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Biomedical subjects

F P Altman

Publications and source records attributed to F P Altman.

16 recordsLinked to original sources
PubMed1979

Tissue stabilizer methods in histochemistry.

Quantitative studies in the 1960s established that the tissue disruption and enzyme loss which occurs when unfixed cryostat sections are incubated could be prevented with high concentrations of polyvinyl alcohol without inhibition of enzyme activity. This use of polymeric stabilizers has been largely confined to studies of 'soluble' dehydrogenases in tissue sections. However, optimum conditions for 'soluble' enzymes in cut sections may not be ideal for membrane-bound enzymes or for whole cells, where an over-stabilization of membranes can lead to restricted entry of reagents and thereby low activities. Lower concentrations, or other stabilizers such as Ficoll (a synthetic polysucrose) and collagen polypeptides, have been used in such cases. Suggested criteria for a tissue stabilizer are: (i) The stabilizer should be chemically inert, of defined and constant composition, and generally available; (ii) The tissue must remain structurally intact during the incubation, and the final preparation should look 'clean' and have the proper morphology; (iii) The component being assayed must remain inside the section, and not diffuse into the incubation medium. Ideally, it and any reaction product should remain at their original loci, although it may not always be possible to verify this; (iv) Recorded activities should be comparable to those found in biochemical systems under similar conditions.

Collagen↗
PubMed1977

Quantitative microscopy of enzyme reactions in tissue sections.

Microdensitometry makes it possible to measure reaction products in discrete regions of tissue sections. Single cells, or groups of cells, can be selected for measurement. In this way, it is possible to obtain quantitative data from enzyme reactions, and to relate activities to histology. Some examples are given to illustrate the application of this technique.

Animals↗
PubMed1976

The quantification of formazans in tissue sections by microdensitometry. I. The use of neotetrazolium chloride.

This article describes the use of a microdensitometer for the measurement of formazan deposits in tissue sections. Some examples are given to illustrate the various applications of this technique in the assessment of glucose-6-phosphate dehydrogenase activity. These are (I) the separate measurement of the red half-formazan intermediate and purple diformazan of neotetrazolium, and the effect of incubation time on their production, (2) the measurement of activities in different regions of the liver lobule, and the selective effect of phenobarbitone, and (3) the measurement of enzyme activity in individual cartilage cells in normal and osteoarthrosis-prone animals. All activities can be expressed in absolute units as nmol hydrogen/mm3/hr, and thus compared with standard biochemical data. The activities obtained all fall within the range of published values for biochemical systems.

Animals↗
PubMed1976

Tetrazolium salts: a consumer's guide.

The purities of seven tetrazolium salts, obtained from various commercial sources, have been assessed by thin layer chromatography, relative extinction coefficients, and melting points. MTT and INT were largely homogeneous on thin layer chromatography, although significant variations occurred in the melting point behaviour. All the samples of TT examined were contaminated to a small extent with non-tetrazolium u.v.-absorbing material. TNBT and NBT were contaminated with small amounts of mono-tetrazolium salts, although one sample of each was heavily contaminated with another di-tetrazolium compound. Four samples of TNBT contained high melting point contaminants. BT was also contaminated with mono-tetrazolium salts, and some samples also contained di-tetrazolium salt contaminants. NT was the most heavily contaminated of all, most samples containing no less than five separate tetrazolium compounds. Prices varied widely, and in general were not related to purity. Some catalogue entries were very easy to find; others were more difficult. Few specifications were given; of these, most were arbitrary (for example, pure, grade I, and ... probably the finest INT offered anywhere.

Chromatography, Thin Layer↗
PubMed1976

The quantification of formazans in tissue sections by microdensitometry. II. The use of BPST, a new tetrazolium salt.

This article describes the use of a microdensitometer for the measurement of BPST formazan in tissue sections. BPST is a new tetrazolium salt, 2-(2-benzothiazolyl)-3-(4-phthalhydrazidyl)-5-styryl-tetrazolium chloride, which produces a single, well-defined formazan, and is thus easily quantified. The formazan gives an excellent localization, since BPST was originally designed for ultrastructural work. Activities are expressed in absolute units as n moles hydrogen/mm3, and are thus directly comparable with standard biochemical data.

Animals↗
PubMed1976

The quantification of ormazans in tissue sections by microdensitometry. III. The effect of objective power and scanning spot size.

In this article, it is reported that the formazans derived from neotetrazolium chloride (NT) and 2-(2-benzothiazolyl)-3-(4-phthalhydrazidyl)-5-styryl-tetrazolium chloride (BPST) can be measured by microdensitometry of tissue sections with a wide range of scanning spot sizes, without any significant effect on the recorded extinctions. The spot sizes tested ranged from 0.20 to 16 mum. Thus when large fields have to be measured, it is possible to use low-power objectives and still obtain valid results.

Animals↗
PubMed1976

Tetrazolium salts and formazans.

The history of the tetrazolium salts and formazans goes back 100 years, to when Friese (1875) reacted benzene diazonium nitrate with nitromethane, to produce a cherry-red "Neue Verbindung". This was the first formazan. 19 years later, Von Pechmann and Runge (1894) oxidised a formazan to produce the first tetrazolium salt. Many hundreds of tetrazolium salts and formazans were prepared in the following years, but only a handful have found applications in biological research. This article has attempted to describe the properties of these compounds, and to illustrate how the tetrazolium salt-formazan reaction has been exploited to serve an extremely wide variety of functions.

Animals↗
PubMed1975

The ultra-structural localization of enzyme activity in unfixed sections.

A technique is described for using conventional unfixed cryostat sections for localising enzyme activities in the electron microscope. The sections are incubated on the slide in the presence of a stabiliser, and then only fixed and embedded after the reaction is complete. Thin sections can then be cut of the reacted section, for electron microscopy. The present article shows that good ultra-structural morphology is retained during the freezing and cutting stages, and although some loss of detail occurs after the incubation, sub-cellular membranes are still intact, and membrane-associated reaction product can be clearly seen.

Animals↗
PubMed1975

The direct measurement of cytochrome P450 in unfixed tissue sections.

A method for the measurement of cytochrome P-450 in unfixed cryostat sections is described. The sections are incubated for 10 minutes at room temperature in a buffered solution containing polyvinyl alcohol and sodium dithionite. Two incubations are performed on serial sections, one in nitrogen and the other in carbon monoxide. Readings are taken on a Vickers M85 microdensitometer fitted with a high sensitivity photomultiplier amplifier system, the measurements being made on corresponding fields in the serial sections. Subtraction of the nitrogen values from the carbon monoxide values, after allowing for an absorption shift, gives the absolute spectrum of cytochrome P450. The subtraction corrects for the tissue content of other haem-containing proteins. The cytochrome P450 spectrum shows a sharp maximum at 450 nm, and two other minor components absorbing at 444 nm and 458 nm. The content of cytochrome P450 in animals fed with phenobarbitone was 2.4 times greater than in control animals.

Animals↗