Properties of electroretinographic intensity-response functions in retinitis pigmentosa

Dark-adapted electroretinogram (ERG) b-wave amplitudes and implicit times were recorded as a function of stimulus luminance for 15 retinitis pigmentosa (RP) patients and 15 normal subjects. B-wave amplitude as a function of log stimulus luminance was fit by non-linear regression with the Naka-Rushton equation, which has 3 independent parameters: The maximum response (Rmax), slope (n) and half-saturation constant (K). B-wave implicit-time as a function of log stimulus luminance was fit by linear regression. Compared to normal, the RP Rmax values were markedly reduced, suggesting response compression; the RP K values were elevated by an average of 0.76 log unit, suggesting relatively small losses in retinal sensitivity. There was no correspondence between Rmax and visual field area for the RP patients (coefficient of correlation = -0.02). All but 2 of the 15 RP patients had normal or shallower-than-normal implicit-time intensity-response functions, indicating that over most of the dynamic range of the ERG, the implicit-times were either normal or faster-than-normal. These results are discussed in terms of possible RP disease mechanisms.

Mitochondrial oxidative enzyme activity in individual fibre types in hypo- and hyperthyroid rat skeletal muscles

Quantitative cytochemical and biochemical techniques have been used in combination to study the response of mitochondrial oxidative enzymes in individual muscle fibre types to hypo- and hyperthyroidism. Hypothyroidism resulted in decreased activity of succinate dehydrogenase (SDH), L-glycerol-3-phosphate dehydrogenase (L-GPDH), and D-3-hydroxybutyrate dehydrogenase (D-HBDH) in all fibre types of both slow-twitch soleus and fast-twitch extensor digitorum longus (e.d.l.) muscles. In hyperthyroidism, only L-GPDH activity increased in e.d.l. but more marked increases were seen in soleus muscles, which also showed increased SDH activity. In addition to these alterations in the enzyme activity in individual fibre types the metabolic profile of the muscle is further modified by the hormone-induced interconversion of slow- to fast-twitch fibres and vice versa.

Potassium protection against lesions of the renal tubules, arteries, and glomeruli and nephron loss in salt-loaded hypertensive Dahl S rats

Dahl S rats (20/group) were given three Purina diets for 24 weeks: 4% NaCl-no added potassium (BP 171 mm Hg); 4% NaCl-3.8% K citrate (BP 174 mm Hg); 4% NaCl-2.6% KCl (BP 173 mm Hg). The added potassium did not lower blood pressure (BP) but strikingly reduced microscopic renal lesions. Focal tubular dilation was scored blindly (100, severest lesions; 0, normal). Scores were: renal cortex: no potassium (41); K citrate (20); KCl (22), 50% improvement p less than 0.001; outer medulla: no potassium (79); K citrate (54); KCl (58), 30% improvement p less than 0.001; renal papilla: no potassium (49); K citrate (28); KCl (28), 43% improvement, p less than 0.001. Both K citrate and KCl also eliminated the thickened walls and relatively narrowed lumens of the hypertensive renal arterioles, without lowering BP. In these same rats, the wall thickness of arterioles from 20 normotensive salt-resistant (R) rats on 4% NaCl averaged 18.9 mu vs 26.1 mu in arterioles from 18 hypertensive salt-sensitive (S) rats on 4% NaCl with no added potassium. Adding either KCl or K citrate to the 4% NaCl diet strikingly reduced the wall thickness to that found in the R rat, even though the BP was not reduced at all. Potassium did not lower the high BP but apparently reduced the severity of the arteriolar lesions resulting from that high BP.(ABSTRACT TRUNCATED AT 250 WORDS)

Transport of potassium, amino acids, and glucose in cells transformed by Rous sarcoma virus

Transport rates of a number of nutrients and ions have been surveyed in chicken embryo fibroblasts that were density inhibited, growing exponentially, or transformed by Rous sarcoma virus. All the transport systems examined displayed changes associated with changes in growth rate. The rate of ouabain-sensitive potassium transport declined in density-inhibited cells, and increased rapidly in response to serum stimulation. This transport system was regulated both by changes in the activity of the transporters and by the number of transporters in the cell membrane. The rate of transport of the amino acid analog alpha-aminoisobutyric acid declined when cells became density inhibited, but also showed alterations in regulation that were associated with malignant transformation. The rate of glucose transport displayed both growth state-related and transformation-specific changes. The increased rate of glucose transport seen in transformed cells is due to an increase in the number of glucose transporters in the cell membrane. Increased glucose transport is necessary for subsequent changes in glycolysis, and temporally precedes some of the changes in activity of glycolytic enzymes.

