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Biomedical subjects

G Locher

Publications and source records attributed to G Locher.

At least 19 recordsLinked to original sources
PubMed1993

Automatic bioprocess control. 4. A prototype batch of Saccharomyces cerevisiae.

The recent investigations in our high performance bioreactors have shown that living cells can be extremely sensitive to physical-chemical environmental conditions and their changes. Consequently, the relationship bioreactor-living cell must thoroughly be investigated in order to discuss both: whether bioreactor characteristics are limiting/dominating during cultivation and to what extent controlled changes of the cellular environment can lead the cells to a desired physiological state. For these investigations, a generally accepted biological test organism would be helpful, of which the requirements and reactions under certain conditions are well known. Saccharomyces cerevisiae is a well known, very robust but nevertheless sensitive organism, eligible for this purpose. In this article a typical batch cultivation on glucose is presented, collected from approx. 300 experiments. Regarding metabolite production and consumption, seven different phases are distinguished on the basis of approx. 20 sensor signals and their metabolic background is discussed. Prerequisite, however, was an exhaustive knowledge upon extracellular conditions, a task which could successfully be fulfilled with the highly automated equipment introduced in the preceding articles of this series.

Acetates↗
PubMed1993

Automatic bioprocess control. 5. Biologically and technically caused effects during cultivation.

Experimental programs are the basis for the development of new processes as well as for basic biological research. Hence, an unbiased approach is essential, otherwise the interpretation of results will be misleading. The complex chemical composition of cultivation media in combination with the impedded measuring under monoseptic conditions are ideal circumstances for misinterpretations and unsuited experimental approaches. In this article, practical examples for such pitfalls are given. They are undervalued in mass transfer and mixing effects, error propagation during RQ determination and possible influence of the medium preparation on the time evolution of the growth process. Further, the difficulty of sound interpretation is demonstrated by a batch cultivation carried out under sinusoidal changes of the stirrer speed. Summary conclusions close this series about equipment, methodology and benefits of bioprocess automation.

Biotechnology↗
PubMed1992

Biomass determination.

The reasons for and historical backgrounds of biomass determination are discussed under the aspects of theoretical and practical importance, usefulness and representativity. Off-line methods are evaluated and compared with on-line methods; constraints of applications and conclusiveness of results are rated. Special emphasis is given to the fact that mere knowledge of a bio-mass concentration is not sufficiently valuable to learn more about physiology nor to determine the effectiveness of a biotechnological process. A combination of several different alternative measuring principles in parallel as well as the exploitation of software sensors is proposed as a promising future solution.

Ecology↗
PubMed1992

On-line measurement in biotechnology: techniques.

Bioprocesses are generally ill controlled. This is due to the fact that the measurement of relevant variables is difficult. Therefore, fundamental knowledge of metabolic interrelations is, at least in vivo, limited. In this article, some of the most important measurement techniques are reviewed in order to provide an evaluation of their current state. Emphasis is given to the underlying principles and on-line capability which allow to judge their importance and potential for exploitation resulting in well (maybe entirely) controlled bioprocesses in the future.

Biosensing Techniques↗
PubMed1992

On-line measurement in biotechnology: exploitation, objectives and benefits.

Sound data biologically relevant are prerequisites when developing high-performance bioprocesses. Understanding of physiological regulation as well as sophisticated control strategies are highly dependent on the observability of the culture, i.e. the generation and exploitation of suited signals even under complex environmental measurement conditions. Against this background, the increasing number of analytical systems is very supportive and, accordingly, an appropriate handling of sensors and measured data is of decisive importance. This article reports on practical experience with routines for maintenance, service and calibration of hardware sensors which improve the quality of measurements significantly. Verification and validation of signals is outlined in order to make the value of data exploitation tools obvious. A method for the characterization of information is introduced by practical examples of Saccharomyces cerevisiae cultures when explaining the specific properties of extracting biological information from raw data. Finally, examples for advantageous exploitation of on-line data are given.

Biosensing Techniques↗
PubMed1991

[Health and disease in single homeless men: a secondary analysis of findings in a deaconess facility in the Federal German Republic].

Only few empirical investigations on living conditions and health status of single homeless men have been conducted in Germany. The secondary analysis of a sample of 342 homeless men in a welfare hotel was conducted to describe the health status of this group and to gather informations for a possibly higher illness-risk in this group. For this purpose the medical documents and other socio-demographic data were evaluated at one point (one day in February 1985) along the ICD. A relatively high multi-morbidity for the homeless men, especially for the elder ones, could be stated. The results emphasize in etiological perspective the need to take a deeper insight into factors of workload before getting homeless and to strengthen socioepidemiological, socio-therapeutical and political efforts.

Adult↗
PubMed1991

Automatic bioprocess control. 2. Implementations and practical experiences.

Our improved implementation for bioprocess control allows flexible responses to many process needs. It is based on computer equipment consisting of three hierarchically ordered levels. On the lowest level, a DDC slave computer handles setpoints and simple tasks generating the chemical and physical environment for the cells. It can be designed manually by the user or automatically by the supervisory computer on the second level. This provides for raw data organization, analysis and interpretation either to support personnel on line in decision making, to select predefined control strategies, or even to search for others. In the coordinating computer on the third level, common tasks of different supervisory computers (bioprocesses) are shared, saving money for the equipment. Tasks and concepts as well as experimental experiences are described to outline the capabilities of the configuration.

Biotechnology↗
PubMed1991

Automatic bioprocess control. 1. A general concept.

