Unilateral diaphragm paralysis: etiology, impact, and natural history

AIM

The etiology, clinical impact, natural history and best therapy of unilateral diaphragm paralysis (UDP) are incompletely understood. This condition is not amenable to pacing, which requires an intact phrenic nerve.

METHODS

Clinical records of patients with UDP referred to our diaphragm center were reviewed.

RESULTS

Thirty-six patients (28 male, 8 female) aged 1 month to 78 years (mean 47.8 years) with UDP evaluated from 1983 to February 2007 were reviewed. Etiology was postsurgical in 13 (36%), tumor (with surgery or radiation therapy) in 7 (19%), idiopathic in 6 (17%), trauma (motor vehicle accident or head injury) in 5 (14%), polio in 3 (8%), and viral in 2 (6%) patients. 28 patients (78%) were symptomatic; 8 (22%) carried a diagnosis of coexisting chronic obstructive pulmonary disease. Mean duration of paralysis was 57.9 months (range up to 261 months). The left diaphragm was involved in 23 cases (64%) and the right in 13 (36%). Mean forced expiratory volume (FEV1) was 1 915 mL (61.3% of predicted) and mean forced vital capacity (FVC) was 2 432 mL (62.9% of predicted). Mean pO2 was 69.9 mmHg (range 49 to 124), indicating considerable shunting through underventilated lung. Pulmonary infection affected 3 patients (8.4%). Diaphragm function returned in 17% of patients (mainly children) at mean of 10.3 months. Four incapacitated patients (11 %) were treated surgically, with resection of the hemi-diaphragm. Surgical exploration revealed neurogenic atrophy of the diaphragm muscle. All 4 resected patients showed clinical, oxymetric, and spirometric improvement.

CONCLUSION

The conclusion is drawn that: 1) UDP may be traumatic, tumor-related, iatrogenic, or idiopathic; 2) UDP decreases pO(2) substantially and breathing capacity by more than 1/3; 3) spontaneous recovery is possible; 4) UDP is not intrinsically lethal; 5) occasional patients are incapacited; 6) diaphragm resection produces clinical improvement via lower lobe re-expansion; 7) the incapacity incurred by UDP is mild compared to the clinical spectrum of bilateral diaphragm paralysis.

Contraceptive development: targets, approaches and challenges

The control of fertility constitutes a global health issue, since overpopulation and unintended pregnancy have both major personal and societal impact. Although some regions of the world are seeing neutral or negative population growth, many developing countries are seeing explosive growth of their populations and these population changes will affect the entire globe. It is estimated that in a decade, the largest cohort of young women worldwide in human history will reach adolescence thus necessitating the need for a wide range of contraceptive options that can be used by both females and males. The contraceptive revolution that occurred in the 1960s with the development of the hormonal-based oral contraceptive for women has subsequently made a significant impact on societal dynamics in several cultures, yet there has been virtually no innovation in this field since that time. This lack of innovation contrasts dramatically with the vast enhancement of our knowledge base of the basic processes of reproduction. The genomic and proteomic revolutions have provided new tools and new targets for contraceptive development, and the results of such approaches have identified gene products that play critical roles in female and male reproduction, thus expanding the array of targets for novel and innovative female- and male-based contraceptives. This normally would herald a renaissance in contraceptive development, yet the commitment of industry to this endeavor is limited to a few firms due to the economics of contraceptive development. This chapter will consider the types of targets being considered in the development of new generations of contraceptives and will also focus on the challenges that industry has in meeting these goals.

Comparison of two culture systems for the in-vitro growth and maturation of mouse preantral follicles

The objective of our study was to compare to ability of collagen-treated membranes and bovine collagen gels to maintain murine preantral follicle growth and development in-vitro. To fulfill that objective, murine follicle and oocyte growth rates were followed for ten days in culture. Meiotic competence and the capacity to reach the two-cell stage after in-vitro maturation and fertilization, respectively, were then assessed. We used preantral follicles from 12 day-old CF-1 female mice that were isolated by enzymatic digestion from ovaries. Follicles were placed either on collagen-treated membranes or embedded in a bovine collagen matrix. The follicles were grown, changing the media and obtaining measurements every other day for ten days. Following culture, the granulosa-oocyte complexes were matured; the resultant metaphase II arrested oocytes were inseminated and cultured to the two-cell stage. The data was analyzed with significance considered for probability values of p < 0.05. We performed individual measurements on 650 follicles in seven separate experiments. Forty-eight hours after initial seeding and throughout the entire length of culture, both the follicles and oocytes grown in the collagen matrix were larger than follicles cultured on collagen-treated membranes (p < .0001). However, oocyte recovery rates were higher among follicles cultured on collagen-treated membranes (p < .01). Similar percentages of meiotically competent oocytes, fertilization and cleavage rates were observed in both groups. Our results show that mouse preantral follicles display a greater growth rate when grown embedded in a collagen gel matrix. This may be due to the maintenance of a normal three-dimensional organization of the follicle within the collagen matrix. However, this system does not enhance meiotic competency or fertilization rates in the mouse when compared to culture on collagen-treated membranes.

Expression and localization of caveolin-1, and the presence of membrane rafts, in mouse and Guinea pig spermatozoa

In somatic cells, caveolin-1 plays several roles in membrane dynamics, including organization of detergent-insoluble lipid rafts, trafficking of cholesterol, and anchoring of signaling molecules. Events in sperm capacitation and fertilization require similar cellular functions, suggesting a possible role for caveolin-1 in spermatozoa. Immunoblot analysis demonstrated that caveolin-1 was indeed present in developing mouse male germ cells and both mouse and guinea pig spermatozoa. In mature spermatozoa, caveolin-1 was enriched in a Triton X-100-insoluble membrane fraction, as well as in membrane subdomains separable by means of their light buoyant densities through sucrose density gradient centrifugation. These data indicated the presence of membrane rafts enriched in caveolin-1 in spermatozoa. Indirect immunofluorescence analysis revealed caveolin-1 in the regions of the acrosome and flagellum in sperm of both species. Confocal immunofluorescence analysis of developing mouse male germ cells demonstrated partial co-localization with a marker for the acrosome. Furthermore, syntaxin-2, a protein involved in acrosomal exocytosis, was present in both raft and nonraft fractions in mature sperm. Together, these data indicated that sperm membranes possess distinct raft subdomains, and that caveolin-1 localized to regions appropriate for involvement with acrosomal biogenesis and exocytosis, as well as signaling pathways regulating such processes as capacitation and flagellar motility.

Stroke in surgery of the thoracic aorta: incidence, impact, etiology, and prevention

OBJECTIVES

To determine the incidence, impact, etiology, and methods for prevention of stroke after surgery of the thoracic aorta.

METHODS

A total of 317 thoracic aortic operations on 303 patients (194 male, 109 female) aged 13 to 87 years (mean 61 years) were reviewed. There were 218 procedures on the ascending aorta and arch and 99 on the descending aorta. Of the 218 procedures on the ascending aorta and arch, 86 involved cardiopulmonary bypass, 122 involved deep hypothermic circulatory arrest, 2 involved antegrade cerebral perfusion, and 8 involved "clamp and sew" or left heart bypass. Of the 99 procedures on the descending aorta, 20 involved "clamp and sew," 69 involved left heart or full bypass, and 10 involved deep hypothermic circulatory arrest. A total of 206 cases were elective and 97 were emergency operations.

RESULTS

Twenty-three (7.3%) of 317 patients had a stroke. Fifteen strokes occurred in operations on the ascending aorta and 8 in operations on the descending aorta (6.9% vs 8.1%; P =.703). Stroke occurred in 16 (16.5%) of 97 emergency operations and 7 (3.4%) of 206 elective operations (P =.001). In the 300 patients surviving the operation, stroke was a significant predictor of postoperative death (9/23 [39.1%] vs 23/277 [8.3%]; P =.001). Analysis of operative reports, brain images, and neurologic consultations revealed 15 of the 23 strokes were embolic, 3 were ischemic, 3 hemorrhagic, and 2 indeterminate. Patients with stroke had longer intensive care unit stays (18.4 vs 6.8 days; P =.0001), longer times to extubation (12.7 vs 3.8 days; P <.0012), longer postoperative stays (31.4 vs 14.3 days; P =.001), and decreased age-adjusted survival (relative risk 2.775; P =.0013). After implementation of a rigorous antiembolic regimen, both strokes and mortality trended downward.

CONCLUSIONS

(1) Stroke complicates surgery of both the ascending and descending thoracic aorta and warrants consideration in decision making. (2) Strokes are largely embolic. (3) Antiembolic measures for particles and air are essential, including gentle aortic manipulation, thorough debridement, transesophageal echocardiography to identify aortic atheromas, carbon dioxide flooding of the field, and (in descending cases) proximal clamp application before initiating femoral perfusion.

Cloning and chromosomal localization of a gene encoding a novel serine/threonine kinase belonging to the subfamily of testis-specific kinases

Using reverse transcription-polymerase chain reaction (RT-PCR) with degenerate oligonucleotides corresponding to two highly conserved motifs within the protein kinase family of catalytic domains, we isolated a PCR fragment encoding a novel member of the testis-specific serine/threonine kinases (STK) from mouse male mixed germ cell mRNA. This PCR fragment recognized a 1020-bp transcript in male germ cells by northern blot analysis and was used to clone a full-length cDNA from a mouse mixed germ cell cDNA library. This cDNA has an open reading frame of 804 bases encoding a protein of 268 amino acids. This novel gene is almost identical to Stk22c, encoding a recently described testis-specific protein kinase, except for base-pair deletions that result in a shift in the coding region and an alteration of 22 amino acids (residues 109-131). Due to its homology with Stk22c, we have called this protein kinase gene Stk22d. Northern blot analysis revealed that this protein kinase is developmentally expressed in testicular germ cells and is not present in brain, ovary, kidney, liver, or early embryonic cells. We then cloned the human homologue of this protein kinase gene (STK22C) and found it to be expressed exclusively in the testis. Fluorescence in situ hybridization with both the human and mouse cDNA clones revealed syntenic localization on chromosomes 1p34-p35 and 4E1, respectively.

