John J. Taylor

An ultrastructural study of the role of calcification nodules in the mineralization of woven bone

SummaryOsteolathyrism has been used as an experimental model for the study of calcification nodules during the mineralization process. Periosteal exostoses developing in osteolathyrism characteristically have spherical basophilic structures (calcification nodules) in the vicinity of developing bone spicules. In thin sections, the nodules were seen scattered between collagen fibers in the intercellular matrix. Collagen fibers did not appear to be present within the nodules but sometimes were packed just outside them. Matrix vesicles were also present in areas of early mineralization.After EDTA decalcification, the majority of the nodules consisted of a fine granular material surrounded by an electron-dense peripheral zone. The peripheral dense zone was occasionally incomplete in small nodules in areas of early mineralization. An electron-dense central area could be observed in the center of the nodules.Evidence has been presented indicating that the calcification nodules arise from smaller mineralization foci, presumably matrix vesicles. The calcification nodules enlarge to approximately 1.0 µm in size, at which point development is slowed or halted allowing the formation of the peripheral dense zone.Although coalescence of nodules was observed, this was more a random event. The further mineralization of the trabeculae was achieved by the calcification of the collagen fibers. The mineralized trabeculae reflected this pattern of nodular and collagenous calcification. It is suggested that this pattern of calcification is characteristic of rapidly developing woven bone.

Effect of chronic administration of nicotine on acetylcholinesterase activity in the hypothalamus and medulla oblongata of the rat brain. An ultrastructural study

Abstract Acetylcholinesterase (AChE) was found to be mainly localized in the perinuclear space and in the cisteranae of the rough surfaced endoplasmic reticulum in the neurons of the posterior hypothalamic nucleus and the hypoglossal nucleus of the rat brain. Enzyme activity was also noted in the neuroglial cells. Chronic administration of nicotine (1 mg/kg, subcutaneously 5 times a day for 8–16 weeks) decreased the AChE activity in the perinuclear space and in the rough surfaced endoplasmic reticulum of the neurons of the hypoglossal nucleus. Since experiments were performed 12 h after the last injection of nicotine when no or very little nicotine was left in the brain, it is concluded that administration of nicotine exerts a sustained decrease in AChE in the neurons of the hypoglossal nucleus of the medulla oblongata of the rat brain.

Ultrastructural changes in chick cerebellum induced by vitamin E deficiency

SummaryFocal lesions were induced in the cerebellum by feeding chickens a diet high in unsaturated fats and deficient in vitamin E. Ultrastructurally, the lesions consisted of central and peripheral zones. The central zone was characterized in the cortex and white matter by enlargement of the intercellular space, swelling of astrocytes, vacuolization of oligodendrocytes, ballooning of nerve fibers, degenerative changes in small blood vessels, and extravasation of plasma and blood cells. The peripheral zone was characterized by enlargement of the intercellular space in the white matter, swelling of astrocytes in the cortex, and the accumulation of dark bodies in the endothelium of small blood vessels. The results suggest that this nutritional encephalopathy is caused by alterations in the permeability of the vascular bed due to the dietary stress of unsaturated fatty acids in the absence of vitamin E.

Central nervous system demyelinating diseases and increased release of cholesterol into the urinary system of rats.

The question of what happens to cholesterol in the adult central nervous system during its slow turnover has been addressed using rats with brain and spinal cord labeled with [4-14C]cholesterol upon intracerebral injection of labeled cholesterol into rats at 10–12 days of age. At six months after injection,14C was found only in the brain and spinal cord and was slowly releasedvia the rats urine. When labeled rats were given demyelinating agents (triethyl tin chloride, hexachlorophene, sodium cyanide) and when experimental allergic encephalomyelitis was induced, a measurable increase in urinary14C label above control levels was found. It was concluded that there is a direct relationship between the experimental demyelination induced and the increased release of cholesterol metabolites into urine. The study suggests that a clinical method could be developed to determine the rate of central nervous system demyelination by measuring the amount of urinary cholesterol metabolites.

Bone Resorption by Osteocytes

Summary Osteocyte lacunae were measured in normal rats and in rats in which periosteal hypertrophy had been induced at the adductor longus-pectineus insertion. Lacunae in the cortex beneath the periosteal hypertrophy were significantly larger than lacunae in the cortex of the opposite side of the femur from the hypertrophy. Lacunae in both sides of the femoral cortex of experimental rats were significantly larger than lacunae in the cortex of normal femur. This supports the view that the osteocyte is capable of resorbing bone.

