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At least 19 recordsLinked to original sources
PubMed1978

Fixation variables in horseradish peroxidase neurohistochemistry. I. The effect of fixation time and perfusion procedures upon enzyme activity.

In a series of neurohistochemical experiments the effect of aldehyde fixation upon the detection of horseradish peroxidase (HRP) was examined. These experiments demonstrated that: a) Increments in fixation of as little as 1 hr significantly decreased the number of labeled neurons; 12-hr fixation abolished HRP activity in many neuronal populations and significantly reduced the apparent size of the injection site. b) This negative fixation effect was greatest where the HRP concentration was low (e.g. in small, lightly labeled neurons) but was still evident in areas of high concentration (e.g. large, heavily labeled neurons). c) This effect was also most prominent when a less sensitive diaminobenzidine histochemical procedure was employed but was still apparent with a more sensitive benzidine dihydrochloride procedure. d) Immersion of the brain in fixative after perfusion produced a greater attenuation of HRP activity in more superficial areas. e) Immersion of the brain in buffer to terminate fixation produced a prolonged and unpredictable gradient of fixation. f) Excess, unbound fixative inhibited the histochemical reaction per se and had to be removed from the tissue but prolonged washing did not resurrect enzyme activity which was lost by fixation. To obviate these problems and optimize HRP enzyme activity a new perfusion-fixation procedure was developed. It entails 30 min fixation by perfusion which is terminated by a subsequent 30 min perfusion with cold sucrose-fuller to wash out unbound fixative. This allows the tissue to be processed immediately, produces a uniform and morphologically adequate fixation, and minimizes the negative effects of fixation on HRP enzyme activity.

Animals↗
PubMed1975

The role of pH in the regulation of carbon fixation in the chloroplast stroma. Studies on CO2 fixation in the light and dark.

1. The pH in the stroma and in the thylakoid space has been measured in a number of chloroplast preparations in the dark and in the light at 20 degrees C. Illumination causes a decrease of the pH in the thylakoid space by 1.5 and an increase of the pH in the stroma by almost 1 pH unit. 2. CO2 fixation is shown to be strongly dependent on the pH in the stroma. The pH optimum was 8.1, with almost zero activity below pH 7.3.Phosphoglycerate reduction, which is a partial reaction of CO2 fixation, shows very little pH dependency. 3. Low concentrations of the uncoupler m-chlorocarbonylcyanide phenylhydrazone (CCCP) inhibit CO2 fixation without affecting phosphoglycerate reduction. This inhibition of CO2 fixation appears to be caused by reversal of light induced alkalisation in the stroma by CCCP. 4. Methylamine has a very different effect compared to CCCP. Increasing concentrations of methylamine inhibit CO2 fixation and phosphoglycerate reduction to the same extent. The light induced alkalisation of the stroma appears not to be significantly inhibited by methylamine, but the protons in the thylakoid space are neutralized. The inhibition of CO2 fixation by higher concentrations of methylamine is explained by an inhibition of photophosphorylation. It appears that methylamine does not abolish proton transport. 5. It is shown that intact chloroplasts are able to fix CO2 in the dark, yielding 3-phosphoglycerate. This requires the addition of dihydroxyacetone phosphate as precursor of ribulosemonophosphate and also to supply ATP, and the addition of oxaloacetate for reoxidation of the NADPH in the stroma. 6. Dark CO2 fixation in the presence of dihydroxyacetone phosphate and oxaloacetate has the same pH dependency as CO2 fixation in the light. This demonstrates that CO2 fixation in the dark is not possible, unless the pH in the medium is artificially raised to pH 8.8.

Adenosine Triphosphate↗
PubMed1977

Comparison of immediate polyvinyl alcohol (PVA) fixation with delayed Schaudinn's fixation for the demonstration of protozoa in stool specimens.

Immediate fixation of stool specimens in polyvinyl alcohol fixative (PVA) was compared with Schaudinn's fixation delayed until the specimens were received in the laboratory, in a series of 100 consecutive positive stool specimens. More specimens were found positive following PVA fixation, and the numbers of organisms present on the slides were greater in specimens processed by this technique than after Schaudinn's fixation. It is concluded that immediate fixation results in the preservation of larger numbers of organisms in a recognizable state. The routine use of PVA fixation prior to transportation of the specimen to the laboratory is recommended.

Amebiasis↗
PubMed1978

Microwave fixation versus formalin fixation of surgical and autopsy tissue.

