Biomedical subjects

H Lohrer

Publications and source records attributed to H Lohrer.

28 records · Page 2Linked to original sources

PubMed1991

[Rare causes and differential diagnoses of Achilles tendinitis].

Especially in sports disciplines involving high uniform stress by running, such as all running competitions in athletics, the condition known as achillodynia is a much-dreaded lesion. We evaluated an own series of 74 consecutive patients who reported pain at the achilles tendon, with regard to etiological aspects. It was a remarkable fact that besides the well-known classical reasons (degenerative changes in the center of the achilles tendon with spindle-shaped distension, aseptic irritated condition of the paratenon, bursitis subachillea mostly associated with Haglund's exostosis) numerous other syndromes may seem to be achilles tendon pain to individual athletes. To arrive at on-target therapy directed etiologically at the root cause of the disease, it will be necessary to differentiate them from one another: insertion tendopathies of the achilles tendon; metabolic diseases; arthritis and chondropathic disease of the ankle joint; hallux rigidus --rotation anomalies; tibia vara; os trigonum impingement syndrome --tendovaginitis of the flexor tendon at the retinaculum flexorum; stress fractures (calcaneus, fibula, tibia) Diagnosis is assisted, besides a detailed and exact clinical examination and an inspection of the sports shoes worn by the patient, by a biomechanical analysis of the running behaviour, an x-ray of the ankle joint, sonographic examination and clarification with the help of laboratory examinations, i.e. clinical pathology.

Achilles Tendon↗

PubMed1990

Purification and characterization of lipoamide dehydrogenase from Trypanosoma cruzi.

From Trypanosoma cruzi, the causative agent of Chagas' disease, a lipoamide dehydrogenase was isolated. The enzyme, an FAD-cystine oxidoreductase, shares many physical and chemical properties with T. cruzi trypanothione reductase, the key enzyme of the parasite's thiol metabolism. 1. From 60 g epimastigotic T. cruzi cells, 2.7 mg lipoamide dehydrogenase was extracted. The flavoenzyme was purified 3000-fold to homogeneity with an overall yield of 26%. 2. The enzyme is a dimer with a subunit Mr of 55,000. With 1 mM lipoamide (Km approximately 5 mM) and 100 microM NADH (Km = 23 microM), the specific activity at pH 7.0 is 297 U/mg. 3. With excess NADH, the enzyme is reduced to the EH2.NADH complex and, by addition of lipoamide, it is reoxidized, indicating that it can cycle between the oxidized state E and the two-electron-reduced state, EH2. 4. As shown by N-terminal sequencing of the enzyme, 21 out of 30 positions are identical with those of pig heart and human liver lipoamide dehydrogenase. The sequenced section comprises the GGGPGG stretch, which represents the binding site for the pyrophosphate moiety of FAD. 5. After reduction of Eox to the two-electron-reduced state, the enzyme is specifically inhibited by the nitrosourea drug 1,3-bis(2-chloroethyl)-1-nitrosourea (Carmustine), presumably by carbamoylation at one of the nascent active-site thiols. 6. Polyclonal rabbit antibodies raised against T. cruzi lipoamide dehydrogenase and trypanothione reductase are specific for the respective enzyme, as shown by immunoblots of the pure proteins and of cell extracts.

Amino Acid Sequence↗

PubMed1990

Overexpressed human metallothionein IIA gene protects Chinese hamster ovary cells from killing by alkylating agents.

