Autoradiographic localization of subcomponents of the macromolecular GABA receptor complex

The autoradiographic localization of subcomponents of the gamma-aminobutyric acid (GABA) receptor-chloride ionophore complex has provided insight into the distribution of this macromolecular system. GABA inhibits neurons by preferentially increasing the permeability of the affected membrane to chloride ions. This inhibition can be modified by the presence of other substances which bind to the GABA receptor complex. Autoradiographic localization of specific receptor subtypes associated with this complex has been accomplished in the central nervous system. This type of analysis has been performed on high and low affinity GABAA, benzodiazepine (BZ; both BZ1 and BZ2) and convulsant sites. These receptor sites are situated in distinct brain regions and co-exist in several areas. Other receptor subtypes, which may be influenced by the presence of GABA, can be analyzed for comparison in order to define regions of the brain where GABA may be exerting independent effects (i.e., those not associated with chloride channels). Microscopic localization of receptor sites indicates specific areas to investigate in further studies concerning the characterization of subcomponents of the macromolecular GABA complex associated with chloride ion channels.     

Production of platelet-activating factor by washed rabbit platelets

Production of platelet-activating factor by washed rabbit platelets under stimulation with the ionophore A23187 was investigated utilizing two groups of platelet preparations. The first platelet preparation contained 0.03 +/- 0.02% contaminating white cells, while the second preparation contained 0.48 +/- 0.27% white cells. The latter preparation produced platelet-activating factor, mainly 1-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, 8.3 +/- 6.3 pmol (mean +/- standard deviation) with a range of 2.6 to 21.4 pmol (n = 9), followed by small quantities of 1-octadecenyl- and 1-octadecyl-2-acetyl-sn-glycero-3-phosphocholine. In contrast, there was no production of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine by the former platelet preparation having 0.03% leukocytes. These quantitative analyses were carried out by the selected ion monitoring technique and it was concluded that it is necessary to consider the presence of contaminating white cells in studies on the production of platelet-activating factor by platelets.     

Peroxisomes in sebaceous glands. IV. Aggregates of tubular peroxisomes in the mouse Meibomian gland

The occurrence of peroxisomes, their morphogenesis during the process of sebaceous transformation and their spatial relationship to the endoplasmic reticulum and lipid droplets were investigated by light and electron microscopy after visualization of the peroxidatic activity of catalase using an alkaline diaminobenzidine medium. The morphological alterations of peroxisomes display a characteristic sequence: During cellular differentiation, a remarkable proliferation of exclusively tubular, diaminobenzidine-reactive peroxisomes occurs. As maturation proceeds, an extensive elongation of tubular peroxisomes is seen. Concomitantly, they are densely packed in a regular, hexagonal arrangement and both the diameter and the catalase content gradually decreases. The most conspicuous feature of mature glandular cells are numerous highly organized aggregates of tubular, almost unstained peroxisomes with a diameter of 50 nm, arranged in a hexagonal pattern. They resemble adjacent tubular profiles of smooth endoplasmic reticulum. However, membrane continuities between these two compartments were never observed. During lethal disintegration peroxisomes subsequently decrease in number, probably by rapid sequestration within autophagolysosomes. The role of tubular peroxisomes in the biosynthesis of wax esters in the mouse Meibomian gland is discussed.     

The mechanism of action of 4-hydroxynonenal in cell injury

The effect of the C9 ketoaldehyde, 4-hydroxynonenal (HNE), a cytotoxic product of lipid peroxidation, on DNA, RNA and protein synthesis has been investigated in cells in culture. Macromolecular synthesis is powerfully inhibited by this agent which readily enters the lipid-rich membranes and is considerably more toxic than the polar ketoaldehyde, methyl glyoxal (MG). The entry of HNE into membranes lowers their glutathione GSH content. This is associated with an increased lipid peroxidation measured in vitro which is blocked by added GSH or alpha-tocopherol. It is proposed that this latter sequence of events is the underlying cause of the cytopathic effect of HNE in cells in culture.     

LH concentrations in two cattle with XY gonadal dysgenesis

Two animals with XY gonadal dysgenesis both had a reproductive tract similar in size to that found in sexually immature heifers, but neither had normal testicular or ovarian tissue. All cells examined in both animals contained XY chromosomes and spinal cord neurones were sex chromatin negative. Basal LH concentrations averaged 3.1 ng/ml in Animal 1 and 2.4 ng/ml in Animal 2 but increased within 12 h of injecting oestradiol to peak concentrations of 125 and 11 ng/ml respectively. Animal 1 displayed a distinct pulsatile LH release pattern with a highly repeatable decline phase at each pulse. A GnRH injection produced a rapid rise in plasma LH in both animals, sustained in Animal 1 at greater than 500 ng/ml for more than 2 h. Each animal displayed behavioural symptoms of oestrus within 12 h of being injected with 3 mg oestradiol benzoate and was repeatedly served by a bull. These studies indicated that both animals differed from freemartins and had some hypothalamic and pituitary response patterns resembling those reported for female cattle.     

Cosinor analysis of diurnal changes of the reduced glutathione level in the blood, brain, liver and kidneys of mice, induced by ACTH administration

The influence of a single dose of ACTH(100 I.U. /kg body weight) on the diurnal rhythm of reduced glutathione (GSH) was studied in the blood and brain, liver and kidney homogenates of male mice. Cosinor analysis revealed that ACTH induces changes in the mean diurnal amount of GSH in the blood, brain, liver and kidneys. At the same time, GSH amplitudes in the blood and kidneys increased significantly, whereas in the case of brain and liver they decreased markedly. Moreover, it was found that ACTH induces a shift in GSH acrophases in the blood, brain, liver and kidneys as compared with the control values.