Infection by polyomavirus of murine cells deficient in class I major histocompatibility complex expression

Embryonic fibroblasts and kidney epithelial cells from beta 2-microglobulin-deficient mice were as infectible by polyomavirus as cells from normal littermates were, as judged by expression of nuclear viral capsid antigen, development of cytopathic effects, and yields of infectious virus. We conclude that expression of intact class I major histocompatibility complex molecules is not essential for polyomavirus infection.

Spontaneous cytosolic calcium oscillations driven by inositol trisphosphate occur during in vitro maturation of mouse oocytes

Immature mouse oocytes undergo spontaneous meiotic maturation when released from antral follicles into culture media. The first sign of meiotic resumption is germinal vesicle breakdown (GVB). Cytosolic free Ca2+ was measured in mouse oocytes during spontaneous maturation by monitoring fluorescence of indo-1 or fluo-3. The majority of oocytes showed a series of Ca2+ oscillations that continued for 1-3 h. Repetitive Ca2+ increases occurred every 1-3 min and lasted for 10-60 s. The Ca2+ oscillations appeared to be caused by an increase in inositol 1,4,5-trisphosphate (InsP3) because once they ceased, similar oscillations were triggered by injection of exogenous InsP3. Also, injection of the InsP3 receptor antagonist heparin (final concentration, 100 micrograms/ml) blocked the spontaneous Ca2+ oscillations. In contrast, Ca2+ oscillations induced by thimerosal were not inhibited by heparin. Treating oocytes with media containing 20 microM BAPTA/AM abolished Ca2+ oscillations in oocytes but did not affect the rate of GVB. The data show that cytosolic Ca2+ oscillations apparently caused by polyphosphoinositide turnover occur during mammalian oocyte maturation. However, the spontaneous oscillations do not appear to trigger GVB. Also, the data indicate that there are two separate Ca2+ release mechanisms in mouse oocytes, one sensitive to InsP3, the other to thimerosal.

Left ventricular mass in diabetes-hypertension

BACKGROUND

This study was undertaken to identify whether diabetes mellitus (DM) accelerates the development of left ventricular hypertrophy (LVH) in hypertensive patients.

METHODS

Cardiac structure, systolic function, and hemodynamics were evaluated by two-dimensional M-mode echocardiography in diabetic and nondiabetic patients with essential hypertension.

RESULTS

Patients with hypertension with and without DM had the same end-systolic and end-diastolic dimensions, cardiac output, total peripheral resistance, and ejection fraction. Diabetic hypertensive patients had greater interventricular septum (1.32 +/- 0.20 vs 1.07 +/- 0.20 cm) and posterior wall (1.20 +/- 0.20 vs 1.00 +/- 0.10 cm) thickness than did nondiabetic hypertensive patients. Consequently, left ventricular mass index was greater in patients with hypertension and DM than in those without DM (158 +/- 45 vs 113 +/- 20 g/m2). With the use of Devereux criteria for recognition of LVH (left ventricular mass index above 134 g/m2 in men and above 110 g/m2 in women), 72% of the diabetic patients had LVH, whereas only 32% of the nondiabetic patients had LVH. Left ventricular contractility, as reflected by the ratio of end-systolic wall stress to end-systolic volume index, was decreased in diabetic compared with nondiabetic hypertensive patients.

CONCLUSIONS

The data suggest that DM accelerates the development of LVH in patients with essential hypertension independent of arterial pressure and, therefore, may contribute to the increased cardiovascular morbidity and mortality in patients with hypertension.

Insulin resistance in secondary hypertension

The insulin sensitivity of five essential hypertensive patients was compared to five patients with renovascular hypertension, five patients with primary hyperaldosteronism, and five normotensive subjects, using the euglycemic hyperinsulinemic clamp technique. Essential hypertensive patients had significantly lower insulin sensitivity than patients with hyperaldosteronism and renovascular hypertensive patients (P = .0066, P = .004, respectively). Hyperaldosteronism patients also had less insulin sensitivity than renovascular hypertensive patients (P = .016). A significant negative correlation was found between body mass index and insulin sensitivity index for essential hypertension patients only (r = -0.87, P less than .003). No such correlation was found in the secondary hypertension patients. The findings suggest a causal relationship between insulin resistance and the development of essential hypertension. Secondary hypertension, on the other hand, is not such an insulin resistant state.

