Mechanisms controlling egg size and number in the rainbow trout, Oncorhynchus mykiss

Female rainbow trout (Oncorhynchus mykiss) produce a single batch of eggs each year; synchronous growth of oocytes, all of which are ovulated at the same time, occurs in the two ovaries. To examine the regulatory mechanisms controlling egg size and number, virgin female rainbow trout were subjected to unilateral ovariectomy (ULO) during early vitellogenesis, and oocyte recruitment and growth in the remaining ovary were monitored. The study also set out to determine whether the presence of a second population of smaller oocytes in the maturing pool (induced by ULO) affected the timing of ovulation and/or the size of the eggs ovulated. Two months after ULO, there was no difference in the gonadosomatic index between ULO fish and controls. Compensatory ovarian hypertrophy resulted from the recruitment of a second population of primary oocytes into the vitellogenic pool. This population of smaller maturing oocytes in the ULO fish displayed growth rates up to twice those of the population of larger oocytes in the same ovary and of oocytes in controls. The growth rate of the population of larger oocytes in the ULO fish was not altered by the recruitment of a second maturing population. One month after ULO, fish had a lower concentration of plasma estradiol-17 beta than did controls; subsequently the concentrations of plasma estradiol-17 beta in the ULO and control groups were similar. After ULO, plasma levels of vitellogenin in the ULO fish did not differ from those in the control group throughout the study. At or close to ovulation, the fecundity of ULO fish was 75-80% that of controls. In the control group, oocytes appeared to reach a certain critical size before they were ovulated, and fish with higher fecundity ovulated later than their less fecund counterparts. ULO did not affect the timing of ovulation, and ULO fish ovulated eggs with a considerably greater size-range than did controls.

[Transpapillary endoscopic drainage of pancreatic pseudocyst]

Drainage of pancreatic pseudocysts can be achieved by means of endoscopy. In this paper we report a case of a pancreatic pseudocyst of ten centimeters in diameter, that was successfully managed by insertion of a nasocystic drainage through the papilla of Vater. The procedure was simple and complications were absent. Transpapillary drainage of pancreatic pseudocysts is an effective procedure.

A novel insertional mutation in the TC21 gene activates its transforming activity in a human leiomyosarcoma cell line

TC21 is the fourth member of the ras gene family to exhibit oncogenic activation in human tumor cells. To assess the prevalence of activated TC21 oncogenes in human tumors, we have developed sensitive single-strand conformational polymorphism (SSCP) conditions and immunological reagents for the detection of both single base alterations and/or overt overexpression in a wide spectrum of human tumor cell lines and surgical samples. In an initial examination of 33 human tumor specimens, we observed a novel nine basepair three amino acids insertion at TC21 codon 24 in one human uterine leiomyosarcoma cell line, SK-UT-1. This mutant allele when transfected into NIH3T3 cells, displayed high transforming activity comparable to that of the Leu72 oncogenic mutant identified by expression cDNA cloning from a human ovarian carcinoma cell line. Comparing the level of GTP-binding by the mutant and normal TC21 products revealed that this novel lesion increases the GTP-bound form of the TC21 molecule. These findings imply that the mechanism by which mutations activate the oncogenic properties of this ras-related molecule is analogous to that of previously known ras family members.

Vav and Ras induce fibroblast transformation by overlapping signaling pathways which require c-Myc function

Recent evidence has suggested that the Vav oncoprotein may function as a hematopoietic-specific GTP exchange factor for the Ras superfamily of proteins. However, transformation of NIH3T3 fibroblast cells by Vav is morphologically distinct from that induced by activated Ras oncogenes, suggesting that the two oncoproteins induce separate signal transduction pathways which promote transformation. To address this issue, the effects of dominant negative mutants of H-ras and proto-Vav (proto-VavR695L, a mutation in the VavSH2 domain) were tested on Vav- and Ras-induced transformation. These mutants partially inhibited both Vav- and Ras-induced transformation, suggesting that they may induce a common downstream signaling pathway which potentiates transformation. As an independent measure of Vav function we also tested the ability of the purified protein encoded by VavSH2 to influence Germinal Vesicle Breakdown (GVBD) during Xenopus oocyte maturation. Microinjection of the VavSH2 protein alone, but not mutant VavR695L SH2 protein, was sufficient to induce GVBD and accelerated maturation induced by normal Ras, suggesting that in this system as well Vav and Ras signals overlap through a common effector. A key target of multiple signalling pathways is c-Myc. Dominant negative versions of c-Myc totally abolished morphologic transformation of NIH3T3 cells by both Vav and Ras oncogenes. These results suggest that distinct, but overlapping, signalling pathways are induced by Vav and Ras and that fibroblast cell transformation by either oncogene requires c-Myc functions.

