Quantitation of cutaneous toxicity: an in vitro approach using skin organ culture

A short-term (48 hr) organ culture system for maintaining metabolically viable and structurally intact mouse skin has been developed. With the culture system, the responses of skin to in vitro physical and chemical insults were assessed by histologic examination and selected biochemical measurements in an attempt to establish a quantitative basis for the evaluation of cutaneous toxicity in vitro. In studies with mouse skin in organ culture following either freeze-thaw treatment (physical insult) or a single in vitro topical application of tributyltin chloride (10 to 1000 nmole/cm2), deleterious morphologic changes were observed. The degree of cellular injury was reflected by inhibition of in vitro incorporation of [3H]thymidine and [14C]leucine into epidermal DNA and protein, respectively; there also was leakage of intracellular enzymes into the culture medium in a dose and time related manner. These biochemical parameters are sensitive indicators of cellular injury; as such they may offer a simple, sensitive, and quantitative measure for assessing cutaneous toxicity of chemicals in vitro.

Retinofugal pathways from albino eyes embryonically transplanted to normal and albino axolotls

Albino axolotl eyes were transplanted embryonically to normal and albino axolotl hosts. The animals were allowed to mature for several months and then their transplanted eyes were injected with tritiated proline. The projections from these albino eyes were compared with those obtained from similar transplants of normally pigmented eyes. Special attention was paid to the crossed and uncrossed components of the projections. No differences were found between normal and albino transplants. These results indicate that abnormal retinofugal crossing, which results from a lack of pigmentation in the mammalian eye, does not occur in the axolotl even when the fraction of retinal cells projecting ipsilaterally is experimentally increased by transplanting supernumerary eyes into embryos.

Effects of conjunctival resection on the corneal immune response

In order to evaluate the effect of perilimbal conjunctival resection on the corneal immune response, we immunized rabbits with either intravenous or topical administration of bovine gamma globulin. After unilateral perilimbal conjunctival resection, the corneas were challenged with intracorneal injections of bovine gamma globulin. Perilimbal conjunctival resection prevented the development of peripheral corneal infiltrates in the rabbits immunized intravenously (P less than .0016) but not in those immunized topically. All the animals developed antibody titers to bovine gamma globulin. Similarly, perilimbal conjunctival resection did not prevent corneal graft rejection in rabbits sensitized to their donors by previous skin grafting.

Alamethicin channels incorporated into frog node of ranvier: calcium-induced inactivation and membrane surface charges

Alamethicin, a peptide antibiotic, partitions into artificial lipid bilayer membranes and into frog myelinated nerve membranes, inducing a voltage-dependent conductance. Discrete changes in conductance representing single-channel events with multiple open states can be detected in either frog node or lipid bilayer membranes. In 120 mM salt solution, the average conductance of a single channel is approximately 600 pS. The channel lifetimes are roughly two times longer in the node membrane than in a phosphatidylethanolamine bilayer at the same membrane potential. With 2 or 20 mM external Ca and internal CsCl, the alamethicin-induced conductance of frog nodal membrane inactivates. Inactivation is abolished by internal EGTA, suggesting that internal accumulation of calcium ions is responsible for the inactivation, through binding of Ca to negative internal surface charges. As a probe for both external and internal surface charges, alamethicin indicates a surface potential difference of approximately -20 to -30 mV, with the inner surface more negative. This surface charge asymmetry is opposite to the surface potential distribution near sodium channels.

Sodium intakes of infants from 1 to 18 months of age

The daily sodium content in the diets of infants was determined. Milk and milk products were the main contributor of sodium during early infancy. Commercial baby foods contributed little sodium. As table foods were introduced, the daily sodium intake of the infants rose dramatically. The main sources of sodium in table foods were salt-containing canned foods and added table salt.