Single-clamp technique does not protect against cerebrovascular accident in coronary artery bypass grafting

OBJECTIVES

By potentially avoiding the embolic consequences of a side-biting aortic clamp, the single-clamp technique may decrease cerebrovascular accidents in coronary artery bypass grafting. However, this theoretical superiority in stroke prevention has not been conclusively demonstrated and use of this technique may lead to adverse myocardial effects due to longer cross-clamp times. In this study, we sought to determine if the single-clamp technique prevents postoperative stroke in clinical practice.

METHODS

Of 607 consecutive isolated coronary bypass operations completed over a 3 year period, 301 (50%) were performed by one surgeon using exclusively the single-clamp technique and 306 (50%) were performed by a second surgeon using exclusively the two-clamp technique. Postoperative adverse events were retrospectively compared between these two groups.

RESULTS

There were no differences between groups in terms of postoperative stroke (1.7% single-clamp vs. 2.0% two-clamp, P=0.78), hospital mortality (2.7% single-clamp vs. 1.6% two-clamp, P=0.38), or perioperative myocardial infarction (2.6% single-clamp vs. 0.7% two-clamp, P=0.052). The two-clamp technique was not a significant predictor of stroke by logistic regression analysis (P=0.72).

CONCLUSIONS

We conclude that there are no statistically significant differences between clamp techniques with regard to stroke prevention or myocardial protection. We find no compelling evidence for surgeons successfully utilizing one technique to change to the other.

Functional relationships between capacitation-dependent cell signaling and compartmentalized metabolic pathways in murine spermatozoa

Spermatozoa are highly polarized cells with specific metabolic pathways compartmentalized in different regions. Previously, we hypothesized that glycolysis is organized in the fibrous sheath of the flagellum to provide ATP to dynein ATPases that generate motility and to protein kinases that regulate motility. Although a recent report suggested that glucose is not essential for murine sperm capacitation, we demonstrated that glucose (but not lactate or pyruvate) was necessary and sufficient to support the protein tyrosine phosphorylation events associated with capacitation. The effect of glucose on this signaling pathway was downstream of cAMP, and appeared to arise indirectly as a consequence of metabolism as opposed to a direct signaling effect. Moreover, the phosphorylation events were not affected by uncouplers of oxidative respiration, inhibitors of electron transfer, or by a lack of substrates for oxidative respiration in the medium. Further experiments aimed at identifying potential regulators of sperm glycolysis focused on a germ cell-specific isoform of hexokinase, HK1-SC, which localizes to the fibrous sheath. HK1-SC activity and biochemical localization did not change during sperm capacitation, suggesting that glycolysis in sperm is regulated either at the level of substrate availability or by downstream enzymes. These data support the hypothesis that ATP specifically produced by a compartmentalized glycolytic pathway in the principal piece of the flagellum, as opposed to ATP generated by mitochondria in the mid-piece, is strictly required for protein tyrosine phosphorylation events that take place during sperm capacitation. The relationship between these pathways suggests that spermatozoa offer a model system for the study of integration of compartmentalized metabolic and signaling pathways.

Differential expression of the coxsackievirus and adenovirus receptor regulates adenovirus infection of the placenta

The molecular mechanisms and pathologic significance of placental viral infections are poorly understood. We investigated factors that regulate placental infection by adenovirus, which is the most common viral pathogen identified in fetal samples from abnormal pregnancies (i.e., fetal growth restriction, oligohydramnios, and nonimmune fetal hydrops). We also determined the pathologic significance of placental adenovirus infection. Northern hybridization, flow cytometry, and immunostaining revealed that placental expression of the coxsackievirus and adenovirus receptor (CAR) varied with gestational age and trophoblast phenotype. The CAR was continuously expressed in invasive or extravillous trophoblast cells but not in villous trophoblast cells. We postulate that the villous syncytiotrophoblast, which does not express CAR and is resistant to adenovirus infection, limits the transplacental transmission of viral pathogens, including adenovirus. Conversely, extravillous trophoblast cells underwent apoptosis when infected by adenovirus in the presence of decidual lymphocytes (which simulated the maternal immune response to viral infection). Thus, adenovirus infection and/or the maternal immune response to adenovirus infection induced the death of placental cell types that expressed CAR. Consequently, we speculate that adenovirus infection of extra-villous trophoblast cells may negatively impact the process of placental invasion and predispose the mother and fetus to adverse reproductive outcomes that result from placental dysfunction.

Function of basonuclin in increasing transcription of the ribosomal RNA genes during mouse oogenesis

Active protein synthesis during early oogenesis requires accelerated transcription of ribosomal RNA genes (rDNAs). In response to this demand, rDNAs are amplified more than 1000-fold early in Xenopus oogenesis. Here, we report evidence that rDNA is not amplified in mouse oocytes, but these cells may instead employ the zinc-finger protein basonuclin, a putative rDNA transcription factor, to enhance rRNA synthesis. This conclusion is based on observations that basonuclin is localized in the nucleolus in the mouse oocyte early in its growth phase, when rRNA transcription is highly active; and that the binding sites of basonuclin zinc fingers on the human and mouse rDNA promoters are homologous. In a co-transfection assay, basonuclin can elevate transcription from an rDNA promoter, and its zinc-finger domain can inhibit RNA polymerase I transcription, as detected by a run-on assay, in growing mouse oocytes.

Acquisition of meiotic competence in mouse oocytes: absolute amounts of p34(cdc2), cyclin B1, cdc25C, and wee1 in meiotically incompetent and competent oocytes

M-Phase promoting factor (MPF) is a complex of p34(cdc2) and cyclin B. Results of previous studies in which relative mass amounts of these cell cycle regulators were determined suggested that the accumulation of p34(cdc2), rather than cyclin B, could be a limiting factor in the acquisition of meiotic competence in mouse oocytes. Nevertheless, in the absence of measurements of the absolute amount of these components of MPF, it is possible that the molar amount of p34(cdc2) is in excess to that of cyclin B, i.e., the accumulation of p34(cdc2) is not a limiting factor. We report measurements of the absolute mass of p34(cdc2) and cyclin B1, as well as the two proximal regulators of MPF, namely cdc25C and wee1, in meiotically incompetent and competent mouse oocytes. We find that the numbers of molecules of p34(cdc2), cyclin B1, cdc25C, and wee1 in meiotically incompetent oocytes are 1.4 x 10(6), 11.3 x 10(6), 24.6 x 10(6), 15. 6 x 10(6), respectively, and in meiotically competent oocytes the numbers are 14.3 x 10(6), 95.5 x 10(6), 80.0 x 10(6), 40.1 x 10(6), respectively. Thus, the concentration of cyclin B1 is always in excess to that of p34(cdc2), and this is consistent with the hypothesis that the accumulation of p34(cdc2) plays a role in the acquisition of meiotic competence. Last, the concentration of cdc25C is greater than that of wee1 and the concentration of each is greater than that of p34(cdc2) in both meiotically incompetent and competent oocytes.

Surgical Management of Giant Descending Aortic Thrombus Detected by Transesophageal Echocardiography

With the advent of transesophageal echocardiography (TEE), giant thrombi of the descending aorta are becoming increasingly recognized as possible sources of peripheral emboli. This report describes the management of three patients presenting with multiple unexplained peripheral emboli. All three patients were treated successfully with aortic thrombectomy and long-term anticoagulation.

Dual regulation of the T-type Ca(2+) current by serum albumin and beta-estradiol in mammalian spermatogenic cells

This study provides evidence for a novel mechanism of voltage-gated Ca(2+) channel regulation in mammalian spermatogenic cells by two agents that affect sperm capacitation and the acrosome reaction (AR). Patch-clamp experiments demonstrated that serum albumin induced an increase in Ca(2+) T current density in a concentration-dependent manner, and significant shifts in the voltage dependence of both steady-state activation and inactivation of the channels. These actions were not related to the ability of albumin to remove cholesterol from the membrane. In contrast, beta-estradiol significantly inhibited Ca(2+) channel activity in a concentration-dependent and essentially voltage-independent fashion. In mature sperm this dual regulation may influence capacitation and/or the AR.

Comparative analysis of blood plasma epidermal growth factor concentrations, hormonal profiles and semen parameters of fertile and infertile males

The relationship between male reproductive function and the blood plasma level of epidermal growth factor (EGF) is of interest in the light of the role that circulating EGF appears to play in regulating mouse spermatogenesis. We measured the concentrations of EGF in the blood plasma of 39 fertile men (sperm count > 20 x 10(6)/ml) and compared them with those of 31 infertile men (sperm < 20 x 10(6)/ml). Blood plasma levels of follicle stimulating hormone (FSH), luiteinising hormone (LH), prolactin and testosterone were also determined. The infertile patients had mean blood plasma EGF concentrations of 0.75 +/- 0.10 ug/L. The value was significantly lower than that of the fertile group (1.28 +/- 0.14 ug/L; P < 0.005). There were statistically significant differences between the fertile and infertile groups in sperm count, sperm viability, mean forward progression, testosterone, LH and FSH (P values between 0.0001 and 0.023). There was no significant difference in the prolactin concentrations between the two groups. Although overall average blood plasma EGF concentrations are significantly lower in the infertile males, regression analysis failed to reveal any direct relationships among the various parameters studied.