Microwave irradiation of surgical and autopsy tissue penetrates, fixes, and hardens the tissue almost immediately (the fluid media used in the microwave consisted of saline, ten percent phosphate buffered formalin, and distilled water). Tissue sections from a representative sample of organs were tested. Comparable sections were simultaneously fixed in a phosphate buffered ten percent formalin bath in a vaccum oven as a control. Hematoxylin and eosin were used to stain the sections. Results equal to and superior to the control method were obtained. Saline microwave fixation was superior to formalin microwave fixation. Tissues placed in Zenker's solution and fixed in standard microwave oven (for approximately one minute) yielded results at least equal to conventional Zenker fixation (approximately two hours). No tissue hardening resulted from Zenker microwave fixation. A unique time versus temperature graph (microwave heating curve) reduces individual variation with this technique.

Autopsy↗
PubMed1979

Fixation of mammalian tissues in different fixatives and its influence on the staining with methyl green-pyronin.

This investigation is a study on the role of fixation of different mammalian tissues in different fixatives as well as in 10% neutral formalin containing different metal cations and its effect on the staining with the dye-mixture, methyl green-pyronin. The results indicate variation in the colour of the nuclei in tissues fixed in the different fixatives. The possible role of the fixatives on nuclear colouration has been discussed.

Animals↗
PubMed1979

Differential fixation of poly(L-arginine) and poly(L-lysine) by tannic acid and its application to the fixation of collagen in electron microscopy.

A differential fixation of poly(L-arginine) and poly(L-lysine) has been demonstrated by means of cellulose acetate electrophoresis and colorimetric titration. Electrophoresis showed that at pH 3.0 and concentrations between 0.025% and 2% the reagent interacts with poly(L-arginine) but not with poly(L-lysine). At pH 7.5, however, poly(L-lysine) also reacts, although at a higher concentration of tannic acid than was required to fix poly(L-arginine) at this pH. Colorimetric titration revealed that for poly(L-arginine) the reaction with tannic acid commences at pH 3.0 and is complete at pH 4.1 whereas for poly(L-lysine) the reaction commences at pH 3.5 and is complete at pH 4.9. It is suggested that the reaction is predominantly electrostatic. The results are discussed in relation to the use of tannic acid as a protein fixative in electron microscopy.

Animals↗
PubMed1979

Mitotic activity and delay in fixation of tumour tissue. The influence of delay in fixation on mitotic activity of a human osteogenic sarcoma grown in athymic nude mice.

The purpose of the present investigation was to study the effect of delay in fixation on the mitotic activity in tumour tissue. A human osteogenic sarcoma, especially suitable for counting of mitoses, grown in athymic nude mice, was fixed with varying delay and the mitotic, prophase, metaphase and ana-telophase indices were determined. An almost exponential decline of the mitotic index was observed with a reduction to 49.4% and 15.0% after respectively 60 and 180 minutes. The proportional incidence of prophases, metaphases and ana-telophases changed so that a relative accummulation of advanced phases occured during the 180 minutes of observation. It is concluded that delay in fixation of a magnitude, which is not uncommon in routine surgical pathology, may allow the majority of mitoses to terminate, resulting in unreliable assessments of mitotic activity.

Adult↗
PubMed1979

[Fixation of the osteotomised greater trochanter by total hip prosthesis in 181 cases. Advantages of the fixation with intramedullary Kirschner wire and the figure-of-eight wire loop (author's transl)].

It is mostly possible to implant a total hip prosthesis without an osteotomy of the greater trochanter. It is however necessary to do it in some cases such as an ankylosed hip, a reimplantation and a severe form of the coxarthrosis. 181 patients have been followed up. The fixation by intramedullary Kirschner wire and figure-of-eight wire loop has been of success. It is a simple method. No fracture of the greater trochanter has been observed.

Aged↗
PubMed1979

The complement fixation test and African trypanosomiasis. II. The complement fixation test as an aid for assessing therapy.

Complement-fixing antibody titres decline after successful treatment of trypanosoma infected cattle during a fixed period. For investigating the practicability of the resulting double test procedure in the field, cattle under controlled drug regimes were tested at treatment and again 3 weeks later. Alternatively, the results from groups of treated and untreated animals from the same area were compared. Both serological and parasitological test results indicated an insuffieicnt effectiveness of therapy in the area under investibation.

Animals↗
PubMed1978

Lysozyme antigenicity and tissue fixation.

The preservation of lysozyme (LZM) antigenicity was studied in paraffin embedded tissue blocks. The reactivity for LZM varied with the type of tissue studied, the fixative used, the osmolarity and pH of the fixative, fixation time and temperature, and the method of dehydration. In both rat and human tissues aqueous fixatives were superior to nonaqueous fixatives in retaining LZM antigenicity. Brief fixation in fixatives of low osmolarity enhanced LZM staining in the parenchymatous tissues but diminished staining in human cartilage; prolonged fixation in fixatives of high osmolarity gave opposite results. Least affected by fixation was the LZM antigenicity in the serous cells of the glands of the respiratory tract. These cells also stained most intensely for LZM of all autopsy material studied.

