Innervation of the hamster Harderian gland.

Harderian glands of male and female hamsters have nerve endings associated with the secretory cells, myoepithelial cells, and the blood vessels. The nerve endings adjacent to the myoepithelial cells also have myoneural junctions.

Age-dependent changes in the cellularity and ultrastructure of the spleen of Fischer F344 rats.

The age-related changes in the cellularity (cells/gram of tissue) of the spleens and thymuses of Fischer F344 male rats were determined. A decline in the weight of the thymus with age was observed as previously reported by others. The decline was most drastic between 4 and 20 months of age. The spleen, however, increased in weight with age. The increase was almost linear between 4 and 30 months of age. Yet when the number of cells recovered from each organ as a function of age was determined, a decrease for both the thymus and the spleen was observed with increasing age. It was surprising to find that fewer cells were recovered from the spleens of old animals even though the weight of the spleen of the old animals was greater than the spleens from the younger animals. The ultrastructure of the splenic white pulp of rats ranging from 4 to 30 months of age was studied to determine the possible cause for the age-related decrease in cellularity of the spleen. The white pulp of the 4-month-old rats contained a large number of small lymphocytes, and the number of cells was found to decrease with increasing age. The 30-month-old animals had less than 20% the number of lymphocytes in the white pulp as the 4-month-old animals, and the white pulp exhibited an increased number of reticular cells and macrophages with enlarged cytoplasm. The decreased cellularity and increased structural disturbance might be significant in the age-related decline of spleen lymphocyte functions.

Age-related changes in the corneal endothelium of the mouse.

The endothelial cells of the C57BL/6J mouse cornea show a progressive age-related increase in cell area, and an increasing departure from the initial hexagonal form. Mean endothelial surface areas were 304, 386, 458, 499, and 653 micron2 for mice of ages 1, 4, 11, 22, and 27 months, respectively. Increasing cell areas are interpreted to represent a spreading and thinning of surviving cells to compensate for cell loss. These age-related changes correspond to those previously observed in the rat, although the rat endothelial cells tend to have smaller cell areas and show less variation at each age studied.

Age-related changes in the corneal endothelium of the rat.

The endothelial cells of the rat cornea show a progressive decline in numbers and an increase in pleomorphism from age 6 months to 30 months. These age-related changes correspond closely to those reported in the human cornea from approximately age 20 to age 70 years. The corneal endothelium may be found useful as an index of physiological aging in these and other mammals.

Unique morphogenesis in Saccharomyces cerevisiae strain GS1731.

During the lag and early exponential phase of growth, 50-60% of budded cells of Saccharomyces cerevisiae strain GS1731 were multiply budded. During subsequent culture growth, the frequency of multiply budded cells decreased until by stationary phase multiply budded cells were rare. Data from renewed growth of a culture after hydroxyurea treatment indicated that GS1731 mother cells could assemble up to three pre-bud sites and begin bud growth and development in each. Light and scanning electron microscopy showed two or three very small buds emerging simultaneously on a mother cell and either reaching full size at the same time or enlarging sequentially. Immunofluorescence studies revealed that these multiply budded cells had multiple bundles of cytoplasmic microtubules. DAPI staining of nuclei revealed that some of the unbudded mother cells were multinucleate and completed cytokinesis giving rise to normal daughter cells.

Electron microscopic observations of polysaccharide components in polymyxin B treated outer membranes from Serratia marcescens.

Treatment of outer membranes of Serratia marcescens with polymyxin B results in the formation of blebs. This effect is thought to be due to the action of the antibiotic on the lipopolysaccharides, proteins, phospholipids or a combination thereof. It is unclear whether this effect is dissociative, degradative or due to an inhibition of the assembly of outer membrane components. Prior studies showed that lipopolysaccharides and polymyxin B form complexes, but direct visualization of the in situ action of polymyxin B had not been accomplished. Isolated outer membranes normally exhibit a periodicity of the polysaccharide molecules when stained by the thiosemicarbazide-silver technique. Polymyxin B treated outer membranes display a change in their basic morphology. This effect is very drastic in the sensitive strain as demonstrated by the large gaps in the deposition of the granules in the modified outer membrane structure. Thus it appears that the polysaccharide molecules (probably the lipopolysaccharide) either alone or in association with protein or phospholipids are the primary targets of the antibiotic.

Annulate lamellae in hamster pineal gland.

Pineal glands from young adult hamsters (Mesocricetus auratus Water-house) kept on a 14-10 light-dark photoperiod contain annulate lamellae. These annulate lamellae are apparently limited to the light pinealocytes. They are found in close proximity to nuclei, the Golgi apparatus, and agranular endoplasmic reticulum. There is also an interesting association or microtubules with the annulate lamellae. It seems reasonable that the presence of annulate lainellae in the pinealocytes may have some correlation with the physiological function or functions of these cells.

Effect of melatonin implants on gonadal weights and pineal gland fine structure of the golden hamster.

Weekly subcutaneous implants of melatonin in a beeswax pellet prevented the testicular regression which normally occurs in hamsters exposed to short photoperiod for 8 weeks. Normal (14L:10D) hamster testes were indistinguishable from the testes of melatonin-treated (1L:23D) hamsters. The exogenous melatonin had varied effects on the fine structure of the golden hamster pineal gland. Pineal ocyte nuclear characteristics of melatonin-treated hamsters (smaller average diameter, less polymorphism, and more heterochromatin) as well as apparent reductions in the amounts of hypertrophic SER and lipid moieties seemed to indicate that melatonin caused inhibition of pineal gland activity, and in this respect counteracted the effects of short photoperiod. However, an apparent increase in the number of large mitochondria, membrane whorls and dense-cored secretory vesicles in pinealocytes of melatonin-treated hamsters suggests enhanced pineal gland activity.

delta-Aminolevulinate synthase activity in the Harderian glands of male and female golden hamsters.