Automation of bioprocesses is presented and discussed. A general concept is applied to laboratory scale reactors as well as to large scale production facilities consisting of many unit operations with a hierarchical and highly modular structure. The implementation of non-dedicated and intelligent analytical subsystems is foreseen. Hard- and software requirements are discussed in view of the functional requirements of both scientific research and production engineering. Some practical experience is reported using several different components in parallel installations.

Biotechnology↗
PubMed1987

[The heparin-induced thrombosis-thrombocytopenia syndrome].

Severe thrombocytopenia, acute coronary artery thrombosis with myocardial infarction and thrombotic occlusion of both popliteal arteries occurred simultaneously in a 54-year-old man within 11 days of starting an intravenous heparin regimen as prophylaxis against deep-vein thrombosis. Popliteal artery thrombectomy was performed 12 days later and re-administration of heparin again induced thrombocytopenia with recurrent thromboses in the area of the leg arteries.

Coronary Disease↗
PubMed1985

[Total abdominal irradiation following combination chemotherapy and second-look laparotomy in the treatment of advanced ovarian cancer].

From 1980 to 1984 fifty-four patients with advanced ovarian carcinoma after operation and concluding chemotherapy with alkeran (n = 7) or cis-platin/alkeran +/- hexamethylmelamine (n = 47) as well as second-look laparotomy received follow-up radiotherapy either with the moving-strip technique (n = 35) or later the open-field technique (n = 19). 32 patients in CR received radiation therapy. 15 patients in CR are without relapse after undergoing open-field radiation therapy and a mean observation period of 25 months. At this point of time 5 of 17 patients had relapses under the moving-strip radiation treatment. The frequency of the relapses is apparently due to the very long periods of radiation and numerous interruptions in treatment. If residual tumors were present at the begin of ray therapy, a CR could only be achieved in cases where the previous monotherapy was with alkeran.

Adenocarcinoma↗
PubMed1985

The treatment of ovarian cancer by a multimodality approach: remission induction with chemotherapy--hexa PAMP and PAMP regimens--followed by whole-abdominal radiation.

Seventy-six evaluable patients with ovarian carcinoma stages FIGO IIb, IIc, III, and IV, either received cis-platin (P) (80 mg/m2 iv. day 1), melphalan (PAM) (12 mg/m2 i.v. day 2) and hexamethylmelamine (HEXAPAMP) (135 mg/m2 orally days 8 to 21) or the same dose of cis-platin and melphalan but no hexamethylmelamine (PAMP) every four weeks. In 24 patients (32%) a surgically ascertained CR was achieved. 16 of these received follow-up radiation treatment to the whole abdomen. At present 19 patients are without relapse (average time 24 months). The trial has not been concluded. Particularly no predictions can be made on the value of follow-up radiation therapy in obtaining long-term remission rates.

Adult↗
PubMed1984

CO2 laser conization versus conventional conization: a clinico-pathologic appraisal.

Two groups of patients recently underwent either laser or conventional conization at the University Women's Hospital in Bern, Switzerland. Of the total 49 patients treated, 25 underwent laser conization and 24 underwent conventional conization. All patients admitted to the study had cytologic, colposcopic, and/or histologic evidence for cervical intraepithelial neoplasia or chronic cervicitis resistant to conservative therapy. In the conventionally treated group, conization was performed with surgical scalpel, and hemostasis was achieved by Sturmdorff, Bonney, or Kraus sutures. In the laser-treated group, conization was performed by using the combination method of Dorsey and Grundsel. Blood loss was minimal in the laser-coned patients, compared to 119 ml blood loss in the conventionally coned patients. Hospitalization for the laser-treated group was 5.2 days in contrast to 7.0 days for the conventionally treated group. Postoperative bleeding and discharge were also considerably smaller or did not occur in the laser-treated group as compared to the conventionally treated group. With postoperative and long-term follow-up now under way, initial results indicate that laser conization, in comparison to conventional conization, also provides greater visibility of the squamocolumnar junction and a reduced incidence of cervical strictures. The results of this study suggest that the CO2 laser beam, properly and cautiously applied, is an efficacious surgical modality for the treatment of cervical preneoplastic disease.

Cervix Uteri↗
PubMed1984

Whole-abdomen radiation in patients with advanced ovarian carcinoma after surgery, chemotherapy, and second-look laparotomy.

Forty-three patients with ovarian carcinoma were treated with whole-abdomen radiation (moving strip +/- pelvic radiation), 15 patients had not received prior chemotherapy, and 28 patients were irradiated following chemotherapy and second-look laparotomy. Ten of these had been treated with a variety of chemotherapy regimens (L-PAM, CHAD, Hexa-CAF). Eighteen patients were treated in an ongoing prospective trial with combination chemotherapy consisting of melphalan, cis-platinum, and hexamethylmelamine++ (HexaPAMP). Thrombocytopenia was the limiting toxicity. A temporary pause in the radiation schedule allowing platelets to recover made it possible to complete treatment in 80% of the patients. The acute toxic effects, which included the expected side effects of radiation therapy on intestine, liver and lung, were not more frequent or more severe in the patients who had received prior chemotherapy than in those who had radiation therapy alone. Thirty-four of 43 patients (stage I, seven patients; stage II, seven patients; stage III, 27 patients; stage IV, two patients) are alive and without evidence of disease 26 + months (range 7 to 64 months) after entering the postsurgical treatment program.

Antineoplastic Combined Chemotherapy Protocols↗