Patterns of muscle fiber-type disproportion in hypotonic infants

We studied the histochemical characteristics of muscle in five hypotonic infants. A number of different patterns of disproportion in the sizes and numbers of type 1 and type 2 fibers were found. In three cases, type 1 fibers were smaller than type 2 fibers and type 2b or 2c fibers were largest. In one case, type 2 fibers were smaller than type 1 fibers and were reduced in number, while in a case of Prader-Willi syndrome there was a preponderance of type 2 fibers that were smaller than type 1 fibers. Type 2c fibers were increased in number in all but one case. We postulate that these various patterns of fiber-type disproportion are the result of altered neural influences leading to impaired maturation of type 1 or type 2 motor units.

Magnetic resonance imaging: serial observations in multiple sclerosis

Three patients with four or more follow-up magnetic resonance imaging (MRI) examinations over a 15-22 month period are described to illustrate the differing patterns of follow-up seen with MRI in multiple sclerosis (MS). These cases illustrate patterns of remission, exacerbation and remission, and rapid progression. The value of MRI in the follow-up of MS is discussed.

Calcification in a pleural mesothelioma

Extensive calcification in a rapidly growing malignant mixed mesothelioma of the pleura was observed on plain radiography and computed tomography of the chest in a patient with a long history of asbestos exposure and chronic renal failure.

Clinical NMR imaging of the brain in children: normal and neurologic disease

The results of initial clinical nuclear magnetic resonance imaging of the brain in eight normal and 52 children with a wide variety of neurologic diseases were reviewed. The high level of gray-white matter contrast available with inversion-recovery sequences provided a basis for visualizing normal myelination as well as delays or deficits in this process. The appearances seen in cases of parenchymal hemorrhage, cerebral infarction, and porencephalic cysts are described. Ventricular enlargement was readily identified and marginal edema was demonstrated with spin-echo sequences. Abnormalities were seen in cerebral palsy, congenital malformations, Hallervorden-Spatz disease, aminoaciduria, and meningitis. Space-occupying lesions were identified by virtue of their increased relaxation times and mass effects. Nuclear magnetic resonance imaging has considerable potential in pediatric neuroradiologic practice, in some conditions supplying information not available by computed tomography or sonography.

Comparative genotoxicity of adriamycin and menogarol, two anthracycline antitumor agents

Adriamycin and menogarol are anthracyclines which cause more than 100% increase in life span of mice bearing P388 leukemia and B16 melanoma. Unlike Adriamycin, menogarol does not bind strongly to DNA, and it minimally inhibits DNA and RNA synthesis at lethal doses. Adriamycin is a clinically active drug, and menogarol is undergoing preclinical toxicology at National Cancer Institute. In view of the reported mutagenicity of Adriamycin, we have compared the genotoxicity of the two drugs. Our results show that, although Adriamycin and menogarol differ significantly in their bacterial mutagenicity (Ames assay), they have similar genotoxic activity in several mammalian systems. Adriamycin is strongly mutagenic in the Ames assay with TA98 and TA100. Menogarol is nonmutagenic to TA98 and TA100. For the mammalian cell culture systems, V79 (Chinese hamster) cells are exposed for 2 hr to drug, following which cell survival, induction of sister chromatid exchanges, chromosome damage, and production of mutants resistant to 6-thioguanine are measured. The percentage of survival obtained with the two drugs ranges between 25 and 50% at 0.15 microgram/ml and 5 to 15% at 0.3 microgram/ml. At 0.15 microgram/ml, Adriamycin and menogarol increase the percentage of cells with chromosome damage from a background level of 8.8 to 30 and 22.5%, respectively. The same drug concentration causes a small but significant increase in sister chromatid exchange rate. Both drugs are equally active (increase mutation frequency about 3- to 6-fold above background) in producing 6-thioguanine-resistant mutants. The induction of micronuclei in polychromatic erythrocytes of rats is the most sensitive assay system. Both drugs cause 10- to 15-fold increase in micronuclei at nontoxic doses.

