Biomedical subjects
Publications and source records attributed to A Hammer.
37 patients who had been operated upon for trigger thumb, all below 15 years of age, have been reviewed. 75% of the affected thumbs were on the dominant hand and 25% have bow-stringing of 1-2 mm. without any complaints. All had good results. Unlike other authors, we found that operation done after the third year of age gave full correction of the flexion contracture.
We have set out to clone the trypanosomal gene encoding the largest subunit of RNA polymerase I. We screened a genomic library with a synthetic oligonucleotide probe encoding an eleven amino acid sequence motif, YNADFDGDEMN, which has been found in all eukaryotic RNA polymerase largest subunit genes analyzed so far. We isolated the Trp11 locus and determined the complete sequence of the gene encoded within this locus. The deduced amino acid sequence contains the highly conserved RNA polymerase domains as well as the previously identified RNA polymerase I-specific hydrophilic insertions. Therefore, the gene most closely resembles the largest subunit of RNA polymerase I.
The C-terminal domain of the largest subunit of RNA polymerase II in higher eukaryotes is present in the protozoan parasite Trypanosoma brucei in a strongly modified form. To determine whether this is a general feature of the Kinetoplastida and to determine the role of this domain in RNA polymerase II transcription, we have analysed the C-terminal domain of the distantly related species Crithidia fasciculata. No positional identity of amino acid residues between the C-termini of C. fasciculata and T. brucei can be found. Moreover, both domains lack the heptapeptide repeat structure present in higher eukaryotes. The two domains are, however, very similar in amino acid composition, being rich in acidic residues as well as serine and tryosine. The latter observation is compatible with the concept that in vivo phosphorylation of the C-terminus activates RNA polymerase II.
We have identified and cloned four trypanosomal RNA polymerase largest subunit genes. Here, we present the molecular analysis of two genes, Trp4.8 and Trp5.9. The sequence of these genes shows that they are almost identical to each other and indicates that they encode the largest subunit of RNA polymerase II. Both genes contain a C-terminal extension that is clearly distinct from that of other eukaryotic RNA polymerase II genes, because it lacks the common tandemly repeated heptapeptide sequence and is rich in acidic amino acids. It shares many potential phosphorylation sites, however, with the C-terminal extension of other eukaryotic RNA polymerase II large subunits. The presence of two RNA polymerase II loci suggests that a fourth RNA polymerase could be formed. Interestingly, the fourth gene is only found in species exhibiting antigenic variation.
The purpose of this study was to find further experimental evidence for the postulated negative association between the extent of lipid peroxidation in tumor cells and their proliferative behavior. After incubation of Ehrlich ascites tumor cells at 37 degrees C for 30 min with increasing concentrations of Fe(II) histidinate (Fe/His) the following parameters were determined: the formation of lipid hydroperoxides was measured fluorimetrically after reaction with dichlorofluorescein; 4-hydroxynonenal was determined by reversed-phase high-pressure chromatography after derivatization with dinitrophenylhydrazine; as a third parameter of lipid peroxidation the formation of 2-thiobarbituric-acid-reactive substances was determined. The proliferative activity was determined by measuring the growth rate in vivo after reimplantation i.p. of the tumor cells into mice. Trypan-blue exclusion tests for viability were performed before reimplantation. The reliability of the trypan-blue exclusion tests was checked by comparing the results with another parameter of viability, the release of the cytosolic enzyme lactate dehydrogenase. The concentration both of lipid hydroperoxides and of 2-thiobarbituric-acid-reactive substances showed a biphasic dependence on the concentration of Fe/His with maximal increase at iron concentrations of 0.25 mM and 0.1 mM respectively. 4-Hydroxynonenal, in contrast, showed a continuous increase up to 41.1 nM (corresponding to 0.58 pmol/10(9) cells) with increasing iron concentration in the range from 0.1 mM to 0.6 mM. The total number of tumor cells, when determined 5 days after reimplantation, continuously decreased with increasing iron concentration, showing half-maximal inhibition at about 0.22 mM Fe. The exclusion of the trypan-blue dye was unaffected by the presence of iron at any concentration used. Similarly, iron had no influence on the release of lactate dehydrogenase. The results support the hypothesis that 4-hydroxynonenal may act as an inhibiting messenger between endogenic lipid peroxidation and proliferation.
