Smoking-related alterations in epidermal growth factor and insulin receptors in human placenta

Studies characterized insulin and EGF receptors in human placental tissue from smokers and nonsmokers. Specific binding of 125I-labeled insulin and EGF to placental membranes was not different for nonsmokers compared with smokers. EGF and insulin receptor kinases were further studied using a wheat germ agglutinin-purified preparation of solubilized placental membrane proteins. In extracts from the nonsmoker group, EGF stimulated the active phosphorylation of Mr 170,000 and 140,000 protein bands, which was half-maximal (EC50) at 5 x 10(-8) M. In extracts from the smokers group, however, phosphorylation of these two protein bands was barely detectable over a range of 0 to 10(-6) M EGF. Thus, EGF-stimulated phosphorylation of the 170,000 and 140,000 bands was markedly decreased in placental membranes from smokers. In contrast, insulin stimulated the phosphorylation of a 95,000 protein that was immunoprecipitated with anti-insulin receptor antiserum in membrane preparations from both nonsmokers and smokers. Dose-response curves for autophosphorylation indicate that EC50 values were 2.6 and 7.0 nM insulin for nonsmokers and smokers, respectively. Laser densitometry scan of the 95,000 band on autoradiograms further showed that maximal 32P incorporation was 30% greater in smokers compared with nonsmokers. Analysis of the insulin-dependent phosphorylation of an exogenous substrate, poly(Glu,Tyr) (4:1), showed a similar pattern of values for nonsmokers versus smokers. These results indicate that insulin receptor autophosphorylation and tyrosine kinase activity were normal or increased, whereas EGF-stimulated kinase activity was markedly decreased in placental membrane proteins from smokers. Western blot analysis using an antiserum to the EGF receptor showed the presence of immunoreactive bands of 126,000 and 150,000-170,000 in receptor preparations from nonsmokers, whereas only the 126,000 protein was detected in preparations from smokers. Thus, the smoking-related deficiency in EGF receptor autophosphorylation appeared to be due to the absence of a 150,000-170,000 receptor protein. In conclusion, maternal cigarette smoking is associated with selective alterations in two major receptor-mediated pathways thought to be involved in cell growth and differentiation in human placenta.     

Identical twins with subretinal neovascularization complicating senile macular degeneration

This is the first report, to our knowledge, of proliferative macular degeneration developing in the same eye of identical twins. The concept of a familial predisposition in age related macular degeneration is consistent with other known risk factors including race, iris pigmentation, hyperopia and macular drusen which are known to be genetically determined. Monozygotic twins provide ophthalmology with an excellent opportunity to study the hereditary aspects of ocular disease.     

Characterization of a cytosolic steroid-binding protein in the liver of the winter flounder, Pseudopleuronectes americanus

The winter flounder liver contains significant concentrations of estrogen binding protein(s) that fulfill some of the criteria normally assigned to receptor proteins, in that these proteins are saturated at low substrate concentrations (<5 nm) and have a high affinity for ligand (K_d approximately 6 × 10^?10M for $\text{[}{}^3\text{H]17β-estradiol}$). Sedimentation analysis of the 17β-estradiol-binding protein complex on 5–20% sucrose density gradients detected an 8 S form of the binding protein under low salt conditions. Nonspecific sites sedimented in the 4 S region. These sedimentation characteristics are similar to those observed for the estrogen receptor and nonspecific binding sites in mammalian tissues. In contrast to mammalian estrogen receptor, which binds selectively to estrogens, the binding protein(s) investigated in our studies also binds other steroids. Competitive binding studies demonstrated that 10-fold excess of unlabeled testosterone and progesterone displaced 50 and 45% of $\text{[}{}^3\text{H]17β-estradiol}$ from the binding protein, respectively. These studies demonstrate the presence of steroid-binding protein in liver of female winter flounder which might play a role in regulating hepatic steroid hormone action.     

