Congenital myotonic dystrophy: fiber type abnormalities in two cases

Histometric data on muscle fiber types were studied in two cases of congenital myotonic dystrophy (CMD); one underwent biopsy at the age of 5 months and the other at the age of 10 years. A previously unreported severe deficiency of type IIB fibers were found in both cases. In addition, in the first case, there was type I fiber preponderance and hypotrophy as described in cases of congenital fiber type disproportion (CFTD). It is suggested that an abnormality of motor unit maturation may be common to CMD and to CFTD, and that this results from a disorder of neural trophic influences during muscle development.

A histochemical study of fibre types in rat extraocular muscles

The histochemical fibre type composition of the rat superior and medial rectus (SR and MR), superior oblique (SO) and levator palpebrae superioris (LPS) muscles was studied using the myofibrillar ATPase and NADH-tetrazolium reductase (NADH-TR) techniques. In the SR, MR and SO a peripheral zone containing small fibres and a central zone containing both small and large fibres could be identified. Four fibre types were present in the central zone of these muscles and were categorised as Type 1, Type 2a. Type 2a'. and Type 2b. Four fibre types were also identified in the peripheral zone--Type 1, Type 2a, Type 2a' and Type 2c. In the LPS Type 1, Type 2, Type 2a', Type 2b and Type 2c fibres were evenly intermixed without a zonal arrangement. The Type 1, Type 2a, Type 2b and Type 2c fibres correspond to accepted fibres types in the rat limb muscles. The type 2a' and Type 2a" fibres were differentiated from the Type 2a fibres on the basis of size and pattern and intensity of staining with the NADH-TR technique. The Type 2c fibres, which possess both acid-stable and alkali-stable myofibrillar ATPase, are considered to represent intermediate fibres in the process of transformation from Type 2 to Type 1, rather than fibres with a dual innervation as has been suggested in the past. The implications of these histochemical findings are considered in relationship to the physiology of individual motor units and to the function of the extraocular muscles.

Serum stimulation of potassium fluxes, ouabain binding, and sodium fluxes in quiescent chicken embryo fibroblasts

Growth-contingent alterations in potassium and sodium fluxes, ouabain binding, and potassium ion content were examined following serum stimulation of quiescent, density-inhibited chicken embryo fibroblasts. Serum stimulation resulted in very rapid 1.5- to 1.8-fold increases in ouabain-sensitive potassium influx and lesser 1.4- to 1.5-fold increases in potassium efflux and sodium influx. Potassium influx stimulation was maximal after addition of 5-20% calf serum and was unaffected by cycloheximide inhibition of protein synthesis. Reflecting the slightly greater stimulation of potassium influx versus potassium efflux, potassium ion levels were 10-15% higher in serum-stimulated compared to unstimulated cells. Specific ouabain binding levels in stimulated and unstimulated control cells were initially similar, however, by four hours after stimulation a 40-50% increase in specific ouabain binding was observed. Incubation with ouabain was found also to inhibit later serum-stimulated hexose uptake and thymidine incorporation; this blockage may be consequence of subnormal potassium levels rather than ouabain inhibition of the serum-stimulated potassium influx.

Potassium fluxes and ouabain binding in growing, density-inhibited and Rous sarcoma virus-transformed chicken embryo cells

Potassium fluxes, ouabain binding, and Na+ and K+ intracellular concentrations were determined for cultures of growing normal, density-inhibited and Rous sarcoma virus-transformed chicken embryo fibroblasts. No significant differences in K+ influx or ouabain binding were detected between growing normal cells and Rous sarcoma virus-transformed cells; however, ouabain binding and ouabain-sensitive K+ influx were 1.5- to 1.8-fold lower in density-inhibited cells. Thus, potassium influx in this system can be classified as a growth-related, but not transformation-specific change. As determined by both flame photometry and radioisotopic (42K) equilibration, growing normal and density-inhibited cells had similar potassium contents, whereas transformed cells exhibited 1.4-fold higher potassium levels. Sodium ion levels, as measured by flame photometry, were also 2- to 4.5-fold higher in transformed than normal or density-inhibited cells. Complementary studies of potassium efflux showed a 1.3- to 1.5-fold higher rate (based on the percentage of pool exiting the cell) in growing normal versus density-inhibited or transformed fibroblasts. Because of the larger potassium pool in transformed cells, efflux based on absolute number of potassium ions is similar in normal and transformed chicken embryo fibroblasts.

Legionnaires' disease in Vancouver

A female patient presented at the end of a holiday cruise with the pneumonitis of Legionnaires' disease. The radiographic appearance was indistinguishable from any other cause of air-space consolidation.