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Visual callosal transfer during development was studied in order to reveal plasticity-related compensation for the absence of direct contralateral inputs. The optic chiasm was midsagittally sectioned in 6-8 weeks old kittens (OCK) and for comparison, in adult cats (OCA). Unit recording was made during adulthood in the border area between visual cortex areas 17 and 18, namely the callosal projection zone. The proportion of cells showing interhemispheric transfer in the OCK group, as indicated by the presence of visual input from the contralateral eye was 10.5%; in the OCA cats their proportion was 4.0%. Moreover, 2.3% of the cells showed a pure transfer of input from the contralateral eye in the OCK, although none was seen in the OCA cats. Thus, during the developmental period, a plasticity induced process, albeit limited, takes place in the enhancement of interhemispheric transfer of visual information.
The geniculocortical pathways from the contralateral eye and the callosal pathway were interrupted in cats in order to study how cortical cells are influenced by changes induced in the interhemispheric transfer of visual information. Unit recording was carried out from areas 17 and 18 boundary, the callosal projection zone. The ocular dominance distribution of cortical cells showed absence of interhemispheric interaction. The visual areas in the two sides of the brain thus functioned independently, presenting a condition of visual split brain. This also has been reflected by the absence of compensatory visual inputs via an alternative commissural pathway. Furthermore, remarkable diminution in the excitability level was found as indicated by the reduction in the proportion of visually responsive cells. Finally, the results of the split brain cat reflect the condition of the individual operations from which it is composed.
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The ocular dominance, responsiveness level and receptive field properties of single cortical cells were studied in 12 acute and chronic split chiasm adult cats (729 cells) and in 13 normal controls (544 cells). Recording was made from the border between visual areas 17/18. Responsive cells in the operated cats were obtained exclusively (87.1%) following stimulation of the ipsilateral eye, except for a very few cells (2.5%) which were binocularly driven. In comparison, only few (10.9%) of the cells in the normal control cats were driven ipsilaterally and the majority of them (74.5%) were binocularly driven. Relatively small proportions of cells (46.1%) were visually responsive in the acute (less than 1 week postoperatively) and in the most chronic (greater than 6 months) cats, in comparison to the normal cats (87.3%). No consistent change was found in the responsiveness level of cortical cells as function of length of the survival time (correlation coefficient: -0.45). Only a very slight tendency for a relative increase in binocularly driven cells with survival time was found as well as a reduction in the proportion of nonspecific cells. However, in view of the general absence of binocularity and responsivity in these cats, it was concluded that no recovery was found, even long after the elimination of the contralateral inputs.
Single unit recording from visual cortex areas 17 and 18 and in the border region between them was performed on adult cats with unilateral optic tract section (OTX) either on the day of the operation (acute) or three to six months postoperatively (chronic). Visual activity from both hemispheres was analyzed with respect to the responsiveness level, the ocular dominance distribution and selectivity to orientation and direction. The results showed almost a complete absence of visual responsiveness in the deafferented hemisphere and a considerable reduction of responsiveness in the intact hemisphere. Following surgery an increase in visually responsive cells was found in the intact hemisphere as postoperative recovery continued. In addition, a reduction in the proportion of cells selective for orientation and direction was also found in the intact hemisphere of the OTX animals as compared to the control cats. Furthermore, cortical binocularity was not affected in the intact hemisphere of all OTX cats. We conclude that an almost total absence of interhemispheric callosal transfer of visual functions from the intact to the deafferented hemisphere is induced as a result of the unilateral OTX in adult cats. Moreover, the fact that the absence of cortical binocularity in the hemisphere receiving direct geniculate input was not disrupted, indicates the absence of callosal transfer from the deafferented to the intact hemisphere.
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Unit recording was carried out in the visual cortex of split chiasm and optic tract-sectioned adult cats. From the proportions of the visually responsive and unresponsive cells found in each hemisphere of the operated cats it was concluded that the indirect pathway via the corpus callosum becomes visually inactive under these conditions. However, the direct geniculocortical pathway remains visually active. Thus, it was assumed that unilateral or bilateral elimination of the decussating pathway has a crucial effect on the amount of interhemispheric callosal transfer of basic visual functions.
A rapid RIA for insulin and its application to localising occult insulinomas during surgical exploration is described. A standard curve and twelve serum samples can be assayed within 45 min. The assay is equivalent with respect to accuracy and precision to conventional RIAs for insulin. Pancreatic vein catheterisation at laparotomy and immediate insulin determination made it possible to localize and resect two insulinomas which were not demonstrated by arteriography, computed tomography, ultrasound, and not palpable at surgery. We suggest that the new technique will end the long controversy concerning subsequent management of occult insulinomas.
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Four case histories out of 75 significant trampoline injuries (from a total of 198 injuries re-examined) plus two recent accidents (1979) are presented, illustrating that the trampoline is posing an undue risk of serious injury. It is argued that the only single factor capable of preventing trampoline injuries is a trampoline ban. This is imperative in schools. Trampoline clubs are advised to reconsider the risk factors involved.