Theophylline prescribing, serum concentrations, and toxicity

Slow-release theophylline preparations have been prescribed increasingly at the Brompton Hospital, and a serum theophylline assay is requested about once for every ten prescriptions. In a period of eighteen months 1913 such assays were performed, and their influence on management was assessed by retrospective analysis in two groups--113 outpatients on stable dosage with no recent exacerbations of disease; and 28 inpatients and outpatients with concentrations exceeding 25 mg/l. In those with stable treatment, there was only a loose relation between dose and serum theophylline level. High serum levels were associated with abnormal liver function, diuretic use, and duplicate prescribing. When serum theophylline levels were reported high, dosage was always reduced, whereas a low serum theophylline prompted dosage increase in only one-third of patients. Of the patients with very high serum theophylline concentrations (over 25 mg/l), 18 had been receiving oral theophylline and 10 aminophylline by infusion. 3 had seizures, of whom 2 died, and 1 patient was resuscitated after cardiac arrest. Unsuspected theophylline toxicity may be responsible for considerable hidden morbidity.

Endotoxin-induced hemodynamic changes in dogs: role of thromboxane and prostaglandin I2

Plasma concentrations of thromboxane and prostaglandin I2 (PGI2) before and after IV injection of endotoxin and resulting hemodynamic changes were evaluated. Effects of flunixin meglumine on plasma concentrations of these prostaglandins and the related hemodynamic changes were also determined. Shock was induced in 2 groups of anesthetized dogs. Four dogs were given endotoxin only and 4 dogs were given endotoxin and then were treated with flunixin meglumine. Arterial blood pressure (BP), cardiac output (CO), and heart rate were measured, and blood samples were collected at postendotoxin hours (PEH) 0, 0.1, 0.25, 0.5, 1, 2, 3, and 4. Plasma thromboxane and PGI2 concentrations were increased in canine endotoxic shock. Thromboxane concentration was highest early in shock, and appeared to be associated with an initial decrease in BP and CO. The increased concentration of PGI2 was associated with systemic hypotension at PEH 1 to 2. Treatment of dogs with flunixin meglumine at PEH 0.07 prevented further increase of thromboxane and blocked the release of PGI2, resulting in an increased CO, BP, and tissue aerobic metabolism.

Fatal infantile mitochondrial myopathy due to cytochrome c oxidase deficiency

A case of cytochrome c oxidase deficiency primarily affecting skeletal muscle is described. The child was admitted at 4 weeks due to failure to thrive and examination at that time revealed weakness and hypotonia. His condition deteriorated until at 11 weeks respiratory arrest necessitated artificial ventilation and death occurred at 14 weeks. Biochemical investigation showed lactic acidaemia and generalised aminoaciduria. Histochemical examination of muscle obtained at biopsy showed strong reactions for some oxidative enzymes, but by contrast cytochrome c oxidase could not be detected. Cytochrome c oxidase activity was less than 5% of control values in an extract of fresh muscle. The reduced-minus oxidised absorption spectra of muscle mitochondrial fractions prepared from post-mortem tissue showed an absence of cytochrome aa3 and a partial deficiency of cytochrome b. Ultra-structural examination showed abnormal mitochondria with loss of cristae and an abnormal granular matrix. The family history suggests autosomal recessive inheritance.