Experiments were designed to detect survival advantages that cells gain by overexpressing metallothionein (MT). Chinese hamster ovary K1-2 cells and an x-ray-sensitive derivative were transfected with a bovine papillomavirus (BPV)-linked construct carrying the human metallothionein IIA (hMT-IIA) gene. Transfectants survived 40-fold higher levels of cadmium chloride, harbored at least 30 copies of hMT-IIA, and contained 25- to 166-fold more MT than the parent cells. Even under conditions of reduced glutathione synthesis, the transfectants were not more resistant to the lethal effects of ionizing radiation and bleomycin than the parent cells. Thus free radicals generated by these agents cannot be scavenged efficiently by MT in vivo. The hMT-IIA transfectants, however, but not control transfectants harboring a BPV-MT promoter-neo construct, tolerated significantly higher doses of the alkylating agents N-methyl-N-nitrosourea and N-methyl-N'-nitro-N-nitrosoguanidine. Resistance and MT overexpression occurred irrespective of selection and cultivation in cadmium and zinc. There was no increase in resistance to methyl methanesulfonate and N-hydroxyethyl-N-chloroethylnitrosourea. MT did not affect the degree of overall DNA methylation after N-methyl-N-nitrosourea treatment nor the level of O6-methylguanine-DNA methyltransferase. The results suggest that MT participates as a cofactor or regulatory element in repair or tolerance of toxic alkylation lesions.

Alkylating Agents↗

PubMed1990

Differential effects on cell killing in metallothionein overexpressing CHO mutant cell lines.

An increased level of metallothionein (MT) within the cytosol has been associated with the development of resistance to the cytotoxic effects of alkylating agents, but the mechanism of this effect is unclear. To verify the possible role of MT as a direct scavenger of alkylating agents we transfected two alkylating agent sensitive CHO mutant cell lines, methyl methanesulphate-1 and -2 (MMS-1 and MMS-2), with the human metallothionein II-A (hMTII-A) gene. From each mutant two transfected cell clones were isolated which were found to bear episomally 50 to 70 copies of the plasmid pMTII-BPV coding for the hMTII-A gene. The transfected cell lines contained between 1.4 and 4.9 micrograms of MT per 10(7) cells. This could be increased 2- to 9-fold by heavy metal induction. Transfectants derived from mutant MMS-1 were equally sensitive as the parental cells to a set of alkylating agents. However, transfectants derived from mutant cell line MMS-2 gained significant resistance to both N-methyl-N'-nitro-N-nitrosoguanidine and N-nitroso-N-methylurea, whilst retaining sensitivity to MMS. The degree of resistance was not increased by MT induction after heavy metal ion exposure. These results indicate that although resistance to alkylating agents may be mediated by a process which involves MT expression, this is not due to simple scavenging of the cytotoxic agent by the MT protein.

Animals↗

PubMed1989

A promising genomic transfectant into Xeroderma pigmentosum group A with highly amplified mouse DNA and intermediate UV resistance turns revertant.

Following transfection of genomic mouse DNA into an SV40 transformed fibroblast cell line from a patient with Xeroderma pigmentosum (complementation group A, XPA), a single UV resistant cell clone was isolated out of a total of 10(4) independent transfectants. The recipient XPA cell line has as yet not produced spontaneous revertants among 2.2 x 10(8) cells. The isolated cell clone contains 50-70 kb of mouse sequences which are heavily amplified (500-fold), and has acquired both intermediate resistance to UV killing and intermediate unscheduled DNA synthesis (UDS) capacity. By continued passage without selective pressure, cells were generated, which had lost both the dominant marker gene and repetitive mouse sequences. Single colonies of these cells were still intermediately resistant to UV suggesting that either undetected unique mouse DNA had segregated from the bulk of repetitive DNA, or, more likely, that the initially isolated transfectant was a spontaneous revertant. This documents that a persuasive clone isolated can still be a false positive (spontaneous revertant) and that an extremely laborious approach may lead into a dead end.

Animals↗

PubMed1989

[Design and effect of sports shoe insoles for the runner].

Running injuries of the lower extremities are more frequent with increasing intensity and extent of training. Biomechanical investigations demonstrate that exertion induced injuries of the foot, achillotendinitis, patellar tendinitis and shin splint syndrome are correlated with disorders in footstrike patterns. Therefore running shoe insoles can eliminate peak forces by exactly placing supporting elements. Furthermore peak forces may be distributed and complaints may be reduced. 50 runners with exertion induced injuries of the lower extremity were provided with appropriate running shoe insoles. There were excellent results in 34% and good results in 42%. 20% had moderate improvements while only 4% had unchanged complaints.

