Involvement of growth factor receptor-bound protein-2 in rat hepatocyte growth

Growth factor receptor-bound protein-2 (GRB-2) is a protein linking receptor tyrosine kinase and Sos ( Son of Sevenless gene; Ras GDP/GTP exchange protein), leading to activation of the Ras-mitogen-activated protein kinase (MAPK) cascade. So far, it remains unclear how GRB-2 plays a role in signal transduction pathways evoked by hepatotrophic factors. This study was attempted to evaluate the involvement of GRB-2 in signalling in rat hepatocyte growth. Using rat cultured hepatocytes stimulated by hepatotrophic factors and regenerating livers after partial hepatectomy (PH) we examined GRB-2-mediated linkage of hepatotrophic factor receptors to signal transducing molecules such as Sos or dynamin-II by immunoprecipitation and western blot analysis. In primary cultured hepatocytes stimulated with hepatocyte growth factor (HGF) or epidermal growth factor (EGF), GRB-2 linked HGF receptor or EGF receptor, respectively, to Sos which activated the mitogen-activated protein kinase (MAPK) cascade. In contrast, in primary cultured hepatocytes stimulated with insulin, GRB-2 linked insulin receptor substrate-1 (IRS-1) to dynamin-II as well as Sos. In the early phase after PH, GRB-2 activated the Ras-MAPK cascade by linking HGF receptor, IRS-1, or EGF receptor to Sos. In the late phase after PH, a complex of IRS-1-GRB-2 associated with dynamin-II, indicating that GRB-2 may transduce signals from IRS-1 to dynamin-II. We conclude that GRB-2 may play a role in transmitting signals from hepatotrophic factors to not only MAPK but also to other signalling pathways in hepatocyte growth.     

Amino acids and peptides

The Gln-Val-Val-Ala-Gly sequence, which occurs frequently in several natural thiol proteinase inhibitors, and derivatives were synthesized by conventional solution methods and their effect on thiol proteinases were examined. The studies led us to the conclusion that certain of these peptides exhibited a weak inhibitory effect on the thiol proteinase, papain. One of them, Z-Gln-Val-Val-Ala-Gly-OMe, showed a protective effect on papain from natural thiol proteinase inhibitor-induced inactivation. The relationship between structure and activity of these derivatives was studied and certain conclusions were derived on possible mode of action of these inhibitors. From these studies, it was concluded that Z-Gln-Val-Val-OMe was the smallest peptide to exhibit some effect on papain.     

Cryoglobulinaemia among maintenance haemodialysis patients and its relation to hepatitis C infection

It has been shown that hepatitis C virus (HCV) infection is closely associated with mixed type cryoglobulinaemia. It is also known that HCV infection is rampant among chronic haemodialysis patients. We studied 531 renal failure patients on maintenance dialysis including 170 with positive HCV antibodies for cryoglobulinaemia, and its incidence was compared with controls which consisted of 242 chronic hepatitis C patients without renal failure and 183 healthy adults. Cryoglobulinaemia was present in 30.6% of dialysis patients with HCV infection, 10.8% of dialysis patients without HCV infection, 29.8% of patients with chronic hepatitis C without renal failure, and 0% of healthy adults. Among the 30 new renal failure patients who were started on dialysis within 6 months, four were positive for HCV antibodies, and one of them had cryoglobulinaemia; of the 26 HCV-negative patients, four (15%) were cryoglobulinaemic. The cryocrit values among dialysis patients were much lower than those of the control cases and other reports on non-dialysis cases. Patients with cryoglobulinaemia were generally younger compared with patients negative for this condition. There was no correlation between cryoglobulinaemia and past blood transfusion, underlying disease or length of dialysis. Cryoglobulinaemic patients seem to develop renal failure at relatively young ages and a considerable proportion of cryoglobulinaemic dialysis patients may have already had cryoglobulinaemia at the time of the start of haemodialysis. There was no indication that the presence of cryoglobulin in serum adversely affects the liver disease nor increases serum virus load in HCV-infected dialysis patients. Thus, it was concluded that although HCV infection has a certain role in the development of cryoglobulinaemia in dialysis patients, they develop cryoglobulinaemia less frequently and produce cryoglobulin to a lesser degree in the presence of HCV infection as compared with non-dialysis patients.     

