An improved detection system applied to the study of serum lipoproteins after single-step density gradient ultracentrifugation

Starting from a single-spin ultracentrifugation procedure described previously (Foreman et al., J. Lipid Res. 18, 759, 1977), we have improved the system for detection of the fractions eluted from the gradient by monitoring them continuously at 280 nm. A graphic display readily permits assessment of the distribution of the lipoproteins and their quantification with the aid of a computer program. By the use of appropriate factors, one can convert absorbance readings into actual lipoprotein values which correspond well (±7% for low-density lipoproteins and ±5% for high-density lipoproteins) to those obtained by means of chemical analyses. The examples provided indicate the versatility of the method and its sensitivity (down to 0.1 ml of serum).     

Enzyme Thermistor Analysis of Penicillin in Standard Solutions and in Fermentation Broth

Immobilized penicillinase was applied in an enzyme thermistor for calorimetric analysis of samples containing penicillin G. Standard solutions as well as extracts from fermentation broth were analyzed. The enzyme was applied bound either to porous glass or, when dealing with crude preparations, to the inner surface of nylon tubing. In the fermentation system studied, high concentrations of penicillin were present, thus allowing dilution to reduce the influence of the composition of the medium on the analysis. The useful linear concentration range was from 0.1 to 100 mM. The coefficient of correlation between analytical results obtained with the present method and those from conventional assays was 0.997.     

Structure at restriction endonuclease MboI cleavage sites protected by actinomycin D or distamycin A

Restriction endonuclease MboI cleavage of DNA was inhibited by actinomycin D and distamycin A. The two inhibitors protected different subsets of the 8 cleavage sites in polyoma DNA. The cleavage reactions were analyzed both in the presence of minimal inhibitory concentrations of the compounds and at higher concentrations, allowing cleavage at only 1 site/DNA molecule. The experiments showed that cleavage sites most efficiently protected by actinomycin D had putative inhibitor binding sites at a distance of 1-2 base pairs from the MboI recognition sequence. Distamycin A, in contrast, apparently has to bind immediately adjacent to the MboI recognition sequence to protect from cleavage.     

Accumulation of Glucosylceramide and Glucosylsphingosine (Psychosine) in Cerebrum and Cerebellum in Infantile and Juvenile Gaucher Disease

Abstract: Three major clinical variants of Gaucher disease have been defined: Type I, chronic nonneuronopathic; Type II, acute neuronopathic; and Type III, subacute neuronopathic. In a search for the underlying molecular basis of the neurological manifestations, the concentration and composition of cholesterol, phospholipids, neutral glycosphingolipids, and gangliosides were examined in cerebral and cerebellar cortices of five cases of Type II, eight cases of Type III, and one case of presumed Type I/III. In Type II the concentration of glucosylceramide was 140-530 μmol/kg in cerebral cortex and 51-450 μmol/kg in cerebellar cortex, the highest values found in the most fulminant cases. These concentrations were 20-80 times greater than normal in cerebral cortex and 5-40 times normal in cerebellar cortex. In Type III the concentration of glucosylceramide was 37-65 and 59-1750 μmol/kg in cerebral and cerebellar cortex, respectively. The highest concentrations were found in the cerebellum of patients who had survived splenectomy for several years. The ceramide composition of the accumulated glucosylceramide suggested that brain gangliosides were the major precursors of the glucosylceramide in brains of Type II but in cerebellar cortex in Type III was partly of extracerebral origin. The levels of lactosylceramide and oligohexaosylceramides were slightly raised in all brain specimens from the Gaucher cases. The ganglioside concentration was normal, whereas there was a certain increase in the proportion of GM2 and GM3 gangliosides. The brain glycosphingolipid changes in the Type I/III case were similar but slightly less than those in Type III cases of corresponding age. Glucosylsphingosine (psychosine), never detected in normal human brain, was demonstrated in brains from all the Gaucher cases. The psychosine concentration was highest in Type II cases, 3.8-8.8 and 3.9-12.3 μmol/kg in cerebral and cerebellar cortex, respectively, with the highest values found in the most fulminant cases. In Type III the psychosine concentration varied more widely, 0.8-4.6 and 1.4-6.3 μmol/kg in cerebral and cerebellar cortex, respectively. The lowest value, 0.7 μmol/kg, was found in the Type I/III case. Our method detected psychosine down to 0.01 μmol/kg, which means that the concentration of psychosine was increased at least 100- to 1000-fold in Gaucher grey matter. We suggest that the accumulation of the cell-toxic substance psychosine is the basis for the extensive neuronal cell loss in Gaucher disease, which is most striking in Type II disease.     

