Human, mouse, and rat calnexin cDNA cloning: identification of potential calcium binding motifs and gene localization to human chromosome 5

Calnexin is a 90-kDa integral membrane protein of the endoplasmic reticulum (ER). Calnexin binds Ca2+ and may function as a chaperone in the transition of proteins from the ER to the outer cellular membrane. We have purified human calnexin in association with the human interferon-gamma receptor and cloned calnexin cDNA from placenta. Fragments of calnexin have been prepared as glutathione S-transferase fusion proteins and analyzed for their abilities to bind 45Ca2+ and ruthenium red. A subdomain containing four internal repeats binds Ca2+ with the highest affinity. This sequence is highly conserved when compared to calreticulin (a luminal ER protein), an Onchocerca surface antigen, and yeast and plant calnexin homologues. Consequently, this sequence represents a conserved motif for the high-affinity binding of Ca2+, which is clearly distinct from the "E-F hand" motif. An adjacent subdomain, also highly conserved and containing four internal repeats, fails to bind Ca2+. The carboxyl-terminal, cytosolic domain is highly charged and binds Ca2+ with moderate affinity, presumably by electrostatic interactions. The calnexin amino-terminal domain (residues 1-253) also binds Ca2+, in contrast to the amino-terminal domain of calreticulin, which is relatively less acidic. We have also determined the cDNA sequences of mouse and rat calnexins. Comparison of the known mammalian calnexin sequences reveals very high conservation of sequence identity (93-98%), suggesting that calnexin performs important cellular functions. The gene for human calnexin is located on the distal end of the long arm of human chromosome 5, at 5q35.     

Phenomenologic comparison of the idiopathic psychosis of schizophrenia and drug-induced cocaine and phencyclidine psychoses: a retrospective study

Both stimulant-induced and phencyclidine (PCP)-induced psychoses have been proposed as models of the idiopathic psychosis of schizopherenia. In this two-part study, the phenomenology of the psychosis associated with a period of cocaine intoxication was evaluated retrospectively in 34 male crack cocaine-dependent patients without concomitant psychiatric disorder and then was compared with the psychosis of 16 actively psychotic schizophrenic men (without a history of drug or alcohol abuse in the past year). Certain First Rank Schneiderian Symptoms (FRSS) were more commonly observed in the schizophrenic patients (e.g., thought broadcasting, thought withdrawal) than in the cocaine addicts. In the second part of this study, we retrospectively examined the cocaine and PCP experiences of an additional 22 cocaine addicts who had a past history of separate periods of cocaine and PCP use. Overall, the frequency of FRSS recalled during periods of cocaine and PCP intoxication was similar. However, the psychosis related to cocaine intoxication was more associated with an intense suspiciousness and paranoia related to a fear of being discovered or harmed while using cocaine. PCP-induced psychosis was less associated with suspiciousness and more associated with delusions of physical power, altered sensations, and unusual experiences [e.g., out of body experiences, experiencing religious figures or events directly (e.g., being with Noah at the time of the Arc)]. As elements of both cocaine and PCP psychosis can be found in schizophrenia, a model integrating the mechanisms of several psychotogenic drugs may be more informative. Such an integrative model might better capture the heterogeneity of psychotic symptoms that can be seen in schizophrenia. Furthermore, different pharmacologic interventions (e.g., "anti-stimulant" versus "anti-PCP") might address different aspects of the positive symptom picture in schizophrenia.     

Prognostic significance of prior preterm twin delivery on subsequent singleton pregnancy

OBJECTIVE: Our purpose was to determine whether preterm birth of twins is associated with an increased risk of preterm birth in a subsequent singleton pregnancy. STUDY DESIGN: The Medical University of South Carolina perinatal database was accessed to identify a cohort of patients who were delivered of twins followed by a singleton gestation (1981 to 1993). Maternal transports were excluded to minimize referral bias. Preterm birth was defined as < 37 weeks' gestation. Relative risks with 95% confidence intervals were calculated. RESULTS: One hundred forty-four patients were identified who were delivered of twins followed by a singleton gestation. Preterm delivery occurred in 86 (59.7%) of the twins and 21 (14.6%) of the subsequent singletons. Preterm birth of twins was associated with a significantly increased risk of preterm delivery in a subsequent singleton pregnancy (relative risk 2.87, 95% confidence interval 1.02 to 8.09). In the subset of women who were delivered of twins at < 30 weeks' gestation, 42% of the subsequent singletons were delivered preterm (relative risk 6.11, 95% confidence interval 2.07 to 18.02). The relative risk of preterm birth of a singleton after delivery of twins between 30 and 34 weeks' gestation was 3.63 (95% confidence interval 1.02 to 12.92). However, if the preceding twins delivered between 34 and 37 weeks' gestation, the relative risk of preterm birth of the subsequent singleton was not significantly increased (relative risk 1.42, 95% confidence interval 0.40 to 5.01). CONCLUSIONS: Preterm birth of twins before 34 weeks' gestation is associated with a significant risk for preterm delivery in a subsequent singleton pregnancy. The magnitude of risk increases with decreasing gestational age of the preceding twin delivery.     

