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Biomedical subjects

P Talbot

Publications and source records attributed to P Talbot.

At least 73 records · Page 4Linked to original sources
PubMed1983

Videotape analysis of hamster ovulation in vitro.

Videotape recordings were made of hamster follicles ovulating in vitro. These recordings were analyzed to characterize the morphological changes occurring in ovulating follicles and to time various events in the ovulation sequence. Before rupture, the shape of the follicle is transformed from a low to tall profile as shown previously (Martin and Talbot, '81). The complete transition from a low to tall profile required about 22.5 min. During the profile transition, the smooth muscle cells (SMC) in the base of the follicle contract (Martin and Talbot, '81), and the following events were observed. The base of the follicle moved apically. This pressed the cumulus and oocyte against the apical follicle wall, which appeared granular rather than smooth. The size of the antrum decreased presumably due to obliteration of the basal part of the antrum and movement of follicular fluid through the developing rupture site in the apex. The pressing of the cumulus against the apical wall appeared to cause final thinning and opening of the rupture site. The cumulus was extruded in two phases. Phase 1 was rapid (10-60 sec) and resulted in evacuation of about 25% of the cumulus and usually the oocyte from the antrum. Phase 2 required 2-10 min for completion and was accompanied by collapse of the follicle wall. After collapse, the cumulus remained with its follicle and could not be removed by pulling with Watchmaker's forceps. These observations provide new information on the role of SMC in hamster ovulation and characterize extrusion of the cumulus as a two-phase event.

Animals↗
PubMed1983

An impurity of malathion alters the morphology of rat lung bronchiolar epithelium.

Oral administration of O,O,S-trimethyl phosphorothioate (OOS), an impurity in technical malathion, caused morphological changes in the bronchiolar epithelium of rat lungs. OOS-treated rat lungs had fewer but larger Clara (non-ciliated) cells than lungs from control rats given either corn oil or purified malathion. Moreover, lactate dehydrogenase (LDH) activity in bronchopulmonary lavage fluid was significantly higher in OOS than in control rats. We interpret these data to mean that OOS, and/or its metabolite(s) causes a lesion in the lung. Because of the widespread agricultural use of technical malathion, future work should address the significance of our findings and the possible toxic effect of OOS on lung tissue.

Animals↗
PubMed1983

Adverse acute and chronic effects of electrical defibrillation and cardioversion on implanted unipolar cardiac pacing systems.

Six cases are presented in which a transient or chronic rise in the stimulation threshold of a permanently implanted unipolar pacemaker resulted in the loss of effective pacing after therapeutic defibrillation or cardioversion. Although damage to the pulse generator may still occur, leading to a loss of function as demonstrated in a seventh patient, improvements in the internal protection circuits of the present generation of pacemakers makes this less likely while possibly predisposing to endocardial burns and increased fibrosis at the electrode-endocardial interface. The theoretical explanations for this phenomenon are discussed, along with recommendations for the prospective and retrospective management of the pacemaker patient who requires defibrillation or cardioversion.

Adult↗
PubMed1983

Phenobarbital pretreatment protects against morphologic changes in rat bronchiolar epithelium caused by an impurity of malathion.

Oral administration (20 mg/kg) of O,O,S-trimethyl phosphorothioate (OOS) causes delayed toxicity in rats; ie, death occurs as late as 28 days after treatment. OOS-treated rats show morphologic changes in the bronchiolar epithelium of the lung; nonciliated (Clara) cells are fewer but larger 3 days after treatment. We have now found that pretreatment with the P-450-dependent mixed-function oxidase inducer, phenobarbital, protects against the morphologic changes caused by OOS. These results support the view that the lung is a target organ of the delayed toxicity caused by OOS and that OOS detoxification is mediated by P-450-dependent metabolism.

Animals↗
PubMed1982

In vitro ovulation of hamster oocytes depends on contraction of follicular smooth muscle cells.

