Dental management of patients irradiated for oral cancer

Management of patients irradiated for oral cancer should include consideration of their oral health prior to, and after, radiation therapy. Data from 130 patients, followed for a period of 1 to 10 years, are presented and evaluated. The philosophy of retention and maintenance of as many teeth as possible is supported by this data. Extraction of teeth with severe periodontal disease after irradiation also proves to be a relatively safe operation. Osteoradionecrosis tends to be limited in extent and is generally well tolerated by the patient when treated conservatively. A treatment regimen is presented that significantly reduces the morbidity from therapeutic irradiation of the jaws. A comprehensive dental evaluation and follow-up plan coupled with patient cooperation are instrumental to the success of this program.     

On the question of an electrokinetic requirement for phospholipase C action

The phospholipase C of clostridium welchii (alpha toxin) has an absolute requirement for trace quantities of Ca2+. It attacks pure phosphatidylcholine particles (smectic mesophases) having a close-packed bilayer structure only when their surface zeta potential is made positive by the addition of certain divalent ions (e.g., Ca2+) to the aqueous phase or by the presence of low concentrations of long chain cations to the lipid. Alternatively, if the rotational freedom of individual phospholipid molecules is increased by the insertion of short n-alkanols (e.g., hexanol) into the bilayer or when a monolayer of the substrate at an air/water interface is expended, enzymic hydrolysis can occur without any requirement for a net postive charge on the surface.     

Direct innervation of the mantle edge gland by neurosecretory axons in Helisoma duryi (Mollusca: Pulmonata)

The mantle edge gland of Helisoma duryi is innervated by neurosecretory axons from the pallial nerves. Synaptoid contacts occur between axons and gland cells, and there is ultrastructural evidence for the release of neurosecretory material. The mantle edge gland contributes to the deposition of periostracum during shell formation, and direct neurosecretory innervation may control shell growth and regeneration.     

A pharmacological study of Renshaw cell inhibition

1. In cats anaesthetized with pentobarbitone a pharmacological investigation was made of the inhibition of Renshaw cells by dorsal root afferent volleys and ventral root antidromic volleys, and of the inhibition of motoneurones by Renshaw cells. 2. The effects of strychnine, bicuculline and tetanus toxin indicate that both glycine and GABA operate as inhibitory transmitters released on Renshaw cells by dorsal root volleys. 3. The 'mutual' inhibition of Renshaw cells, and the recurrent inhibition of motoneurones by Renshaw cells, are suppressed by strychnine: Renshaw cells are thus glycinergic inhibitory neurones, a proposal consistant with recent evidence for strychnine-sensitive inhibition of Ia interneurones by Renshaw cells. 4. The 'pause' which follows high frequency synaptic excitation of Renshaw cells is insensitive to strychnine, bicuculline and tetanus toxin, and is considered unlikely to be the consequence of synaptic inhibition.     

Simple mathematical models with very complicated dynamics

First-order difference equations arise in many contexts in the biological, economic and social sciences. Such equations, even though simple and deterministic, can exhibit a surprising array of dynamical behaviour, from stable points, to a bifurcating hiearchy of stable cycles, to apparently random fluctuations. There are consequently many fascinating problems, some concerned with delicate mathematical aspects of the fine structure of the trajectories, and some concerned with the practical implications and applications. This is an interpretive review of them.     

Differing effects of the vasodilator drugs, prazosin and diazoxide on plasma renin activity in the dog

1. The effects of intravenous (i.v.) administration of the vasodilator drugs prazosin or diazoxide on blood pressure and plasma renin activity were evaluated in the anaesthetized dog. 2. Prazosin and diazoxide both induced a rapid reduction in the mean arterial pressure to 73% and 75% of control values respectively. 3. Prazosin lowered plasma renin activity to 62% (P less than 0-025) of the control value whereas diazoxide raised plasma renin activity to 178% (P less than 0.05) of the control value. 4. The combination of vasodilatation and low renin activity observed following the administration of prazosin is unique, and may have clinical significance if these factors reduce the vascular complications of hypertension.     

Mortality and some biochemical changes in mink (Mustela vison) given sublethal doses of aflatoxin each day

Two feeding trials were done to study the susceptibility of mink (Mustela vison) to multiple sublethal doses of aflatoxins. In the 1st trial, twenty 3-month-old male mink were divided equally among groups. Each mink in groups 1, 2, 3, and 4 was given a meatball daily that contained 15, 30, 45, or 0 mug of aflatoxins (B1:G1, 40:60), respectively. All mink in group 3 died between the 25th and the 30th days of the feeding trial. Each mink had ingested 1,035 to 1,480 mug of aflatoxins. Four of the mink in group 2 died almost as soon as did mink in group 3. Four mink in group 1 died between 40 and 59 days after the start of the feeding trial. Generally, a marked increase in plasma cholesterol and alkaline phosphatase activity appeared before mink died. The liver from animals that died of aflatoxicosis showed prominent pathologic changes which included hemorrhages and appearance of pink yellow spots. Histopathologic examination of liver from dead mink revealed fatty infiltration, bile duct proliferation, bile stasis, pseudotubular formation, congestion, and fibrosis. The feeding trial was repeated with 20 mink (8 males and 12 females) that were 1.5 to 2 years old. In this instance, 0, 20, 40, and 60 mug of aflatoxins were administered each day. All treated animals, except 1, were dead within 37 days after the experiment started. The survivor was given the lowest dosage of toxins and died after 52 days by which time 960 mug of aflatoxins were consumed. Plasma cholesterol content and alkaline phosphatase activity generally were similar to those observed in younger mink of the 1st feeding trial.     

Calciphylaxis in man. A syndrome of tissue necrosis and vascular calcification in 11 patients with chronic renal failure

Eleven patients with chronic renal failure and presumed secondary hyperparathyroidism developed a syndrome of medial calcinosis of the arteries and painful ischemic ulcers of the fingers, legs, or thighs, or any combination of the three. Five patients required maintenance hemodialysis; six had functioning renal homografts. Severe hyperphosphatemia had existed in each; seven showed roentgenographic evidence of subperiosteal resorption. Similarities are evident between the lesions and experimentally produced calciphylaxix. The lesions demonstrated a relentless, progressive course, with serious morbidity and mortality. Hyperplastic or adenomatours parathyroid tissue was removed from ten of 11 patients unergoing surgical procedures; healing followed in seven patients. Treatment with phosphate-binding antacids to lower serum phosphorus levels may prevent this syndrome. Total or subtotal parathyroidectomy should be considered when ischemic skin lesions appear in uremic patients or in renal transplant recipients.     

Experimental electrocoagulation of dog esophageal and duodenal mucosa

The per review system for the assessment of research proposals is widely respected by working scientists. Nevertheless two problems associated with the operation of this system by the US National Institutes of Health are identified. First the scientist has no control over which committee will review an application and it may be considered by a quite inappropriate group. Second analysis of the committee composition suggests that in some of the groups several members are not active scientists and therefore not the "peers" of the applicant.