Transmission electron microscopy of early microbial colonization of human enamel and root surfaces in vivo

Abstract – This study describes the early microbial colomization of teeth by the use of light-and transmission electron microscopy. Six dental students carried a total of 60 test pieces of unerupted enamel and root surface in intraoral acrylic appliances for 4, 8, 12, 24 and 48 h, during which periods oral hygiene was abandoned. Pronounced variations were recorded in structure and thickness of the pellicle across the individual surfaces of both dental tissues. Bacterial single-cell colonization increased the electron density of the adjoining pellicle. Micro-colonies of bacteria were observed in relation to enamel surface irregularities such as perikymata, while the distribution on root surfaces appeared incidental. Root surfaces were generally colonized by thicker deposits than homologous enamel surfaces although the structural composition of the microbiota was similar. Gram-positive bacteria with thick cell walls appeared in coccoid or rod-shaped configurations depending on the age of the bacterial deposit. These bacteria were further characterized by selective invasion between collagen fibers. After 48 h the complexity of the microbiota was increased by the establishment of new bacterial species in the superficial layer. It is concluded that the pattern and composition of the early microbiota on teeth is more complex and variable than hitherto assumed.     

Dependency of renal potassium excretion on Na,K-ATPase transport rate

Potassium secretion may depend on the transport rate of Na, K-ATPase in basolateral cell membranes of distal tubular cells. To examine this hypothesis experiments were performed in anaesthetized dogs during inhibition of proximal potassium reabsorption by acetazolamide or mannitol (fractional potassium excretion 1.2-1.4) or additional stimulation of potassium secretion by ethacrynic acid (fractional potassium excretion 2.1). Ouabain in a dose which inhibits 70–80% of the Na, K-ATPase activity reduced fractional potassium excretion to 0.8-0.9 by an effect on distal tubular secretion since potassium transport in the proximal tubules was not affected. Ouabain-sensitive potassium excretion varied in proportion to ouabain-sensitive sodium reabsorption during variation in glomerular nitration rate, even at urinary sodium concentrations exceeding 80 mmol 1^-1. In experiments without ouabain, saline infusion raised potassium excretion and sodium reabsorption until maximal Na, K-ATPase transport rate was reached, as judged from heat production measurements, but not during further increments in urine flow. After inhibition of Na, K-ATPase activity by hypokalaemia, potassium excretion and cortical heat production remained constant over a wide range of urine flow and sodium excretion. We conclude that potassium secretion is dependent on intact Na, K-ATPase activity and is stimulated by sodium delivery to the distal nephron until maximal transport rate of the enzyme is reached.     

Toxicokinetics of Nickel in Mice Studied with the {gamma}-Emitting Isotope 57Ni

The -emitting isotope ⁵⁷Ni was generated in a cyclotron to allowwhole-body counting of laboratory animals dosed with nickel.⁵⁷NiCl₂ was administered either orally by gastric intubationor by intraperitoneal injection to groups of mice in doses equivalentto the average human daily dietary nickel intake per mass unit.When given orally, the whole-body retention (WBR) was 0.02–0.36%of the administered dose at 45–75 hr. When given intraperitoneally,the WBR was 1–6% at 20–50 hr. After adjustment forthe rapid excretion of systemic nickel, the intestinal absorptioncould be estimated to be 1.7–10%. The relative WBR didnot vary with the magnitude of the dose within 0.05–5µmol Ni/kg given orally or 0.005–0.5 µmol/kggiven intraperitoneally. At 8 hr, the tissue concentration washighest in the kidneys, followed by the carcass, lungs, testicles,liver, and the spleen. After 20 hr, the highest concentrationswere still found in the kidneys followed by the lungs, the liver,and the carcass. At 20 hr after oral administration, 50–70%of ⁵⁷Ni retained in the body was within the carcass. The secondhighest nickel content was found in the kidneys, followed bythe liver and lungs. Whereas nickel in the kidneys was rapidlyexcreted, the elimination from the lungs and liver was relativelyslow, thereby, after 40 hr, resulting in a higher nickel contentin the liver than that in the kidneys. When nickel was givenintraperitoneally, practically no nickel was transported viathe portal vein to the liver after 20 hr, resulting in a lownickel content in the liver and a higher content in the kidney.These results document that the use of ⁵⁷Ni for studies on nickeltoxicokinetics is feasible and useful, and that the method isespecially well suited for comparative studies with a durationof up to 6 days.     