Human dual specificity phosphatase VHR activates maturation promotion factor and triggers meiotic maturation in Xenopus oocytes

Bacterially expressed, dual specificity phosphatase VHR protein induced germinal vesicle breakdown (GVBD) when microinjected into Xenopus oocytes, albeit with slower kinetics than that observed in progesterone- or insulin-induced maturation. A mutant VHR protein missing an essential cysteine residue for its in vitro phosphatase activity completely lacked activity in injected oocytes. VHR injection done in conjunction with progesterone or insulin treatment resulted in highly synergized GVBD responses showing much faster kinetics than that produced by VHR or either hormone alone. The delayed kinetics of VHR-induced GVBD and the synergistic responses obtained in the presence of hormones suggested that this protein may be promoting G2/M transition by weakly mimicking the action of cdc25, the dual specificity phosphatase that physiologically activates the maturation promotion factor. Various experimental observations are consistent with such a role for the injected VHR in oocytes: 1) as opposed to hormone-treated oocytes, histone H1 kinase activation is not preceded by MAPK activation in the process of GVBD in VHR-injected oocytes; 2) incubation of purified VHR with highly concentrated cell-free extracts of untreated oocytes resulted in activation of histone H1 kinase activity in the lysates; 3) coinjection of VHR with activated Ras proteins resulted in synergized responses, faster than those produced by either protein alone; 4) coinjection of VHR with the purified amino-terminal SH2 domain of the p85 subunit of phosphatidylinositol 3-kinase (which blocks insulin-induced GVBD) does not affect VHR-induced maturation. The biological actions of VHR in oocytes clearly distinguish it from other dual specificity phosphatases, which have shown inhibitory effects when tested in oocytes. We speculate that VHR may represent a dual specificity phosphatase responsible for activation of cdk-cyclin complex(es) at a still undetermined stage of the cell cycle.

A divalent metal ion binding site in the kinase insert domain of the alpha-platelet-derived growth factor receptor regulates its association with SH2 domains

To investigate the effects of metal ion binding to the alpha-PDGFR kinase insert domain, a PCR product representing amino acid residues 691-795 (104 amino acids) was bacterially expressed and purified. Secondary structure prediction and circular dichroism spectroscopy indicated this domain to be a mixed alpha + beta protein with a large coil/turn contribution. This 16 kDa, soluble, nonphosphorylated domain bound to 45Ca2+ and 65Zn2+ through a common shared site. Of the unlabeled divalent and trivalent metal ions tested, Ho3+ = Zn2+ > Ni2+ > Ca2+ = Mn2+ > Mg2+, Ba2+ in competing for 45Ca2+ binding to this domain. In the presence of Ca2+ ions, the conformation of the KI domain changed significantly, and this changed conformation was resistant to subtilisin proteolysis. However, in the presence of Zn2+ ions, the conformation of the KI domain changed only slightly. Nevertheless, Zn2+ ions were more effective in rendering the KI domain resistant to proteolysis as compared to that shown by Ca2+ ions. In vitro binding studies using purified baculovirus-expressed alpha-PDGFR showed a marked increase in binding the p85 N-SH2 domain in the presence of Ca2+ or Zn2+ ions (KD = 0.5 microM), suggesting that metal ion binding enhances association of the p85 N-SH2 domain with the receptor. To confirm this, association of the alpha-PDGFR with the p85 N-SH2 domain was tested in the presence of the KI domain. The nonphosphorylated KI domain was effective in competing with the alpha-PDGFR for the binding of the p85 N-SH2 domain. This effect was more pronounced in the presence of Ca2+ ions. Microinjection of this domain into Xenopus oocytes delayed maturation in the presence of insulin but not progesterone. This suggests that the KI domain has a correctly folded three-dimensional structure compatible with biological activity. Together these findings indicate that the recombinant alpha-PDGFR KI domain binds the p85 N-SH2 domain and this binding is modulated by the presence of a novel divalent metal ion binding site within its structure.

Unexpected isolation of Bordetella pertussis from a blood culture

Bordetella pertussis was isolated from a culture of blood from a 31-year-old man with Wegener's granulomatosis. The organism was detected with the BACTEC 9240 system after 6 days of incubation and was confirmed as B. pertussis by the Centers for Disease Control and Prevention. To our knowledge, this is the first published report of the recovery of B. pertussis from blood.

