Degradation of circulating thyroglobulin

Reported half lives of rat Tg were different according to various investigators. In order to elucidate whether the derivatives of rat Tg in the peripheral circulation affect the results of kinetic studies of Tg, the present study was performed to investigate kinetics of rat Tg after separation of 19S Tg from its derivatives using gel-filtration. Radiolabeled Tg was obtained from thyroids of rats injected with 125I 24 hours before death, and subsequently purified by ammonium sulfate precipitation. The plasma samples obtained at varying time intervals after intravenous injection of 125I-rat Tg were fractionated on a Sephacryl S-300 column. As determined by sucrose density gradient, 99% of in vivo radiolabeled Tg was 19S. On gel-filtration, the injected labeled Tg and plasma samples obtained within two hours after injection showed a single peak in an identical area. A second peak in an area corresponding to a molecular weight of 60,000 to 70,000 appeared within six hours, and became as high as the first within 24 hours. In the second peak, 22.8 +/- 3.8% (mean +/- SE) of radioactivity was precipitated by anti-rat Tg antibody, and 14.4 +/- 1.7% (mean +/- SE) of radioactivity of its TCA precipitate was not extracted by n-butanol. Thus, the second peak could affect the results of Tg kinetic studies which utilize TCA precipitation, n-butanol extraction or RIA procedures. The half life of rat Tg in the present study was calculated from the disappearance curves of radioactivity of 19S Tg separated from other radioactive substances.(ABSTRACT TRUNCATED AT 250 WORDS)     

Age-related expression analysis of mouse liver nuclear protein binding to 3′-untranslated region of <Emphasis Type="Italic">Period2</Emphasis> gene

In mammals, both circadian rhythm and aging play important roles in regulating time-dependent homeostasis. We previously discovered an age-related increase element binding protein, hnRNP A3, which binds to the 3′-untranslated region (UTR) of blood coagulation factor IX (FIX). Here, we describe other members of this protein family, hnRNP C and hnRNP H, which bind to the 3′-UTR of the mouse circadian clock gene Period 2 (mPer2). RNA electrophoretic mobility shift assays using a ³²P-labeled Per2 RNA probe coupled with two-dimensional gel electrophoresis followed by MALDI-TOF/MS peptide mass fingerprint analysis was used to analyze these proteins. Western blotting suggested that the total expression of these proteins in mouse liver cell nuclei does not increase with age. Two-dimensional gel electrophoresis analysis of age-related protein expression showed that many isoforms of these proteins exist in the liver and that each protein exhibits a complex age-related expression pattern. These results suggest that many isoforms of proteins are regulated by different aging systems and that many age regulation systems function in the liver.     

Skeletal muscle glucose transporter gene expression is not affected by injecting growth-hormone-secreting cells in young rats

Summary To elucidate the diabetogenic effect of growth hormone on glucose metabolism the regulation of glucose transporter (GLUT) gene expression was examined in rat skeletal muscles. Female Wistar-Furth rats were implanted subcutaneously with growth-hormone-producing pituitary tumour (GH₃) cells. Animals were killed 4 or 9 weeks after GH₃ cell injection. Although body weight, serum growth hormone and insulin-like growth factor I levels were remarkably elevated during the 4–9 week period, serum blood glucose levels were within normal range. Muscles were obtained from the quadriceps muscle, diaphragm and heart, respectively. Northern blot analysis and Western blot analysis were performed using specific cDNA probes and antibodies. During the 4–9 week period, the levels of muscle GLUT 1 and 4 mRNA (corrected by β-actin mRNA level) in each muscle from the rats injected with tumour cells were not significantly different from those of control rats. Chronic elevation of growth hormone in these rats did not cause any change in GLUT1 and 4 expression compared to the controls during the euglycaemic period. These results provide the first evidence that chronic growth hormone elevation itself does not affect a key gene of in vivo glucose metabolism.     