Right ventricle-sparing heart transplant: promising new technique for recipients with pulmonary hypertension

BACKGROUND

Right heart failure remains the leading early cause of mortality after heart transplantation, especially with antecedent pulmonary hypertension. Paradoxically, the discarded recipient right heart, acclimated to pulmonary hypertension, is often stronger than its nonconditioned donor replacement. Heterotopic ("piggyback") transplantation is plagued by problems related to the retained, dilated, hypocontractile left ventricle (lung compression, systemic emboli, arrhythmias). Were it possible to retain the recipient's right heart, excising only the left ventricle, this could have important advantages, especially in severe pulmonary hypertension. This report describes such a technique.

METHODS AND RESULTS

In four transplantation experiments (dogs), right ventricular-sparing transplantation proved technically feasible and hemodynamically successful. Bleeding after excision of the left ventricle was easily controlled. Back-bleeding from the native aortic valve (now open into the pericardial space) was not problematic. All atrial, aortic, and pulmonary arterial connections proved feasible. The preserved recipient right heart of all animals remained in stable sinus rhythm. All recipients were easily weaned from cardiopulmonary bypass, maintaining mean arterial pressures 60 to 110 mm Hg.

CONCLUSIONS

This investigation develops a technique for donor right ventricle sparing in cardiac transplantation, demonstrating technical and hemodynamic feasibility. This method holds promise for the unsolved clinical problem of right heart failure after orthotopic heart transplantation with antecedent pulmonary hypertension.

"Cobrahead" graft for intercostal artery implantation during descending aortic replacement

A technique for a separate sidearm graft ("cobrahead") to facilitate reattachment of intercostal arteries in descending aortic replacement is described. The technique allows for very prompt restoration of spinal cord blood flow (via a Y attachment from the arterial perfusion circuit). The technique permits a simple, quick, and fully accessible anastomosis, technically more facile than the traditional side-to-side anastomosis. None of 7 patients treated with this technique had early or late paraplegia. Preliminary computed tomographic follow-up scans confirm patency of the cobrahead graft.

Effects of perturbation of cell polarity on molecular markers of sperm-egg binding sites on mouse eggs

The mouse germinal vesicle (GV)-intact oocyte is a symmetric cell, with the GV centrally localized and with components of the plasma membrane and cortex symmetrically distributed around the periphery of the oocyte. During oocyte maturation, two distinct regions of the egg plasma membrane and cortex develop: the amicrovillar region overlying the meiotic spindle and the microvillar region. The development of this polarity is significant, since sperm bind to and fuse with the microvillar region. We are interested in the development of egg polarity and have characterized the localizations of several markers for egg polarity in normal metaphase II eggs and GV-intact oocytes. The asymmetric distributions of these markers (including actin, cortical granules, binding sites for the sperm proteins fertilin alpha and fertilin beta, and two different beta(1) integrin epitopes) develop during oocyte maturation in vitro, and this polarity can be perturbed by treatments that disrupt the actin microfilaments or microtubules. In addition, immunoelectron microscopy reveals that binding sites for recombinant fertilin beta are specifically localized to the microvillar region, suggesting that the binding sites for this sperm ligand are either specifically localized or activated in this region. These results indicate that structural remodeling of the mouse egg plasma membrane is accompanied by molecular remodeling, resulting in the localization or activation of specific molecules in subdomains of the plasma membrane.

A novel NH(2)-terminal, nonhydrophobic motif targets a male germ cell-specific hexokinase to the endoplasmic reticulum and plasma membrane

Although three germ cell-specific transcripts of type 1 hexokinase exist in murine male germ cells, only one form, HK1-sc, is found at the protein level. This single isoform localizes to three distinct structures in mouse spermatozoa: the membranes of the head, the mitochondria in the midpiece, and the fibrous sheath in the flagellum (Travis, A. J., Foster, J. A., Rosenbaum, N. A., Visconti, P. E., Gerton, G. L., Kopf, G. S., and Moss, S. B. (1998) Mol. Biol. Cell 9, 263-276). The mechanism by which one protein is targeted to multiple sites within this highly polarized cell poses important questions of protein targeting. Because the study of protein targeting in germ cells is hampered by the lack of established cell lines in culture, constructs containing different domains of the germ cell-specific hexokinase transcripts were linked to a green fluorescent protein and transfected into hexokinase-deficient M+R42 cells. Constructs containing a nonhydrophobic, germ cell-specific domain, present at the amino terminus of the HK1-SC protein, were targeted to the endoplasmic reticulum and the plasma membrane. Mutational analysis of this domain demonstrated that a complex motif, PKIRPPLTE (with essential residues italicized), represented a novel endoplasmic reticulum-targeting motif. Constructs based on another germ cell-specific hexokinase transcript, HK1-sa, demonstrated the specific proteolytic removal of an amino-terminal domain, resulting in a protein product identical to HK1-SC. Such processing might constitute a regulatory mechanism governing the spatial and/or temporal expression of the protein.

Regulation of human sperm capacitation by a cholesterol efflux-stimulated signal transduction pathway leading to protein kinase A-mediated up-regulation of protein tyrosine phosphorylation

Protein tyrosine phosphorylation is an important intracellular event accompanying the in-vitro capacitation of mouse, bovine and human spermatozoa. Here, we demonstrate that bovine serum albumin (BSA) and NaHCO(3) are required for protein tyrosine phosphorylation in ejaculated human spermatozoa. The absence of protein tyrosine phosphorylation in media minus these two constituents could be recovered by addition to the media of cAMP analogues and/or phosphodiesterase inhibitors. Since BSA is postulated to modulate capacitation by removal of cholesterol from the sperm plasma membrane, we determined whether cholesterol release leads to changes in protein tyrosine phosphorylation. Incubation of spermatozoa in media containing BSA resulted in the release of significant amounts of cholesterol when compared with media devoid of BSA. Preloading BSA with cholesterol-SO(4) inhibited protein tyrosine phosphorylation, as well as capacitation, and this inhibitory effect was overcome by the addition of dibutyryl cAMP plus isobutylmethylxanthine (IBMX). The functional significance of BSA-mediated cholesterol release, protein tyrosine phosphorylation and capacitation was confirmed by examining the effects of the cholesterol-binding heptasaccharides, methyl-beta-cyclodextrin or OH-propyl-beta-cyclodextrin. Both cyclodextrins caused cholesterol efflux from the spermatozoa, increased protein tyrosine phosphorylation, and stimulated capacitation. Therefore, cholesterol release is associated with the activation of a signal transduction pathway involving protein kinase A and tyrosine kinase second messenger systems, and resulting in protein tyrosine phosphorylation and capacitation.

Cholesterol efflux-mediated signal transduction in mammalian sperm: cholesterol release signals an increase in protein tyrosine phosphorylation during mouse sperm capacitation

We previously demonstrated that mouse sperm capacitation is accompanied by a time-dependent increase in protein tyrosine phosphorylation that is dependent on the presence of BSA, Ca2+, and NaHCO(3), all three of which are also required for this maturational event. We also demonstrated that activation of protein kinase A (PK-A) is upstream of this capacitation-associated increase in protein tyrosine phosphorylation. BSA is hypothesized to modulate capacitation through the removal of cholesterol from the sperm plasma membrane. In this report, we demonstrate that incubation of mouse sperm medium containing BSA results in a release of cholesterol from the sperm plasma membrane to the medium; release of this sterol does not occur in medium devoid of BSA. We next determined whether cholesterol release leads to changes in protein tyrosine phosphorylation. Blocking the action of BSA by adding exogenous cholesterol-SO-(4) to the BSA-containing medium inhibits the increase in protein tyrosine phosphorylation as well as capacitation. This inhibitory effect is overcome by (1) the addition of increasing concentrations of BSA at a given concentration of cholesterol-SO-(4) and (2) the addition of dibutyryl cAMP plus IBMX. High-density lipoprotein (HDL), another cholesterol binding protein, also supports the capacitation-associated increase in protein tyrosine phosphorylation through a cAMP-dependent pathway, whereas proteins that do not interact with cholesterol have no effect. HDL also supports sperm capacitation, as assessed by fertilization in vitro. Finally, we previously demonstrated that HCO-(3) is necessary for the capacitation-associated increase in protein tyrosine phosphorylation and demonstrate here, by examining the effectiveness of HCO-(3) or BSA addition to sperm on protein tyrosine phosphorylation, that the HCO-(3) effect is downstream of the site of BSA action. Taken together, these data demonstrate that cholesterol release is associated with the activation of a transmembrane signal transduction pathway involving PK-A and protein tyrosine phosphorylation, leading to functional maturation of the sperm.

