unidentified low molecular weight factor.

It was confirmed, using an objective assay of motility, that fowl seminal plasma restores and stimulates the motility of fowl spermatozoa at 40 degrees C in a dose-dependent manner. By separation of a 100,000 g supernatant of fowl seminal plasma with Sephadex G-15, two peaks of motility-stimulating activity were distinguished. One peak coincided with that of calcium and was absent when calcium was removed from the seminal plasma with Dowex 50. The other peak, which accounted for 44% of motility-stimulating activity, contained a low molecular weight, dialysable factor which remains to be identified.

Animals↗
PubMed1979

Demonstration of two functionally heterogenous groups within the activities of UDP-glucuronosyltransferase towards a series of 4-alkyl-substituted phenols.

1. A simple colorimetric assay for UDP-glucuronosyltransferase activities towards phenolic substrates, using Folin & Ciocalteu's phenol reagent, is described. The assay is used to measure rat liver transferase activities towards substrates from a series of 4-alkyl-substituted phenols. 2. Activities towards phenol, 4-methylphenol and 4-ethylphenol develop near-adult values before birth, are precociously stimulated by dexa methasone in utero and are stimulated 3--4-fold by 3-methylcholanthrene in adult liver. These are assigned to a "late-foetal" group of transferase activities. 3. Activities towards 4-n-propylphenol, 4-s-butylphenol and 4-t-butylphenol are negligible in late-foetal liver, developing to near-adult values in the first 4 postnatal days, and are not affected by dexamethasone or 3-methylcholanthrene. They are assigned to a "neonatal" group of transferase activities. 4. Although 4-ethylphenol and 4-n-propylphenol differ only by a single --CH2-- moiety, this is sufficient to change the acceptability of these substrates respectively from the late-foetal to the neonatal group of transferase activities. The change is distinct, with no overlapping of substrate acceptability between the two groups of transferase activities. 5. From consideration of the above and other substrates, the two groups of transferase activities do not distinguish substrates on the basis of their molecular weights or lipophilicity. The distinguishing feature appears to be the specific molecular configurations of the substrates.

Animals↗
PubMed1979

Differential stimulation of hepatic mono-oxygenase and glucuronidating systems in chick embryo and neonatal rat by glucocorticoids.

White Leghorn embryos infused with corticosterone precociously reproduced the hatching surges of hepatic UDPglucuronosyltransferase activity to 2-aminophenol, aminopyrine N-demethylase activity and cytochrome P-450 concentration. Onset of transferase activity followed that of the others by 48 h over hatching and on infusion. Competence of demethylase and transferase to respond to corticosterone appeared over days 12--14. Glucocorticoids are suggested as the natural triggers of both transferase and monooxygenase activities in chick and both processes may share a further control. Exposure of CD rat foetuses at 18 1/2 days to dexamethasone by maternal injection evoked precocious onset of transferase activity to 2-aminophenol but not to bilirubin, nor of demethylase activity or cytochrome P-450 content. Injection of hour-old or infant rats with dexamethasone did reproduce precociously onset of the three latter and stimulated the former. Competence for glucocorticoid response thus appeared before birth for transferase activity to 2-aminophenol and at birth for the others. Onset of transferase following hatching or glucocorticoid lagged behind that of demethylase or cytochrome P-450 by 48 h in chick embryo and 36 h in newborn and infant rats; only in foetal rat was response of transferase rapid to administered glucocorticoid.

Aminophenols↗
PubMed1978

Functional heterogeneity of UDP-glucuronosyltransferase as indicated by its differential development and inducibility by glucocorticoids. Demonstration of two groups within the enzyme's activity towards twelve substrates.

