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At least 991 records · Page 55Linked to original sources
PubMed1995

The solution structure of the F42A mutant of human interleukin 2.

Interleukin 2 (IL-2) is one of the major cytokines produced by T lymphocytes in response to antigen. It is a potent growth and differentiation factor for several cell-types and is structurally related to the four-helix bundle family of cytokines. Mutation of residue Phe42 to Ala abolishes binding to the alpha chain of the tri-partite IL-2 receptor. The three-dimensional structure of the F42A mutant IL-2 has been calculated by two dimensional NMR methods and compared to a structure of wild-type IL-2 determined by X-ray crystallography. The overall topology of the two structures is the same. The main differences between the structures are within the ill-defined loops connecting the helices and the region of the protein that is believed to interact with the alpha-chain of the receptor. Thus, the mutation of Phe42 to Ala does not perturb the overall three-dimensional structure of IL-2, and does not appear to change the putative binding sites for the beta and gamma chains of the receptor. The structural differences observed in this mutant suggest that the replacement of Phe42 with Ala causes the re-orientation of neighbouring side-chains that are also involved in binding the alpha-chain of the receptor.

Alanine↗
PubMed1995

Effect of asphyxia on the composition of cationic elements in the perilymph.

To elucidate the role of free radicals in the cochlea, cationic elements in the perilymph of the scala tympani in normal and asphyxic guinea pigs were measured by an inductively coupled plasma atomic emission spectrometer. The concentrations of 7 cationic elements (i.e., calcium, copper, iron, magnesium, phosphorus, lead and zinc) were measured simultaneously in a sample of the perilymph taken before, during and after asphyxia. There was no significant change in these cationic elements during asphyxia for 3 min. In contrast to the stationary level during asphyxia, the iron concentration was significantly elevated at 5 min after re-ventilation following asphyxia and decreased rapidly toward the pre-asphyxic level thereafter, although no significant change was observed in other cationic elements. These results were comparable to the theory of non-protein-bound iron accumulation produced by an O2-dependent mechanism during re-perfusion.

Animals↗
PubMed2001

Gamma radiation effects on potassium pertechnetate in carbonate media.

Gamma radiation effects on the stability of the oxidation state of radioelements and diffusion within the framework of nuclear waste repositories are often neglected, although it may influence physicochemical processes and thus transfer to biosphere and geosphere. This knowledge is essential to model transport phenomena. This study reports on effects of gamma irradiation on technetium in carbonate media, which is representative of natural systems. Depending on media compositions, the gamma irradiation on pertechnetate leads to formation of Tc(IV) only in the absence of carbonate. CO3*- radicals are able to re-oxidise technetium intermediate oxidation states to the +7 state.

Carbonates↗
PubMed1993

Severe diffuse intracranial vasospasm as a cause of extensive migrainous cerebral infarction.

We report on a 47-year-old white female with a long history of recurrent episodes of migraine with aura, who progressed to develop a continuous intractable headache during the course of which cortical blindness and quadriparesis occurred due to extensive and bilateral hemispheric cerebral infarction. Severe diffuse intracranial major arterial vasospasm was demonstrated by arteriogram. All studies were negative for CNS vasculitis, including cerebral biopsy. The arterial spasm reversed itself, but the patient did not improve. Smoking was the only additional risk factor. Vasospasm is an important cause to be considered in migrainous infarctions. The use of vasoconstrictor agents such as DHE in patients with migraine with prolonged aura has to be carefully re-evaluated.

Blindness↗
PubMed2002

[Diagnosis and therapy of stapes fractures and luxations].