Muscle strength and balance in post-stroke patients

Isokinetic torque of the knee and elbow during maximal extension and flexion and isometric strength of the handgrip, as well as balance and some circulatory variables, were tested in 37 patients one year after an acute stroke. Correlations with locomotion, household work and other activities of daily living (ADL) were tested. Male patients who had received special activation on the ward for up to 4 weeks after the stroke showed a significantly smaller difference in strength between the paretic and non-paretic knee at an angular velocity of 90 degrees per second than males who had received only routine activation on their ward. There was a high correlation between locomotion and the isokinetic torque of the paretic knee and also between locomotion and balance. The correlations between elbow strength and ADL functions were weaker. It was concluded that the evaluation of the isokinetic muscle torque of the knee and the balance tests are valid instruments for estimating functional capacity after a stroke.

Iron intake of infants: the importance of infant cereals

Since 1976 many baby foods have been reformulated and the iron used to fortify infant cereals has been changed to a more bioavailable form. Therefore, the dietary intake of iron by infants from 1 to 18 months of age was assessed in a longitudinal survey conducted in Toronto and Montreal between 1977 and 1979. Except in the 1st and 18th months the mean daily iron consumption of the infants was above that recommended in the Dietary Standard for Canada. The main source of this nutrient was infant cereals. Examination of the diets of the infants who did not have the recommended daily intake of iron showed that they did not consume sufficient amounts of infant cereals and other iron-rich foods. These results indicate that without such cereals it is difficult to provide infants with the amount of iron they need. Therefore, infants should receive these cereals during the first 2 years of life.

Infant fatness and feeding practices: a longitudinal assessment

In recent years, bottle feeding and the early introduction of solid foods in infants' diets have been proposed as factors contributing to overweight in infancy that might continue into childhood. These hypotheses were examined in a longitudinal survey of 403 infants from birth to 18 months of age. Results from this survey do not support either (a) a relationship between type of milk feeding or time of introduction of solid food and fatness at 6 months of age or (b) the hypothesis that fat infants remain fat.

Diastrophic dysplasia: the death of a variant

Diastrophic dysplasia is a distinct autosomal recessive disorder originally described in 1960. Since that time, a number of patients with similar but less severe involvement have been diagnosed as having a "diastrophic variant" disorder. This study reviews the radiological features of classic diastrophic dysplasia and compares them with the radiological findings in 26 patients with the diastrophic variant disorder. It is concluded that there is a wide variability in the phenotypic expression of diastrophic dysplasia even within sibships, and that cases of diastrophic variant disorder are actually mild forms of diastrophic dysplasia.

Are oral cathartics of value in optimizing the gallium scan? Concise communication

The normal intestinal secretion of 9-15% of an administered dose of gallium-67 may prevent early detection of intra-abdominal disease. We randomized 50 patients to receive either no bowel preparation or 30 cc of milk of magnesia plus 5 cc of cascara. No significant difference was found between the two groups in frequency with which gallium interfered with readings or time to complete the study.

Use of an acoustic helium analyzer for measuring lung volumes

We have evaluated the use of an acoustic gas analyzer (AGA) for the measurement of total lung capacity (TLC) by single-breath helium dilution. The AGA has a rapid response time (0-90% response = 160 ms for 10% He), is linear for helium concentration of 0.1-10%, is stable over a wide range of ambient temperatures, and is small and portable. We plotted the output of the AGA vs. expired lung volume after a vital capacity breath of 10% He. However, since the AGA is sensitive to changes in speed of sound relative to air, the AGA output signal also reports an artifact due to alveolar gases. We corrected for this artifact by replotting a single-breath expiration after a vital capacity breath of room air. Mean alveolar helium concentration (HeA) was then measured by planimetry, using this alveolar gas curve as the base line. TLC was calculated using the HeA from the corrected AGA output and compared with TLC calculated from HeA simultaneously measured using a mass spectrometer (MS). In 12 normal subjects and 9 patients with chronic obstructive pulmonary disease (COPD) TLC-AGA and TLC-MS were compared by linear regression analysis; correlation coefficient (r) was 0.973 for normals and 0.968 for COPD patients (P less than 0.001). This single-breath; estimation of TLC using the corrected signal of the AGA vs. Expired volume seems ideally suited for the measurement of subdivisions of lung volume in field studies.