Roles of bicarbonate, cAMP, and protein tyrosine phosphorylation on capacitation and the spontaneous acrosome reaction of hamster sperm

Capacitation is a prerequisite for successful fertilization by mammalian spermatozoa. This process is generally observed in vitro in defined NaHCO3-buffered media and has been shown to be associated with changes in cAMP metabolism and protein tyrosine phosphorylation. In this study, we observed that when NaHCO3 was replaced by 4-(2-hydroxyethyl)1-piperazine ethanesulfonic acid (HEPES), hamster sperm capacitation, measured as the ability of the sperm to undergo a spontaneous acrosome reaction, did not take place. Addition of 25 mM NaHCO3 to NaHCO3-free medium in which spermatozoa had been preincubated for 3.5 h, increased the percentage of spontaneous acrosome reactions from 0% to 80% in the following 4 h. Addition of anion transport blockers such as 4,4'-diiso thiocyano-2, 2'-stilbenedisulfonate (DIDS) or 4-acetomido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) to the NaHCO3-containing medium inhibited the acrosome reaction, with maximal inhibition at 600 microM, and with an EC50 of 100 microM. Increasing either extracellular or intracellular pH did not induce the acrosome reaction in NaHCO3-free medium. In contrast, addition of 500 microM dibutyryl cAMP (dbcAMP), alone or together with 100 microM 1-methyl-3-isobutylxanthine (IBMX), induced the acrosome reaction in spermatozoa incubated in NaHCO3-free medium. These compounds also partially reversed the inhibition of the acrosome reaction caused by the DIDS or SITS in complete medium. In contrast to these results, IBMX or dbcAMP did not induce acrosome reactions in cells incubated in Ca2+-free medium. When hamster sperm were incubated in the absence of NaHCO3 or in the presence of NaHCO3 and DIDS, cAMP concentrations were significantly lower than the values obtained from sperm incubated in complete medium. Protein tyrosine phosphorylation has also been shown to be highly correlated with the onset of capacitation in many species. During the first hour of capacitation, an increase in protein tyrosine phosphorylation was observed in complete medium. In the absence of NaHCO3, the increase in protein tyrosine phosphorylation was delayed for 45 min, and this delay was overcome by the addition of dbcAMP and IBMX. The induction of the acrosome reaction by calcium ionophore A23187 in NaHCO3-free medium was delayed 2 h, as compared with control medium. This delay was not observed in the presence of dbcAMP and IBMX. Taken together, these results suggest that a cAMP pathway may mediate the role of NaHCO3 in the capacitation of hamster spermatozoa and that protein tyrosine phosphorylation is necessary but not sufficient for complete capacitation.

Control of the low voltage-activated calcium channel of mouse sperm by egg ZP3 and by membrane hyperpolarization during capacitation

Sperm adhesion to egg zonae pellucidae initiates sperm acrosome reactions, an exocytotic event that is an early step during fertilization. Previously, it was suggested that zona pellucida-evoked Ca2+ entry into sperm through low voltage-activated Ca2+ channels is an essential step in acrosome reactions, based on the inhibitory effects of Ca2+ channel antagonists. However, analysis of this channel is limited by the inability to apply electrophysiological methods directly to sperm. In this report, optical methods of determining membrane potential and internal Ca2+ levels were used to demonstrate that (i) contact with zonae pellucidae activates a transient Ca2+ response in sperm that has a time course and antagonist sensitivity anticipated of low voltage-activated Ca2+ channels; (ii) these channels are unavailable for opening in uncapacitated sperm because of voltage-dependent, steady state inactivation; (iii) membrane hyperpolarization during sperm capacitation is sufficient to recruit channels into a closed state, from which they are available for opening during fertilization; and (iv) channel conductance state may be a factor in determines the efficacy with which channel antagonists inhibit fertilization. This study provides evidence for the activation of sperm Ca2+ channels during gamete adhesion and offers a mechanism that may account for aspects of the regulation of sperm fertility during capacitation through the control of channel availability. Finally, these results suggest that channel conductance state may be a central feature in the design of channel antagonists that inhibit sperm function.

Surgical intervention criteria for thoracic aortic aneurysms: a study of growth rates and complications

BACKGROUND

Evidence regarding the behavior of thoracic aortic aneurysm (TAA) is limited. This study reviews our ongoing efforts to understand the factors influencing aortic growth rates and the complications of rupture and dissection in order to define scientifically sound criteria for surgical intervention.

METHODS

Data from 370 patients with TAA treated at Yale University School of Medicine from January 1985 to June 1997 were analyzed. This computerized data base included 1063 imaging studies (magnetic resonance imaging, computed tomography, and echocardiography).

RESULTS

The mean size of the thoracic aorta in these patients at initial presentation was 5.2 cm (range 3.5-10). The mean growth rate was 0.10 cm/year. Median size at the time of rupture or dissection was 5.9 cm for ascending and 7.2 cm for descending aneurysms. The incidence of dissection or rupture increased with aneurysm size. Multivariable regression analysis to isolate risk factors for acute dissection or rupture revealed that size > or = 6.0 cm increased the probability of these devastating complications by 25.2% for ascending aneurysms (p = 0.006 compared with aneurysms 4.0-4.9 cm). For descending aneurysms > or = 7.0 cm, risk of dissection or rupture was increased by 37.3% (p = 0.031).

CONCLUSIONS

If the median size at time of dissection or rupture had been used as the indication for intervention, half the patients would have suffered a devastating complication before surgery. Accordingly, a criterion lower than the median is appropriate. We recommend 5.5 cm as an acceptable size for elective resection of ascending aortic aneurysms because this operation can be performed with relatively low mortality. For aneurysms of the descending aorta, where perioperative complications are greater and the median size at the time of complication is larger, we recommend intervention at 6.5 cm.

Management of descending aortic dissection

BACKGROUND

Experience with 100 consecutive patients with acute dissection of the descending aorta seen at the Yale Center for Thoracic Aortic Disease over a 10-year period is reported.

METHODS

Clinical records from the Yale Center for Thoracic Aortic Disease from 1988 to 1998 were analyzed. This computerized data base included information regarding patients' demographics, history, presenting symptomatology, diagnostic imaging, early hospital course, treatment strategy, and long term follow up (office visits, echocardiography, computerized tomography, magnetic resonance imaging, and home phone calls).

RESULTS

The average size of the aorta at the time of dissection was 5.05 cm. Nine patients died (six of complications directly related to the thoracic aorta). Sixty of the 91 surviving patients had a benign course, and 31 had a course complicated by rupture (8), vascular occlusion (17), early expansion or extension (12), and continued pain (4); multiple complications were seen in some patients. Forty-two patients came to operation (22 early and 20 late): 32 direct aortic replacements, 6 fenestration procedures, and 4 thromboexclusions. There were six postoperative deaths and six paraplegias. Clinical experience with the alternative procedures of fenestration and thromboexclusion found both procedures safe and effective for selected categories of patients. Review of the literature indicated that direct aortic replacement in the setting of acute descending aortic dissection continues to carry a very high mortality (28%-65%) and paraplegia rate (30%-35%), leaving room for consideration of alternative procedures.

CONCLUSIONS

We recommend a "complication-specific" approach to acute descending aortic dissection: medical management with "antiimpulse therapy" for uncomplicated acute descending dissections and surgical intervention for complicated dissections. Surgical therapy varies for the specific complication: for rupture, direct aortic replacement is recommended; for vascular occlusion, fenestration; and for acute expansion or impending rupture, direct aortic replacement, with thromboexclusion as an option. Chronic descending aortic dissection is treated according to general guidelines for descending aortic aneurysms, with operation for symptoms or enlargement > 6.5 cm.

Familial patterns of thoracic aortic aneurysms

HYPOTHESIS

To provide evidence that genetic factors contribute to the development of thoracic aortic aneurysms (TAA) by demonstrating familial patterns of the disease.

DESIGN

Retrospective review.

SETTING

University hospital.

PATIENTS AND METHODS

We sought to identify familial patterns of TAA from a database of 598 patients evaluated or treated for TAA at the Yale Center for Thoracic Aortic Disease, New Haven, Conn, from January 1985 to August 1998. Of the 598 patients, 45 patients had a diagnosis of Marfan syndrome and 553 patients had no known history of any collagen vascular disorder. Of the 553 patients in the latter category, 398 patients had confirmed TAA, 66 had TAA with concomitant aortic dissections, and 89 had aortic dissections. From the group of 464 patients with TAA with or without concomitant aortic dissections, 2 interviewers attempted to contact 150 randomly selected patients for telephone screening to determine the presence of familial patterns of aortic disease. Fifteen of these patients were lost to follow-up. Complete medical and family histories of the remaining 135 patients (85 men, 50 women) were reviewed. Of the 135 individuals screened, 26 (18 men, 8 women) (19.3%) were found to belong to multiplex pedigrees. These 26 patients with familial nonsyndromic TAA were compared with the remaining 109 patients with sporadic TAA and the 45 patients with Marfan syndrome-associated TAA.

MAIN OUTCOME MEASURES

Groups were examined for statistical differences in age and aortic size at the time of diagnosis, growth rates of TAA, and rates of concomitant diseases. Nonsyndromic family pedigrees were analyzed and potential modes of inheritance were determined.

RESULTS

The mean age at presentation for patients with familial nonsyndromic TAA (56.8 years) was significantly younger than the mean age of presentation in sporadic cases (64.3 years, P< or =.03), and significantly older than that of patients with Marfan syndrome (24.8 years, P< or =.001). Patients with a family history of aortic aneurysms had faster growth rates (0.22 cm/y) compared with patients with sporadic TAA (0.03 cm/y) (P< or =.001) and patients with Marfan syndrome (0.10 cm/y) (P< or =.04). Familial nonsyndromic TAA in patients with a concomitant aortic dissection had a growth rate of 0.33 cm/y, which was greater than that of patients with sporadic TAA (0.10 cm/y) and patients with Marfan syndrome (0.08 cm/y) with associated aortic dissection. This growth of 0.33 cm/y was significantly faster than the overall growth rate estimate of aneurysms in patients with aortic dissection (0.14 cm/y) (P< or =.05). Ten pedigrees (38.5%) showed direct father to son transmission, consistent with an autosomal dominant mode of inheritance. Six family pedigrees (23.1%) suggested an autosomal dominant or X-linked mode of inheritance. Seven pedigrees (26.9%) suggested a recessive mode of inheritance; 2 an autosomal recessive mode, and 5 an X-linked recessive or autosomal recessive mode. The remaining 3 pedigrees displayed more complex modes of inheritance.

