The photomyoclonic reflex: an artefact in the clinical electroretinogram

An artefact may appear in the clinical electroretinogram (ERG) that can interfere with the recording and interpretation of the ERG b wave. This artefact, the photomyoclonic reflex (PMR), was studied by covering the eye containing the recording electrode and stimulating the fellow eye. Records obtained by this technique before and after administration of a modified Van Lint lid block demonstrated that most of the PMR is due to a reflex contraction of the orbicularis muscle. The remaining part of the PMR was ascertained by eye movement recordings to be a 1.5 degrees to 3.5 degrees downward and medial eye movement. In most persons the PMR occurs with a latency that is fast enough (59 ms +2- 7 ms) to interfere with interpretation of the b wave under most conditions. The PMR can be minimised in some cases by habituation or conditioned suppression. However, these methods generally do not extinguish the PMR but reduce it enough so that it would not readily be rejected as artefact. In such cases the PMR may produce a wave form that mimics a normal amplitude ERG but with delayed implicit time.

Thromboxane, prostaglandin I2 (epoprostenol), and the hemodynamic changes in equine endotoxin shock

This study had 2 objectives: (i) to correlate plasma thromboxane and prostaglandin I2 (epoprostenol) concentrations with hemodynamic changes occurring in equine endotoxin shock, and (ii) to determine the effects of flunixin meglumine on plasma concentrations of these prostaglandins relative to hemodynamic changes. Shock was induced in 2 groups, each of 4 anesthetized ponies, and in a 3rd group of 2 ponies. Group A ponies were given endotoxin only (and were not treated), and group B ponies were given endotoxin and then treated with flunixin meglumine. Group C ponies were treated with flunixin meglumine 5 minutes before they were fiven endotoxin. Arterial, pulmonary arterial, and central venous pressures were measured and blood samples were collected at 0, 0.1, 0.25, 0.5, 1, 1, 3, and 4 hours after ponies were given the endotoxin. The plasma thromboxane and prostaglandin I2 concentrations were increased in equine endotoxic shock. Increased thromboxane concentration was associated with the high pulmonary arterial and central venous pressures and low arterial blood pressure in the minutes immediately after the ponies were given endotoxin. The increased prostaglandin I2 concentration was associated with systemic hypotension at 1 to 2 hours after endotoxin. Treatment of ponies with flunixin meglumine after endotoxin was given (group B) prevented the prostaglandin I2 rise and the associated hypotension. Treatment with fluixin meglumine before endotoxin was given prevented the increase of the plasma thromboxane and prostaglandin I2 values, along with the associated hemodynamic changes.

Effects of dietary tin on zinc, copper, iron, manganese, and magnesium metabolism of adult males

The effects of dietary tin on zinc, copper, iron, manganese, and magnesium metabolism were determined in eight adult males. Subjects were fed mixed diets containing 0.11 mg tin daily (control diet) and 49.67 tin daily (test diet) in this 40-day study. The level of tin in the control diet was typical of the levels of tin found in diets that contain only fresh and frozen foods; the level of tin in the test diet was typical of the amount of tin in diets that contain 2 cups of certain canned foods. When subjects were fed the test diet they lost significantly more zinc (p less than 0.01) in their feces and significantly less zinc (p less than 0.05) in their urine. Subjects retained significantly less zinc (p less than 0.01) when fed the test diet rather than the control diet. The fecal and urinary losses of copper, iron, manganese, and magnesium were not significantly affected by the dietary treatments.

Abnormal endometrial echoes: sonographic spectrum of endometrial pathology

This report reviews the cases of 12 patients in whom ultrasound examination revealed endometrial cavity echoes that were more prominent than expected. Dilatation and curettage or hysterectomy, or both, in these patients revealed a spectrum of endometrial pathology in 83 per cent of the patients, including carcinoma in 33 per cent and normal findings in 17 per cent.

