Experimental periodontal breakdown in the dog

abstract – This paper describes a method for inducing rapidly progressing and reproducible periodontal lesions around selected teeth in dogs. The experiments were performed on 10 beagles which were fed a diet favoring gross formation of plaque. Approximately 1 mm of the marginal alveolar bone around ₄P and P₄ was removed and a notch prepared in the root. A ligature of cotton floss was placed around ₄P and P₄ at the cemento-enamel junction. Radiographs and sections prepared 230 d later revealed that a progressive breakdown of the periodontal tissues had occurred. The average bone loss was 2.4 mm and the distance between the apical cells of the pocket epithelium and the notch was 854μm.     

Immunohistochemical localization of peripheral nitric oxide synthase-containing nerves using antibodies raised against synthesized C- and N-terminal fragments of a cloned enzyme from rat brain

Antibodies were raised in rabbits against C- or N-terminal fragments of a cloned nitric oxide synthase (NOS) enzyme from rat cerebellum, and used for demonstration of NOS-immunoreactive (NOS-IR) nerves in different tissues from the rat (colon, duodenum, adrenal gland, aorta, caval vein, penis and urethra). Both antisera demonstrated the same neuronal elements, although with differences in intensity in the immunoreaction in some tissues. Sections incubated with antisera preabsorbed with excess of the antigens showed no NOS immunoreactivity. In duodenum and colon, NOS-immunoreactivity was found in the cytoplasm of numerous cell bodies in myenteric ganglia and in some nerve cell bodies in the submucosa. NOS-IR nerve fibres were numerous in the circular muscle layer, while few were found in the longitudinal layer or the mucosa and submucosa. In the penis, strong NOS immunoreactivity was found in nerves surrounding the deep penile and dorsal arteries, and in nerves in the stroma of the cavernous tissue. In the urethra, NOS immunoreactivity was found in nerves in the mucosa. No NOS immunoreactivity was found in the urothelium. The adrenal medulla, and occasionally the cortex, contained nerve cell bodies with strong cytoplasmic NOS immunoreactivity as well as scattered nerve fibres. No NOS immunoreactivity was found in the abdominal aorta or inferior caval vein. Combined NOS immunostaining and NADPH diaphorase staining showed that virtually all NOS-IR nerve structures were also NADPH diaphorase-positive. However, thin nerve fibres and cell linings were sometimes better visualized by NOS-immunohistochemistry. Furthermore, the adrenal cortex, which only occasionally showed NOS immunoreactivity, was strongly NADPH diaphorase-positive. A positive NADPH diaphorase reaction, but a negative NOS immunoreactivity, was also found in other structures, such as urothelium, epithelial cells in duodenum and colon, and endothelium of some vessels. It is concluded that the antibodies raised against the synthesized sequences of neuronal NOS are highly specific and may be used in immunohistochemistry in order to detect neuronal NOS.     

Cerebrovascular response during and following severe insulin-induced hypoglycemia: CO2-sensitivity,autoregulation, and influence of prostaglandin synthesis inhibition

The objective of the present experiments was to study mechanisms governing cerebrovascular responses during severe hypoglycemia, and in the posthypoglycemic recovery period. To that end, lightly anesthetized (70% N₂O) and artificially ventilated rats were injected with insulin so as to abolish spontaneous EEG activity for 15 or 30 min (“coma”). In separate animals, recovery was induced by glucose administration. Previous experiments have shown that in normo- or moderately hypertensive animals hypoglycemic coma is accompanied by a relatively marked increase in cerebral blood flow (CBF), and that a delayed hypoperfusion develops in the recovery period. The present results demonstrate that oxygen supply is in excess of the demands during coma, and falls below control during recovery. During hypoglycemic coma, the CO₂ response of the circulation was retained but autoregulation was lost. In the recovery period, both CO₂ response and autoregulation were lost. Pretreatment with indomethacin was introduced in order to evaluate the possible influence of fatty acid cyclo-oxygenase products on the pattern of CBF changes. Measurements of local cerebral blood flow (1-CBF) showed that, in the majority of structures analysed, indomethacin failed to modulate the changes in CBF. It is concluded that alterations in cerebrovascular tone and loss of autoregulation induce flow changes that may influence substrate and oxygen availability during hypoglycemia. The pronounced decrease in CBF and the loss of autoregulation and CO₂-response in the posthypoglycemic period may influence functional, metabolic and morphological recovery. The 1-CBF findings indicate that neither the increase in CBF during hypoglycemia nor the reduction in flow in the posthypoglycemic period are mediated by mechanisms related to prostaglandin metabolism.     