CONCLUSIONS

This study supports the role of genetic factors influencing familial aggregation of TAA. Thoracic aortic aneurysms in association with multiplex pedigrees represent a new risk factor for aneurysm growth. Pedigree analysis suggests genetic heterogeneity. The primary mode of inheritance seems to be autosomal dominant, but X-linked dominant and recessive modes are also evident.

Interval or permanent nonoperative management of acute type A aortic dissection

HYPOTHESIS

Selected patients with acute type A (ascending) aortic dissection who are treated with delayed operation or nonoperative therapy may have better early and short-term outcomes than was previously expected.

DESIGN AND SETTING

Retrospective cohort at a university hospital.

SUBJECTS

Data on 75 patients with acute or chronic type A aortic dissection treated at one institution from January 1, 1985, to November 30, 1997, were analyzed. Of these 75 patients, 34 (21 male and 13 female, with a mean age of 65.5 years) did not undergo initial operative treatment, and 15 (10 male and 5 female, with a mean age of 72.6 years) never underwent surgery. For the 19 patients who underwent delayed surgery, the mean period between aortic dissection and intervention was 11.4+/-4.83 days. The follow-up period ranged from 0.27 to 149 months, with a mean of 20.2 months.

MAIN OUTCOME MEASURES

Vascular complications, hospital mortality, and early survival.

RESULTS

Reasons for interval delay in surgical treatment included initial misdiagnosis or delay in diagnosis (13 [68%] of 19), need to address significant comorbidity (4 [21%] of 19), and initial refusal of operative intervention (2 [11%] of 19). For the 15 patients treated entirely by medical therapy, reasons for electing nonoperative management included extensive comorbidity (5 [33%] of 15), refusal of surgical intervention (6 [40%] of 15), and misdiagnosis or long delay in diagnosis (4 [27%] of 15). Of the 34 patients, 15 (44%) presented with moderate or severe aortic insufficiency, 5 (14%) had evidence of pericardial effusion, 6 (21%) had evidence of concomitant coronary ischemia on electrocardiogram, and 8 (24%) had extension of the dissection into the descending aorta. Four patients (11.8%) died while in the hospital. Of the 34 patients, 30 (88%) who underwent either delayed or no surgery received aggressive medical treatment (beta-adrenergic blocking agents and afterload-reducing agents) and were discharged from the hospital. All patients who were operative candidates in the interval treatment group survived to reach definitive operation. There was no statistically significant difference in short-term survival between the group of patients undergoing delayed surgery or medical treatment only and the group of 41 patients undergoing early operation (P = .42).

CONCLUSIONS

Immediate surgical therapy is still recommended for acceptable operative candidates with acute type A aortic dissection who seek immediate treatment. However, this study permits the following 2 conclusions: (1) patients with type A aortic dissection who are referred or whose conditions are diagnosed several days after presentation have survived the early dangerous period and can safely undergo surgery semielectively (rather than emergently); and (2) selected patients who are not considered operative candidates and who survive the initial type A aortic dissection without complication may be treated with aggressive medical therapy and achieve acceptable early and short-term outcomes, which is better than previously expected.

Cholesterol efflux-mediated signal transduction in mammalian sperm. beta-cyclodextrins initiate transmembrane signaling leading to an increase in protein tyrosine phosphorylation and capacitation

Sperm capacitation in vitro is highly correlated with an increase in protein tyrosine phosphorylation that is regulated by cAMP through a unique mode of signal transduction cross-talk. The activation of this signaling pathway, as well as capacitation, requires bovine serum albumin (BSA) in the incubation medium. BSA is hypothesized to modulate capacitation through its ability to remove cholesterol from the sperm plasma membrane. Here we demonstrate that the cholesterol-binding heptasaccharides, methyl-beta-cyclodextrin and OH-propyl-beta-cyclodextrin, promote the release of cholesterol from the mouse sperm plasma membrane in media devoid of BSA. Both of these beta-cyclodextrins were also demonstrated to increase protein tyrosine phosphorylation in the absence of BSA in both mouse and bull sperm, and the patterns of phosphorylation were similar to those induced by media containing BSA. The potency of the different beta-cyclodextrins to increase protein tyrosine phosphorylation in sperm was correlated with their cholesterol binding efficiencies, and preincubation of the beta-cyclodextrins with cholesterol-SO4- to saturate their cholesterol-binding sites blocked the ability of these compounds to stimulate protein tyrosine phosphorylation. The beta-cyclodextrin effect on protein tyrosine phosphorylation was both NaHCO3 and protein kinase A-dependent. The beta-cyclodextrins were also able to capacitate mouse sperm in the absence of BSA, as measured by the ability of the zona pellucida to induce the acrosome reaction and by successful fertilization in vitro. In summary, beta-cyclodextrins can completely replace BSA in media to support signal transduction leading to capacitation. These data further support the coupling of cholesterol efflux to the activation of membrane and transmembrane signaling events leading to the activation of a unique signaling pathway involving the cross-talk between cAMP and tyrosine kinase second messenger systems, thus defining a new mode of cellular signal transduction initiated by cholesterol release.

Evidence for the role of heterotrimeric guanine nucleotide-binding regulatory proteins in the regulation of the mouse sperm adenylyl cyclase by the egg's zona pellucida

Sperm acrosomal exocytosis is the result of a complex set of signal transduction pathways activated physiologically by the egg's extracellular matrix, the zona pellucida. In the mouse, the zona pellucida has been demonstrated to induce an increase in sperm intracellular pH, Ca2+, and cyclic adenosine monophosphate (cAMP) concentrations as well as to activate proteins of the Gi class (G; guanine nucleotide-binding regulatory proteins). We recently reported that the mouse zona pellucida could activate the adenylyl cyclase of mouse sperm. It is not known, however, whether zona pellucida stimulation of adenylyl cyclase activity is mediated through G proteins. In the present study, we demonstrate that the sperm membrane-bound adenylyl cyclase activity is stimulated by the G protein activators guanosine-5'-O-thiotriphosphate (GTPgammaS) and mastoparan in a concentration-dependent manner. The maximal adenylyl cyclase activity measured with these two G protein activators is similar to the stimulation observed with the zona pellucida, but the effect of GTPgammaS is not additive or synergistic with the effects of mastoparan or the zona pellucida. Pertussis toxin treatment of sperm membranes inhibits the zona pellucida stimulation of adenylyl cyclase activity, while the basal or forskolin-induced activation of the enzyme is not affected. Partial inhibition of the stimulatory effect of the zona pellucida on the adenylyl cyclase activity is observed with guanosine-5'-O-thiodiphosphate (GDPbetaS), another G protein antagonist. To a reconstitution system containing Lubrol-PX, where zona pellucida or GTPgammaS stimulation of the sperm enzyme is not observed, addition of G protein betagamma subunits restores the activation of the sperm adenylyl cyclase by the zona pellucida and GTPgammaS without affecting the enzyme activity under basal or forskolin-stimulated conditions. These results support our hypothesis that mouse sperm adenylyl cyclase is stimulated by the zona pellucida through a pertussis toxin-sensitive pathway involving G proteins of the Gi class.

In vitro culture retards spontaneous activation of cell cycle progression and cortical granule exocytosis that normally occur in in vivo unfertilized mouse eggs

We have previously demonstrated that metaphase II-arrested eggs recovered from oviducts at increasing times after hCG administration display a time-dependent spontaneous entry into anaphase, as well as release of cortical granules (CGs) and the associated modifications of the zona pellucida (ZP), a decrease in histone H1 and mitogen-activated protein kinase activities, and the recruitment of maternal mRNAs [Xu et al., Biol Reprod 1997; 57:743-750). These changes are correlated with the time-dependent increase in susceptibility of these eggs to undergo parthenogenetic activation. We report here the effect of culture of ovulated eggs, retrieved 13 or 16 h post-hCG administration and cultured in vitro for various periods of time, on the aforementioned parameters of egg activation and cell cycle resumption. In contrast to extended residence of the eggs in the oviduct, culture in vitro retarded cell cycle events associated with completion of the second meiotic reduction and inhibited CG release and the associated modifications of the ZP, as well as the recruitment of maternal mRNAs. The retardation or inhibition of these changes during in vitro culture resulted in eggs that were less susceptible to parthenogenetic activation than eggs that resided in the oviduct for comparable time periods. Results of these experiments indicate that egg culture in vitro (which likely occurs under suboptimal conditions) inhibits, rather than accelerates, the progression into the interphase-like state as compared to that seen in eggs residing in the oviduct for increasing periods of time. These results also suggest that, for studies focused on in vitro fertilization or egg activation, the ovulated eggs should be placed under appropriate in vitro conditions as soon as possible.

Involvement of the cytoskeleton in the movement of cortical granules during oocyte maturation, and cortical granule anchoring in mouse eggs

Exocytosis of cortical granules in mouse eggs is required to produce the zona pellucida block to polyspermy. In this study, we examined the role of microfilaments and microtubules in the regulation of cortical granule movement toward the cortex during oocyte maturation and anchoring of cortical granules in the cortex. Fluorescently labeled cortical granules, microfilaments, and microtubules were visualized using laser-scanning confocal microscopy. It was observed that cortical granules migrate to the periphery of the oocyte during oocyte maturation. This movement is blocked by the treatment of oocytes with cytochalasin D, an inhibitor of microfilament polymerization, but not with nocodazole or colchicine, inhibitors of microtubule polymerization. Cortical granules, once anchored at the cortex, remained in the cortex following treatment of metaphase II-arrested eggs with each of these inhibitors; i.e., there was neither inward movement nor precocious exocytosis. Finally, the single cortical granule-free domain that normally becomes localized over the metaphase II spindle was not observed when the chromosomes become scattered following microtubule disruption with nocodazole or colchicine. In these instances a cortical granule-free domain was observed over each individual chromosome, suggesting that the chromosome or chromosome-associated material, and not the spindle, dictates the localization of the cortical granule-free domain.