Smooth muscle cells (SMC) of the hamster follicle contract prior to ovulation, and their contraction produces a V-shaped constriction in the base of the follicle. We have determined when basal constrictions first appear in follicles removed from females at various preovulatory times by examining stained, thick sections with a brightfield microscope. The time to ovulation was controlled by injecting the female with human chorionic gonadotropin (hCG). The shape of the follicle was classified as flat, small V, medium V, or large V depending on the size of the basal constriction. Twenty-nine out of 30 follicles removed 12 hours after the hCG injection had flat bases or small V-shaped constrictions. However, by 12.5 and 13.0 hours after hCG injection, 45 and 54%, respectively, of the follicles had medium and large V-shaped constrictions in their bases. Transmission electron microscopy was used to confirm that flat follicles had uncontracted SMC, follicles with small V's had uncontracted or slightly contracted SMC, and follicles with medium and large V's had highly contracted SMC. When 12 hour follicles were removed from females and cultured in vitro, ovulation did not occur. Microscopic examinations showed that SMC had not contracted in these follicles during culture. Some (36.6%) 12.5 hour follicles and most (69.9%) 13 hour follicles ovulated when cultured in vitro. The majority of those which failed to do so, did not have contracted SMCs. We interpret these data to mean that in hamsters follicular SMC begin to contract in some follicles between 12-12.5 hours after the hCG injection. If contraction has begun in vivo, then the ovary may be removed from the female and ovulation will occur during in vitro culture. If contraction has not begun in vivo, it will not do so using the in vitro conditions described in this study and ovulation will not occur. These observations are consistent with the idea that the contraction of follicular SMC is necessary for hamster ovulation, and suggest that either stretch or neurotransmitters may initiate SMC contraction in vivo.

Animals↗
PubMed1982

Intrafollicular pressure decreases in hamster preovulatory follicles during smooth muscle cell contraction in vitro.

Smooth muscle cells in the base of hamster follicles contract minutes prior to ovulation; during this contraction the profile of the follicle changes from low to tall. Our purpose was to measure intrafollicular pressure, independent of an intact circulatory system to the ovary, at the time when follicular smooth muscles are known to be contracting. Hamster ovaries were removed 13 hours after hCG injection and placed in a culture medium which supports in vitro ovulation. Intrafollicular pressure was measured continuously with a WPI Model 900 Micropressure system, while the follicle was being observed and photographed using a dissecting microscope and Zeiss 35 mm camera. Initial intrafollicular pressure was 2.1 +/- 1.1 mmHg (n = 47) in the absence of a blood supply. This pressure decreased slowly (0.03 mmHg/min.) until the transition from a low to tall profile occurred at which time the pressure decreased at a rate of 0.09 mmHg/min. At ovulation, the pressure drops precipitously to 0.0 mmHg. The condition of the follicle, in particular the apex, was examined using scanning electron microscopy (SEM). At 13 hours after hCG, rupture sites had started forming in the apices of 94.3% of the unovulated follicles. In some instances, surface epithelial cells were stretched apart and gaps were present between cells. More often portions of the surface epithelium were missing and the underlying cell layers were exposed. Fluid and erythrocytes were observed passing through the developing rupture sites. Taken together these observations demonstrate that intrafollicular pressure in hamster preovulatory follicles decreases gradually at the time follicular smooth muscle cells contract. We suggest that contraction of follicular SMC is a slow, gradual process which causes formation and/or enlargement of holes in the rupture site. An increase in the size or number of these apertures would lead to increased leakiness and could account for the observed acceleration in the rate of pressure decrease during profile transition. Our observations are the first to correlate changes in intrafollicular pressure with the contraction of smooth muscle cells and condition of the apex.

Animals↗
PubMed1982

Ultrastructural observations on binding and membrane fusion between human sperm and zona pellucida-free hamster oocytes.

It has been shown previously by others that capacitated human sperm will penetrate zona pellucida-free (ZPF) hamster oocytes. We have made ultrastructural observations on the binding and fusion of sperm to the oolemma in this cross. Our results show that only human sperm without acrosomes bind to ZPF hamster oocytes. Bound sperm had undergone either a normal or degenerative acrosome reaction and in some cases were morphologically abnormal. Initial binding of oocyte microvilli occurred over the sperm's inner acrosomal membrane. In later stages, microvilli were observed closely apposed to the sperm's plasma membrane overlying the equatorial segment of the acrosome and the postacrosomal region. Gamete membrane fusion occurred between the plasma membrane of the oocyte's microvilli and the sperm's plasma membrane overlying the equatorial segment and the anterior third of the postacrosomal sheath. In most experiments, sperm nuclear envelope breakdown and nuclear decondensation began soon after membrane fusion. As the sperm's chromatin dispersed, a zone devoid of organelles appeared in the cortex of the oocyte. The significance of these results as they relate to the use of the ZPF hamster oocyte in fertility testing and to the general topic of fertilization is discussed.

Acrosome↗
PubMed1981

Structure of bursae ovaricae surrounding the ovaries of golden hamster.