[Successful endoscopic therapy in a case of Bouveret's syndrome]

We present a case of duodenal gallstone ileus (Bouveret's syndrome) that evolved with its classical symptomatology and was successfully managed by endoscopic extraction of the stone, an extremely unusual circumstance. Although difficult and laborious, endoscopic therapy in the Bouveret's syndrome, by using the Dormia basket, may prove useful.

Suppression of the endogenous luteinizing hormone surge by the gonadotrophin-releasing hormone antagonist Cetrorelix during ovarian stimulation

Surges of luteinizing hormone (LH) that result in luteinization but occur prematurely with respect to the diameter of the leading follicle, prevent attempts to induce multiple follicular maturation for in-vitro fertilization (IVF) in a significant number of women. We examined the possibility of blocking premature LH surges by the administration of Cetrorelix, a potent antagonist of gonadotrophin-releasing hormone (GnRH), in a study including 20 patients, some of whom had previously shown premature LH surges. All patients were treated with human menopausal gonadotrophins (HMG) starting on day 2. From day 7 until the induction of ovulation by human chorionic gonadotrophin (HCG) the GnRH antagonist Cetrorelix was given daily. HCG was injected when the dominant follicle had reached a diameter of > or = 18 mm and oestradiol concentration was > 300 pg/ml for each follicle having a diameter of > 15 mm. Oocyte collection was performed 36 h later by transvaginal ultrasound puncture, followed by IVF and embryo transfer. The hormone profiles of these patients and the results of IVF and embryo transfer are comparable to those treated with GnRH agonists and HMG. However, less time and especially less HMG is needed in comparison to patients stimulated with a long agonist protocol. Hence, treatment with Cetrorelix proved to be much more comfortable for the patient. In this study we showed that combined treatment with gonadotrophins and the GnRH antagonist Cetrorelix is a promising method for ovarian stimulation in patients who frequently exhibit premature LH surges and therefore fail to complete treatment.

Dissociation between activation of Raf-1 kinase and the 42-kDa mitogen-activated protein kinase/90-kDa S6 kinase (MAPK/RSK) cascade in the insulin/Ras pathway of adipocytic differentiation of 3T3 L1 cells

Insulin treatment of untransfected 3T3 L1 cells quickly induced activation of a cytosolic 42-kDa mitogen-activated protein kinase (MAPK) and a 90-kDa S6 kinase (RSK). The activation of these cytosolic kinases was also mimicked by Ras expression (in the absence of insulin) in the same cells transfected with inducible ras oncogenes. Furthermore, insulin-induced activation of MAPK and RSK could be blocked by expression of a transfected inducible dominant negative Ras mutant (Asn-17). These results indicate that Ras proteins are obligatory intermediates in the activation of the cytosolic MAPK/RSK cascade by insulin. Insulin treatment of 3T3 L1 cells or expression of transfected ras oncogenes resulted also in hyperphosphorylation of cellular Raf-1. Insulin-induced Raf hyperphosphorylation was inhibited by expression of an inducible dominant negative Ras mutant (Asn-17). We also showed that expression of transfected raf oncogenes induces adipocytic differentiation, as detected by expression of the specific adipocytic marker aP2. In addition, insulin-induced differentiation was significantly blocked by expression of a dominant negative raf mutant. Interestingly, however, the expression of transfected raf oncogenes did not induce MAPK or RSK activation, and the insulin-induced activation of these kinases was not blocked by expression of transfected dominant negative raf mutants. These results are consistent with Raf kinases acting downstream of Ras, but not upstream of MAPK and RSK in insulin-signaling pathways leading to 3T3 L1 differentiation.

[Suppression of endogenous LH increase in ovarian stimulation with the GnRH antagonist Cetrorelix]

Surges of LH in serum, which result in luteinization, but occur prematurely with respect to the diameter of the leading follicle, frustrate attemps to induce multiple follicular maturation for in-vitro fertilisation in a number of women. We examined the possibility of blocking premature LH-surges by the administration of Cetrorelix, a potent antagonist of gonadotrophin releasing hormone. Twenty patients, who had repeatedly shown premature LH surges, were treated with human menopausal gonadotrophins from the 2nd day onwards. From the 7th day until the induction of ovulation by HCG, the GNRH-antagonist Cetrorelix was given daily. HCG was injected when the dominant follicle had reached the diameter of at least 18 mm and oestradiol levels were above 300 pg for each follicle and more than 15 mm. Oocyte collection was performed 36 hours later by transvaginal ultrasound puncture, followed by IVF and embryo transfer. The hormone profiles of these patients and the results of in-vitro fertilisation and embryo transfer are discussed. It could be demonstrated in this study, that combined treatment with gonadotrophins and the GNRH-antagonist seems to be a promising method for ovarian stimulation in patients, who frequently exhibit premature LH discharges and therefore fail to complete treatment.

