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Biomedical subjects

O Hockwin

Publications and source records attributed to O Hockwin.

At least 127 records · Page 7Linked to original sources
PubMed1983

Fructose, fructose 1-phosphate, and glyceraldehyde breakdown in carbohydrate metabolism.

Recent investigations showed that all enzymes that are involved in the catabolism of fructose via fructose 1-phosphate (F-1-p) are present in the bovine lens. The present studies were performed to provide information regarding the extent to which fructose, F-1-p and glyceraldehyde (GA) are actually catabolized via this pathway, and how they increase the lactate, alpha-glycerophosphate and glycerol concentrations. Incubation was performed with a homogenate of bovine lens equator. F-1-p, and particularly fructose + ATP, considerably increased lactate and alpha-glycerophosphate concentrations, while the glycerol concentration remained unchanged compared to controls. Lactate formation through GA was not observed; while small amounts of glycerol and alpha-glycerophosphate are formed, it seems that the major part is transformed to glycerate. The results show that the further breakdown of lenticular fructose occurs via F-1-p and that the phosphorylated C3 fragments (dihydroxyacetone phosphate) are transferred to the energy metabolism, which is not the case with GA.

Animals↗
PubMed1983

Biometry of the anterior eye segment by Scheimpflug photography.

Scheimpflug photos of 262 cataract patients, classified according to various forms of opacifications characteristic for senile cataracts were evaluated by biometric methods. The measured values on cornea thickness, depth of anterior chamber, lens thickness, and radii of curvatures of cornea and anterior lens surface show that a correlation between some of the parameters and certain forms of opacities must be assumed.

Adolescent↗
PubMed1983

Studies of lens enzyme activities in relation to cataract type and plasma constituents.

The specific activities of glutathione reductase (GR), EC 1.6.4.2, and aldolase, (ALD) EC 4.1.2.13, were determined in the homogenates of 60 cataractous lenses. Concentrations of certain plasma constituents and the morphological types of cataract of the patients were known. Investigations were aimed at establishing a possible correlation between enzyme activities and plasma constituents as well as between the specific activities of GR and ALD and type of cataract. A correlation between the specific activity of GR and the urea content of the blood could be identified. Results also indicated a relationship between the decrease in GR activity and the formation of cortical cataracts.

Alkaline Phosphatase↗
PubMed1983

Enhancement of the stimulating effect of fructose-1.6-diphosphate on the metabolic energy balance of carbohydrate-deficient bovine lenses by additional supply with ADP.

The energy supply in carbohydrate-deficient bovine lenses was disturbed, as could be demonstrated by measuring the content of free adenine nucleotides. It could be regenerated in part by a 3-hour-incubation in TCM 199 in the presence of fructose-1.6-diphosphate (FDP). Additional supply of ADP enhanced the stimulating effect of FDP towards formation of ATP, providing sufficient receptor molecules for the activated rate of glycolysis and probably also for the citric acid cycle.

Adenosine Diphosphate↗
PubMed1983

Biochemistry of the ageing rat lens. I. Lens wet weight and lens dry weight with respect to sex differences.

The lens wet weight differed from the age of 136 days: the male lenses were significantly heavier than the female lenses. The dry weight, in percent of the lens wet and dry weight, of the water-soluble proteins decreased and the dry weight of the water-insoluble proteins increased during ageing. At an age of 870 days, when the dry weight curves crossed each other, the lens contains equal amounts of water-soluble and water-insoluble proteins. At the end of the life expectancy, the relation between the water-soluble and water-insoluble moiety was 0.7 for the rat and 3.5 for the bovine lens. The dry weight percent of the water-soluble proteins was lower for the female lens, whereas that of the water-insoluble proteins was higher for the female lens. The male lens, on the contrary, showed a higher percentage of water-soluble and a lower percentage of water-insoluble proteins with increasing age. The ratio R of the dry weight of water-soluble to water-insoluble proteins was, from the age of 429 days, lower for the female lens. During ageing, the proportion of the lens-water was higher for the male lens.

Age Factors↗
PubMed1983

In vitro incubation of lenses: a model for investigations on lens transparency by varying the perfusion rate, osmolarity and temperature of the culture medium.

A Beckman photometer was modified so that the unfiltered beam of a tungsten lamp could pass vertically through a special chamber. This particular chamber, containing two compartments, allowed certain modifications of the incubation conditions with respect to the anterior and/or posterior lens surface. The temperature of the incubation media was variable between 15 degrees and 37 degrees C; they were led into the chamber by hose gauge at different perfusion rates. The light transmission measured by the photometer was registered by a Honeywell recorder. Preliminary results of the various incubation conditions on the lens transparency of pig lenses are presented.

Animals↗
PubMed1983

Biochemistry of the ageing rat lens. II. Isoelectric focusing of water-soluble crystallins.

Thin-layer isoelectric focusing of the water-soluble crystallins shows with increasing age of the animals an increase of alpha-crystallins of high and low molecular weight and of the total beta-crystallins content. The beta-crystallin components of high molecular weight also increased during ageing, but the beta-crystallins of lower molecular weight decreased considerably. The total gamma-crystallin content, as well as certain gamma-crystallin components also decreased considerably with increasing age, or vanished completely. From 429 to 1,211 days of age the male gamma-crystallins as percent of the water-soluble moiety, were higher than the female gamma-crystallins. As a consequence of ascending age, the content of water-insoluble proteins of the rat lens increased gradually and continuously, e.g. by a process of insolubilization of soluble beta- and gamma-crystallins.