A partial deficiency of cytochrome c oxidase in chronic progressive external ophthalmoplegia

A partial deficiency of cytochrome oxidase has been found in 7 patients with chronic progressive external ophthalmoplegia and proximal myopathy or craniosomatic abnormalities. Muscle biopsies from all these patients showed morphological mitochondrial abnormalities ("ragged red" fibres) and cytochemical assay of cytochrome oxidase showed that these fibres contained no demonstrable enzyme activity. The incidence of cytochrome oxidase-negative fibres was greater than that of "ragged-red" fibres suggesting that the enzyme defect preceded the development of morphological mitochondrial changes. Biochemical analysis of skeletal muscle mitochondrial fractions from 3 patients revealed in 1 case a significantly lower concentration of cytochrome aa3 and a decreased ratio of cytochrome oxidase/succinate-cytochrome c reductase. Fasting blood metabolites were elevated in 2 patients. We suggest that partial cytochrome oxidase deficiency is the underlying defect in mitochondrial myopathy associated with the oculocraniosomatic syndromes.

Dihydrocodeine for breathlessness in "pink puffers"

Eighteen patients with severe breathlessness due to chronic airflow obstruction completed a randomised placebo controlled double blind cross over trial of the effect of dihydrocodeine 15 mg on breathlessness, disability, and exercise tolerance. There were three periods of one week each. During the first two weeks patients were instructed to take dihydrocodeine 15 mg or placebo 30 minutes before exercise as required up to three times daily. During the third week patients received either dihydrocodeine or placebo on alternate days. During the weekly dihydrocodeine period patients were more mobile (pedometer distance increased by 16.8%) and less breathless (daily visual analogue score of breathlessness reduced by 17.8%). This benefit was confirmed by treadmill testing at the end of each treatment period, when maximum distance walked was 16.5% higher and breathlessness 11.8% less after dihydrocodeine compared with placebo. Similar benefit in breathlessness occurred during alternate day treatment. No adverse effects were encountered. Dihydrocodeine 15 mg 30 minutes before exercise offers appreciable benefit to patients with severe breathlessness due to chronic airflow obstruction.

Are "pink puffers" more breathless than "blue bloaters"?

Breathlessness, disability, and exercise tolerance were assessed in 26 patients with severe chronic airflow limitation (forced expiratory volume in one second (FEV1) less than or equal to 1 litre) divided into two groups--15 patients who were normocapnic (pressure of arterial carbon dioxide (Paco2) less than 5.5 kPa (less than 41.4 mm Hg)), and 11 patients who were hypercapnic (Paco2 greater than 6 kPa (greater than than 45.1 mm Hg)). The two groups were well matched for spirometric values (FEV1 0.59 1 and 0.62 1, respectively). All of the hypercapnic patients could improve blood gas tensions towards normal by hyperventilation. There were no significant differences in visual analogue scores of breathlessness during treadmill exercise, disability (oxygen-cost diagram, dyspnoea grade), or exercise tolerance (six-minute walk, maximal consumption of oxygen during bicycle ergometry, distance walked to exhaustion in progressive treadmill test). The findings show that the "fight" to maintain normal blood gas tensions in the face of severe airflow limitation does not have an appreciable cost in terms of disability.

Changes in histochemical profile of rat respiratory muscles in hypo- and hyperthyroidism

Rat respiratory muscles underwent considerable changes in histochemical fibre type profile in response to hypo- and hyperthyroidism. Hypothyroidism increased the proportion of type 1 slow oxidative fibres in diaphragm and to a lesser extent in intercostal muscles. Hyperthyroidism resulted in a decreased proportion of type 1 fibres in both diaphragm and intercostals. These changes were broadly comparable to those reported previously in rat limb muscles. In normal rat respiratory muscles, the type 1 fibres were characterized by very high levels of beta-hydroxybutyrate dehydrogenase which was thought to contribute to the fatigue-resistance of these muscles. The type 2B fast glycolytic fibres, and to a lesser extent type 2A fast oxidative fibres, contained high levels of mitochondrial alpha-glycerophosphate dehydrogenase, an enzyme known to be specifically affected in dysthyroid states. The implications of the observed changes in fibre type profile with respect to the oxidative metabolism of rat respiratory muscles are discussed.