Organ-cultured chick embryonic hearts of various ages. I. Electrophysiology

Tetrodotoxin (TTX)-insensitive slow Na⁺ channels are converted or replaced by TTX-sensitive fast Na⁺ channels during normal embryonic development of the chick heart, and rapid reversion occurs in monolayer cell culture (denervated). Fast Na⁺ channels first appear at 4 to 5 days, which is about the time of innervation. Studies were done to determine whether changes in cation channels will occur while hearts are in organ culture. To test whether fast Na⁺ channels will develop in the absence of innervation, hearts from chick embryos 2 to 3 days old were placed into culture for 6 to 8 days. Although the resting potentials of the ventricular cells were about the same as those obtained from fresh 8 to 10 day old hearts, the maximum rate of rise of the action potentials ($\text{+}\text{V}\text{?}{}_{\mathrm{<mtext>max</mtext>}}$) did not reach the high value (about 80 V/s) expected from the calendar age. Instead $\text{+}\text{V}\text{?}{}_{\mathrm{<mtext>max</mtext>}}$ remained at about the same value (12 V/s) that the hearts had when placed into culture. The action potentials were completely insensitive to TTX. The slow channels admit primarily Na⁺ and not Ca²⁺ because Mn²⁺ (1 mm) and lowering [Ca²⁺]₀ to nearly zero by EGTA did not diminish $\text{+}\text{V}\text{?}{}_{\mathrm{<mtext>max</mtext>}}$. To test whether the fast Na⁺ channels disappear in organ culture, hearts from embryos 15 to 19 days old were cultured as whole hearts or minced hearts. The whole hearts survived well for 1 to 6 days; the $\text{+}\text{V}\text{?}{}_{\mathrm{<mtext>max</mtext>}}$ values remained high (～ 100 V/s), and TTX completely blocked the action potentials. The minced hearts had variable $\text{+}\text{V}\text{?}{}_{\mathrm{<mtext>max</mtext>}}$ values, depending on the piece. Those pieces which had a low $\text{+}\text{V}\text{?}{}_{\mathrm{<mtext>max</mtext>}}$ were insensitive to TTX, and those which had a high or intermediate $\text{+}\text{V}\text{?}{}_{\mathrm{<mtext>max</mtext>}}$, were reduced to 5 to 20 V/s by TTX; these persisting responses in TTX were not blocked by Mn²⁺ or zero [Ca²⁺]₀. The results suggest that, while in organ culture, young hearts do not gain fast Na⁺ channels or lose the slow Na⁺ channels that would normally occur in situ. Organ-cultured old hearts left intact do not lose their fast Na⁺ channels. Thus, young or old hearts retain the channels that they originally possessed when placed into culture. Mincing initiates a gain of slow Na⁺ channels, and in some pieces, a partial loss of fast Na⁺ channels.     

Pancreatic tissue damage by transcatheter arterial embolization for hepatoma

We analyzed the serial changes in serum pancreatic enzyme activities by transcatheter arterial embolization (TAE) in 20 hepatoma patients with liver cirrhosis in an attempt to evaluate the incidence of the pancreatic tissue damage by TAE. Serum amylase activities increased in two (10%) cases, elastase 1 levels in six (30%) cases, and trypsin and pancreatic secretory trypsin inhibitor (PSTI) levels in each of five (25%) cases. Consequently, TAE resulted in the elevation of at least more than one serum pancreatic enzyme in eitht (40%) of 20 cases, although none had clinical symptoms related to pancreatitis When the adverse effect on the pancreatic tissue was compared among 6 cases of the superselective TAE and 14 cases of the nonsuperselective TAE, which were perfomed from the segmental and the nonsegmental hepatic arteries, respectively, the elevation of serum pancreatic enzymes was caused only by nonsuperselective TAE, not by superselective TAE. The volumes of Spongel and lipiodol used or the injected doses of the anticancer agent mitomycin C were not different between the two groups. These results indicate that TAE for the treatment of hepatoma frequently causes pancreatic tissue damage, and the position of the inserted catheter tip is very important to avoid the pancreatic tissue damage by TAE.     

Magnetic resonance imaging detection of aortic and pulmonary artery wall thickening in the acute stage of takayasu arteritis. Improvement of clinical and radiologic findings after steroid therapy

Objective. Early diagnosis of Takayasu arteritis in the acute stage (prepulseless stage) is extremely difficult. Identification of a useful approach to detecting the initial changes of arteritis is therefore desirable. Methods. Careful clinical examination of a young woman with persistent fever and dry cough revealed faintly audible bruits at the cervical, supraclavicular, and abdominal regions. Aortographic features suggested thickening of the wall of the descending thoracic aorta. Magnetic resonance imaging (MRI) of this area was diagnostic. Results. MRI demonstrated involvement of the ascending aorta and right main pulmonary artery. Steroid therapy (prednisolone 60 mg/day) induced dramatic clinical and radiologic improvement in 2 months. Conclusion. This is the first report of MRI-documented reduction in the thickness of the walls of both the aorta and the pulmonary artery following steroid therapy.     

High seroprevalence of anti–HTLV-I antibody in rheumatoid arthritis

Objective. To investigate the association between human T lymphotropic virus type I (HTLV-I) infection and rheumatoid arthritis (RA) in Nagasaki, an area highly endemic for HTLV-I infection. Methods. Sera from 113 female patients with RA and 19,796 female blood donors were screened for anti–HTLV-I antibodies with a gelatin particle agglutination kit and confirmed using an immunoblotting kits. Results. The age-adjusted summary odds ratio of HTLV-I infection among RA patients, as compared with blood donors, was 2.8 (95% confidence interval [95% CI] 1.8–4.6). The etiologic fraction, i.e., the proportion of RA in the study population that is attributable to HTLV-I infection, was estimated to be 13.2% (95% CI 5.1–21.2). There was no significant difference in the clinical and laboratory findings between HTLV-I–infected and HTLV-I–uninfected RA patients. Conclusion. These epidemiologic findings support the idea that HTLV-I infection is a risk factor for RA, and suggest that ∼13% of the cases of RA in females living in Nagasaki are associated with HTLV-I infection.