Effects of dietary tin on tin and calcium metabolism of adult males

The effects of dietary tin on tin and calcium metabolism were determined in eight adult males. Subjects were fed mixed diets containing 0.11 mg tin daily (control diet) and 49.67 mg tin daily (test diet) for 20 days each in a cross-over design. The level of tin in the control diet was typical of the level of tin found in diets that contained only fresh and frozen foods; the level of tin in the test diet was typical of the amount of tin in diets that contained several servings of certain canned foods. Subjects apparently absorbed 3 and 50% of their dietary tin intake when fed the test and control diets, respectively. Subjects lost significantly more tin in their urine, but retained significantly more tin when fed the test diet rather than the control diet. The fecal and urinary losses and serum levels of calcium were not affected by the dietary treatments.

Brain lesions in the paraventricular nuclei and catecholaminergic neurons minimize salt hypertension in Dahl salt-sensitive rats

1. The rise in blood pressure in Dahl salt-sensitive rats that received intracerebroventricular 6-hydroxydopamine was almost half that of the control rats throughout 20 weeks of high (8%) NaCl feeding. 2. The rise in blood pressure in Dahl salt-sensitive rats with bilateral complete electrolytic lesions of the paraventricular nuclei was almost half that of the control rats during 12 weeks of high (8%) NaCl feeding. 3. The bilateral complete electrolytic lesions of the suprachiasmatic nuclei enhanced the development of NaCl hypertension in Dahl salt-sensitive rats. 4. These results show that NaCl-induced hypertension in Dahl salt-sensitive rats requires the integrity of the central nervous system catecholaminergic neurones and the paraventricular nuclei for its full expression.

Potassium citrate feeding protects against nephron loss in severe sodium chloride hypertension in rats

1. Potassium citrate did not significantly increase plasma flow to the renal papilla in normotensive Dahl R rats on either low or high NaCl diets. Similarly, potassium citrate did not significantly increase papillary plasma flow in mildly hypertensive Dahl S rats on low NaCl diets. Thus potassium citrate feeding did not ordinarily alter papillary plasma flow.

2. When S rats were fed on a high (4%) NaCl diet for 24 weeks, they became severely hypertensive and developed nephrosclerosis with nephron loss. This accounted for the significant reduction in papillary plasma flow in S rats on 4% high NaCl diet with no potassium supplementation.

3. When S rats on high NaCl diet were given a supplement of KCl, they still developed severe hypertension and almost the same fall in papillary plasma flow, suggesting a similar degree of nephron loss from nephrosclerosis.

4. However, when S rats on high NaCl diet were given a supplement of potassium citrate, they still developed the same severe hypertension but, in contrast, they did not have a decrease in papillary plasma flow. This actually increased to 7% higher than in comparable S rats eating the low NaCl diet. Moreover, S rats receiving potassium citrate supplements in their high NaCl diet had a papillary plasma flow which was 34% higher than that of S rats receiving no potassium supplement in the high NaCl diet (P < 0.005) and was 19% higher than that of S rats receiving KCl supplements in the high NaCl diet (P < 0.04). This occurred even though the rats receiving potassium citrate were severely hypertensive.

5. Thus potassium citrate feeding protected against nephron loss from nephrosclerosis during severe NaCl-induced hypertension, whereas KCl feeding did not provide such protection.