BACKGROUND: Injuries of the ossicular chain have various etiologies. Skull traumas from blows to the temporal, parietal or occipital region with or without fracture of the temporal bone are the main causes of the ossicular injury; other modes of injury are rare. It depends on the type of trauma which kind of injury occurs. Mainly subluxations, luxations and fractures are to be observed. The incus is the ossicle which is the most often injured. Mostly, only one ossicle is injured, rarely two or all of them. PATIENTS: From January 1997 to June 1999 we operated 19 patients with traumatic lesions of the membrane and the middle ear. In 4 cases the reason for the operation was an injury of the stapes. We observed 2 cases with broken stapes crura, 1 case with an impression of the stapes into the vestibulum with perilymphatic fistula and 1 case with subluxation of the stapes in the direction of the promontorium. By presenting 4 cases we want to point out the diagnostic possibilities and the operative management of such rare injuries. In all cases we applied the transmeatal approach for the operation of the middle ear. In 2 cases it was possible to place the stapes back in their anatomic position in order to re-establish the ossicular chain. In the other 2 cases we had to use middle ear prostheses which were interpositioned between the manubrium of the malleus and the footplate of the stapes. RESULTS: In all cases the immediate post-operative hearing results and the long-term hearing results after 10 to 28 months were satisfying. We did not notice any post-operative complications, especially no vestibular symptoms. One patient's tinnitus was the same as before the operation. CONCLUSIONS: The diagnosis of a stapes injury is despite the use of sophisticated technology, especially the CT-scan of the temporal bone, often very difficult. A sensitive anamnesis seems to be very important. It depends on the kind of injury which operative technique is to be applied in order to re-establish the ossicular chain. In our opinion, it is useful to take - if it is possible - the autolog stapes for the surgical re-establishment of transmission.

Adult↗
PubMed2000

X-Ray emission following low-energy charge exchange collisions of highly charged ions

K-shell x-ray emission following low-energy charge exchange collisions ( </=11 eV/amu) has been measured for ten bare and hydrogenic ions up to U91+. The data resolve capture into angular momentum states with l = 1 and provide a stringent test of theory. The assumption of Stark mixing of angular momentum states is inappropriate at such energies. Results from detailed calculations give a better description of the data, but significant discrepancies are noted. The measurements show that the hardness ratio of charge-exchange induced K-shell x-ray emission represents a diagnostic of the dynamics of ion-atom interactions in situations where the energy is below 1 keV/amu, e.g., in solar wind collisions.

Journal Article↗
PubMed1993

Improved high-performance liquid chromatographic analysis of 8-methoxypsoralen monoadducts and cross-links in polynucleotide, DNA, and cellular systems: analysis of split-dose protocols.

The distribution of 8-methoxypsoralen-thymidine photoadducts from polynucleotides, calf thymus DNA and mammalian cells treated with [3H]8-methoxypsoralen under a variety of irradiation conditions was determined using high-performance liquid chromatography and scintillation analysis. The split-dose protocol, with samples treated with 8-methoxypsoralen and low doses of long-wavelength UV radiation to generate monoadducts, washed to remove unreacted 8-methoxypsoralen, then irradiated further to convert the monoadducts to cross-links, was examined. The photoadduct distribution in the first step is dependent upon the UVA dose and the wavelength of the radiation, but it is relatively independent of 8-methoxypsoralen concentration. Low fluence and longer wavelengths generate mainly 4',5'-monoadducts, whereas higher fluences and shorter wavelengths yield more cross-links. The second irradiation step converts the 4',5'-monoadducts to cross-links as well as to 3,4-monoadducts. The overall yield of cross-links after the second irradiation step is not dependent upon the wavelength used in the first step. Cellular studies demonstrated that the split-dose protocol is applicable to mammalian systems. These results may affect the interpretation of mutagenesis studies based on the split-dose protocol, because the second step can convert 4',5'-monoadducts to both 3,4-monoadducts, the expected cross-links. Therefore, interpretations that link increases in mutagenicity after the second step in a split-dose study solely to cross-link formation may need re-examination.

Animals↗
PubMedDate not supplied

[Cystic dilatation of the common bile duct].

The Authors report a case of cystic dilatation of the common bile duct and a review of the Literature. The lesion is a congenital malformation of infancy or childhood, being rare in adult life. The main symptoms are biliary colic with jaundice and fever. Modern techniques such as abdominal ultrasonography, CT, ERCP, PTC generally provide to achieve preoperative diagnosis. When radical surgery is possible the complete excision of the cyst is the management of choice. The case reported is classified as type 1 of Todani's classification. Surgical management consisted in a complete excision of the cyst. Bile flow was re-established by hepaticojejunostomy.

Adult↗
PubMed2003

Chondroblastoma of the lumbar spine with cauda equina syndrome.