Molecular mechanisms of sperm-egg interactions and egg activation

The binding of acrosome reacted mammalian sperm to the egg plasma membrane initiates a series of signaling events in the egg, termed "egg activation", which lead to the completion of meiosis II and the initiation of a mitotic cell cycle. Many of these signaling events have characteristics of classical signal transduction events in somatic cells. Currently, there are two hypotheses for how sperm-induced egg activation is initiated. In the "receptor" hypothesis, the fertilizing sperm interacts with a specific egg surface receptor, and this interaction leads to signal transduction and effector activation. In the "fusion" hypothesis it is postulated that following fusion of the sperm and egg plasma membranes a soluble sperm-derived factor enters the egg's cytoplasm and activates pathways leading to egg activation. This chapter will provide an overview of the processes of cell-cell interaction and signal transduction leading to mammalian egg activation. It will concentrate on specific molecules proposed to be involved in sperm-egg interaction, signal transduction and effector mechanisms involved in egg activation, and a discussion of sperm-associated factors that have been implicated in egg activation.

Roles of the disintegrin domains of mouse fertilins alpha and beta in fertilization

Fertilin is a heterodimer of alpha and beta subunits, both of which are members of the ADAM (A Disintegrin and A Metalloprotease domain)/MDC (Metalloprotease-Disintegrin-Cysteine-rich) family of proteins. We have previously demonstrated that recombinant forms of the putative extracellular domains of mouse fertilin alpha and fertilin beta bind to mouse eggs and inhibit sperm-egg membrane binding. In this study, we examined the roles of the disintegrin domains of fertilins alpha and beta by producing recombinant forms of fertilins alpha and beta that included the disintegrin domains (alphaDCE and betaDCE) or that were truncated so that they lack the disintegrin domains (alphaCE and betaCE) and tested the abilities of these proteins to bind to eggs and to inhibit sperm-egg binding. Fertilin betaDCE was able to inhibit sperm-egg binding, but fertilin betaCE was relatively ineffective, indicating that the disintegrin domain of fertilin beta is required for interactions with egg binding sites and/or for proper protein folding. Fertilins alphaDCE and alphaCE both inhibited sperm-egg interactions, but fertilin alphaDCE tended to be more effective. Thus, the presence of the disintegrin domain in fertilin alphaDCE apparently enhanced the ability of this recombinant protein to inhibit sperm-egg binding, either by interacting with egg binding sites or by improving the efficiency of protein folding. These data also indicate that the other domains of the fertilin alpha extracellular region (cysteine-rich and/or epidermal growth factor-like repeat) have the ability to block sperm binding and suggest that these domains of fertilin alpha may participate in sperm-egg adhesion.

Penetrating ulcer of the thoracic aorta: what is it? How do we recognize it? How do we manage it?

BACKGROUND

Although classic type A and B aortic dissections have been well described, less is known about the natural history of penetrating atherosclerotic ulcers of the thoracic aorta. This study differentiates penetrating ulcer from aortic dissection, determines the clinical features and natural history of these ulcers, and establishes appropriate correlates regarding optimal treatment.

METHODS

A retrospective review of patient records and imaging studies was conducted with 198 patients with initial diagnoses of aortic dissection (86 type A, 112 type B) at our institution from 1985 to 1997.

RESULTS

Of the 198 patients, 15 (7.6%) were found to have a penetrating aortic ulcer on re-review of computed tomographic scans, magnetic resonance images, angiograms, echocardiograms, intraoperative findings, or pathology reports. Two ulcers (13.3%) were located in the ascending aorta; the other 13 (86.7%) were in the descending aorta. In comparison with those with type A or B aortic dissection, patients with penetrating ulcer were older (mean age 76.6 years, p = 0.018); had larger aortic diameters (mean diameter 6.5 cm); had ulcers primarily in the descending aorta (13 of 15 patients, 86.7%); and more often had ulcers associated with a prior diagnosed or managed AAA (6 of 15 patients, 40.0%; p = 0.0001). Risk for aortic rupture was higher among patients with penetrating ulcers (40.0%) than patients with type A (7.0%) or type B (3.6%) aortic dissection (p = 0.0001).

CONCLUSIONS

Accurate recognition and differentiation of penetrating ulcers from classic aortic dissection at initial presentation is critical for optimal treatment of these patients. For penetrating ulcer, the prognosis may be more serious than with classic type A or B aortic dissection. Surgical management is advocated for penetrating ulcers in the ascending aorta and for penetrating ulcers in the descending aorta that exhibit early clinical or radiologic signs of deterioration.

Evidence that Gq family G proteins do not function in mouse egg activation at fertilization

Embryonic development is initiated after the fertilizing sperm contacts the egg and triggers a process termed "egg activation," resulting in calcium release, cortical granule exocytosis, recruitment of maternal mRNAs, and cell cycle resumption. Heterotrimeric guanine nucleotide-binding proteins (G proteins) may be involved in mouse egg activation since inhibition of G protein beta gamma subunits partially inhibits sperm-induced cell cycle resumption. In addition, specific events of egg activation can be initiated in the absence of sperm by acetylcholine stimulation of mouse eggs overexpressing the human m1 muscarinic receptor, a G protein-coupled receptor. In somatic cell, G proteins in the Gq family couple ligand stimulation of the m1 muscarinic receptor to activation of phospholipase C, resulting in the production of inositol 1,4,5-trisphosphate (IP3) and IP3-mediated release of intracellular calcium. Since IP3-mediated calcium release is involved in egg activation at fertilization, we have examined the role of Gq family G proteins in both sperm-independent (muscarinic receptor-mediated) and sperm-induced egg activation using a function-blocking antibody raised against the common C-terminal region of Gq and G11 proteins. We show that this antibody effectively inhibits Gq family G proteins in mouse eggs by demonstrating that the antibody inhibits egg activation in response to stimulation of the m1 muscarinic receptor. This same antibody, however, does not inhibit sperm-induced egg activation events. These results indicate that although activation of Gq family G proteins can result in egg activation in the mouse, it is unlikely that these proteins are used by the sperm to initiate egg activation at fertilization.

Targeting of a germ cell-specific type 1 hexokinase lacking a porin-binding domain to the mitochondria as well as to the head and fibrous sheath of murine spermatozoa

Multiple isoforms of type 1 hexokinase (HK1) are transcribed during spermatogenesis in the mouse, including at least three that are presumably germ cell specific: HK1-sa, HK1-sb, and HK1-sc. Each of these predicted proteins contains a common, germ cell-specific sequence that replaces the porin-binding domain found in somatic HK1. Although HK1 protein is present in mature sperm and is tyrosine phosphorylated, it is not known whether the various potential isoforms are differentially translated and localized within the developing germ cells and mature sperm. Using antipeptide antisera against unique regions of HK1-sa and HK1-sb, it was demonstrated that these isoforms were not found in pachytene spermatocytes, round spermatids, condensing spermatids, or sperm, suggesting that HK1-sa and HK1-sb are not translated during spermatogenesis. Immunoreactivity was detected in protein from round spermatids, condensing spermatids, and mature sperm using an antipeptide antiserum against the common, germ cell-specific region, suggesting that HK1-sc was the only germ cell-specific isoform present in these cells. Two-dimensional SDS-PAGE suggested that all of the sperm HK1-sc was tyrosine phosphorylated, and that the somatic HK1 isoform was not present. Immunoelectron microscopy revealed that HK1-sc was associated with the mitochondria and with the fibrous sheath of the flagellum and was found in discrete clusters in the region of the membranes of the sperm head. The unusual distribution of HK1-sc in sperm suggests novel functions, such as extramitochondrial energy production, and also demonstrates that a hexokinase without a classical porin-binding domain can localize to mitochondria.

Should angiographically disease-free saphenous vein grafts be replaced at the time of redo coronary artery bypass grafting?

BACKGROUND

Controversy exists regarding the management of angiographically disease-free saphenous vein grafts at the time of redo coronary artery bypass grafting (CABG). Some authorities favor replacement of these disease-free grafts, arguing that occlusion is likely in the near future. Others believe that these grafts are "biologically privileged" and should not be replaced.

METHODS

One hundred thirty-two consecutive patients (113 men, 19 women, aged 46 to 88 years, mean 67 years) underwent redo revascularization with one or more angiographically disease-free saphenous vein grafts at the time of redo CABG. Thirty-six patients had the disease-free grafts replaced (R) and 96 did not (NR). The mean interval from the first CABG was 9.25 years.

RESULTS

Surgical mortality was comparable in the NR and R groups (5 of 96 or 5.2% versus 3 of 36 or 8.3%, respectively; p < 0.5). Survival at 1 and 3 years was higher in the NR group than the R group (98% versus 80%, and 95% vs. 66% respectively; p < 0.0001). Late myocardial infarction was less common in the NR group than in the R group (12 of 91 or 12.9% versus 12 of 33 or 36.4%; p < 0.003). Recurrent angina was less common in the NR than in the R group (21 of 91 or 23.1% versus 15 of 33 or 45.5%; p < 0.015). Cardiac hospitalization was required less commonly in the NR than in the R group (11 of 91 or 12.1% versus 12 of 33 or 36.4%; p < 0.002). In nondiseased grafts undergoing angiographic evaluation late after redo CABG, rate of new stenosis was lower in NR grafts than in R grafts (2 of 12 or 16.7% versus 2 of 3 or 66.7%; p < 0.05).