Electron-microscopic study of the maturing rat red nucleus

The maturing large neurons of the rat red nucleus in animals ranging in age from 1 to 21 days of postnatal life were studied ultrastructurally. Days 1–6 were characterized by rapid morphologic maturation occurring concomitantly with the onset of synaptogenesis. Morphogenesis was confined to the soma, while the first synaptic contacts were also formed in relationship to the soma. Days 6–9 demonstrated continued somal morphogenesis exemplified by cytoplasmic expansion and by the conspicuous presence of perisomatic and growth cone processes. Proximal dendritic morphogenesis was initiated, and synaptogenesis became complex with synaptic sites occurring in relation to the neuronal soma, the perisomatic processes and proximal dendrites. Days 9–15 were characterized by the completion of somal and proximal dendritic morphogenesis and by a massive degree of synaptogenic activity. During this interval, the soma lost perisomatic and growth cone processes, while somatic spines appeared. By the end of this period the neuronal soma and the proximal dendrites appeared mature in terms of both morphology and synaptic input. Complete neuronal maturation was ultimately attained by day 21 of postnatal life.

Lathyrism and Aging

Summary The effect of BAPN on traumatized and nontraumatized periosteum in rats of 1, 3, or 15 months of age was studied. The BAPN caused marked hypertrophy of nontraumatized periosteum in 1-month old rats but not in 3- or 15-month old rats. Response of traumatized periosteum to BAPN was similar in all 3 age groups. It is concluded that BAPN acts on newly formed collagen irrespective of age, but does not act significantly on mature collagen.

Psychosocial Outcomes of Participating in Pediatric Diabetes Camp

OBJECTIVE There are approximately 18,400 youth who are newly diagnosed with Type 1 diabetes mellitus (T1DM) in the United States each year. Because of the potential for hypoglycemia, frequent need to monitor blood glucose, and other medical care associated with T1DM, children may not be able to participate in the typical summer camp experience. The aims of this study were (1) to evaluate the impact of camp on the childs attitude toward their illness, (2) to evaluate the childs confidence in self-care management of their diabetes, (3) to assess the childs perception and satisfaction with the camp experience, and (4) to evaluate the perception of camp experience by the parents. DESIGN AND SAMPLE Thirty-eight parent-child dyads participated in a pretest, posttest quasi-experimental research study evaluating the benefits of a camping experience for the child with T1DM. RESULTS Pre- and postcamp comparisons revealed improved attitude toward illness and improved self-efficacy after the camping experience. CONCLUSION Results of the study support the psychosocial benefits of a camping experience for children with T1DM. Findings from the study can be used by health care providers as evidence to support the benefits of sending children with T1DM to residential summer camp.

Neurofibrillary tangles in experimental neurolathyrism in rats induced by imino-dipropionitrile (IDPN)

SummaryAnterior horns of the spinal cord from cervical and lumbar regions and dorsal root ganglia from these same levels were studied for ultrastructural changes in imino-dipropionitrile (IDPN) treated rats. Normal saline-injected rats, treated identically, served as controls for this study. In the spinal cord axonal balloons or dystrophic axons appeared in lightly myelinated or unmyelinated axons within 24 h after the third injection of IDPN. At this time hind leg paralysis had not yet developed. In addition to axonal changes, a few dendrites also showed neurofibrillary degeneration. Central chromatolytic changes were observed in most of the neurons, with evidence of generalized edema present within the cord. In the dorsal root ganglia axonal balloons were very prominent and showed neurofibrillary hypertrophy. Neurofibrillary material was also noted in the perikarya of medium-sized ganglion cells.

Suppression of Connective Tissue Impregnation in a Silver Technique for Demonstrating Nerve Fibers

A tissue pretreatment is introduced which effectively suppresses the silver impregnation of connective tissue and nonspecific background elements in peripheral nerve. The result is a selective impregnation of nerve fibers. The procedure utilizes fresh frozen sections and can be used with the Holmes (1947) or Bodian (1936) techniques. Fresh frozen sections are cut at 10 microns, mounted on slides and air dried for 5 minutes. They are fixed for 30 minutes in formol-sublimate (10% formalin saturated with mercuric chloride) and then placed into 0.5% iodine in 70% alcohol for 5 minutes followed by bleaching in 2.5% sodium thiosulfate for 2 minutes. After washing in running tap water for 10 minutes and a brief rinse in distilled water, impregnation is accomplished by the Holmes (1947) or Bodian (1936) procedure beginning with the step containing the aqueous silver solution. The results show an absence of impregnation of connective tissue and nonspecific background. The technique is simple, rapid, and, by utilizing fresh frozen sections, can be used for other histological and histochemical purposes. Several experiments were done to determine the causes of the connective tissue and background suppression. The air drying step was omitted; the sections were fixed in formalin without mercuric chloride; and the formol-sublimate fixation time was increased. The results suggest that connective tissue impregnation is suppressed by the use of mercuric chloride in the fixative and that the background suppression is related to the short fixation time with formolsublimate.