Leukotriene C4 and dimethylphenylpiperazinium-induced responses in canine airway tracheal muscle contraction and fluid secretion

Leukotrienes have been implicated as putative mediators in several air way diseases. In previous canine studies it was shown that leukotriene C4 (LTC4) enhanced fluid secretion over baseline values and this enhancement could be blocked by hexamethonium. This indicates that leukotrienes have as one of their actions, stimulation of ganglionic motor neurons. In the present study, we determined that LTC4 acts at a similar site as the specific nicotinic receptor agonist dimethylphenylpiperazinium (DMPP). Both LTC4 and DMPP when given alone enhanced mucus secretion and induced tracheal muscle contraction over control baseline (p less than 0.05). When added to DMPP, LTC4 enhanced the DMPP effect of muscle contraction at 5 and 8 micrograms by a synergistic amount, while the secretion was only additive. The slopes of the dose-response curves for DMPP + LTC4 did not differ by a statistically significant amount. LTC4 and DMPP act on a similar, if not the same, ganglionic receptor.

Effect of an anteroventral third ventricle lesion on NaCl hypertension in Dahl salt-sensitive rats

An anteroventral third ventricle (AV3V) lesion in the brain prevents several forms of experimental hypertension. The present experiment was designed to determine whether the AV3V lesion prevents NaCl-induced hypertension in Dahl salt-sensitive (S) rats and whether attenuation of vasopressin release reported in lesioned rats contributes to the protective effect of the AV3V lesion against hypertension. After the AV3V lesion Dahl S rats received daily injections of either vasopressin (pitressin tannate, 500 mU/kg) or vehicle during 10 wk of 8% high-NaCl diet. Sham-lesioned rats served as controls. The blood pressure in sham-lesioned rats receiving vehicle was 189 mmHg after 10 wk of high-NaCl diet. Lesioned rats given vehicle showed a significantly smaller increase in blood pressure than sham-lesioned rats (P less than 0.001), the blood pressure averaging 161 mmHg at 10 wk. Lesioned rats given vasopressin also showed a smaller increase in blood pressure than sham-lesioned rats (P less than 0.05), but the final blood pressure averaged 176 mmHg and was significantly higher than that of lesioned rats given vehicle (P less than 0.025). Vasopressin injections corrected the hypernatremia in lesioned rats. In another experiment the effect of the AV3V lesion on the renal papillary plasma flow (RPPF) in Dahl S rats was studied. Dahl S rats have a lower RPPF than Dahl salt-resistant (R) rats even on a low-NaCl intake. The AV3V lesion increased the RPPF by 14% in S rats (P less than 0.025). These findings suggest that NaCl-induced hypertension in Dahl S rats requires the integrity of the AV3V region for its full expression, and the ability of the AV3V lesion to attenuate the NaCl-induced hypertension in Dahl S rats is partly related to the attenuation of vasopressin release. Moreover, the AV3V lesion partly corrected one of the characteristic features of Dahl S rats, the reduction in RPPF, when compared with Dahl R rats, with both strains on a low-NaCl intake.

Solubilization and initial biochemical characterization of an IgE-destroying enzyme on rat peritoneal mast cells

Previous studies had demonstrated that incubation of IgE with purified rat mast cells can result in the time and cell concentration-dependent destruction of the ability of the IgE to be bound to specific receptors on rat basophil leukemia cells. The IgE-destroying activity, which has an extremely acid pH optimum, resisted attempts at solubilization using detergents. However, it was solubilized in good yield by use of chaotropic salts and especially KOCN. The soluble activity is stable to freezing and thawing, and to heating to 68 degrees C for 60 min. It is promptly destroyed upon boiling. IgE destruction was linear with time up to 20 min and a series of products, mol. wts 138,000, 92,500, 60,000 and 36,500, are formed during the reaction. No pH optimum for the reaction could be found because, as the pH was lowered below 4.0, the spontaneous destruction of IgE became too great. At pH 4.75 the apparent Km for the reaction was 0.55 microM and Vmax was 0.4 nmoles IgE/10(4) mast cell equivalents/min. IgE-destroying activity could be inhibited by heat-inactivated serum, and by relatively high concentrations of crude alpha 1-antitrypsin, aprotinin, lima bean and soybean trypsin inhibitors and by p-nitroguanidinobenzoate. A large number of other protease inhibitors were inactive.