CONCLUSIONS

With a conservative approach that does not replace nondiseased saphenous vein grafts at redo CABG (1) there is no increase in operative mortality, (2) good late survival is obtained, (3) clinical ischemia related to the NR saphenous vein grafts is uncommon, and (4) NR grafts continue to be patent. We conclude that disease-free vein grafts may not require routine replacement at redo CABG. A randomized study is required for definitive resolution.

Regulation, localization, and anchoring of protein kinase A subunits during mouse sperm capacitation

The molecular basis of mammalian sperm capacitation, defined as those biochemical and functional changes that render the sperm competent to fertilize the egg, is poorly understood. This extratesticular maturational process is accompanied by the activation of a unique signal transduction pathway involving the cAMP-dependent up-regulation of protein tyrosine phosphorylation presumably through the activation of protein kinase A (PK-A). We demonstrate in this report that capacitation of cauda epididymal mouse sperm in vitro was accompanied by a time-dependent increase in PK-A activity. This increase in PK-A activity did not occur in a medium that does not support capacitation. While PK-A catalytic and RI/RII regulatory subunits, as well as PK-A enzyme activity, were found in both the Triton X-100-soluble and -insoluble fractions of the sperm, the increase in PK-A activity accompanying capacitation was associated with enzyme activity found in the soluble fraction. Moreover, the regulatory and catalytic subunits of PK-A were observed by indirect immunofluorescence to be present throughout the head, midpiece, and principal piece of the sperm. Thus, PK-A appears to be functional in multiple compartments of this highly differentiated cell. A fraction of the Triton X-100-insoluble PK-A is presumably tethered by AKAP82, the major protein of the fibrous sheath of the sperm flagellum which anchors and compartmentalizes PK-A to the cytoskeleton via the RII subunit of PK-A. Using various recombinant truncated AKAP82 constructs in a gel overlay assay, the RII subunit-binding domain of this protein was mapped to a 57-amino-acid residue region at its N-terminus. Computer analysis revealed a 14-amino-acid region that resembled the RII-binding domains of other A Kinase Anchor Proteins. A synthetic peptide corresponding to this domain inhibited AKAP82-RII binding in a gel overlay assay, providing further support that AKAP82 is an anchoring protein for the subcellular localization of PK-A in the mouse sperm fibrous sheath. This work, along with previous findings that cAMP is a key intermediary second messenger in regulating protein tyrosine phosphorylation and capacitation, further supports the importance of PK-A in these processes and necessitates a further understanding of the contribution of both the soluble and insoluble forms of PK-A, as well as AKAP82, to sperm function.

Spontaneous activation of ovulated mouse eggs: time-dependent effects on M-phase exit, cortical granule exocytosis, maternal messenger ribonucleic acid recruitment, and inositol 1,4,5-trisphosphate sensitivity

With increasing time after ovulation, mammalian eggs become more sensitive to agonists of activation in vitro or may undergo spontaneous activation in vivo. We have tested the hypothesis that postovulatory eggs undergo time-dependent cell cycle and cytoplasmic changes that result in a partially activated state, accounting for their time-dependent susceptibility to activate. In vivo changes in key activation markers in mouse eggs were quantified at 13, 16, and 22 h post-hCG (1, 4, and 10 h postovulation). Spontaneous activation was first detected at 16 h, with a 20-25% decrease in the activities of histone H1 and mitogen-activated protein (MAP) kinases and with 3% of eggs undergoing both anaphase onset and a partial loss of cortical granules. By 22 h, more than 60% of eggs were in anaphase, H1 and MAP kinase activities had decreased 40-50%, the extent of zona pellucida modification had increased, and proteins normally synthesized after fertilization had appeared. Pronuclear formation in response to inositol 1,4,5-trisphosphate injection increased dramatically from 10% at 13 h to about 40% and 90% at 16 h and 22 h, respectively. The partial decreases (less than those after fertilization) in H1 and MAP kinase activities provide a likely biochemical basis for the increased sensitivity of eggs to agonists, seen over time, that results in pronuclear formation. Also, all of these time-dependent changes caution against the use of mouse eggs > 16 h after hCG administration in studying the mechanism of normal fertilization and have implications for animal and human in vitro fertilization.

Characterization of the binding of recombinant mouse sperm fertilin alpha subunit to mouse eggs: evidence for function as a cell adhesion molecule in sperm-egg binding

Fertilin (previously known as PH-30) is a sperm protein that is a candidate molecule for mediating the binding and fusion of the sperm and egg plasma membranes. Fertilin is a heterodimer, with a beta subunit that has a region of homology to the disintegrin family of integrin ligands and an alpha subunit that has a region of homology to viral fusion peptides. It has been hypothesized that fertilin beta and alpha subunits mediate the interactions between sperm and egg plasma membranes, namely, binding and fusion, respectively. To address this hypothesis and to examine specifically the role of fertilin alpha in fertilization, we have expressed the predicted extracellular domain of mouse fertilin alpha as a bacterial fusion protein with maltose-binding protein. This fusion protein (hereafter referred to as recombinant fertilin alpha-EC) binds to the microvillar region of zona pellucida (ZP)-free eggs, the region of the membrane to which sperm bind. This binding is reduced in the absence of divalent cations and is supported by Ca2+, Mg2+, or Mn2+. Eggs that have been treated with chymotrypsin bind less recombinant fertilin alpha-EC than do untreated eggs, suggesting that a chymotrypsin-sensitive binding site for recombinant fertilin alpha-EC is present on egg surfaces. Binding to eggs is also affected by the method used to remove the ZP. Finally, recombinant fertilin alpha-EC inhibits the binding of sperm to eggs during in vitro fertilization of ZP-free eggs. These data are the first evidence to suggest that fertilin alpha can function as a cell adhesion molecule during fertilization, mediating the binding of sperm and egg plasma membranes.

Characterization of the binding of recombinant mouse sperm fertilin beta subunit to mouse eggs: evidence for adhesive activity via an egg beta1 integrin-mediated interaction

The sperm protein fertilin (also known as PH-30) is a candidate for mediating the interactions between sperm and egg plasma membranes. Fertilin is a heterodimer. The beta subunit, which has a region with homology to the family of integrin ligands known as disintegrins, has been hypothesized to be involved in the binding of sperm to the egg surface. To investigate this hypothesis and determine what role fertilin beta plays in fertilization, we have expressed the putative extracellular domain of mouse fertilin beta in bacteria as a fusion protein with maltose-binding protein (hereafter referred to as recombinant fertilin beta-EC) and used two assays to characterize its binding to mouse eggs. Immunocytochemistry was used to examine the localization of recombinant fertilin beta-EC binding. A luminometric assay was also developed to quantify levels of binding of recombinant fertilin beta-EC to single eggs. We find that recombinant fertilin beta-EC binds to the region of the plasma membrane of the egg to which sperm bind, thus providing the first direct evidence that fertilin beta has adhesive properties. Peptides corresponding to the disintegrin domain of fertilin beta reduce its binding to eggs, suggesting that this domain is at least partially involved in the recognition of fertilin beta by binding sites on the egg. Treatment of zona pellucida-free eggs with chymotrypsin reduces the ability of the eggs to support the binding of recombinant fertilin beta-EC, implicating an egg surface protein as a binding site for recombinant fertilin beta-EC. Binding of recombinant fertilin beta-EC to eggs is also reduced in the absence of divalent cations and is supported by 2.0 mM Ca2+, Mg2+, or Mn2+. Furthermore, eggs incubated in recombinant fertilin beta-EC prior to in vitro fertilization show reduced levels of sperm binding. Finally, we have examined the possible role of integrins on eggs as receptors for fertilin beta, since an anti-alpha6 integrin subunit monoclonal antibody, GoH3, has been shown to inhibit sperm binding (E. A. C. Almeida et al. (1995) Cell 81, 1095-1104). We find that: (a) an increased amount of GoH3 epitope on the egg surface does not correlate with an increased ability of the eggs to bind sperm or recombinant fertilin beta-EC; (b) the GoH3 antibody has virtually no inhibitory effect on recombinant fertilin beta-EC binding; and (c) recombinant fertilin beta-EC binding is reduced in the presence of anti-beta1 integrin antibodies. These results suggest that a beta1-containing integrin participates in the binding of recombinant fertilin beta-EC to mouse eggs.

Minimally invasive coronary artery bypass grafting: initial Connecticut experience

We report the initial Connecticut experience with minimally invasive coronary artery bypass grafting. This procedure allows bypass grafting to the left anterior descending coronary artery utilizing the internal mammary artery as the conduit. The procedure is minimally invasive because it is performed through a mini-thoracotomy incision in the fourth anterior intercostal space and it is conducted without the use of cardiopulmonary bypass. The procedure has been applied to 13 patients operated between February and October 1996. All but one patient selected were poor candidates for conventional coronary artery bypass surgery because of advanced age (6), chronic renal failure/dialysis/kidney transplant (4), redo status with vulnerable grafts (1), severe peripheral vascular disease (6), severe chronic obstructive pulmonary disease (4). All patients survived operation and were discharged in good condition. Mean postoperative intubation time was seven hours and mean hospital stay was 4.5 days despite the very high pre-existing comorbidity of these patients. All patients are alive at the current follow-up time. Two patients required a conventional bypass procedure for occlusion of the minimally invasive graft, the first because of diffuse disease in the target artery and the second attributable to the technical limitations of minimally invasive coronary artery bypass grafting; both tolerated the subsequent procedure well. All patients are now angina-free. All four grafts studied by routine postoperative angiography were widely patent. Routine post-operative exercise nuclear imaging was normal in an additional patient. This procedure of minimally invasive coronary artery bypass grafting offers significant advantages compared to the conventional bypass procedure (short hospital stay, quick recovery, and, especially, avoidance of cerebrovascular accidents caused by the heart-lung machine). This minimally invasive procedure is expected to apply to a growing percentage of patients. The procedure, especially vis-à-vis angioplasty, may well offer the superior long-term patency of the mammary conduit achieved with a modest initial "investment" in hospital stay, costs of medical care, and discomfort and disability. A prospective, randomized trial comparing angioplasty and minimally invasive coronary artery bypass grafting is warranted.