Free Fatty Acids in the Rat Brain in Moderate and Severe Hypoxia

Abstract: The effects of mild, moderate, and severe hypoxia on cerebral cortical concentrations of free fatty acids (FFAs) were investigated in artificially ventilated rats under nitrous oxide anaesthesia. No change occurred during either mild (arterial Po₂ 35–40 mm Hg) or moderate (Po₂ 25–30 mm Hg) hypoxia. The effects of severe hypoxia (Po₂ about 20 mm Hg) combined with hypotension (mean arterial blood pressure 80–85 mm Hg) varied with the EEG pattern and the tissue energy state. Thus, a major increase in total as well as in individual FFAs occurred first when EEG was severely depressed (almost isoelectric) and energy homeostasis disrupted. On a relative basis the greatest change occurred in free arachidonic acid. It is concluded that hypoxia is associated with an increase in the concentrations of FFAs in brain tissue, provided that tissue oxygen deficiency is severe enough to cause tissue energy failure. However, an increase in FFAs does not invariably accompany minor reductions in the adenylate energy charge (EC) of the tissue.     

Classification of amphipod compound eyes — The fine structure of the ommatidial units (Crustacea,Amphipoda)

Summary The ultrastructure of the compound eyes of 13 amphipod species has been investigated. An amphipod type of compound eye can be characterized by the constellation and consistency of a number of morphological features, most of which are also found in other compound eyes. The amphipod eye falls into four sub-categories (types). The ampeliscid type has a tripartite aberrant lens eye; the lysianassid type has a reduced or no dioptric apparatus and a hypertrophied rhabdom; the hyperid type possesses a large number of ommatidial units with long crystalline cones and dark instead of reflecting accessory pigment; and finally, the gammarid type can be interpreted as a generalized amphipod type. The lysianassid type is adapted to low light intensities and demonstrates convergent development with the compound eyes of other deep-sea crustaceans. The ampeliscid type is more similar to the gammarid type. The type characterization of the amphipod compound eye might well serve as a basis and incentive for functional studies also revealing adaptational mechanisms.This paper is dedicated to Professor Erik Dahl on his 65th birthday and retirement from the Chair of Structural Zoology, Department of Zoology, University of LundThe investigation has been supported by grants from the Swedish Natural Science Research Council (Grants 2760-009 and 009-43). Our thanks are due to the staffs of the marine biological stations in Espegrend (Norway) and Kristineberg (Sweden) and of the research vessel Jean Charcot, Brest, France. The skilled technical assistance of Mrs. Rita Wallén and Miss Maria Walles is gratefully acknowledged     

Cyclic AMP formation of isolated human corpora lutea in response to HCG - interference by PGF2 alpha.

Human corpora lutea of defined ages were excised at operation, cut into pieces and incubated in the presence of HCG, PGF2 alpha and PGE2 alone or in combination. Following incubation cAMP formation in tissue and medium was determined. HCG-stimulated tissue cAMP content was most pronounced at a corpus luteum age of 7-10 days after ovulation. This stimulation was antagonized by PGF2 alpha in corpora lutea older than 6 days. PGE2 stimulated cAMP formation per se and this effect was more pronounced when HCG and PGE2 were combined. A possible role for PGF2 alpha as a luteolytic substance in the human is suggested.