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Biomedical subjects

K Olander

Publications and source records attributed to K Olander.

11 recordsLinked to original sources
PubMed1996

Comparison of the effect of four viscoelastic agents on early postoperative intraocular pressure.

PURPOSE: To compare the effect of four commercially available viscoelastic agents on postoperative intraocular pressure (IOP). SETTING: Four outpatient sites. METHODS: Sixty-nine patients having routine extracapsular cataract extraction were enrolled in the study; 54 were available for a 3 month follow-up examination. The four viscoelastic agents were Amvisc, Amvisc Plus, Healon, and Viscoat. Intraocular pressure was measured preoperatively and at 2, 3, 4, 5, 6, 8, 10, 12, and 24 hours and 3 months postoperatively. Pachymetry and endothelial cell counts were performed preoperatively and 3 months postoperatively. RESULTS: Mean postoperative IOP and IOP changes from baseline did not differ among the four treatment groups at any time. However, when mean maximal IOP was compared, the Healon group demonstrated the highest IOP increases (P = .0033). There was also a significant difference (P = .0015) among the treatment groups in the mean maximum postoperative change from baseline; the Healon group exhibited the largest mean change in IOP. At 3 months postoperatively, IOP values and pachymetry were normal for all treatment groups and were not statistically different among groups, indicating the four agents provided similar degree of endothelial protection and IOP stability. CONCLUSION: These results suggest that IOP increases occur in varying degrees and at varying times in the early postoperative period after cataract surgery using a viscoelastic agent.

Adolescent↗
PubMed1983

Thioamides as false melanin precursors: studies in murine melanomas.

Melanotic melanomas show a high rate of melanin synthesis. Foreign substances that are accepted as precursors in the formation of melanin may therefore be useful in the diagnosis and therapy of malignant melanotic melanomas, if labelled with suitable radionuclides. We have earlier reported that 2-thiouracil is incorporated in melanotic melanomas, apparently as a false melanin precursor. In the present study it is shown that methimazole and 5-iodo-2-thiouracil are as well accepted as melanin precursors. 5-Iodo-2-thiouracil is of special interest, since iodine has many clinically useful radioisotopes. The chemical properties that characterize substances which are incorporated as false precursors into melanin are discussed. A free sulfur ligand of the thioamides (2-thiouracil, 5-iodo-2-thiouracil, methimazole and thiourea are all incorporated into melanin) seems to be essential and the link between these substances and the melanin. Uracil (which lacks sulfur) and 2-benzylthiouracil (where the sulfur is blocked with a benzyl group) do not attach to melanin. Our conclusion therefore is that the thioureylene structure is the smallest common molecular fragment of the false melanin precursors.

Amides↗
PubMed1983

An analytical electron microscopic study of a corneal tattoo.

A case of corneal tattoo was studied histologically, and by electron microscopy. Most of the electron dense granules were seen in keratocytes, either singly or in clumps; some were found between collagen fibrils. Platinum was localized in the granules by means of x-ray microanalysis.

Adolescent↗
PubMed1982

A new melanoma seeker for possible clinical use: selective accumulation of radiolabelled thiouracil.

In a previous report we have shown that a few substances, especially thiouracil, are incorporated as false precursors into melanin during its synthesis. In the present investigation, we have intensified our studies on the incorporation of thiouracil into melanotic melanomas. Firstly, the distribution and retention of both 14C- and 35S-labelled thiouracil in mice with transplanted melanomas were studied. A high and selective accumulation was found in the melanotic tumours. The concentration in the rest of the body was low, with the exception of the thyroid gland. Secondly, melanoma-bearing mice were given increasing doses of thiouracil, and cultured melanoma cells were exposed to different concentrations of thiouracil, to investigate the relation between dose and uptake in melanomas and melanoma cells, respectively. A relatively linear increase in uptake with dose was found, indicating that the melanin incorporation of thiouracil is non-saturable up to subtoxic levels.

Animals↗
PubMed1982

Accumulation of 125I-labelled thiouracil and propylthiouracil in murine melanotic melanomas.

We have shown that thioamides are incorporated as false precursors into melanin during its synthesis. To be clinically useful in the diagnosis or therapy of melanotic melanomas, they would have to be tagged with an appropriate isotope or possibly a cytotoxic moiety. 125I-Thiouracil (125I-TU) is here shown to be accumulated in the melanin of melanotic melanomas transplanted into mice in a similar way as is 14C-thiouracil (14C-TU). 125I-TU gives tumour/liver and tumour/muscle ratios up to 22 and 778 respectively, at 4 days after administration. 125I-TU is accumulated by melanoma cells in vitro more effectively than 14C-TU (125I-TU/14C-TU, 2.7), while the in vivo accumulation into melanomas is slightly lower for 125I-TU as compared to 14C-TU (125I-TU/14C-TU, 0.35). This appears to be due to a partial deiodination (less than 14% of the dose within 4 days) and probably a more rapid excretion of 125I-TU or its metabolite(s). The accumulation of radioactivity in the thyroid can essentially be eliminated by pretreatment with potassium iodide and/or thyroxine. 125I-Propylthiouracil is also accumulated in melanotic melanoma cells in vivo and in vitro, but at a lower level than in 125I-TU and 14C-TU.