Morphology and physiology of skeletal muscle in aging rodents

Aging in the rodent is accompanied by a progressive loss of skeletal muscle fibers. The muscle twitch also becomes slower, probably as a result of fiber-type conversion from "fast-twitch" to "slow-twitch." The loss of muscle fibers precedes signs of obvious weakness and appears to involve the loss of entire functioning motor units. In the mouse, this loss of motor units correlated with a loss of axons from the innervating nerve trunks.

Growth, survival, and resistance of the Legionnaires' disease bacterium

The Legionnaires' disease (LD) bacterium can now be readily cultured on artificial media. Studies were done to define the growth and survival of the LD bacterium in these media and ascertain its susceptibility to disinfecting agents. Growth-curve studies of the Philadelphia 1 strain using Mueller-Hinton broth with ferric pyrophosphate and L-cysteine (Feeley-Gorman broth) showed a lag phase of less than 24 h, a generation time of 3.8 h during the logarithmic phase, a plateau of 2 x 10(7) organisms per millilitre, and continued viability for as long as 110 d. Viability on chocolate agar with 1% hemoglobin and 2% IsoVitaleX added reached 150 d. This strain was susceptible to a variety of commonly recommended hospital and laboratory disinfectants, often in low concentrations. These investigations suggest that prolonged survival may occur in natural as well as artificial milieus and that low concentrations of phenolics, quaternary ammonium compounds, glutaraldehyde, formaldehyde, and hypochlorite could eradicate potential reservoirs for human infection.

Regulation of glomerular capillary pressure and filtration rate in young Kyoto hypertensive rats

1. Single nephron pressures, flows and resistances were studied in 17–18 week old genetically hypertensive and normotensive Kyoto rats resembling one another in renal weight, total filtration rate, morphology and number of glomeruli in the kidney.

2. Glomerular capillary pressures were similar in the two groups; however, the hypertensive rats had lower pressures at the end of the efferent arteriole than did the normotensive animals. Nephron filtration rates were similar in both groups. At the same time, the hypertensive rats had higher nephron filtration fractions, and their glomerular blood flow was lower than that of the normotensive rats. These changes in the hypertensive animals were due to their higher afferent and efferent arteriolar resistances. Despite their high blood pressure, the glomerular ultrafiltration forces in hypertensive rats were almost identical with those in normotensive rats.

3. We conclude that the regulation of glomerular capillary pressure and filtration rate in young Kyoto hypertensive rats is due to a balance of afferent—efferent arteriolar tonus. The normal glomerular capillary pressures and low efferent arteriolar pressures of these animals are most likely the functional basis for the lack of structural changes at these sites. These results suggest that the Kyoto animal's renal response to hypertension resembles that of most essential hypertensive patients, both in function and morphology.

A correction in the published nuclear magnetic resonance spectra of trans-camphane-2,3-diols

It is unequivocally shown that the published nmr spectra assigned to 2-endo,3-exo-camphanediol and 2-exo-3-endo-camphanediol should be reversed. The 2-exo,3-endo isomer is prepared unambiguously by hydroboration–oxidation of camphor enol silyl ether.

Albumin/globulin rations, colloid osmotic pressures and Lowry protein microanalysis in rat plasma

1. We have correlated measurements of colloid osmotic pressure with protein concentrations and albumin/globulin ratios. Plasma from normal rats of different genetic strains was used.

2. The Landis and Pappenheimer equation does not accurately predict colloid osmotic pressure properties of the normal rat plasma used, which had an albumin/globulin ratio of 0.74. Over the range 2.2−12.2 g of protein/100 ml, the measured colloid osmotic pressures vary between −5% and +10% from the value predicted by the equation.

3. In Wistar-derived genetically hypertensive and normotensive rats, albumin/globulin ratios were higher than those in common Wistar rats. Owing to the presence of higher globulins, plasma proteins were higher in Wistar than spontaneously hypertensive and normotensive rats, and colloid osmotic pressure was identical in the three groups.

4. When common Sprague—Dawley rats were obtained from two different suppliers, their albumin/globulin ratios were found to be different.

5. As the difference in albumin/globulin ratio between human and rat plasma becomes more pronounced, predicting rat plasma colloid osmotic pressure from the Landis and Pappenheimer equation becomes less accurate. Environmental and/or genetic factors play a role in the albumin/globulin ratio found in normal healthy rats.

6. Therefore albumin/globulin ratios should be measured in each experimental situation. If the ratios are close to that of human plasma, the Landis and Pappenheimer equation can be used. If not, a new colloid osmotic pressure-protein expression should be derived.

