Peter J. Gruber

Fine structural investigation of nuclear inclusions in plants.

Light microscopic observations dating back to 1859 have established that nuclear inclusions occur widely in plant and animal cells. The present fine structural investigation describes nuclear inclusions in thirteen species of plants representing ferns, a gymnosperm, and angiosperms. Ultrastructurally the inclusions are quite diverse and include several morphologically distinct types represented by crystalline, fibrous, or amorphous structures. In some species the inclusions commonly attain lengths of several microns and occupy as much as 20–40 % of the median nuclear cross sectional area. In several species inclusions identical to those in the nucleus have been encountered in the perinuclear space and cytoplasm. Histochemical staining indicates that most of the inclusions are proteinaceous, although spherosome-like bodies presumably consisting of lipid have been observed also. Dissimilarities between the proteinaceous inclusions described here and inclusions observed previously in virus-infected plants are summarized. In many species the inclusions appear to be related to the nucleoli, either through close association or through an inverse size relationship shown during development. In a fern, observations made during cell differentiation indicate that the appearance of nuclear inclusions may coincide with dissolution of the nucleolus. Attention is directed to the possible similarity between the formation of nuclear inclusions in plants and the segregation of material from the nucleolus in animal tissues treated with actinomycin D.

Some biological issues in oral, controlled drug delivery

Abstract Some of the significant biological issues relating to the oral, controlled delivery of drugs have been discussed. Examination of the problem has largely concentrated on macromolecular drugs such as polypeptides and proteins. The prime considerations highlighted concern the presence of both normal and pathological physiological responses and various anatomical (epithelial) barriers which combine to present modern effective drug delivery with formidable problems. Various strategies for overcoming these barriers have been suggested, including (a) localization of dosage form in regions of the GI tract where protease activity is minimal; (b) inhibition of protease activity; (c) reduction in macromolecule potential complexation with immunoglobulins; (d) masking of the antigenicity of protein drugs; and (e) promotion of lymphatic uptake by selected mechanisms.

A correlative ultrastructural and enzymatic study of cotyledonary microbodies following germination of fat-storing seeds.

SummarySunflower, cucumber, and tomato cotyledons, which contain microbodies in both the early lipid-degrading and the later photosynthetic stages of post-germinative growth, were processed for electron microscopy according to conventional procedures and examined 1, 4 and 7 days after germination. Homogenates of sunflower cotyledons were assayed for enzymes characteristic of glyoxysomes and leaf peroxisomes (both of which are defined morphologically as microbodies) at stages corresponding to the fixations for electron microscopy. The particulate nature of these enzymes was demonstrated by differential and equilibrium density centrifugation, making it possible to relate them to the microbodies seen in situ.One day after germination, the microbodies are present as small organelles among large numbers of protein and lipid storage bodies; the cell homogenate contains catalase but no detectable isocitrate lyase (characteristic of glyoxysomes) or glycolic acid oxidase (characteristic of leaf peroxisomes). 4 days after germination, numerous microbodies (glyoxysomes) are in extensive and frequent contact with lipid bodies. The microbodies often have cytoplasmic invaginations. At this stage the cells are rapidly converting lipids to carbohydrates, and the homogenate has high isocitrate lyase activity. 7 days after germination, microbodies (peroxisomes) are appressed to chloroplasts and frequently squeezed between them in the green photosynthetic cells. The homogenate at this stage has substantial glycolic acid oxidase activity but a reduced level of isocitrate lyase. It is yet to be determined whether the peroxisomes present at day 7 are derived from preexisting glyoxysomes or arise as a separate population of organelles.

The occurrence of microbodies and peroxisomal enzymes in achlorophyllous leaves.

SummarySeveral types of leaves of leaf parts lacking chlorophyll were fixed and embedded according to conventional procedures and examined electron-microscopically for microbodies. Comparisons of relative abundance of microbodies, plastids and mitochondria were made by computing the average numbers of organelle profiles per cell section. Similar leaves were homogenized and assayed for three enzymes characteristic of leaf peroxisomes. The localization of these enzymes in microbodies was indicated for the achlorophyllous tissues by the positive result obtained when 3,3′-diaminobenzidine was used as an electron cytochemical stain for catalase activity.Microbodies were present in all non-photosynthetic leaves or leaf parts examined, including yellowish-white segments of variegated leaves, albino leaves, and etiolated leaves of two species. In several cases, the numbers of microbody profiles per cell section were as great in the achlorophyllous leaves as in the chlorophyllous. The levels of peroxisomal enzyme activity in the yellowish-white leaves were substantial, although often not as high as in the green leaves. It was concluded that enzymatically these microbodies are probably similar to the peroxisomes characterized from chlorophyllous leaves. In the absence of the photosynthetic product, glycolate, however, it seems unlikely that the organelle is performing the same functions as in green leaves. It is also apparent that the initial formation of peroxisomes in leaves can occur when neither light nor a photosynthate such as glycolate is present as an inducer.

Improved intestinal cannula for drug delivery studies in the dog

A modified light-weight intestinal cannula, based on the modified Thomas type (Thomas, 1941; Jones et al., 1971) was fabricated and tested. The design extends the useful life of the cannula and expands the versatility of the canine gastrointestinal (GI) system for pharmaceutical and physiological research. The cannula permits easy administration of pharmaceutical dosage forms directly into or access to ingested substances anywhere along the small intestine.