Regulation of protein tyrosine phosphorylation during bovine sperm capacitation by a cyclic adenosine 3'5'-monophosphate-dependent pathway

Mammalian sperm capacitation, defined as an obligatory maturational process leading to the development of the fertilization-competent state, results from a poorly understood series of morphological and molecular events. We report here that ejaculated bovine sperm, incubated under conditions that support capacitation in vitro, display a reproducible pattern of protein tyrosine phosphorylations that are regulated by a cAMP-dependent pathway. The appearance of these tyrosine phosphorylated proteins correlated temporally with the time course of capacitation induced by heparin, and these phosphorylations displayed a similar heparin concentration dependence. Glucose, which inhibits capacitation, inhibited these protein tyrosine phosphorylations in media containing heparin. The biologically active cAMP analogues (dibutyryl cAMP [db-cAMP], 8-bromo cAMP, sp-cAMPS) and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) induced the same protein tyrosine phosphorylation patterns as seen with heparin. Moreover, these cAMP agonists could overcome the inhibition of the heparin-induced tyrosine phosphorylations by glucose. In contrast, Rp-adenosine-3',5'-cyclic monophosphorothioate (Rp-cAMPS), a protein kinase A (PK-A) antagonist, blocked the capacitation-associated increases in protein tyrosine phosphorylation. This cAMP regulation of the protein tyrosine phosphorylation pattern is mediated by PK-A since N-[2-(p-bromocinnamylamino) ethyl]-5-isoquinolinesulfonamide-dihydrochloride (H89), another inhibitor of PK-A, inhibited the heparin-induced protein tyrosine phosphorylation pattern in a concentration-dependent manner in either the absence or presence of db-cAMP, IBMX, and glucose. These data support a model for sperm capacitation that includes protein tyrosine phosphorylation as an important regulatory pathway, and a role for cAMP/PK-A in the regulation of this pathway leading to capacitation. These studies are the first to report a unique interrelationship between tyrosine kinase/phosphatase and cAMP signaling pathways at the level of PK-A in bovine sperm capacitation.

What is the appropriate size criterion for resection of thoracic aortic aneurysms?

Although many articles have described techniques for resection of thoracic aortic aneurysms, limited information on the natural history of this disorder is available to aid in defining criteria for surgical intervention. Data on 230 patients with thoracic aortic aneurysms treated at Yale University School of Medicine from 1985 to 1996 were analyzed. This computerized database included 714 imaging studies (magnetic resonance imaging, computed tomography, echocardiography). Mean size of the thoracic aorta in these patients at initial presentation was 5.2 cm (range 3.5 to 10 cm). The mean growth rate was 0.12 cm/yr. Overall survivals at 1 and 5 years were 85% and 64%, respectively. Patients having aortic dissection had lower survival (83% 1 year; 46% 5 year) than the cohort without dissection (89% 1 year; 71% 5 year). One hundred thirty-six patients underwent surgery for their thoracic aortic aneurysms. For elective operations, the mortality was 9.0%; for emergency operations, 21.7%. Median size at time of rupture or dissection was 6.0 cm for ascending aneurysms and 7.2 cm for descending aneurysms. The incidence of dissection or rupture increased with aneurysm size. Multivariable regression analysis to isolate risk factors for acute dissection or rupture revealed that size larger than 6.0 cm increased the probability by 32.1 percentage points for ascending aneurysms (p = 0.005). For descending aneurysms, this probability increased by 43.0 percentage points at a size greater than 7.0 cm (p = 0.006). If the median size at the time of dissection or rupture were used as the intervention criterion, half of the patients would suffer a devastating complication before the operation. Accordingly, a criterion lower than the median is appropriate. We recommend 5.5 cm as an acceptable size for elective resection of ascending aortic aneurysms, because resection can be performed with relatively low mortality. For aneurysms of the descending aorta, in which perioperative complications are greater and the median size at the time of complications is larger, we recommend intervention at 6.5 cm.

Effects of calcium-BAPTA buffers and the calmodulin antagonist W-7 on mouse egg activation

Results of numerous experiments indicate that the transient rise in intracellular Ca2+ following sperm-egg fusion is essential for the subsequent events that constitute egg activation. Some events of egg activation, e.g., cortical granule exocytosis, however, appear more sensitive to intracellular Ca2+ than other events, e.g., cell cycle resumption. To examine if specific events of egg activation have different thresholds for Ca2+, we manipulated buffered intracellular Ca2+ concentrations by microinjecting Ca2+-BAPTA buffers and then examined the effect on the cortical granule exocytosis, recruitment of maternal mRNAs, and cell cycle resumption. We find that whereas cortical granule exocytosis occurs over a narrow threshold range of injected free Ca2+ concentrations between 0.5 and 1.0 microM, recruitment of maternal mRNAs is only partially stimulated at injected free Ca2+ concentrations of 2.5 microM, and no evidence for cell cycle resumption was observed (up to 2.5 microM Ca2+). Although the Ca2+- and phospholipid-dependent protein kinase, protein kinase C, is implicated in aspects of egg activation, calmodulin is also a potential target for the transient increase in Ca2+ that occurs following fertilization. Whereas incubation of eggs in the presence of the calmodulin antagonist W-7 followed by insemination does not block cortical granule exocytosis, cell cycle resumption, as assessed by the metaphase-to-anaphase transition, a decrease in histone H1 kinase activity and the time course for the emission of the second polar body are significantly delayed/inhibited.

Regulation of protein tyrosine phosphorylation in human sperm by a calcium/calmodulin-dependent mechanism: identification of A kinase anchor proteins as major substrates for tyrosine phosphorylation

Signal transduction pathways regulate various aspects of mammalian sperm function. When human sperm were incubated in a medium supporting capacitation, proteins became tyrosine-phosphorylated in a time-dependent manner. This phosphorylation was inhibited by genistein, a protein tyrosine kinase inhibitor. Phosphorylation was also reduced when sperm were incubated either in the presence of increasing concentrations of extracellular Ca2+ or in a medium containing the Ca2+ ionophore A23187. This Ca2+-induced dephosphorylation was calmodulin-dependent, suggesting that calcineurin was involved. In this regard, the calcineurin inhibitor deltamethrin inhibited the Ca2+ ionophore-induced dephosphorylation. A limited number of Mr 80,000-105,000 polypeptides were the most prominent phosphotyrosine-containing proteins present in human sperm. Unlike mouse sperm, which contains a tyrosine-phosphorylated isoform of hexokinase, a phosphotyrosine-containing hexokinase in human sperm was not detected. Most of the tyrosine-phosphorylated proteins were Triton X-100-insoluble and were localized to the principal piece of the flagellum, the region where the cytoskeletal fibrous sheath is found. Prominent phosphotyrosine-containing proteins of Mr 82,000 and 97,000 were identified as the human homologues of mouse sperm AKAP82, the major fibrous sheath protein, and pro-AKAP82, its precursor polypeptide, respectively. These proteins are A Kinase Anchor Proteins, polypeptides that sequester protein kinase A to subcellular locations. Taken together, these results suggest that protein tyrosine phosphorylation may be part of a signal transduction cascade(s) regulating events pertaining to capacitation and/or motility in mammalian sperm and that an interrelationship between tyrosine kinase and cAMP signaling pathways exists in these cells.

Temporal patterns of gene expression of G1-S cyclins and cdks during the first and second mitotic cell cycles in mouse embryos

Cell-cycle progression in somatic cells is regulated by a family of cyclins and cyclindependent kinases (cdks) that form specific complexes as a function of cell-cycle progression. However, the transcript abundance of G1-S cyclins and cdks during the meiotic and mitotic cell cycles of mammalian embryos has not been previously reported. Using a reverse transcription-polymerase chain reaction (PCR) assay that detects changes in either mRNA abundance or polyadenylation state, we examined the relative levels of gene expression for the G1-S cyclins and cdks, as well as for p21, p27, and the retinoblastoma (Rb) gene in mouse oocytes, metaphase II-arrested eggs, and 1-2-cell embryos. The PCR products for cyclins D1, D3, and A, as well as cdk4, p21, and Rb, displayed similar levels in meiotically incompetent and competent oocytes, as well as in metaphase II-arrested eggs. The levels of PCR products for cyclin D2, p27, and two forms of cdk2 were similar in meiotically incompetent and competent oocytes but decreased during oocyte maturation. Finally, the level of PCR products for cyclin E and cdk2 gradually decreased during the progression from meiotically incompetent oocytes to metaphase II-arrested eggs. When the levels of PCR products for the G1-S regulatory genes were evaluated during the first and second mitotic cell cycles, four main patterns were found: 1) steady levels for cyclin A; 2) steady levels followed by a 2-3-fold increase during the G2 phase of the second mitotic cell cycle for cyclins D1, E, cdk2, and p21; 3) a transient increase during the S and/or G2 phases of the first mitotic cell cycle for p27, cyclin D3, and the two forms of cdk2; and 4) higher levels during the first cell cycle and then a decrease with lower levels during the second mitotic cell cycle for cyclin D2 and Rb. cdk4 expression displayed a combination of patterns 2 and 3. The increase in the amount of PCR product for the cdk4 gene during the first mitotic cell cycle was due to polyadenylation, whereas the increase in the amount of PCR product for cdk4, cdk2, and cyclins D1 and E in the second mitotic cell cycle was a product of activation of the embryonic genome.