Dose-Response Effects of a Web-Based Physical Activity Program on Body Composition and Metabolic Health in Inactive Older Adults: Additional Analyses of a Randomized Controlled Trial

BackgroundLow physical activity is a major risk factor for several age-related diseases. Recently, we showed in a randomized controlled trial that a 12-week Web-based intervention (Philips DirectLife) to increase physical activity was effective in increasing physical activity levels and metabolic health in an inactive population aged 60-70 years.ObjectiveThe goal of this paper was to assess how many participants successfully reached the physical activity level as targeted by the intervention and what the effects of the intervention on body composition and metabolic health in these successful individuals were to provide insight in the maximum attainable effect of the intervention.MethodsAmong the 235 participants in a randomized controlled trial of the Actief en Gezond Oud (AGO) study, we assessed the effects of the intervention on metabolic parameters in those who had successfully reached their personalized physical activity target compared with the entire intervention group. Furthermore, we studied the dose-response effect of increase in physical activity on metabolic outcome within the intervention group.ResultsOf the intervention group, 50 of 119 (42.0%) participants successfully reached the physical activity target (corresponding to a 10% increased daily physical activity on average). This group showed markedly higher effects of the intervention compared to the entire intervention group, with greater decreases in body weight (2.74 vs 1.49 kg), waist circumference (3.74 vs 2.33 cm), insulin resistance (HOMA index: 0.23 vs 0.20), and in cholesterol/HDL ratio (0.39 vs 0.20) and Framingham risk score (0.90% vs 0.54%). We found that men compared to women were more likely to be successful. The dose-response analysis showed that there was a significant association between increase in minutes spent in moderate-to-vigorous activity and body weight loss, BMI reduction, waist circumference reduction, HDL cholesterol increasing, and cholesterol/HDL ratio lowering.ConclusionsOf the intervention group, 42.0% (50/119) reached their daily physical activity end goal, which was associated with a markedly better effect on body composition and metabolic health compared to the effect in the entire intervention group. In this population, men are more likely to be successful in increasing physical activity. Findings demonstrate that improving the effect of such physical activity interventions requires finding new ways to increase the proportion of the population reaching the targeted goal.

Trial Registration

Dutch Trial Registry: NTR 3045; http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=3045 (Archived by WebCite at http://www.webcitation.org/6KPw52dCc).     

Cardiovascular regulation by endogenous nitric oxide is essential for survival after acute haemorrhage

Our previous studies have indicated that endogenous nitric oxide serves as a physiologically important inhibitor of vascular tone during acute haemorrhage. This vasodilator action attenuates the concomitant reflex adrenergic constriction and thereby prevents critical reduction of tissue blood flow. The present study aimed to evaluate the overall importance of this nitric oxide regulation for survival after acute haemorrhage. This was done by comparative observations of survival time and circulatory. metabolic and histopathological changes after an acute standardized lethal blood loss (45%) in cats exposed to nitric oxide synthase (NOS) inhibition and in matched control animals with intact nitric oxide regulation. NOS inhibition was instituted by intravenously administered N-nitro-L-arginine methyl ester. The survival time averaged 2 h 49 min in the NOS-blocked animals and 10 h 14 min in the control animals (P ? 0.001). NOS inhibition thus reduced the posthaemorrhagic survival time to ? 30% of that in the control cats. Haemorrhage in the NOS-blocked animals led to rapidly developing arterial hypotension. increased anaerobic metabolism. metabolic lactacidosis. hyperkalaemia. and morphological tissue damage especially in heart and liver. in spite of maintained arterial normoxia, which signifies tissue hypoxia caused by seriously impaired nutritional blood supply. At the time of death of the NOS-blocked cats. the control animals still exhibited a virtually normal circulatory/metabolic state. A much later. and more slowly developing circulatory/metabolic deterioration was observed in the control animals. These differences between the two groups of animals indicate that nitric oxide release. by its vasodilator action. to a significant extent helps to maintain an adequate nutritional blood supply to the tissues in acute haemorrhage.     

CONGENITAL HYPOTHYROIDISM AND CHANGES IN THE ENAMEL OF DECIDUOUS TEETH

ABSTRACT. Deciduous teeth from children with congenital hypothyroidism were collected and ground sections were prepared. The sections were analysed by means of polarised light and microradiography. The enamel in ground sections of deciduous teeth from children with congenital hypothyroidism showed an increase in areas with elevated pore volume distribution in both the pre- and postnatal enamel. The findings suggest that thyroid hormone influences enamel maturation. Further, alterations in enamel structure, presumably due to prenatal thyroid deficiency, were found to be more common among children with neurological abnormalities at the age of 7 to 9 years.     

Morphologic and Antigenic Maturation of Lymphocytes in the Mouse Thymus In Vitro

A simple technique for organ culture of the thymus of 14-day-old mouse embryos is decribed. It allowed a characteristic time-dependent development of the immature thymus into a lymphoid thymus with large numbers of nondividing small lymphocytes. Most of these cells carried the T-lymphocyte antigenic markers Thy-1 and TL, and all expressed H-2 antigens as determined in cytotoxicity assays. They probably developed from precursor cells without detectable Thy-1 and TL. This development appeared to be dependent on the thymic microenvironment, since it also occurred in serum-free organ cultures and in cultures with medium supplemented with serum from nude mice.