Crystal structure of insecticidal delta-endotoxin from Bacillus thuringiensis at 2.5 A resolution

The structure of the delta-endotoxin from Bacillus thuringiensis subsp. tenebrionis that is specifically toxic to Coleoptera insects (beetle toxin) has been determined at 2.5 A resolution. It comprises three domains which are, from the N- to C-termini, a seven-helix bundle, a three-sheet domain, and a beta sandwich. The core of the molecule encompassing all the domain interfaces is built from conserved sequence segments of the active delta-endotoxins. Therefore the structure represents the general fold of this family of insecticidal proteins. The bundle of long, hydrophobic and amphipathic helices is equipped for pore formation in the insect membrane, and regions of the three-sheet domain are probably responsible for receptor binding.

Effect of gonadotrophin environment on growth and development of isolated mouse primary ovarian follicles

Collagen gels containing isolated primary follicles devoid of other ovarian tissue were transferred beneath the kidney capsule of 3 types of female recipients: cycling, ovariectomized and hypogonadal, known to have different circulating concentrations of gonadotrophins. After 10 days the gels were recovered and processed for histology or the oocytes were recovered and their diameters measured and their ability to resume meiosis was determined. The growth of isolated primary follicles was positively correlated with the concentrations of circulating gonadotrophins in the recipient mice, but the numbers of oocytes recovered, the rate of oocyte growth and resumption of meiosis did not differ in the 3 types of recipient studied. This indicates that, in the conditions provided, oocyte growth was not related to the extent of follicular development.

Effect of dibutyryl cyclic adenosine monophosphate on granulosa cell proliferation, oocyte growth and meiotic maturation in isolated mouse primary ovarian follicles cultured in collagen gels

Isolated primary follicles from 10-day-old mice were cultured in a collagen gel matrix for 6 days in Minimum Essential Medium + foetal calf serum, followed by culture in unsupplemented medium (control) or in medium containing hypoxanthine (2 mM) or dibutyryl cyclic adenosine monophosphate (dbcAMP, 0.25 mM) for a further 3 or 6 days. Less than 10% of oocytes resumed meiosis during the culture period in all groups. At recovery, the diameter of oocytes at the germinal vesicle stage was recorded and their ability to resume meiosis was determined. Hypoxanthine had little effect on oocyte growth and meiotic competence, but culture in dbcAMP resulted in oocytes that were larger (60.2 +/- 0.6 microns) than those of controls (55.8 +/- 0.5 microns) and more competent to resume meiosis than were controls (42.9% and 10.8%, respectively). The addition of dbcAMP to the culture medium induced a 4-5-fold increase in the number of granulosa cells oocyte compared with controls (3757 +/- 423 and 838 +/- 93, respectively). These results indicate that increased oocyte growth and meiotic competence is primarily mediated via dbcAMP effects on the granulosa cells.

Localization of cardiac parasympathetic preganglionic neurons in the medulla oblongata of pigeon, Columba livia: a study using fragment C of tetanus toxin

The binding fragment of tetanus toxin, fragment C, was injected into several different regions of the pigeon heart. Retrogradely and/or transneuronally labeled cardiomotor parasympathetic preganglionic neurons were found in two separate nuclei within the medulla oblongata. The majority of fragment C-immunolabeled cells was confined to the caudal division of the nucleus ambiguus. This nuclear region is likely to be homologous to the ventrolateral nucleus of the external formation of the nucleus ambiguus in mammals. A smaller fraction (10-30%) of fragment C-positive cardiomotor preganglionic neurons were localized within a restricted portion of the ventrolateral subnucleus of the dorsal motor nucleus of the vagus nerve. This dual cardiac representation in an avian is very similar to the organization established in several mammalian species, and suggests that the brainstem organisation of cardiac parasympathetic efferents is evolutionarily stable across avians and mammals.

Retrograde, trans-synaptic and transneuronal transport of fragment C of tetanus toxin by sympathetic preganglionic neurons