Aging↗
PubMed1982

[Is there a drug treatment for cataract?].

The formation of lens opacities in older people, generally known as senile cataract, is due to multifactorial processes. The interactions of age changes (for instance by postsynthetic molecule transformation of lens proteins) and additional risk factors condition the various forms of opacities and the wide range in age of manifestation. This means that they also represent a working point for a drug treatment aiming at inhibition of such risk factors, thereby inhibiting the formation of opacification or delaying the progress of already existing opacities.

Adult↗
PubMed1982

Measurements of lens transparency or its disturbances by densitometric image analysis of Scheimpflug photographs.

Scheimpflug photography of the anterior eye segment with densitometric image analysis to measure lens transparency has proven its value in long-term follow-up studies of lens changes. The necessary technical conditions of the SL 45 Topcon camera guarantee high reproducibility. The technical control with respect to quality in case of repeated photography is ensured by an internal standard, the camera being equipped with a five-step scale of known density values. External standardization is done by taking the densitometer height of the cornea as standard. The coefficients of variation of internal and external standards were nearly equal (approximately 5%) over the 9-month period of observation of 100 patients (3,200 photos). The coefficients of variation correspond to the standard error found with repeated lens photos of volunteers' eyes evaluated by analysis of variance of the respective data sets. The standard error for distance measurements on the x-axis (cornea thickness, depth of anterior chamber, lens thickness, etc.) is less than 3%. Evaluation of follow-up examinations may most successfully be done by densitometric planimetry, which, in case of follow-up studies on opacified lenses, is superior to the usual measurements of densitometer height. The light scatter registered by Scheimpflug photography is highly individual. This is demonstrated by densitograms of normal lenses of persons of different age groups. Besides linear densitometry, various other procedures of densitometric planimetry are possible. The best results so far were obtained by multilinear densitometry, but the enormous amount of data obtained in this way renders routine application rather difficult.

Cataract↗
PubMed1982

[X-ray-induced cataract as a model for investigating cataractogenesis (author's transl)].

X-rays are known to be a true cataractogenic agent. Since they can be accurately dosed and directed they are particularly suitable for inducing experimental cataracts. By means of ionizing rays, lesions are induced in various lens segments. Both the extent of the damage as well as the latency period until it becomes manifest are highly age-dependent. Since lens changes effected by ionizing rays are in many respects, similar to age-related changes, experimental cataracts induced by X-rays provide suitable models for investigating processes involved in the multifactorial genesis of senile cataract.

Animals↗
PubMed1982

Investigations of the enzymes involved in the fructose breakdown in the cattle lens.

By introducing fructose into the glycolysis, it is possible to stimulate ATP formation. As is the case in animal experiments, in human lenses, too, the first step in the phosphorylation to fructose-1-phosphate via the enzyme ketohexokinase. The present investigation deals with the question whether enzymes present in the lens are responsible for the further steps in fructose degradation. Particularly the aldolase isoenzyme C splits fructose-1-phosphate into glyceraldehyde and dihydroxyacetone phosphate in the same way as in glucose catabolism. Dihydroxyacetone phosphate can further be directly degraded and thus utilized to ATP formation. From glyceraldehyde, glycerol (aldose reductase) or glycerate (aldehyde dehydrogenase) can be formed. The presence of triosekinase, which phosphorylates glyceraldehyde directly to glyceraldehyde-3-phosphate, could only be determined in the lens tissue of young animals. The presence of glycerokinase (glycerol leads to glycerophosphate) could not be verified. Thus, in the lens tissue 1 ATP molecule net per fructose molecule can be formed. In older age, the glucose breakdown is limited by hexokinase and phosphofructokinase, so that the glucose, after transformation via the sorbitol pathway to fructose, can also be utilized for the energy metabolism.

Aging↗
PubMed1982

Clinical evaluation of direct and photosensitized ultraviolet radiation damage to the lens.

We are reporting a new, objective, and quantitative method for monitoring age-related molecular changes in the human ocular lens in vivo, as expressed by increases in at least two (nontryptophan) fluorescence wavelengths. These fluorescence wavelengths appear to be caused by photochemically induced changes in the lens, and they reflect the ultraviolet (UV) filtering capacity of the patients' ocular lenses. These data correlate with previously reported in vitro lens fluorescence changes that are associated with the aging process. This method will also detect alterations in lenticular fluorescence caused by photosensitized as well as direct UV radiation damage.

Adolescent↗
PubMed1981

Investigations on the influence of whole body X-irradiation on the activity of rat lens aldose reductase (E.C. 1.1.1.21).

The influence of whole body X-irradiation on the activity of the enzyme aldose reductase (E.C. 1.1.1.21) in the lenses of young rats was investigated. Immediately after irradiation there was no difference between the activity of the enzyme in irradiated and nonirradiated animals. Within 10 days after irradiation, significant differences developed. There was a constant increase of the activity in the control lenses, while the activity in the irradiated lenses remained nearly constant. There was no remarkable difference between the two groups 10 days after irradiation with respect to the kinetics of the enzyme. This meant that irradiation does not affect the enzyme present at the moment of application, but the influence of 440 rad X-irradiation effects an obvious decrease in the synthesis of the enzyme.

Aldehyde Reductase↗