The ovaries of many mammals lie within membranous sacs called bursae ovaricae. In this study, we have examined the morphology of the bursa surrounding the hamster ovary using light and electron microscopy. The bursa is composed of three layers: (1) an inner, discontinuous bursal epithelium that faces the ovary; (2) a middle layer of connective tissue that contains fibroblasts, bundles of smooth muscle cells, and blood vessels; and (3) an outer, continuous epithelium that faces the peritoneal cavity. One side of the bursa has a thin layer of connective tissue, and because the ovary may be seen through it, we refer to this region of the bursa as the "window.' Elsewhere a thick layer of fat joins the connective tissue and blocks visualization of the ovary. Tracers (Evans blue and lanthanum) applied to the peritoneal surface do not penetrate beyond the peritoneal epithelium. Tracers injected into the bursal cavity penetrate all layers of the bursa, but do not pass through the peritoneal epithelium. Therefore, the bursa prevents tracer exchange between the bursal and peritoneal cavities, but exchange does take place between the bursal cavity and blood vessels within the bursa. We suggest that bundles of smooth muscle cells within the bursa may serve to regulate fluid volume and pressure within the bursal cavity. Possible functions of the complete bursa in the hamster are discussed.

Animals↗
PubMed1981

A triple-stain technique for evaluating normal acrosome reactions of human sperm.

A triple-stain technique has been developed to score normal acrosome-reacted human sperm in fixed smears. Live and dead sperm are first differentiated using the vital stain trypan blue. Sperm are then fixed in glutaraldehyde, dried onto slides, and the postacrosomal region and acrosome are differentiated using Bismark brown and Rose Bengal. Slides are examined at 1,000 X with a bright-field microscope and assessed for 1) the percentage of sperm that were alive at the time of fixation and 2) the percentage of sperm that had undergone normal acrosome reactions. Experiments are included that show that trypan blue is a reliable stain for dead sperm and that Rose Bengal stains only sperm having intact acrosomes. This technique may have applications in experimental and clinical studies on sperm capacitation, acrosome reactions, and fertilization in laboratory and domestic animals as well as in man.

Acrosome↗
PubMed1981

Detection of modifications in the tail of capacitated guinea pig sperm using lectins.

The surfaces of uncapacitated, capacitated, and trypsinized guinea pig sperm have been compared using 10 lectins. A previously described assay was used to assess the degree and pattern of agglutination induced by each lectin. Our method of evaluating the agglutination pattern was significantly improved by observing assay plates with an inverted phase contrast microscope at 200 X 320 X magnification rather than with a dissecting microscope. Following in vitro capacitation or trypsinization, the agglutinability of sperm by SBA, DBA, and WGA increased, and the agglutination pattern induced by SBA, DBA, WGA, and RCA120 changed to a predominantly reticular form. These changes did not occur when sperm were incubated in Ham's F-10, a control medium which does not support capacitation. Since binding of these lectins is inhibited by N-acetyl-D-galactosamine (SBA, DBA), D-galactose (SBA, RCA120, DBA), or N-acetyl-D-glucosamine (WGA), we conclude that surface receptors containing these residues are affected by capacitation. By examining assay plates with an inverted phase contrast microscope, we were able to show that the change in the agglutination pattern for all four lectins was due to an increase in agglutinability of the principal piece of the flagellum. It is suggested that the modification of the principal piece detected by this lectin assay may be important in the development of activated motility. Results further show that capacitation and trypsin treatment affect the sperm surface in a similar manner, and are thus consistent with the idea that a trypsin-like enzyme may modify the sperm during capacitation.

Agglutination↗
PubMed1981

An intrabursal injection procedure for the in vivo study of ovulation in hamsters.

A new procedure for studying the effect of various drugs on ovulation in vivo is described. In golden hamsters (Mesocricetus auratus), each ovary is enclosed within a complete bursa that is continuous with the oviduct. Drugs can be applied topically to ovaries by injection of a solution into a bursal cavity of an anesthetized hamster several hours before ovulation; the contralateral ovary serves as an in vivo control and receives no treatment. After ovulation, the number of ruptured follicles on experimental and control ovaries are compared. Data presented show that: (1) the operation and injection procedure per se do not affect ovulation; (2) normal saline is a suitable vehicle for administration of drugs by this route; (3) compounds with molecular weights of less than 1,000 daltons rapidly penetrate all layers of the follicle wall; (4) solutions injected into the bursal cavity 6 hours before ovulation remain there until ovulation. The advantages and limitations of this technique are discussed.

