Experimental study of blood lead kinetics in estuarine crocodiles (Crocodylus porosus) exposed to ingested lead shot.

A previous study of lead (Pb) contamination in estuarine crocodiles (Crocodylus porosus) in Kakadu National Park, Australia, found elevated Pb levels in bone and flesh from individuals caught in habitats where hunting with lead ammunition had occurred. Lead shot was suspected as the potential source of Pb in these animals. An investigation was designed to determine if crocodiles are capable of retaining and dissolving lead shot in their stomachs and absorbing the ionic Pb into the blood. Four of the six juvenile crocodiles (C. porosus) used in the experiment were fed an initial dose of five or ten lead shot each. Most of the lead shot were retained in the stomach over the 20-week experimental period, as confirmed by stomach lavage and radiography of the stomach region. From 13 to 30% of the original weight of individual lead shot had been eroded in that time. In vitro experiments confirmed that lead shot could be dissolved under conditions simulating those known for the crocodilian stomach. Blood Pb concentrations increased by an order of magnitude within a week after dosing three crocodiles with five lead shot each, and then attained steady-state equilibrium 5-20 weeks after dosing, with blood Pb steady-state levels ranging from 278 to 363 microg/dL. The blood Pb concentration-time curves in these crocodiles followed a one-compartment model with first-order loss kinetics that yielded an apparent biological half-life for Pb in blood of about 3.4 days. Throughout the experiment, the crocodiles remained in apparent good physical condition and displayed no clinical signs of Pb toxicosis. These observations, together with the very high blood Pb levels that were sustained for several months, suggest that crocodilians may possess a relatively high degree of resistance to Pb toxicity.

Immunoreactivity of calmodulin, S-100 protein alpha and beta subunits in rat submandibular glands.

The calcium-binding proteins calmodulin and S-100 protein alpha and beta subunits were studied in Rat submandibular salivary gland using monoclonal antibodies and immunoperoxidase staining. Histologically, Rat submandibular gland consists of acinar and ductal components. The latter include intercalated, granular convoluted tubule, striated and excretory ducts. Ultrastructural studies of adult Rat granular convoluted tubule show granular cells, pillar cells and transition cells. Immunostaining for S-100 alpha and calmodulin was observed in granular convoluted tubule pillar cells and transition cells, whereas cells of striated ducts and intercalated ducts stained positive for calmodulin. S-100 beta staining in acinar cells was visible as a fine granular pattern. Although immunohistochemical localization in rat submandibular gland differed for S-100 alpha and beta subunits, expression was similar for S-100 alpha and calmodulin in the granular convoluted tubule segment. No immunodeposition of calmodulin, S-100 alpha or S-100 beta was found in granular cells, which contain growth factors such as EGF and NGF.

Association between surface electromyography of human jaw-closing muscle and quantified food breakdown.

Simultaneous recordings of the activity of the masseter and anterior temporalis and of jaw movement were made on 10 healthy dentate volunteers while they chewed roasted peanuts in their habitual manner. The quantity of food taken was altered by varying (a) its total weight (mouthful) between 8 and 1 g, but with a fixed initial particle size and (b) by varying its initial particle size between median sizes of 9.2 and 2.4 mm, but keeping the mouthful constant. Significant differences were found in the peak and mean (r.m.s.) estimates of muscle activity (particularly in the masseter), and the dimensions of jaw movements. These differences were associated with the variation in both the size of the mouthful and of the initial particles but were much greater with changes in the mouthful. A dimensional argument treating both the weight of food in the mouth and initial particle size as volumes showed that initial particle volume had been varied by approximately 50 times as much as mouthful volume and therefore that the mouthful was a far more critical factor in masticatory physiology than was the particle size of the food. The reasons for this probably lie in an understanding of mechanisms of food comminution.

Morphometric studies on the development and sexual dimorphism of the submandibular gland of the mouse.

A light microscopic morphometric analysis of the development of the mouse submandibular gland has been carried out from birth up to the age of 6 weeks. At birth the bulk of the gland consists of approximately equal volume proportions of acinar, terminal tubule and non-secretory cells. The granular convoluted tubule is absent at birth. The neonatal female gland resembles that of the male in many respects. With the regression of the terminal tubule at 2 weeks of age the duct system of the gland is seen to differentiate into excretory, striated and intercalated ducts. The volume proportions of the gland constituents of the female are similar to those of the male at 2 weeks. At this age, the acini occupy 55%, the striated duct 20% and the intercalated duct 15% of the total gland volume. Sexual dimorphism is clearly evident in the gland at 4 weeks of age when the duct system is seen to differentiate to form its granular convoluted tubule component. The granular tubule occupied 19% of the gland volume in the male but only 8% in the female at 4 weeks. The proportions of acini are only 41% in the total gland volume of the male mouse but 62% in the female at 4 weeks. In the male gland the proportions of granular convoluted tubule increase from 13% to 21% between 4 and 6 weeks and the secretory granule content of these cells from 6% to 24%. At 6 weeks of age the volume proportion of granular convoluted tubule in the male is 45% and that in the female is only 12%. At this age the acini occupy a proportion of 30% in the male gland as opposed to 57% in the female gland. At 6 weeks the volume of granular convoluted tubule cells is 40% lower in the female (1842 microns 3) than in the male gland (2995 microns 3).

Lupoid hepatitis, Rendu-Osler-Weber syndrome, clubbing cyanosis and hypertrophic osteoarthropathy.

Chronic liver disease typical of chronic active 'lupoid' hepatitis together with cyanosis, clubbing and hypertrophic osteoarthropathy in a 42-year-old female is described. In addition she had severe nose bleeds, gastro-intestinal haemorrhages, syncopal attacks with generalised convulsive seizures, pulmonary arterio-venous fistulae as manifestations of Rendu-Osler-Weber syndrome. A study of the literature revealed that similar associations are far more frequent than can be attribtued to chance. Possible mechanisms of the cyanosis, clubbing and osteoarthropathy and possible common pathogenesis for these seemingly unrelated disorders are discussed.