PubMed Health⌕ Search

Biomedical subjects

L R Sweney

Publications and source records attributed to L R Sweney.

10 recordsLinked to original sources
PubMed1981

One to one correlation of histological and histochemical light microscopy with scanning electron microscopy.

Several histological stains were applied to specimens after scanning electron microscopic (SEM) processing. Histochemical stains were applied before SEM fixation. After staining, the specimens were processed and dried by SEM techniques. The specimens were taped to a microslide, specimen side up, scribed and covered with immersion oil. After light micrography (LM), the oil was removed and the specimens mounted and gold coated. The same cells were then relocated and photographed by SEM. Periodic acid Schiff was not usable as a specific tissue aldehyde stain, but did prove to be a useful counterstain for dehydrogenase stained specimens. Colloidal iron, as seen by SEM, resulted in a non-specific granular deposit over the specimen and the substrate. All the other histological stains examined--alcian blue, Grams, Feulgen and toluidine blue--were specific and did not change the specimen ultrastructure. The histochemical stains--acid and alkaline phosphatase and three dehydrogenases--were also specific. There were some minor ultrastructural changes with the AcPase and AlPase stains. However, the tissue surface was not significantly distorted. These and other techniques should prove to be a useful adjunct to SEM studies.

Amniotic Fluid↗
PubMed1980

Differentiation of myoepithelial cells in the developing rat parotid gland.

Parotid glands of rats were prepared for light and electron microscopy and for the histochemical demonstration of myofibrils and alkaline phosphatase (AkPase) activity. Through 18 days in utero, the epithelial cells of the developing gland remain relatively undifferentiated. At 20 days in utero, a few cells in the outer layer of the terminal buds and adjacent segments of ducts acquire a cilium, the initial indication that they are differentiating into myoepithelial cells (MEC). Up until the time of birth, the only additional characteristics of MEC that the outer cells develop are to flatten against the underlying cells, begin to send out processes, and produce a few dilated cisternae of rough endoplasmic reticulum. Myofibrils and AkPase activity are first detected at the light microscopic level at five days after birth, around both the developing acini and intercalated ducts. Progressive increases in AkPase activity and in the size and number of myofibrils continue until the acini and intercalated ducts are invested with well-differentiated MEC at 15 days. Subsequently, as the acini undergo maturation during the weaning period (18-25 days), the MEC cease to surround the acini and assume the adult pattern of investing only the intercalated ducts. The pattern of MEC differentiation in the parotid gland differs from those in the sublingual and submandibular glands of the rat in several important respects. They begin to differentiate last, yet mature almost as early as do the MEC of the sublingual gland; they begin to differentiate prior to, rather than simultaneously with, the secretory cells; and their distribution changes as the acinar cells become mature.

Animals↗
PubMed1979

Scanning electron microscopy of uncoated human metaphase chromosomes.

Human metaphase chromosomes were processed with a 3% glutaraldehydetannic acid technique and examined in a scanning electron microscope at 20 kV either without added metal coating or with 2 nm of sputtered gold coating. Several substrates--aluminum mnium foil, silver mirror deposit and sputtered gold-provided good conductive backgrounds for chromosomal spreads. Silver mirror deposit was the best conductive substrate tested. This method should prove to be a useful tool for monitoring the three-dimensional morphology of mitotic chromosomes with the possibility of studying various banding techniques, chromosomal uncoiling and secondary constrictions currently being examined in chromosomal studies.

Aluminum↗
PubMed1977

Rapid preparation of uncoated biological specimens for scanning electron microscopy.

We have developed a relatively rapid glutaraldehyde-tannic acid (GTA) and osmium tetroxide (OsO4) fixation procedure which permits many types of uncoated biological specimens to be examined in the scanning electron microscope (SEM) at 20 kV without the occurrence of charging. Most specimens taken one day can be examined in the SEM the following afternoon. Types of specimens successfully treated were perfused adult and embryonic rat tissues, confluent human skin fibroblast tissue cultures, plant roots, flowers, seeds, some garden insects, and microcolonies of salivary streptococci. Cells in suspension and extracted human teeth did become electron conductive when treated with the GTA procedure. Most suspended cells must be centrifuged between each solution and the GTA procedure increases the preparation time for these cells. Extracted teeth are usually simply dried and coated. Therefore, the usual SEM preparation techniques are shorter and perhaps more useful for these types of specimens.

Animals↗
PubMed1976

Changes in diet and patterns of feeding activity of developing rats.

The purpose of this study was to determine the amount of milk and stock diet consumed by rats during postnatal development and the extent to which they feed in circadian rhythms when weaned naturally by their dams or when separated from their dams at age 21 days. One approach used in several experiments was to record feed bin weight losses at circadian intervals. The second approach was to analyze the stomach contents of rats killed at circadian intervals at representative ages. Contents were inspected, freeze-dried, weighed and assayed for fat by extraction with solvent. The difference in fat between rat milk solids and stock diet was the basis for estimating proportions of stock diet and milk. The results indicate that 1) natural weaning occurs progressively from 14 to 30 days after birth, with an accelerated phase between 18 and 25 days; 2) pups up to 8 days old and their dams feed mostly by light and darkness, respectively; 3) circadian variations in feeding are weak and inconsistent in 10 to 20 day old pups and their dams; 4) at 21 days pups and dams begin to feed mostly in darkness; 5) the proportions of food consumed by light and darkness approach those of the adult by age 29 days when rats are weaned naturally, and by 25 days when weaned at 21 days; and 6) progression into the nocturnal feeding pattern may be disturbed if larger litters are not provided with sufficient space.

Age Factors↗