Animals↗
PubMed1981

The role of follicular smooth muscle cells in hamster ovulation.

The role of contractile cells in mammalian ovulation is uncertain. In this study, we examined the morphology and distribution of cells within the theca externa of hamster follicles at various times during ovulation. Cells with all the ultrastructural features of smooth muscle (SMC) were found only in the basal hemisphere of the follicle. In contrast, the theca externa in the top half of the follicle was composed of fibroblasts. We next examined living hamster follicles during in vitro ovulation for morphological evidence of follicular contraction. The following changes in follicle shape were observed: (1) The base of the follicle moved apically; (2) follicles, which were initially spherical, became taller and thinner; and (3) after rupture, the apical follicle wall collapsed onto the surface of the ovary. To analyze the cause of these changes, sections of fixed follicles were examined by light and electron microscopy. During the final minutes before rupture, a V-shaped constriction formed in the base of the follicle. This constriction continued to narrow and by the time of rupture, it obliterated the basal part of the antrum. We concluded that the apical movement of the base of the follicle seen in living ovaries corresponds to the formation of the basal constriction seen in fixed sections. To determine if follicular SMC were involved in formation of the constriction, the ultrastructure of SMC was examined before, during, and after the constriction formed. The morphology of the SMC changed from the characteristic of relaxed or stretched SMC to that of contracted SMC when the constriction began to form. No other type of cell in the follicle wall showed these changes in morphology. We conclude that the formation of this constriction, and possibly the increase in height of preovulatory follicles and the collapse of the follicle wall after rupture, are due to contraction of SMC in the theca externa in the basal hemisphere of the follicle. This is the first morphological demonstration that follicular SMC contract prior to rupture of the follicle. The significance of these observations in mammalian ovulation is discussed.

Animals↗
PubMed1981

Drugs that block smooth muscle contraction inhibit in vivo ovulation in hamsters.

We have demonstrated previously that smooth muscle cells (SMC) in the base of hamster follicles contract minutes before ovulation. The contraction of these cells correlates well in time with the development of a constriction in the base of the follicle. The purpose of this study was to determine whether contraction of SMC (1) produces this constriction and (2) is necessary for ovulation. We treated preovulatory hamster ovaries with six classes of drugs (lanthanides, calcium antagonists, local anesthetics, prostaglandins, cAMP modulators, and cytochalasin B) known to inhibit SMC contraction in other tissues. Drugs were injected into the experimental bursal cavity of a hamster 3 hours before ovulation; the contralateral ovary received no treatment and served as a control. Three hours after ovulation, the number of ruptured follicles on experimental and control ovaries were compared by light and electron microscopy. All the smooth muscle (SM) inhibitors, except those that affect cAMP levels and cytochalasin B, prevented (1) contraction of follicular SM, (2) constriction of the base of the follicle, and (3) ovulation. These results support the idea that contraction of follicular SMC constricts the follicle and is required for ovulation. The results further show that follicular SMC are activated by an influx of extracellular calcium and that prostaglandin F2 alpha may be involved in promoting this contraction.

Animals↗
PubMed1981

Factors affecting triple staining of human sperm.

We have previously described a triple stain for evaluating normal acrosome reactions of human sperm. This procedure uses trypan blue to distinguish live and dead sperm, Bismarck brown to stain the sperm's postacrosomal region, and rose Bengal to stain the sperm's acrosome. We have recently found that batches of rose Bengal vary significantly in their ability to produce good staining of the acrosome in this procedure. This appears to be due to variations in the intrinsic pH of rose Bengal solutions and the presence of nondye contaminants in the stain. In this study, we have evaluated acrosomal staining using 6 batches of rose Bengal and report a method for achieving uniform staining quality with each batch. Solutions of rose Bengal (0.8%) are made up in 0.1 M Tris HCl (pH 2.3) buffer and adjusted to pH 5.3 if necessary. For most batches of rose Bengal this promotes precipitation of some of the dye and an unidentified contaminating crystal. The precipitate is removed by centrifugation, and the supernatants have been found to give good to excellent staining of the acrosomes for all batches tested. Solutions of both rose Bengal and Bismarck brown are stable for at least 5 days but their pH values should be monitored daily and adjusted to 5.3 and 1.8 respectively if drifting occurs. We have also observed some variation in the intensity of rose Bengal staining of the acrosome from donor to donor and recommend that staining times in rose Bengal be adjusted for each donor.

Acrosome↗