1. UDP-glucuronosyltransferase activity towards 12 substrates has been assessed in rat liver during the perinatal period. 2. Between days 16 and 20 of gestation, enzyme activities towards the substrates 2-aminophenol, 2-aminobenzoate, 4-nitrophenol, 1-naphthol, 4-methylumbelliferone and 5-hydroxytryptamine (the 'late foetal' group) surge to reach adult values, while activities towards bilirubin, testosterone, beta-oestradiol, morphine, phenolphthalein, and chloramphenicol (the 'neonatal' group) remain negligible or at less than 10% of adult values. 3. By the second postnatal day, enzyme activities towards the neonatal group have attained, or approached adult values. 4. Dexamethasone precociously stimulates in 17-day foetal liver in utero transferase activities in the late foetal, but not the neonatal group. A similar inductive pattern is found for 15-day foetal liver in organ culture. 5. It is suggested that foetal glucocorticoids, whose synthesis markedly increases between days 16 and 20 of gestation, are responsibile for triggering the simultaneous surge of all the hepatic UDP-glucuronosyltransferase activities in the late foetal group. The neonatal group of activities apparently require a different or additional stimulus for their appearance. 6. The relationship of these two groups of transferase activities to other similar groups observed during induction by xenobiotics and enzyme purification is discussed.

Aminophenols↗
PubMed1978

Demonstration of functional heterogeneity of hepatic uridine diphosphate glucuronosyltransferase activities after administration of 3-methylcholanthrene and phenobarbital to rats.

After the administration of 3-methylcholanthrene to adult male rats, activities of hepatic UDP-glucuronosyltransferase towards six from a group of 12 substrates were stimulated by 250-350%. Activities towards the remaining six substrates were unaffected. Conversely, after phenobarbital administration, activities formerly stimulated by 3-methylcholanthrene remained unchanged, and the other six activities were stimulated by 160-280%. The relationship of these two groups of transferase activities to other evidence suggesting the same heterogeneity of the enzyme is discussed.

Animals↗
PubMed1977

Regulation of onset of development of UDP-glucuronosyltransferase activity towards o-aminophenol by glucocorticoids in late-foetal rat liver in utero.

1. A precocious development of UDP-glucuronosyltransferase activity (EC 2.4.1.17) towards o-aminophenol is demonstrated in 15-17 day foetal rat liver in utero after dexamethasone administration to the mother. 2. This stimulation of liver transferase activity in utero is directly proportional to the dose of dexamethasone infected. 3. Precocious development of transferase activity in utero can also be effected with the natural glucocorticoid cortisol by multiple injections of large amounts of this hormone into the mother. 4. Transferase activity towards o-aminophenolin foetal lung, kidney and upper alimentary tract can also be precociously stimulated by dexamethasone in 17-day foetuses in utero. 5. Natural development of hepatic transferase activity between days 18 and 20 of gestation is retarded after foetal hypophysectomy by decapitation in utero. 6. Overall glucuronidation of o-aminophenol, as observed in foetal rat liver, is also precociously stimulated by dexamethasone. 7. From this and from evidence previously presented we suggest that glucocorticoids, which are known to increase in rat foetuses between days 17 and 20 of gestation, trigger the normal development in utero of hepatic transferase activity towards o-aminophenol which occurs at that time. We also suggest that these hormones are responsible for the rise in activity of the enzyme in foetal lung, kidney and upper alimentary tract which occurs during the same gestational period.

Aniline Compounds↗
PubMed1977

Precocious development of uridine diphosphate glucuronosyltransferase activity during organ culture of foetal rat liver in the presence of glucocorticoids.

1. Precocious development of mammalian UDP-glucuronosyltransferase (EC 2.4.1.1.7) induced by endogenous compounds of known chemical composition is reported for the first time. 2. This development occurs in cultured explants of foetal rat liver when exposed to corticosteroids possessing a pregn-4'-ene structure and a hydroxy or an oxo group at C-11. 3. Explants from 14-day foetuses cultured for 3 days in a chemically defined medium containing dexamethasone exhibited transferase activities towards o-aminophenol within adult male values. Those liver transferase activities attained in utero by 17 days were still negligible. 4. Evidence from several approaches indicated that the explants required glucocorticoids for expression of the transferase, not for maintenance of viability. 5. Glucocorticoid-dependent stimulation of transferase activity required incorporation of L-[14C]leucine into protein, as judged from the pulsing of cultures with cycloheximide. 6. The relevance of these culture experiments to the situation in vivo is discussed.

Amino Acids↗