Multiple conformational equilibria of cyclic octapeptide,cyclo (L-Pro-Sar)4 in solution

Cyclo (l -Pro-Sar)₄ is asynthetic cyclic octapeptide composed of only N -substituted amino acids. The conformation of this peptide in different solvents was examined by ¹H-and ¹³C-n.m.r. spectroscopy, ¹H-n.m.r. data of this cyclic peptide demonstrated that multiple conformational equilibria take place in solution and they vary with solvent polarity. Three conformers are interconverting with each other in the nonpolar chloroform (CDCl₃); one C₄-symmetric conformer (49%) and two C₂-symmetric conformers (37% and 14%). While three C₂-symmetric (59%, 19%, and 18%) and one asymmetric conformer (4%) are detected to coexist in acetonitrile (CD₃CN), one largely populated C₂-symmetric one (97%) is favored in the polar dimethyl sulfoxide (Me₂SO-d ₆). N.m.r. measurement employing various strategy predicted the occurrence of trans-cis-cis-cis-trans-cis-cis-cis (two Sar-Pro bonds: trans) (tccctccc) peptide bond sequence in a predominant C₂-symmetric conformer of Me₂SO-d ₆ solution. In the same way, tccctccc and ctttcttt (two Sar-Pro bonds: cis) peptide unit arrangement was proposed for the first and the secondly populated conformer in CD₃CN, respectively. In CDCl₃ a conformer having tctctctc (four Sar-Pro bonds: trans) C₄-symmetric peptide bond sequence was deduced.     

Transient scoliosis in a child with juvenile rheumatoid arthritis

An 8 year old girl was admitted to hospital complaining of arthralgia in a few large joints. According to the clinical course and serological tests, a diagnosis of a polyarticular type of juvenile rheumatoid arthritis was made. About 6 weeks after the onset, scoliosis was observed. The curvature regressed spontaneously over the following 6 months. Generally, scoliosis associated with juvenile rheumatoid arthritis has been noted a few years after the onset. A transient scoliosis in the early phase of this disease is rare.     

Screening for growth hormone deficiency using urinary growth hormone measurement

The diagnostic approach in growth hormone deficiency (GHD) is complicated. Two or more provocative tests are essential for definitive diagnosis of GHD. However, such testing cannot be carried out routinely on all subjects with short stature because of the need for hospitalization and blood sampling. A simple screening method for GHD would be of great value. Human growth hormone (hGH) levels were measured in the early morning urine of 192 children aged 7–15 years with height 2.0 s.d. below the mean for their ages. Sixty-eight subjects were selected because they showed a urinary hGH level < 10 ng/g creatinine. They were further examined in terms of bone age and plasma insulin-like growth factor (IGF-I) levels. In 30 subjects, the ratio of bone age: chronological age was < 0.8 and/or plasma IGF-I level was < 0.7 U/mL. Finally 24 of these subjects were examined with provocative tests and other endocrinological tests. Eleven subjects proved to have poor growth hormone secretion and one subject was diagnosed as having Turner syndrome. In conclusion, 11 patients with GHD were diagnosed from 192 children with short stature using urinary hGH measurement as the first screening method. These findings suggests that urinary hGH measurement could be a useful and simple method for detecting GHD.     

Abnormal Response to Exercise, Face Immersion, and Isoproterenol in Children with the Long QT Syndrome

The present study was performed to observe the change of QT interval by sympathetic stimulations in patients with the long QT syndrome (LQTS). The study group consisted of 6 children with LQTS and 6 healthy children without QT prolongation. All LQTS patients had syncopal episodes. The QT_c and ΔQT_c% ([QT_C interval after examination - QT_c interval at rest]/QT_c interval at rest × 100) by treadmill testing, face immersion, and isoproterenol were examined. One minute after peak exercise of treadmill testing, the changes in the QT_r, interval were not significant in either group, but ΔQT_C% was larger in the LQTS group than in the control group (+ 11.0 ± 12.1% vs -2.6 ± 3.2%;P= 0.02). The QT_c interval at the shortest RR interval during face immersion was prolonged in the LQTS group (0.47 ± 0.01 s to 0.51 ± 0.04 s; P = 0.02), but there were no significant changes in the control group (0.40 ± 0.03 s to 0.41 ± 0.03 s; P = NS). ΔQT_C% was larger in the LQTS group than in the control group (+ 10.0 ± 7.3% vs +1.1 ± 5.5%; P = 0.04). In the LQTS group, the RR interval was shortened (P = 0.009) and QT_c interval was prolonged (P = 0.0008) after isoproterenol infusion. These sympathetic stimulations amplified the TU abnormality in the LQTS group. By observing the TU changes caused by face immersion, we hoped to find a possible new method with which to diagnose LQTS. The combination of these examinations may be helpful in screening the borderline cases of TU abnormalities.     

A New Contact Probe for Intraoperative Laser Ablation

Several clinical factors decrease the accuracy of intraoperative laser ablation. The distance to the target, the irradiation angle, and the media are reported among these factors. We developed a new laser probe to resolve these problems. This probe has a hollow conical tube with a tip covered by a thin film. Zero-degree centigrade saline was fed into this probe. Results from using the new probe were compared with those from the conventional noncontact irradiation method with cooling by sprinkled cooling water. In beating canine hearts, ventricles were irradiated with neodymium-yttrium aluminum garnet (Nd:YAG) lasers at 50–200 //mm². There was no difference in the mean volume of irradiated tissue between the new and the noncontact method. However, the distribution of volume values in the new method was smaller than that in the noncontact method (P < 0.05). In conclusion, results obtained indicate that this new probe could perform more accurate intraoperative ablation than the conventional method. Problems of stabilizing the distance to the target, the irradiation angle, and the media were resolved.