7. Calculation of glomerular capillary pressures from directly measured colloid osmotic pressure values reduces error.

Further observations on the pathological responses of rat skeletal muscle to toxins isolated from the venom of the Australian tiger snake, Notechis scutatus scutatus

1. Some aspects of the response of mammalian skeletal muscle following the injection of purified toxins from the venom of the Australian tiger snake, Notechis scutatus scutatus, are described. 2. The toxins used were notexin, notechis II-5, notechis II-1 and a modified form of notexin (PBP-notexin). They were injected into the dorso-lateral aspect of one himd limb so that the soleus muscle would be exposed to the toxins. 3. Within 1 h after the injection of notexin, the soleus muscles were oedematous and by 3--6 h, polymorphonuclear leucocytes had entered the interstitial spaces. The invasion of necrotic muscle fibers was extensive by this time. Muscle spindles appeared relatively unaffected by the toxin. 4. The muscle regenerated via myoblasts at 2--3 days to myotubes at 3--5 days, immature muscle fibers at 7--14 days and fully differentiated muscle fibers by 21--28 days. Even after 6 months, however, the nuclei of many muscle fibres remained in a central position. 5. A second component of Australian tiger snake venom was also found to be myotoxic. It was slightly less potent than notexin, but caused qualitatively similar damage to that caused by notexin. It was identified as notechis II-5. A third fraction, notechis II-1, was found to be inactive. 6. Notexin could be neutralized by incubation with tiger snake antivenene; the simultaneous injection of antivenene with notexin did not afford complete protection against muscle damage.

Air transport of infants in Newfoundland and Labrador

Air transportation of 33 infants in small unpressurized aircraft over long distances is described. Twenty-six of the infants were transported more than 320 km in environmental temperatures varying from -35 to +21 degrees C. A commercially available incubator was used. Although more than half the infants had a rectal temperature within the normal range at the time of arrival at hospital, 12 infants had rectal temperatures above 37.5 degrees C as a result of efforts to diminish heat loss. Adequate oxygenation of infants at 3000 m in unpressurized aircraft can be difficult. Cold and vibration can affect equipment, and at high altitudes the readings from oxygen analysers may not be true. The use of an expanded transport team, which includes experienced nonmedical personnel, is particularly important in these cases.

Patterns of abnormal histochemical fibre type differentitation in human muscle biopsies

The histochemical profile of individual human skeletal muscle fibres was analysed by correlating mitochondrial oxidative enzyme activity and that of myofibrillar ATPase at pH 9.5 and after pre-incubation at pH 4.3 and pH 4.6. In normal control muscle, only a small percentage of fibres did not conform to one or other of the normal variants of Type I and Type II fibres. In biopsies from early cases of Werdnig-Hoffmann disease, the denervated fibre populations contained many abnormal Type I and Type II fibres, including "IIc" fibres, but the basic distinction between Type I and Type II was preserved. However, in infantile spinal muscular atrophy patients aged two years and over, this distinction was progressively lost, leading to the total dedifferentiation of the atrophied fibres. In the Kugelberg-Welander form of spinal muscular atrophy, many of the constituent fibres of re-innervated groups displayed normal or near-normal histochemical profiles, but chronically denervated fibres became totally dedifferentiated. In Duchenne dystrophy, the spectrum of histochemical types appeared to be more continuous due to the emergence of fibres with properties intermediate between those of the normal variants, but the basic distinction between Type I and Type II fibres was preserved in the majority of cases. The percentage of severely abnormal fibres was higher in Type II than Type I and probably contributed to the observed decrease in the overall proportion of Type II fibres. Although very small atrophied fibres were observed in biopsies from cases of Becker and Duchenne dystrophy, these did not show the total dedifferentiation seen in the chronically denervated fibres in cases of spinal muscular atrophy.

Psoralen-DNA photoreaction: controlled production of mono- and diadducts with nanosecond ultraviolet laser pulses

Samples of DNA which contain adducts of a new psoralen derivative, but no cross-links, have been prepared by irradiating mixtures of DNA and the derivative with single, 15-nanosecond pulses of laser light. Succeeding pulses introduce cross-links. The ability to rapidly and selectively create monoadducts and corss-links may allow the use of psoralens as probes of dynamic processes in living cells.

Experimental serotonin myopathy

One hundred and eight Wistar rats were injected with serotonin (20 mg per kilogram of body weight intraperitoneally) or imipramine hydrochloride (20 mg per kilogram intraperitoneally), or both, in a single cycle or in multiple (up to 18 weeks) weekly cycles. In contrast to previous reports, a characteristic myopathy was produced with serotonin alone, identical to that produced by serotonin and imipramine in combination. Imipramine alone produced no significant change. The myopathy produced was characterized by (1) preferential damage to myofibers with high oxidative capacity (types I and IIA), (2) prominent regenerative activity occurring as early as 48 hours, and (3) degeneratio of capillary endothelium (thickening, vacuolar degeneration, proliferation of marginal folds, dissolution of mitochondria). Small groups of degenerating fibers and increased connective tissue were not observed. There was no loss of myofibers or fat replacement. The changes suggested repeated acute insults followed the complete recovery. These observations suggest that although the pathogenesis of serotonin and serotonin-imipramine myopathy is primarily ischemic, it is not a satisfactory model of human Duchenne muscular dystrophy.