1. delta-Aminolevulinate (A1A) synthase activity was determined in the Harderian glands of male and female Golden Hamsters. 2. The enzyme activity was higher in the female gland than in the male gland. 3. The data suggest that the higher enzyme activity is, at least partly, related to the higher porphyrin content in the female gland. 4. This enzyme activity has not been reported in the male gland previously.

The androgenic effect on the fine structure on the Harderian gland in the male hamster.

A sexual dimorphism of the hamster Harderian gland at the ultrastructural level has been reported. The effect of testosterone on the fine structure of the gland from castrated male golden hamsters is reported here. Harderian glands from the following three groups of animals were examined at regular intervals up to 60 days after castration: (1) castrated; (2) castrated-sham-injected, receiving 0.1 ml sesame oil per day; (3) castrated-testosterone-injected, receiving 2 mg testosterone propionate in 0.1 ml sesame oil per day. In groups 1 and 2, clusters of cylindrical tubules, typical of the male gland, decreased in number and disappeared almost completely 2 wailed in these two groups throughout the remaining period of experiment. On the other hand, these changes were prevented in the group of castrated animals maintained on testosterone propionate. It is concluded that castration modified the ultrastructure of the male hamster Harderian gland toward the female type and that daily administration of testosterone propionate prevented this change.

Effect of testosterone on the female hamster Harderian gland pigmentation and ultrastructure.

Distinct differences occur in the pigmentation and ultrastructural features of the Harderian glands in male and female hamsters. The results of a study on the effect of testosterone on the fine structure of the female Harderian glands are presented here. Glands from three groups of hamsters were examined at intervals up to 49 days: (1) testosterone injected, receiving 2 mg testosterone propionate in 0.1 ml sesame oil per day; (2) sham-injected, receiving 0.1 ml sesame oil per day; (3) untreated controls. Testosterone injections caused a reduction in the number of dark-brown pigment granules in the acinar cells starting on the 6th day, whereas clusters of tubules, typical of adult male glands, appeared on the 4th day and increased in number thereafter. Lamellar structures, normally present in the female gland, decreased in testosterone treated specimens. These changes reversed after cessation of testosterone treatment. It is concluded that exogenous testosterone administered to female hamsters modifies the pigmentation and ultrastructure of their Harderian glands towards the male type and that this is a reversable phenomenon. There also appears to be an inverse relationship between the presence of tubular clusters in the acinar cells, and the degree of pigmentation.

A SIMPLE TUMBLING DEVICE USED IN PREPARING ALGAL SPECIMENS FOR ELECTRON MICROSCOPY.

Screw cap vials are held in a wooden holder which rotates at a 90° angle to the horizontal. The. shaft of a small electric motor with built-in gear box is attached perpendicularly to the wooden vial holder via a hole drilled in the center of the wooden holder. The rotation of the vial holder is about 6 rpm. This motion ensures a thorough tumbling of the contents of the vials. Even viscous embedding media are kept in constant agitation, which provides for superior penetration of the tissue. Tumbling devices to hold a range of vial sizes can be constructed with a minimum of labor at a cost of $10-20 each.

Methicillin-resistant septal peptidoglycan synthesis in a methicillin-resistant Staphylococcus aureus strain.

In a methicillin-resistant Staphylococcus aureus strain, electron micrographs showed that cell wall septa continued to be formed in the presence of methicillin, although they became distorted and enlarged. The results indicated that peripheral cell wall synthesis was inhibited. It is concluded that a methicillin-resistant mode of septal peptidoglycan synthesis is an important determinant of methicillin resistance.

Effect of 2,4-dichlorophenoxyacetic acid on the structure and function of developing chloroplasts.

Dark-grown radish seedlings (Raphanus sativus L.) were sprayed with 10(-3) mol·l(-1) 2,4-dichlorophenoxyacetic acid and then were exposed to a 14:10 light: dark cycle. Cotyledon samples from these seedlings and unsprayed controls were taken for electron microscopy, chlorophyll determinations, and photosynthetic rate measurements at regular intervals for 72 h. A normal development of etioplasts to chloroplasts with formation of typical grana-fret work system was observed in the control cotyledons. The chloroplasts in the 2,4-D-treated cotyledons showed changes in the organization of the grana thylakoids; these thylakoids being more appressed to each other than in the controls. The chlorophyll content of treated plants was less than that of controls but the rate of chlorophyll biosynthesis was unaffected. The photosynthetic rate/mg chlorophyll was considerably higher for treated plants suggesting that 2,4-D treatment resulted in decreased size of the photosynthetic unit.

An ultrastructural survey of the genus Prototheca with special reference to plastids.

An ultrastructural investigation of six different species of Prototheca showed that all of them contained starch grains enclosed in double-membrane-bounded structures recognized as plastids. It is concluded that these unicellular species of Prototheca must be considered as non-photosynthetic algae.

Influence of short photoperiods on the ultrastructure of hamster Harderian glands.

A sexual dimorphism of the hamster Harderian gland at the ultrastructural level, has been reported. Castration of males and the administration of testosterone to females are known to alter the male type gland to the female type and vice versa. In this paper we present data that exposure to a short photoperiod (1L:23D) can induce similar structural alterations between the 4th and 10th week of exposure. Changes in the male included reduction in the number of tubular clusters and large vacuoles, while in the female the number of membrane formations decreased with an accompanying appearance of tubular clusters.