Achilles Tendon↗

PubMed1989

Overexpression of metallothionein in CHO cells and its effect on cell killing by ionizing radiation and alkylating agents.

Metallothionein protein protects cells from the toxic effects of heavy metal ions. To establish its protective function against ionizing radiation and alkylating agents, a model system was created by transfecting two CHO cell lines (wild-type, K1-2 and X-ray sensitive, xrs-2 subclone Bc11) with the human metallothionein II-A (hMTII-A) gene integrated in a bovine papilloma derived autonomously replicating vector. The isolated transfectants are cadmium-resistant (Cdr), due to the overexpression of the hMTII-A gene. Their steady-state level of hMTII-A mRNA can be increased up to 40-fold after Cd treatment and 20-fold after induction with ionizing radiation. The transfected cell lines proved to be as sensitive as the recipient cell lines to ionizing radiation and bleomycin but the transfectants were significantly more resistant to N-methyl-N'-nitro-N'-nitrosoguanidine (MNNG) and mitomycin C (MMC). These results lead to the conclusion that the MT protein does provide a defence mechanism to protect cells from monofunctional alkylating and cross-linking agents but not from free radicals.

Alkylating Agents↗

PubMed1988

Ataxia telangiectasia resists gene cloning: an account of parameters determining gene transfer into human recipient cells.

A subclone of an SV40-transformed fibroblast cell line from a patient with Ataxia telangiectasia (AT) with a relatively high rate of DNA uptake was isolated. However, more than 65000 independent genomic transfectants (using wild-type human DNA) did not contain the functional AT gene. This number represents the statistical distribution of an amount of DNA equivalent to more than three times the haploid human genome. The transfectants were screened by an X ray selection protocol that could rescue a single wild-type cell out of a population of 10(6) AT cells. This suggests a reversion frequency for AT of below 10(-8). The DNA uptake into human cells is compared with that into NIH3T3 cells and future possibilities for the isolation of human repair genes are discussed.

Ataxia Telangiectasia↗

PubMed1985

Double-strand break repair and G2 block in Chinese hamster ovary cells and their radiosensitive mutants.

Two X-ray-sensitive mutants of the CHO K1 cell line were examined for their cell-cycle progression after irradiation with gamma-rays, and for their ability to rejoin double-strand breaks (DSBs) as detected by neutral filter elution. Both mutants were impaired in DSB rejoining and both were irreversibly blocked in the G2 phase of the cell cycle as determined by cytofluorometry. From one mutant we have isolated several revertants. The revertants stem from genomic DNA transfection experiments and may have been caused by gene uptake. All revertants survived gamma-irradiation as did the wild-type CHO line. One of them has been examined for its ability to rejoin DSBs and was found to be similar to the wild type.

Animals↗

PubMedDate not supplied

Neuromuscular properties and functional aspects of taped ankles.

We used electromyographic and goniometric methods to test 40 subjects to describe the neuromuscular and biomechanical adaptation of the ankle with respect to application of two different adhesive tapes and to exercises. The neuromuscular responses to inversion injury simulation, together with the mechanical displacements of the joint complex, were analyzed before and after controlled athletic exercises. The proprioceptive amplification ratio was calculated on the basis of the integrated reflex electromyographic results and on the maximum inversion amplitude. Relevant stability gains were achieved immediately after applying tape. There was reduced tape stability after athletic exercise for one of the two tape materials tested. No further loosening was detected, even after prolonged wearing of tape (24 hours). Compared with the unprotected ankle, the taped ankle had a significant increase in the proprioceptive amplification ratio. Both fatigue and mechanical loosening may be responsible for the significant reduction in this ratio immediately after exercise. After the 24-hour interval, the ratio was increased, which could be explained by physiologic neuromuscular regeneration and mechanical restabilization of the tape itself. The sensitivity of the proprioceptive amplification ratio, both to external stabilization and to internal fatigue, supports its potential value to quantify functional joint stability.

Adolescent↗