[Endoscopic percutaneous gastrostomy. Experience at a general hospital]

Percutaneous endoscopic gastrostomy is a technique scantly used in Spanish hospitals. Its finality is the nutrition of patients with dysphagia, by avoiding the inconveniences and complications of transnasal feeding tubes. Our group has begun a protocol of endoscopically placed gastrostomies and in this work we present its first series; it includes 23 cases of patients with dysphagia secondary to neurological disorders. We have employed the original "pull technique" from Gauderer and Ponsky and we have used homemade gastrostomy tubes. Only two mild complications were observed (stoma infection). In our experience, this technique is easy and has few complications. Furthermore, if homemade tubes are used, the economic cost is very low. In this paper, beside of communicating our results, we summarize the percutaneous endoscopic gastrostomy technique and the way for constructing the tubes.

An epidermal growth factor receptor/ret chimera generates mitogenic and transforming signals: evidence for a ret-specific signaling pathway

A chimeric expression vector which encoded for a molecule encompassing the extracellular domain of the epidermal growth factor (EGF) receptor (EGFR) and the intracellular domain of the ret kinase (EGFR/ret chimera) was generated. Upon ectopic expression in mammalian cells, the EGFR/ret chimera was correctly synthesized and transported to the cell surface, where it was shown capable of binding EGF and transducing an EGF-dependent signal intracellularly. Thus, the EGFR/ret chimera allows us to study the biological effects and biochemical activities of the ret kinase under controlled conditions of activation. Comparative analysis of the growth-promoting activity of the EGFR/ret chimera expressed in fibroblastic or hematopoietic cells revealed a biological phenotype clearly distinguishable from that of the EGFR, indicating that the two kinases couple with mitogenic pathways which are different to some extent. Analysis of biochemical pathways implicated in the transduction of mitogenic signals also evidenced significant differences between the ret kinase and other receptor tyrosine kinases. Thus, the sum of our results indicates the existence of a ret-specific pathway of mitogenic signaling.

Intrafamilial spread of hepatitis C virus infection

We assessed the prevalence of antibodies to hepatitis C virus (anti-HCV) among 401 household contacts of 161 persons with chronic hepatitis C (index patients). None of the index patients had antibodies against HIV. The overall prevalence of anti-HCV was 3.2% (2.5% in the absence of previous parenteral exposure). Sexual partners had a seroprevalence of 4.7% and non-sexual contacts, 2.5%. Among non-sexual contacts, parents showed the highest rate (4.2%). The mean duration of exposure in the anti-HCV-positive sexual partners was 17.3 +/- 8.5 years, vis-à-vis 9.2 +/- 7.4 years in the anti-HCV-negative sexual partners. We conclude that there is little risk of HCV infection through household contact. Although the form of transmission is not well identified, the duration of sexual activity suggests that the time needed to become infected is long.

Establishment of permanent brown adipocyte cell lines achieved by transfection with SV40 large T antigen and ras genes

We established multiple clonal cell lines by transfection of primary rat fetal brown adipocytes (BAT) with constitutive or inducible gene constructs of SV40 large T antigen (SVLTag) alone or in combination with transforming or normal ras genes. While primary BAT cell cultures stop growing and expressing uncoupling protein (UCP) after several passages in culture, our transfected cell lines could be propagated indefinitely and kept properties specific of BAT cells. Interestingly, cells transfected with ras genes alone did not survive as permanent cell lines. In contrast, cells transfected with SVLTag alone or in combination with various ras genes could readily be established as continuous cell lines. BAT cells transfected with SVLTag alone showed fibroblastic, flat morphology and clear contact inhibition of growth. In contrast, cells cotransfected with SVLTag and ras genes were more fusiform and possessed increased proliferative capacity. Thus, cells cotransfected with normal ras reached higher cell density at confluency, while cells cotransfected with transforming ras were clearly refractile, lost contact inhibition of growth, and presented a transformed phenotype. These results are consistent with the notion that ras genes are inefficient at overcoming senescence of primary BAT cells and can only confer improved proliferative ability to cells that have already been immortalized by a cooperating SVLTag gene. RNA analysis showed that most transfected cell lines expressed UCP along with the exogenously transfected genes. This demonstrated that genuine BAT cells, and not other possible contaminating cell lineages, gave rise to our selected cell lines. The variety of cell lines generated may correspond to various stages of progression through BAT development and therefore be useful to characterize signaling pathways and metabolic regulation of this particular tissue.