The atoxic binding fragment of tetanus toxin, Fragment C, was injected into paravertebral ganglion 14, the avian homologue of the mammalian stellate ganglion. Postinjection survival intervals were varied from 2.5 h to 33 days. Experiments performed at the shortest survival time of 2.5 h showed that Fragment C was retrogradely transported by sympathetic preganglionic axons at a rate greater than or equal to 10 mm/h. At survival times ranging from 5 to 15 h. Fragment C-positive, retrogradely labeled sympathetic preganglionic neurons were observed within the last cervical spinal segment and throughout the first three thoracic spinal cord segments. Sporadic retrograde labeling of sympathetic preganglionic neurons was evident within the fourth and fifth thoracic spinal cord segments. Fragment C-labeled perikarya and dendrites exhibited both diffuse cytoplasmic immunostaining as well as intracellular, perinuclear accumulations of small. Fragment C-positive granules. Retrogradely labeled preganglionic neurons were found within both autonomic subnuclei within avian thoracic spinal cord; the column of Terni and the nucleus intercalatus spinalis. The distribution and numerical density of retrogradely labeled sympathetic preganglionic neurons indicated further that: (a) both myelinated and unmyelinated preganglionic axons appear to be capable of intra-axonally transporting Fragment C; and (b) it is unlikely that there is differential Fragment C labeling of a morphologically distinct population of sympathetic preganglionic neurons within or across subnuclei. Fragment C is transferred out of sympathetic preganglionic somas and dendrites into the surrounding neuropil at an aggregate rate greater than or equal to 5 mm/h. Trans-synaptic transport was evident at postinjection survival times as short as 5 h and continued to increase in density within the sympathetic preganglionic neuropil for 24 h. Fragment C-positive terminal labeling persisted for at least 20 days. At survival times greater than or equal to 1 day. Fragment C-positive puncta and weak intracellular labeling of neurons were evident in areas of the spinal gray outside of the nuclear boundaries of the column of Terni and nucleus intercalatus. The regions showing evidence of trans-synaptic and transneuronal labeling included: (a) a group of small cells dorsal to the column of Terni, (b) lamina V and (c) lamina VII. This expansion of Fragment C-labeled neuronal elements was segmental in organization and co-extensive with the retrograde labeling pattern of sympathetic preganglionic neurons. Spinal interneurons in these regions may provide segmental, monosynaptic input to sympathetic preganglionic neurons. Fragment C leaked into the systemic circulation from the site of injection in paravertebral ganglion 14.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth in vitro and acquisition of meiotic competence after the cryopreservation of isolated mouse primary ovarian follicles

The growth and acquisition of meiotic competence of oocytes from fresh and frozen-thawed primary follicles collected from 10-day-old mice was compared during culture in collagen gels for 12 days. The oocytes contained in primary follicles have a mean diameter of about 48 microns and do not resume meiosis without further growth and development. During the 12-day culture period the mean diameter of the oocytes increased to over 60 microns. The oocytes were capable of resuming meiosis when isolated from the gel and cultured in the absence of follicular cells in a manner similar to that observed in vivo. Freezing and thawing did not affect oocyte growth or the ability to resume meiosis; this demonstrates the possibility of storing large numbers of female gametes for subsequent development.

Freeze-thaw-induced changes of the zona pellucida explains decreased rates of fertilization in frozen-thawed mouse oocytes

Frozen-thawed oocytes have a reduced rate of fertilization (48.8%) when compared with unfrozen controls (97%). In this study we have used zona-drilling to bypass the zona pellucida and investigate whether the decreased rate of fertilization is due to freezing-induced changes in the zona pellucida which prevent sperm penetration. After zona drilling the fertilization rate of frozen-thawed oocytes (87.8%) was the same as for zona-intact unfrozen controls (88%), indicating that freeze-thaw-induced changes at the level of the zona pellucida were responsible for the decreased rate of fertilization. To determine whether the changes were occurring during the manipulations before and after freezing or the complete freeze-thaw cycle, oocytes were exposed to the complete set of manipulations normally experienced during cryopreservation and appropriate control groups. A small but significant decrease in the rate of fertilization (82.8%) was apparent in oocytes exposed to the manipulations before and after freezing compared with controls (92.2%). The freeze-thaw-induced changes in the zona pellucida therefore occur primarily during the complete freeze-thaw cycle itself and not the manipulations before and after freezing and are responsible for the decreased rate of fertilization observed in frozen-thawed oocytes.

T-cell lymphomas emerging as epineoplasms in mice bearing transplanted polyoma virus-induced salivary gland tumors

A subset of salivary epithelial tumors induced by mouse polyoma virus (PyV) has been designated lymphoepithelioma on the basis of a prominent lymphocytic component. Serial transplantation of this variant has previously been observed to result in lymphoma development. A recent repetition of this phenomenon allowed us to characterize the lymphoma cell populations with regard to phenotypic markers and PyV content. Lymphomas emerged in recipients of the third, fifth, sixth, and seventh transplant generations of the lymphoepithelioma. Most lymphomas were widely disseminated in hematopoietic and lymphoreticular tissues, and other sites as well. Flow cytometric analysis of lymphocyte populations from lymphomas in six recipients revealed that, while all lymphomas expressed phenotypic markers of immature cortical thymocytes, i.e., Thy-1, Pgp-1, Jlld, and CD5, they were not uniform with regard to other T-cell markers, notably CD4 and CD8. Varying levels of T-cell receptor markers CD3 and alpha/beta, as well as interleukin 2 receptor, were also noted. DNA blot analysis failed to detect PyV in lymphoma cells at a sensitivity level capable of detecting less than one intact copy per cell. It appears improbable the lymphoma was directly induced by PyV. Hypotheses invoking other mechanisms of lymphoma development are outlined.