2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced changes in the hydroxylation of biphenyl by rat liver microsomes

Biphenyl 2- and 4-hydroxylase activities and cytochrome P-450 concentrations in microsomes were increased by oral doses of less than 1 μg TCDD/kg. Female rats were more sensitive than male rats to the inductive effects of TCDD. since highly significant increases in biphenyl-hydroxylating activities were observed at the dose level of 0.2 μg TCDD/kg in female but not in male rats. The inductive effect was very persistent: biphenyl 2- and 4-hydroxylases remained stimulated even after 73 days following a single oral dose of 25 μg TCDD/kg. The levels to which the hydroxylases were stimulated in female rats were the same as in male rats. Rats of all ages from 10 to 335 days responded to hepatic microsomal effects of TCDD to approximately the same degree. The enzyme inductive effect was diminished by the simultaneous administration of actinomycin D. The K_m of biphenyl 2-hydroxylase (1.42 mM) was not altered significantly by TCDD treatment, but the K_m of biphenyl 4-hydroxylase (0.62 mM) was increased to approximately the same value (1.6 mM) as that of the 2-hydroxylase. The V_max of biphenyl 4-hydroxylase was increased 4.5-fold but that of biphenyl 2-hydroxylase was increased 16.5-fold. Rates of 2β- and 16α-hydroxylation of testosterone were suppressed by TCDD but rates of 7α- and 6β-hydroxylation were unaffected. It would appear that the hepatic microsomal mixed-function oxidases responsible for the hydroxylation of biphenyl and testosterone are different.     

Pain after barium enema: effect of CO2 and air on double-contrast study

One hundred fifty-one consecutive patients scheduled for double-contrast barium enema studies were assigned randomly to insufflation with either air or carbon dioxide (CO2) in a double-blind, prospective trial. Within 24 hours after the enema study, the patients were contacted by telephone by an interviewer, who completed a standard questionnaire. Radiographs from the enema studies were assessed for quality by two radiologists. Pain experienced after the procedure was graded from 0 (none) to 4 (severe). Clinically relevant (grades 2-4) pain was experienced by 30% of patients after insufflation with room air, compared with 11% of patients in whom CO2 was used for insufflation (P = .005). The mean pain score for CO2 was 0.4, and for room air, 1.2 (P less than .005). Although five patients experienced grade 4 pain after insufflation with air, no patient reported severe pain after CO2 insufflation. Post-evacuation films confirmed there was significantly less residual gas in the CO2 group. The quality of radiographs was equal in the two groups. CO2 has advantages for use in the double-contrast barium enema examination.     

Characterization of cat nasal afferents and brain stem neurones receiving ethmoidal input

Stimulation of the nasal mucous membrane can initiate protective reflexes, particularly sneezing and apnea. Very little is known about the receptors in the nasal cavity responsible for initiating these reflexes, which are thought to be mediated by trigeminal rather than olfactory pathways. In the cat, the ethmoidal branch of the ophthalmic division of V carries this afferent information. The objectives of the present study were to determine a set of adequate nasal receptor stimuli capable of initiating these protective reflexes; to characterize the types of information carried in the ethmoidal nerve afferents, by recording from single fibers dissected from the nerve; to determine the conduction velocities of these afferents, by recording from the cell bodies of ethmoidal afferents in the trigeminal ganglion; and to study the second-order neurones in the brain stem on which these afferents make contact. Results of single fiber recording indicated that, in addition to being tactile, approximately half of the neurones studied also responded to noxious chemical stimuli. The conduction velocity of the majority of these afferents were found to be in the A-delta range. Second-order neurones in spinal trigeminal nucleus which had an input from the ethmoidal nerve could be divided into two classifications: (i) low threshold mechanoreceptive (LTM) neurones which received light tactile input and did not respond to noxious chemical or mechanical stimuli applied to the nasal cavity, and (ii) wide dynamic range (WDR) neurones which responded to both noxious and nonnoxious chemical or mechanical stimuli applied to the nasal cavity.