Lung injury in guinea pigs caused by multiple exposures to submicron zinc oxide mixed with sulfur dioxide in a humidified furnace

Sulfur dioxide, water vapor, and ultrafine particles rich in oxides of zinc and other surface-deposited trace elements are important products of coal combustion. In order to study the toxicity of zinc oxide generated under conditions simulating combustion, guinea pigs were exposed in a nose-only apparatus for 3 h on 6 consecutive days to 6 mg/m3 of submicron zinc oxide particles (count median diameter of 0.05 micron, sigma g 2.0), which were generated in a humid furnace and mixed with 1 ppm sulfur dioxide. The exposures caused increases in lung weight and [3H] thymidine labeling index of terminal bronchiolar cell nuclei and inflammation of the proximal portion of the alveolar duct. The lung weights and labeling index had returned to normal and inflammatory changes had nearly resolved by 72 h after the last exposure. Total lung capacity, vital capacity, functional residual volume, alveolar volume, and diffusing capacity for carbon monoxide were decreased following exposure and had not returned to normal by 72 h after the last exposure. Large airways were not affected by the repeated exposures, as indicated by normal morphology of trachea and bronchi, unchanged secretory cell concentration, and unaltered epithelial permeability to horseradish peroxidase. These results are essentially identical to changes we reported in guinea pigs exposed to zinc oxide alone, suggesting that surface-deposited sulfur compounds, which are important determinants of the response to a single exposure to these ultrafine particles, become less important as exposure progresses.

Interaction between trophic action and electrical activity in spinal cord cultures

The effect of conditioned medium (CM) on tetrodotoxin (TTX)-mediated neuronal cell death was investigated in dissociated spinal cord-dorsal root ganglion (SC-DRG) cultures. Nutrient medium was collected from donor SC-DRG cultures at 3--4-day intervals throughout development. The presence of survival-promoting neurotrophic material (NTM) in the conditioned medium was tested on TTX-treated cultures which were within the critical period of vulnerability to electrical blockade (days 7-21 in culture). Cultures were assayed by neuronal cell counts, choline acetyltransferase (ChAT) activity or fixation of [125I]tetanus toxin, a neuronal surface marker. Evidence of NTM was found in CM collected prior to day 8 and after day 21 in culture. Increasing the percentage of CM in fresh nutrient medium resulted in a dose-dependent increase in [125I]tetanus toxin fixation and ChAT activity in TTX-treated cultures. In addition, CM plus TTX treatment produced a 25% increase in neuronal cell counts as compared to controls. TTX treatment alone resulted in 20-25% decrease in neuronal number from that of control cultures. Cultures treated with CM alone had neuronal counts that were similar to controls. When electrical activity was blocked with TTX, NTM was not detectable in CM collected from donor cells during days 1-5. CM obtained from control cultures during the same interval had NTM activity. The existence of the critical period for electrical blockade-associated neuron death is associated with a decrease in the availability of NTM. Furthermore, the release of NTM from donor cells and the survival response of target neurons to NTM are apparently dependent on ongoing electrical activity.

Effects of proton release from adenine nucleotide degradation during ischemic necrosis of myocardium in vitro

The effects of the progressive production of hydrogen ions and inorganic phosphate from adenine nucleotides on the lowering of pH in heart muscle has been investigated in dog myocardium maintained under anoxic conditions in vitro at 37 degrees C. Tissue samples were taken at 15-min intervals for up to 105 min and the following biochemical parameters determined: pH, lactate, Pi, ATP, ADP, AMP, G6P, and PC in selected instances. From these data the net proton changes during prolonged anoxia were calculated, assuming homogeneity of the tissue milieu. Net proton change was negative after 15 min and became increasingly more so throughout the remainder of the experimental period, indicating that adenine nucleotide catabolism in fact has a protective effect against fall in pH. When tissue pH falls to ca. 6.2 (45-60 min anoxia), proton production due to lactic acid is reduced by approximately 16% because of absorption of protons by phosphate and ammonia liberated from the nucleotides.