STUDY DESIGN: Case report. OBJECTIVE: To describe the clinical presentations, radiological features and clinical progress of a rare case of chondroblastoma of the lumbar spine. SETTING: Regional Hospital, Hong Kong, China. METHOD: A 54-year-old male patient presented with low back pain and left sciatica. X-ray and MRI revealed tumour infiltration of the fifth lumbar vertebrae and left paraspinal muscles, which was found to be a chondroblastoma by repeated open biopsies. The tumour was removed surgically by combined anterior and posterior approaches, followed by spinal fusion and instrumentation. RESULTS: The anterior tricortical bone graft was complicated with fracture and nonunion. Surgical re-exploration confirmed local recurrence of tumour macroscopically and histologically. The patient developed symptoms and signs of cauda equina syndrome gradually despite repeated surgery and irradiation. The patient eventually died of complications of local recurrence and neurological deficit at 3 years and 8 months after the first operation. CONCLUSION: This is the first case report of chondroblastoma of the lumbar spine. The clinical profile of this patient and the evidence from the literature review suggests that spinal chondroblastoma has a very aggressive behaviour with high recurrence and mortality rate.

Bone Neoplasms↗
PubMed1989

Radiation hormesis. A new concept in radiological science.

Low-dose ionizing radiation caused definite stimulation of immune reactions both in humans and mice. The PFC reaction in response to SRBC immunization and the NK activity of the splenocytes were significantly enhanced after low-dose whole body irradiation. Activation of the T lymphocytes, especially the TH, with increased production of IL-2, might be a critical step in the whole process of immunoenhancement. A single dose of 75 mGy X-rays caused significant lowering of hypothalamic M-Enk content as well as serum corticosterone level. The increased serum testosterone level would exert an inhibitory influence on the CRF-ACTH-CS system to keep the blood corticosterone at a lower than normal level which might facilitate the immune reactions in the SRBC-immunized animals. The increased catecholamines in the spleen would probably reinforce this effect resulting in immunoenhancement. Low-dose ionizing radiation caused increased repair of the genetic material at both the molecular and subcellular levels. The UDS of human and murine lymphocytes was augmented by single or continuous low-dose irradiation. The stimulation of DNA polymerase activity might be responsible for such effects. Exposure to very small doses of low LET radiation could induce in different tissues an adaptive response which alleviated chromosome damage caused by subsequent larger dose radiation. Such an adaptive response could be induced both in vivo and in vitro in different animal species. The induced adaptive response faded away after 3 cell cycles could be re-induced by a second exposure to low-dose radiation. The mechanism of the inductive process needs further study.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The mechanism of muscle contraction. Biochemical, mechanical, and structural approaches to elucidate cross-bridge action in muscle.

Muscle contraction occurs when the thin actin and thick myosin filaments slide past each other. It is generally assumed that this process is driven by cross-bridges which extend from the myosin filaments and cyclically interact with the actin filaments as ATP is hydrolysed. Current biochemical studies suggest that the myosin cross-bridge exists in two main conformations. In one conformation, which occurs in the absence of MgATP, the cross-bridge binds very tightly to actin and detaches very slowly. When all the cross-bridges are bound in this way, the muscle is in rigor and extremely resistant to stretch. The second conformation is induced by the binding of MgATP. In this conformation the cross-bridge binds weakly to actin and attaches and detaches so rapidly that it can slip from actin site to actin site, offering very little resistance to stretch. During ATP hydrolysis by isolated actin and myosin in solution, the cross-bridge cycles back and forth between the weak-binding and strong-binding conformations. Assuming a close correlation between the behaviour of isolated proteins in solution and the cross-bridge action in muscle, Eisenberg and Greene have developed a model for cross-bridge action where, in the fixed filament lattice in muscle, the transition from the weak-binding to the strong-binding conformation causes the elastic cross-bridge to become deformed and exert a positive force, while the transition back to the weak-binding conformation upon binding of MgATP, causes deformation which, during fibre shortening, leads to rapid detachment of the cross-bridge and its re-attachment to a new actin site. From the results of in vitro experiments, it was furthermore suggested that relaxation occurs when the transition from the weak-binding to the strong-binding conformation is blocked. Results of recent mechanical and X-ray diffraction experiments on skinned fibre preparations are consistent with the assumed close correlation between the behaviour of isolated proteins in solution and the behaviour of cross-bridges in muscle. Furthermore, X-ray diffraction experiments allowed to provide experimental evidence for the postulated structural difference between attached weak-binding and attached strong-binding cross-bridges. Finally, recent studies have confirmed the prediction of Eisenberg and Greene that the rate limiting step in vitro determines the rate of force generation in muscle.

Actins↗