Extra-ovarian production of mature viable mouse oocytes from frozen primary follicles

Isolated primary mouse follicles can be frozen successfully and thawed in the presence of 1.5 m-DMSO. Similar proportions of freshly collected and frozen-thawed primary follicles undergo folliculogenesis in the absence of other ovarian tissue. Some of the mature oocytes recovered from these follicles were fertilized in vitro and, after transfer to pseudopregnant recipients at the 2-cell stage, developed into live young. Cryopreservation and extra-ovarian development of immature follicles provide a unique opportunity to store large numbers of female gametes.

The effects of tritium on embryo development: the embryotoxic effects of [3H]tryptophan

The effects of tritiated amino acids on the development of the early mouse embryo in vitro are described. [3H]tryptophan was extremely toxic, compared with [3H]glutamic acid, and inhibited growth of the two-cell embryo to the blastocyst stage. The LD50 values for the two amino acids were, respectively, 1 and 296 kBq/ml of medium. The two-cell embryo was more sensitive to the irradiation from incorporated [3H]tryptophan is selectively incorporated into two chromosomal proteins in the two-cell embryo, and that those proteins were stage-specific markers of development.

Proteolytic processing of a coleopteran-specific delta-endotoxin produced by Bacillus thuringiensis var. tenebrionis

Insecticidal protein delta-endotoxin crystals harvested from sporulated cultures of Bacillus thuringiensis var. tenebrionis contain a major polypeptide of 67 kDa and minor polypeptides of 73, 72, 55 and 46 kDa. During sporulation, only the 73 kDa polypeptide could be detected at stage I. The 67 kDa polypeptide was first detected at stage II and increased in concentration throughout the later stages of sporulation and after crystal release, with a concomitant decrease in the 73 kDa polypeptide. This change could be blocked by the addition of proteinase inhibitors. Trypsin or insect-gut-extract treatment of the delta-endotoxin crystals after solubilization resulted in a cleavage product of 55 kDa with asparagine-159 of the deduced amino acid sequence of the toxin [Höfte, Seurinck, van Houtven & Vaeck (1987) Nucleic Acids Res. 15, 71-83; Sekar, Thompson, Maroney, Bookland & Adang (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 7036-7040; McPherson, Perlak, Fuchs, Marrone, Lavrik & Fischhoff (1988) Biotechnology 6, 61-66] at the N-terminus. This polypeptide was found to be as toxic in vivo as native delta-endotoxin.

Increase in digyny explains polyploidy after in-vitro fertilization of frozen-thawed mouse oocytes

Fewer frozen-thawed mouse oocytes cleaved to the 2-cell stage compared to fresh control oocytes fertilized in vitro (46% vs 79%). The reduced rate of 2-cell formation was only partly explained by a decreased rate of fertilization (63% vs 85%). However, subsequent development to expanded blastocysts was not different (75% vs 78%). An increased frequency of second polar body retention by fertilized frozen-thawed oocytes compared with controls (11.8% vs 1.3%) was shown to be largely responsible for the higher incidence of polyploidy (16.3% vs 3.7%). The frequency of polyspermic fertilization was not different in the two groups (3.9% vs 2.3%).

A cytolytic delta-endotoxin from Bacillus thuringiensis var. israelensis forms cation-selective channels in planar lipid bilayers

In order to determine the mechanism of action of the 27 kDa mosquitocidal delta-endotoxin of Bacillus thuringiensis var. israelensis we have studied its effects on the conductance of planar lipid bilayers. The toxin formed cation-selective channels in the bilayers, permeable to K+ and Na+ but not to N-methylglucamine or Cl-, showing very fast, cooperative opening and closing. Channel opening was greatly reduced in the presence of divalent cations (Ca2+, Mg2+) and the effect was reversed when these ions were removed. These results are consistent with our proposal that B. thuringiensis toxins act by a mechanism of colloid-osmotic lysis.