Animals↗
PubMed1981

Incorporation of thiouracil and some related compounds into growing melanin.

Several drugs, mainly polycyclic amines, are accumulated in melanin-containing tissues. They are bound to preformed melanin (both in vivo and in vitro). Thiouracil is accumulated into melanin according to another principle: It is incorporated as a false precursor during melanin formation. It is thus taken up only in growing melanin, e.g. in the eye of pigmented mouse foetuses or in melanomas. The acceptance of a foreign substance during the formation of a foetal tissue seems theoretically important. We are also interested in the practical viewpoint of using false melanin precursors as selective melanoma seekers. Some related substances are therefore compared with respect to incorporation into growing melanin. The thiouracil uptake in the ocular melanin of a 5 day old mouse was 276 times higher than that of a 3 month old mouse based on weight units of melanin. Thiourea is incorporated in growing melanin as well but also binds slightly to preformed melanin. Uracil and fluorouracil showed no specific uptake into growing melanin. It thus seems as if the sulfur is essential for the incorporation into the melanin polymer. 35S-thiouracil and 2-thio(2-14C)urcal showed the same high uptake, indicating that at least part of the uracil moiety is incorporated together with the sulfur. There seems to be a relation between the property to be incorporated into melanin and the tyrostatic activity. Both in the formation of melanin and thyroid hormones, tyrosine is the physiological precursor and both reactions are catalyzed by oxidizing enzymes. Properly labelled thiouracil derivatives seem to be promising melanoma seekers for diagnostic and radiotherapeutic purposes.

Animals↗
PubMed1980

Burns unit in Stockholm: a report on patients treated 1971--1975 for acute burn injuries.

A review of 297 burn patients treated 1971--1975 is presented to illustrate burn problems in a West European, mainly urban population. Patients were treated by exposure and warm dry air. Tubbing usually started five days after injury. Sequential wound revisions were performed. Surgical excision was usually delayed until days 14--21. Autografting was performed as soon as possible. For temporary cover homografts were frequently used. The majority of the patients were adults. Twelve per cent were older than 65 years. The patients revealed many social problems. Cardiopulmonary disease, mental disorder and alcohol or drug addiction were fairly common. The most common cause of the burn was fire and a majority of the patients sustained injuries in leisure time. 28% were classified as due to accident. 43% were considered diagnosed in 17 patients (5.7%). Five patients died due to septicemia.

Adolescent↗
PubMed1978

Management of pterygia: should thiotepa be used?

Pterygium, a common source of morbidity throughout the world, may appear to be an innocuous, easily excised lesion, yet it plagues the ophthalmologist by its high rate of recurrence, ranging from 20% to 30% after simple excision. Beta irradiation has been used by ophthalmic surgeons for many years. Another method of stemming the high percentage of pterygium recurrence is through local application of thiotepa, a radiomimetic drug that inhibits rapidly proliferating cells. The following report is a review of the literature from 1960 to 1977 on the role of thiotepa in treatment of pterygium, with emphasis on the complications of thiotepa administration. The recurrence rate after topical postoperative use of thiotepa ranges from 0 to 8%, with disturbing variance in results, depending on each investigator's definition of "recurrence", the length of follow-up, the type of pterygium, and the number of patients. The main reported complication from thiotepa's use has been depigmentation of skin around several patients' eyes, sometimes precipitated by exposure to the sun's rays.

Animals↗
PubMedDate not supplied

Uptake of [131I]thiouracil in tumours of patients with disseminated malignant melanoma. A pilot study.

Previous studies on mice carrying melanoma have shown that 5-iodo-2-thiouracil (ITU) is accumulated in the tumours due to its specific incorporation into melanin during its synthesis. ITU is also selectively localized in murine melanoma metastases and in cultured human melanoma cells. Progressive formation of melanin is, however, a prerequisite for the incorporation. Four patients with disseminated melanoma were injected intravenously with 39-62 MBq [131I]TU. Blood and urine samples were gradually collected, and 3-7 days postinjection tumours were biopsied and examined by impulse counting. The patients were scanned with a gamma camera over the total body daily for 3-4 days. The radioactivity was rapidly excreted. Poor melanin pigmentation of the tumours and low proliferation rate (possibly induced by chemotherapy) decreased the uptake of radioactivity by the tumors, and no imaging was possible. One of the patients, however, had clearly progressive disease with darkly pigmented metastases which contained considerably higher levels of radioactivity than the surrounding skin. Calculations indicated that a doubling of the radioiodine dose would probably make visualization of the tumours possible.

Bone Neoplasms↗