Animals↗
PubMed1978

A methodological study for the quantification and the control of the physico-chemical processes occurring during cell fixation. I. The development of a new technology.

Fixation in a traditional sense means the immersion of biological material into a chemical fluid. For permanent preservation the fixative is always "offered" (1) in excess of the cell sample, and the process of fixation is influenced by (2) chemical impurities of the fixative fluid. Both factors influence the succeeding dyeing of cells. In order to avoid these uncontrolled criteria, a new technology for controlled cell fixation has been developed, whereby freshly prepared formaldehyde and methanol gas in an "inert" gas-flow of helium was applied to thin membranes by aid of a capillary flow-in technique. The instrumental equipment consists of (1) an ultra-high vacuum flow-apparatus with a total-pressure measuring unit, (2) a gas-supply device, (3) a mass spectrometer including a pump system, and (4) a Teflon and/or glass-gas chamber for the treatment of synthetic (Hostaphan foils) or biological membranes (mesenterium) with formaldehyde as the fixative gas. The amount of "offered", adsorbed, absorbed, diffused, and desorbed fixative gas could be absolutely estimated after the saturation of the membranes with an "on-line" operating "inert" mass spectrometer of the Omegatron type. The gas treatment of the Hostaphan foils with formaldehyde showed that nearly all adsorbed gas molecules could be desorbed. In contrast to native membranes the greatest proportion of the gas molecules adhered to the biological surface, and only a small quantity were desorbable. Physisorption or physisorption and chemisorption occured depending on the adsorber surface property. A monolayer of formaldehyde of 5.10(14) to 1.10(15) molecules per 10(16) A2 surface area can be postulated on the basis of these preliminary results. This value corresponds to a mass of about 5.10(-8) g CH2O. It resulted in an area-coverage ratio of CH2O molecules per cell of 10(9):1. The membrane surface facing the gas side always amounted to 1 cm2. A fixative gas concentration of 10(6) molecules/cm3, and therefore a degree of coverage of less than 1/1000 monolayer can be estimated absolutely. For a precise determination of the degree of fixation, further experiments and the evaluation of additional physico-chemical parameters are necessary.

Adsorption↗
PubMed2026

Robot-assisted versus freehand cannulated-screw fixation for femoral neck fractures: a systematic review of technical, clinical and adoption outcomes.

Robot-assisted guidance may improve the technical precision of percutaneous cannulated-screw fixation for femoral neck fractures. Whether these procedural advantages translate into better clinical outcomes remains uncertain. We compared robot-assisted and conventional freehand fixation in adults with femoral neck fractures. MEDLINE, Embase and CINAHL were searched from inception to 15 July 2026 without language restrictions. Google Scholar was used only as a supplementary search source, together with forward and backward citation searching. Comparative studies of robot-assisted versus freehand fluoroscopy-guided cannulated-screw fixation were included. Risk of bias was assessed using RoB 2 and ROBINS-I, with the Newcastle-Ottawa Scale used as a complementary appraisal of non-randomised studies. Random-effects meta-analyses included prediction intervals and prespecified sensitivity analyses. The protocol was registered prospectively (PROSPERO CRD420261465038). Sixteen comparative studies involving 1,293 participants were included. Of these, 597 underwent robot-assisted fixation and 696 underwent freehand fixation. Two studies reporting random allocation and 14 non-randomised studies were included in the study. Robot-assisted fixation was associated with fewer guide-wire manipulations, greater screw-placement accuracy and 13.9 fewer fluoroscopic acquisitions per procedure (95% confidence interval [CI] -20.3 to -7.5). Earlier radiographic healing and modestly higher final Harris Hip Scores were also observed. Pooled estimates suggested lower risks of union failure, avascular necrosis and composite complications. Fluoroscopy duration, overall operative time and reoperation did not differ significantly. Heterogeneity was substantial for several continuous outcomes, with prediction intervals crossing the null for several estimates, indicating that the magnitude of benefit varied considerably between studies. Some clinical associations were also sensitive to eligibility-restricted analyses. Robot-assisted cannulated-screw fixation improves technical execution compared with freehand fixation. Patient-important clinical superiority and economic value have not been established, and evidence concerning learning curves, operator acceptability and system reliability remains insufficient. Current evidence does not support routine widespread adoption; adequately powered multicentre randomised trials incorporating economic and implementation evaluation are required.

Humans↗