High-field 13C solid-state NMR studies of stream humic and fulvic acids with fast magic-angle spinning

Standard samples of stream humic and fulvic acids have been studied by high-resolution 13C solid-state NMR. The spectra have been recorded at a high (9.4 T) magnetic field using 1H-13C cross-polarization (CP) and proton high-power decoupling (HPDEC) with fast (up to 15 kHz) magic-angle spinning (MAS). The widths of the spectral lines decrease with increasing spinning rate. This is probably due to the overlap of spinning sidebands with resonances at low speeds and to a more effective averaging of anisotropic broadening at high speeds. However, fast MAS modulates the CP signal intensities, making quantitative analysis very difficult.

The ras signaling pathway mimics insulin action on glucose transporter translocation

Recent observations suggest that insulin increases cellular levels of activated, GTP-bound Ras protein. We tested whether the acute actions of insulin on hexose uptake and glucose-transporter redistribution to the cell surface are mimicked by activated Ras. 3T3-L1 fibroblasts expressing an activated mutant (Lys-61) N-Ras protein exhibited a 3-fold increase in 2-deoxyglucose uptake rates compared with non-transfected cells. Insulin stimulated hexose uptake by approximately 2-fold in parental fibroblasts but did not stimulate hexose uptake in the N-Ras61K-expressing fibroblasts. Overexpression of N-Ras61K also mimicked the large effect of insulin on 2-deoxyglucose transport in 3T3-L1 adipocytes, and again the effects of the two agents were not additive. Total glucose transporter protein (GLUT) 1 was similar between parental and N-Ras61K-expressing 3T3-L1 fibroblasts or adipocytes, whereas total GLUT-4 protein was actually lower in the N-Ras61K-expressing compared with parental adipocytes. However, expression of N-Ras61K in 3T3-L1 adipocytes markedly elevated both GLUT-1 and GLUT-4 in plasma membranes relative to intracellular membranes, and insulin had no further effect. These modulations of glucose transporters by N-Ras61K expression are not due to upstream regulation of insulin receptors because receptor tyrosine phosphorylation and association of phosphatidylinositol 3-kinase with tyrosine-phosphorylated proteins were unaffected. These results show that activated Ras mimics the actions of insulin on membrane trafficking of glucose transporters, consistent with the concept that Ras proteins function as intermediates in this insulin signaling pathway.

p21ras-induced meiotic maturation of Xenopus oocytes in the absence of protein synthesis: MPF activation is preceded by activation of MAP and S6 kinases

Microinjection of transforming p21ras into Xenopus oocytes caused a time-dependent increase in the level of total cell protein phosphorylation that culminated with germinal vesicle breakdown (GVBD). The same pattern of phosphorylation was observed in oocytes matured by either progesterone or insulin. Treatment with cycloheximide (CHX) completely blocked both GVBD and the associated de novo phosphorylations induced by the hormones, but did not abolish p21ras-induced maturation nor the occurrence of associated maturation promoting factor (MPF)-dependent and -independent phosphorylations. Thus, induction of GVBD by p21ras in the absence of protein synthesis correlated with the activation of cytosolic MPF-associated kinase activity similar in specificity on exogenous (histone H1) and endogenous (47 kDa and a 42 kDa proteins) substrates to the MPF activity of hormonally-matured oocytes. The injection of p21ras in the presence of CHX caused also activation of other kinase(s) proceeding MPF activation which were responsible for the phosphorylation of endogenous substrates including a 41 kDa protein and a 92 kDa protein kinase that comigrated, respectively, with bands recognized specifically by antibodies to MAP2 kinase and S6 kinase. The phosphorylation of those bands correlated also with the activation of cytosolic kinases acting specifically on myelin basic protein (MBP) and a S6-derived peptide as substrates. These results indicate that, in the absence of protein synthesis, p21ras is able to activate phosphorylation events leading to GVBD and suggest that this oncoprotein can participate in at least two separate pathways of MPF activation. We propose that the activation of MAP/MBP kinases and S6 kinases is an early effect of p21ras oncoproteins.