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.     

Characteristics of microbial association in secretions of various mammalian sebaceous glands

The following secretions of mammalian skin glands were subjected to a microbiological survey: the middle-abdominal glands of great and Mongolian gerbils, the preputial gland of musk deer, the perineal organ of African civet cat, the interdigital skin regions and interdigital glands of bison, European bison, European roe deer, and musk deer. All the secretions were found to contain microbial associations. The composition of bacterial species in the secretions and the quantity of microorganisms varied among different animal species, during the ontogenesis of an animal, and depended on the topography of a gland on an animal body as well as on its functional state in different seasons or upon hormonal changes. The secretions of certain glands contain factors which determine the composition of microbial species in a particular ecological niche and the stability of such a cenosis.     

Seasonal changes in the pineal gland related to the reproductive cycle in the male hare, Lepus europaeus.

During the autumn months, the gonads and reproductive tract of adult male hares (Lepus europaeus) are regressed and circulating gonadotrophin levels are low. At this time the pineal glands are most active as judged by the organ size, and the nuclear and cytoplasmic size of the pinealocytes. There was an inverse relationship between the size of the pineal gland and the weight of the testis, the plasma and testicular testosterone levels, and possibly also the plasma LH levels.     

The occurrence of mountain hare mitochondrial DNA in wild brown hares

If interspecific hybrids are fertile and backcross to either parental species, transmission of mitochondrial DNA over the species barrier can occur. To investigate if such transmission has occurred between the brown hare Lepus europeus Pall and the mountain hare L. timidus L. in Scandinavia, an analysis of genetic variation in mitochondrial DNA from 36 hares, collected from 15 localities, was performed. Sequence divergence of mtDNA between species was estimated at 8 ± 1% (SD). Intraspecific mtDNA sequence divergence varied between 0.09 and 0.38% in brown hares and 0.10 and 1.44% in mountain hares. In six out of 18 brown hares examined, two different haplotypes of mountain hare origin were detected, demonstrating a transmission of mtDNA haplotypes from mountain hares to brown hares. The results indicate that interspecific hybridization between the two species occurs in wild populations.     

The measurement of histochemically-stained NADP-dependent isocitrate dehydrogenase in the sebaceous glands of hairless hamster.

The effect of substrate, co-factor and Nitroblue Tetrazolium concentration on the production of formazan by the action of NADP-dependent isocitrate dehydrogenase was studied in the sebaceous glands of the hairless hamster. The measurement (in average optical density units per unit area) of formazan in histochemically stained skin sections was carried out by television scanning microdensitometry (Quantimet 720D). Having established optimal conditions for this enzyme, a second study was carried out to determine the effect of different power objectives and wide-band wavelength light instead of white light on the average optical density per unit area, recorded by the instrument, of the formazan produced in a defined number of sebaceous glands in a single skin section. It was found that there was no difference in the average optical density per unit area recorded by the instrument at different power objectives and a peak value of average optical density per unit area could be obtained using a K4 or a K5 Balzer filter (550-650 nm).     

The diel activity pattern of mountain hare (Lepus timidus) on managed heather moorland in Scotland

The research presented in this paper provides an insight into the behavioral ecology of mountain hares on heather moorland in the Lammermuir Hills of southeast Scotland. We examine the seasonal and diel activity patterns using camera traps over a period of 12 months. The rate of camera detections was calculated for the different divisions of the 24‐hr cycle (daylight, dusk, night, and dawn). During autumn and winter (October–February), the activity pattern was crepuscular with greater activity at dusk than at dawn. Daylight activity was relatively low, and there was a regular pattern of small peaks of activity during the night. In spring and summer (March–September), peaks of crepuscular activity remained evident but daylight activity was much more prevalent than during autumn and winter, and night activity was lower. We discuss the problematic definition of twilight and present an explanation for seasonal changes in the pattern of diel activity that is linked to the reproductive cycle of the mountain hare.     

Oxidative enzymes in the sebaceous glands of the domestic cat

Synopsis The distribution and activities of several oxidative enzymes in various regions of the sebaceous glands of the domestic cat have been studied. The results obtained emphasize the outstanding importance of NADP-linked dehydrogenases for lipogenesis during sebum production. In particular, the reactions for glucose-6-phosphate dehydrogenase were very strong. Among the NAD-linked dehydrogenases investigated, lactate dehydrogenase showed strong activity in the peripheral cells of the sebaceous gland. The reactions for cytochrome oxidase and succinate dehydrogenase were weaker.     

Hydrolytic enzymes in the sebaceous glands of the domestic cat

Synopsis The distribution and activities of some hydrolytic enzymes in various portions of the sebaceous glands of the domestic cat have been studied. The results point to the outstanding importance of non-specific esterases and lipases for sebum production, which generally appears to be abundant in thickly-haired mammals. The activities of the lysosomal enzymes demonstrated were connected with autolytic processes during sebaceous gland cell differentiation. There was a strong arylsulphatase reaction in the sebum of the sebaceous gland excretory ducts.     

The 24-hour cycle of the mountain hare Lepus timidus Linnaeus, 1758

The behavioral decisions of wild animals are influenced by the often conflicting needs to both feed efficiently and to avoid predators. Information regarding how lagomorphs such as the mountain hare (Lepus timidus) balance these factors throughout the day-night cycle is largely lacking despite its importance to management.To better understand the type and proportion of various behaviors the mountain hare engages in over the course of a 24-hour period, I monitored the behavior of six mountain hares under controlled conditions from early to mid-winter. The mountain hares spend the majority of their time resting (mean ± standard deviation: 32.4 ± 14.4%) and under canopy (22.4 ± 18.7%), and a smaller proportion of their time feeding (16.2 ± 6.1%). Activity peaks over the course of the 24-hour cycle reflect natural behavior patterns that emphasize the reduction of predation risk. The sunrise phase is characterized by the search for a suitable resting place; the day phase by resting and hiding. The sunset phase is characterized by the search for food, and the night phase by an equal mix of food intake and movement through the home range. These results can help land managers predict how factors such as increasing tourist activity (perceived by the hare as a safety threat) will influence the behavior of free-ranging mountain hares.     

Circadian rhythm of proliferative processes in the sebaceous glands]

The proliferation process indices (such as the mitotic activity 0/00,labelled cell 0/00 and the amoung of mitoses arrested by colchicine 0/00) were studied in two sebaceous glands of rats-the gland of the external auditory meatus and the tarsal sebaceous gland.Ti was established that the diurnal changes of the number of mitotically dividing cells andthe DNA synthesizing cells could be presented as one-peak curves, the maxium falling on the night and morning hours and the minimum-on the day-time and evening. The average diurnalmitotic activity in terminal portions was 16, 3-1, 9 and the average amount of labelled cells was 76, 9-6, 1. In the excretory ducts they were 13, 0-1,6 and 65, 6-5, 4 respectively. The amount of C-mitoses in rats which were given colchicine was 75, 7-5,1 in the morninghours and 58, 1-4, 5% in the evening hours. It permitted to calculate the duration of mitoseswhich were equal to 1, 9 hour in the morning and 1,2 hour in day-time.