Electrical development in spinal cord cell culture

Parallel electrophysiological and neurochemical studies of development are reported for mouse spinal cord cell cultures. The time course of electrical activity and the stage-dependent effects of tetrodotoxin on levels of the neuronal enzyme choline acetyltransferase were compared to establish the presence of spontaneous electrical activity at a time when tetrodotoxin adversely affects development. The extracellular patch electrode makes it possible to examine the ongoing electrical activity of the small cells present in young cultures. A rapid increase in spontaneous electrical activity during the first 2 weeks in culture was found to correlate closely with the onset of tetrodotoxin-induced depression of choline acetyltransferase activity, supporting the idea that ongoing electrical activity plays a role in neuronal development. The development of inhibitory synaptic activity occurs gradually throughout the period of culture, whereas excitatory synaptic activity and action potentials develop in unison, reaching maximal levels during the 2nd week in culture. For all cultures tested, ranging in age from 9 to 45 days old, acute bath application of gamma-aminobutyric acid (GABA) abolished spontaneous electrical activity. Glycine is relatively ineffective in abolishing spontaneous activity in young cultures which have few inhibitory postsynaptic potentials (IPSPs), but glycine becomes as effective as GABA at a later stage of development. This suggests rather different timetables of development for GABA and glycine receptors, with glycine receptors developing in parallel with IPSPs.

The effects of altered cation balance on the fine structure of hypoxic myocardial cells

To determine whether the changes in intracellular/extracellular cation balance which develop in ischaemic myocardium are responsible for the fine structural changes seen in such tissue, thin slices of normal canine ventricle were incubated under hypoxic conditions at 37 degrees C and physiological pH in balanced salt solution (BSS), isotonic NaCl and isotonic KCl. Slices from each solution were fixed at 10-120 min intervals and examined by light and electron microscopy. For 60 min, tissue from both NaCl and KCl showed good overall preservation of cell architecture and only mild subcellular alterations including aggregation of nuclear chromatin, disappearance of glycogen granules, and swelling of sarcoplasmic reticulum. Tissue from BSS showed early development of intramitochondrial dense inclusions together with focal contraction-band damage similar to that seen in temporarily ischaemic, re-perfused heart muscle and at the margins of infarcts. These changes thus appear to be promoted by divalent cations. The progressive reversal of monovalent cation balance in an area of permanent and severe ischaemia does not appear to be a major determinant of fine structural change.

Adverse effects of phenobarbital on morphological and biochemical development of fetal mouse spinal cord neurons in culture

The effects of chronic phenobarbital treatment on neuronal development were assessed in cell cultures of fetal rodent spinal cord. The activity of the principal enzyme involved in acetylcholine synthesis, choline acetyltransferase (CAT), and counts of large spinal cord neurons were used as indicators of neuronal development Phenobarbital (30 to 120 micrograms/ml) added to cultures for two- or six-week periods produced dose-dependent decreases in both CAT activity and neurons counts. Barbituric acid at doses equimolar to those at which phenobarbital produced these decreases had no effect.

The effect of ischaemic injury on the fine structure of canine atrial myocardium

An experimental model for producing a uniformly and maximally ischaemic segment of atrial myocardium has been devised and used in 23 dogs to investigate the effects of severe ischaemia of up to 6 h duration on the fine structure of atrial myocardial cells. Throughout the first 30 min of ischaemia the cells maintained a fine structure comparable with that of control tissue. In the subsequent 2 h they developed morphological alteration at differing rates, despite their uniform deprivation of blood supply. Even at 90 min the ischaemic tissue showed discontinuous change, with many areas differing little from control, and it was only after 3 h that all cells showed well developed and similar alterations. These included glycogen depletion, marked clumping and margination of nuclear chromatin, and the mitochondrial degeneration typically seen in ischaemically injured ventricle. The changes were very severe after 4 and 6 h of ischaemia, when disruption of cellular membrane systems was also evident. At these times the tissue closely resembled ventricular myocardium made ischaemic for similar intervals, except for the persistence of well-preserved 'specific atrial granules'. Atrial muscle cells therefore develop the fine structural changes associated with ischaemia more slowly than ventricular muscle cells and have a more variable response to the initiation of ischaemic injury.

Acute subdural hematomas. Review of 144 cases

The authors report 144 cases in which acute subdural hematomas resulting from closed head injury were surgically treated. The mortality rate was 48% for those treated within 24 hours of injury and 45% for those treated within 72 hours. Patients under 10 years of age had a 33% mortality, while 69% of those over 60 years died. In the first 6 years of the series, 75% of the patients were treated by multiple burr holes and a subtemporal craniectomy, with a mortality of 41% in the last 6 years, 92% of the patients had large craniotomies with a 45% mortality. Of the 32 survivors among the last 60 patients treated, nine require full nursing home care, eight have returned to their own homes, 12 are able to care for themselves but not work, and three have returned to work.