Laryngeal papillomas: the epidemiology in a Danish subpopulation 1965–1984

The incidence rate of laryngeal papillomas in a Danish subpopulation (approximately 2.8 million inhabitants) was 3.84 × 10^-6 per year in the period 1968–1984. For juvenile papillomas the incidence rate was 3.62 × 10^-6, compared with 3.94 × 10^-6 for laryngeal papillomas of adult onset. When comparing different time periods a significantly low incidence was found in the time 1965–1968, while the incidence remained constant in 1969–1984. The low incidence rate in the early period may be real, but selectional bias may have played a part. It is in general anticipated that maternal genital HPV-infections may serve as an HPV-reservoir, and that juvenile laryngeal papilloma is a result of HPV transmission from the mother to the child during birth. In the period in question cervical HPV-infections have been recorded with increasing frequency in younger women, indicating that the prevalence is rising. However, this is not reflected in the incidence of laryngeal papillomas.     

TREATMENT OF CYSTINOSIS WITH A DIET POOR IN CYSTINE AND METHIONINE

Two siblings with cystinosis are presented. Case 1, a 16-month-old boy, presented with a severe renal tubular insufficiency. Case 2, a 7-year-old girl, was a dwarf with both glomerular and tubular renal insufficiency. Case 1 was initially treated with high doses of vitamin D₂ and electrolyte supplements for more than 2 months without significant alteration of the condition. Thereafter he was treated for 23 days with 150 mg penicillamine per day again without any significant clinical or biochemical improvement. Both patients were then followed through 1 year on treatment with a diet poor in cystine and methionine supplemented with cholinechloride, an anabolic steroid, high doses of vitamin D₂, electrolytes, oral iron and a combined vitamin preparation. After some time there was considerable difficulty in giving the patients sufficient amounts of the diet, consequently the diet had to be modified with supplement of cow's milk. On this treatment case 1 attained a distinct clinical improvement with healed rickets and normal growth. There was no evidence of mobilisation of the stored cystine. Case 2 obtained a healing of the rickets and some gain in height during the treatment, but otherwise the general condition was unaltered, and she continued to have increasing renal glomerular insufficiency.     

Pulpal response to dental amalgams

Abstract – The pulpal reactions to amalgams with relatively high Cu content were compared with a conventional amalgam placed in unlined cavities prepared in intact monkey teeth. After a 1-week observation period the pulpal responses from one of the Cucontaining amalgams and the conventional amalgam were of the same magnitude, whereas the two other amalgams gave more pronounced reactions. After observation periods of 1 and 2 months only one o( the amalgams with high Cu content caused more pronounced reactions than the conventional amalgam.     

The permeability of the blood—brain barrier during electrically induced seizures in man

The blood-brain barrier (BBB) in man was studied during various conditions using the indicator dilution method of Crone [8]. Using 113m In-DTPA as reference substance the extraction, E, of the small test substances 24Na+, 36Cl-, 14C-urea and 14C-thiourea was estimated from the areas under the venous outflow curves following intracarotid slug injection of tracers. Interlaminar diffusion and red cell carriage were taken into consideration when calculating E. Cerebral blood flow (CBF) was measured using the intra-arterial 133Xe-injection method. Twenty-two patients receiving electroconvulsive therapy (ECT) were studied before and during seizures and during hypercapnia. Before seizures the extraction values in % were as follows: ENa+ 1.6, ECl- 1.9, Eurea 3.9 and Ethiourea 7.8; the corresponding values for the permeability-surface area products (PS) in ml/100 g x min were 0.5, 0.3, 0.7, 4.1, respectively. During seizure a decrease of Ethiourea and an increase of PSurea were significant. During hypercapnia PSNa and PSthiourea rose significantly. Due to the similarity of the findings in those two high flow situations it is suggested that the changes of CBF and not the epileptic activity are responsible for the changes in permeability. The mechanism of action may be a stretching of endothelial cells in the cerebral vessels or an opening up of new capillaries, or a combination of both.     

Fixed drug eruption: an immunohistochemical investigation of the acute and healing phase

Five patients were each challenged orally with a drug which had previously induced a fixed drug eruption. A positive reaction occurred in all the patients. Punch biopsies were taken 6-12 h, 24 h and 3 weeks after challenge. The specimens were tested with different mouse anti-human monoclonal antibodies to identify T lymphocytes and phenotypic subsets, natural killer cells, B lymphocytes, OKT-6 and HLA-DR-positive cells. T suppressor/cytotoxic cells seemed to play a major role in initiating the flare-up reaction and preserving the cutaneous memory function of the fixed drug eruption.