Ovarian steroid regulation of vascular endothelial growth factor in the human endometrium: implications for angiogenesis during the menstrual cycle and in the pathogenesis of endometriosis

The human endometrium undergoes a complex process of vascular and glandular proliferation, differentiation, and regeneration with each menstrual cycle in preparation for implantation. Vascular endothelial growth factor (VEGF) is an endothelial cell-specific angiogenic protein that appears to play an important role in both physiological and pathological neovascularization. To investigate whether VEGF may regulate human endometrial angiogenesis, we examined VEGF messenger ribonucleic acid (mRNA) and protein throughout the menstrual cycle and studied the regulation of VEGF by reproductive steroids in isolated human endometrial cells. By ribonuclease protection analysis, VEGF mRNA increased relative to early proliferative phase expression by 1.6-,2.0-, and 3.6-fold in midproliferative, late proliferative, and secretory endometrium, respectively. In histological sections, VEGF mRNA and protein were localized focally in glandular epithelial cells and more diffusely in surrounding stroma, with greatest VEGF expression in secretory endometrium. Consistent with these in vivo results, the treatment of isolated human endometrial cells with estradiol (E2), medroxyprogesterone acetate (MPA), or E2 plus MPA significantly increased VEGF mRNA expression over the control value by 3.1-, 2.8-, and 4.7-fold, respectively. The VEGF response to E2 was rapid, with steady state levels of VEGF mRNA reaching 85% maximum 1 h after the addition of steroid. E2 also caused a 46% increase in secreted VEGF protein, and the combination of E2 and MPA caused an 18% increase. VEGF expression in endometriosis, an angiogenesis-dependent, estrogen-sensitive disease was similar to that seen in eutopic endometrium. Peritoneal fluid concentrations of VEGF were significantly higher in women with moderate to severe endometriosis than in women with minimal to mild endometriosis or no disease. VEGF, therefore, may be important in both physiological and pathological angiogenesis of human endometrium, as it is an estrogen-responsive angiogenic factor that varies throughout the menstrual cycle and is elevated in women with endometriosis.     

Folic acid supplementation--when and how

The periconceptional intake of 400 micrograms of folic acid can prevent 50-70% of neural tube defects. It is difficult to achieve this intake with diet alone, even with the recently approved levels for grain-food fortification. Therefore, a daily multivitamin with folic acid is recommended for all women of childbearing potential. Obstetrician-gynecologists should exercise every opportunity to educate their patients to this end. Although raised as a concern, the potential of masking the megaloblastic anemia of pernicious anemia is unlikely with these levels of supplementation, and considering the rarity of the disease in women of reproductive age.     

Effect of triiodothyronine administration in experimental myocardial injury

Twelve healthy pigs were subjected to a 20-min, period of regional myocardial ischemia by snaring the left anterior descending coronary artery (LAD) between its first and second diagonal branches. The resulting myocardial injury caused significant acute hemodynamic impairments. Cardiac index declined significantly during reperfusion interval and returned to preischemic level by postoperative day 7. Plasma total triiodothyronine (TT3), free triiodothyronine (FT3) and free fatty acid (FFA) decreased gradually and reached the nadir at 6 h after LAD occlusion. In contrast, plasma reverse triiodothyronine (rT3) increased progressively after LAD occlusion and reperfusion. To investigate the effect of T3 on ischemic myocardium, T3 (0.2 microgram/kg/dose; n = 5) or saline (placebo; n = 6) was administered immediately, 30 min, 60 min, 90 min, and 120 min after reperfusion. Plasma TT3 and FT3 increased dramatically after triiodothyronine supplement but declined to presichemic level at six h after LAD occlusion. The pigs treated with T3 demonstrated a rapid improvement in cardiac index over the reperfusion interval, whereas cardiac index in the placebo group remained depressed. Myocardial oxygen consumption estimated by rate pressure product showed no difference between placebo and T3-treated groups. Oxygen extraction as O2 saturation difference between aorta and coronary sinus was less in T3-treated group. Nine pigs (four in the T3-treated group and five in the placebo group) were subjected to euthanasia with hypertonic KCl solution on postoperative day 7. Myocardial infarct size determined by triphenyltetrazolium chloride (TTC) tissue enzyme staining technique was not significantly different between T3-treated and placebo groups. We concluded that this animal model is a useful model of myocardial injury simulating "euthyroid sick syndrome" as seen in patients with cardiopulmonary bypass, and T3 supplementation after reperfusion significantly enhanced postischemic left ventricular functional recovery but did not affect myocardial oxygen consumption and myocardial infarct size.     

Maternal and neonatal plasma inorganic fluoride levels after methoxyflurane analgesia for labor and delivery

At the time of the experiment, lean animals weighed 226-235 gm and the fatty rats 330-440 gm. On Day 5 after castration, rats received injections of estradiol-17beta (E2) for a 3-day period. Doses were .01-100 mcg/100 gm of body weight. Radioiodine uptake was determined by injecting 50 microCi of iodine-125 ip 24 hours before sacrifice. Beginning 12 hours after the last dose of E2, pairs of rats including a fatty and lean rat were sacrificed until all had been killed. Ovaries (at castration or autopsy), pituitary, and thyroid were removed and weighed. Uteri in obese rats were significantly smaller than in lean rats. There was a close dose-response relationship between E2 and the weight of the uteri; this was more marked in the obese rats. The radioactivity of the thyroid was increased more in the lean rats. Fatty rats ate more food than lean rats. The highest dose of E2 did not increase the food intake of obese rats but did increase that of the lean animals. It is concluded that the small uteri in the fatty rats may be due to decreased estrogenization and that this may also partly account for the small pituitary and low thyroid uptake of radioiodine.