Effects of dexamethasone on fibre subtypes in rat muscle

The extent to which dexamethasone treatment produced atrophy of fast-twitch (EDL) and slow-twitch (SOL) muscles in rat was investigated. The mean weight of steroid-treated EDL muscles was decreased as compared to normal, whereas SOL muscles from normal and dexamethasone-treated animals showed no significant difference. Muscle fibre diameters also showed comparatively minor changes in SOL, which consists of Type 1 (slow oxidative) and Type 2A (fast oxidative/glycolytic) fibres. Rat EDL contains, in addition to Type 1 and Type 2A fibres, two sub-populations of fast glycolytic fibres (Types 2B and 2B'). These fibre types showed the most severe degree of atrophy both after dexamethasone treatment and after denervation. The mean ratio of the weights of denervated to innervated EDL muscles was lower in steroid-treated rats than in normal animals suggesting that the atrophy produced by steroid treatment in conjunction with denervation was more than simply additive. Analysis of the proportions of histochemical fibre types in SOL and EDL showed that dexamethasone treatment produced no major alterations in the fibre type constitution of these muscles. However, further histochemical studies showed that there was relatively severe impairment of myophosphorylase activity in Type 2B' (fast glycolytic) fibres as compared to other fibre types; conversely Type 1 fibres frequently contained increased myophosphorylase. Levels of beta-hydroxybutyrate dehydrogenase were low in both normal and steroid-treated EDL but high in SOL which also showed higher general oxidative activity. It is suggested that the particular susceptibility of fast glycolytic fibres to atrophy as a result of steroid treatment may be linked to: 1 the relatively severe reduction of myophosphorylase activity in these fibres and 2 their comparative inability to utilize alternative energy sources, especially substrates derived from free fatty acids.

Sideband generation in frequency-modulated continuous-wave light through nonlinear near-resonant propagation in an atomic vapor

We have observed sideband generation in the spectrum of frequency-modulated light when the light is transmitted near resonance to the D(1) line in Na vapor. The temporal pulse reshaping that gives rise to the self-phase modulation phenomenon is in good agreement with the predictions of a one-dimensional two-level off-resonant Maxwell-Bloch computer code.

Branhamella (Neisseria) catarrhalis--a lower respiratory tract pathogen?

Branhamella (Neisseria) catarrhalis was identified as a probable respiratory tract pathogen in seven patients, four with pneumonia and three with bronchitis. Five of the B. catarrhalis isolates produced beta-lactamase. Production of beta-lactamase correlated with penicillin resistance by the standardized disk diffusion method and also with high minimal inhibitory concentrations of penicillin for the two strains which were tested.

Peripheral absolute threshold spectral sensitivity in retinitis pigmentosa

Dark-adapted spectral sensitivities were measured in the peripheral retinas of 38 patients diagnosed as having typical retinitis pigmentosa (RP) and in 3 normal volunteers. The patients included those having autosomal dominant and autosomal recessive inheritance patterns. Results were analysed by comparisons with the CIE standard scotopic spectral visibility function and with Judd's modification of the photopic spectral visibility function, with consideration of contributions from changes in spectral transmission of preretinal media. The data show 3 general patterns. One group of patients had absolute threshold spectral sensitivities that were fit by Judd's photopic visibility curve. Absolute threshold spectral sensitivities for a second group of patients were fit by a normal scotopic spectral visibility curve. The third group of patients had absolute threshold spectral sensitivities that were fit by a combination of scotopic and photopic spectral visibility curves. The autosomal dominant and autosomal recessive modes of inheritance were represented in each group of patients. These data indicate that RP patients have normal rod and/or cone spectral sensitivities, and support the subclassification of patients described previously by Massof and Finkelstein.

Clinical use of a gadolinium filter in pediatric radiography

Patient exposure is an important consideration in pediatric radiography. Gadolinium filtration can be used to reduce exposure while maintaining contrast. Matched sets of pediatric radiographs were produced using aluminum and gadolinium filtration. In almost all cases, no difference or only a minimal difference in diagnostic quality was judged to be present. Patient exposure can be reduced up to a factor of 2 using a gadolinium filter, despite doubling the product of tube current and exposure time (mAs). Because images of comparable diagnostic quality can be produced using gadolinium filtration, with a reduction in radiation exposure to the patient, its use is recommended in pediatric radiography.

Spontaneous splenic rupture in infectious mononucleosis: sonographic diagnosis and follow-up

Spontaneous rupture of the spleen occurs as a serious but relatively infrequent complication of infectious mononucleosis. Over 100 such cases have been reported. In all but one of the cases previously reported, diagnosis of splenic rupture was made at laparotomy. Three new cases are reported where the diagnosis of splenic rupture was made using sonography. The patients were followed by sonography and none required laparotomy. Aspiration of the hematoma under sonographic control confirms the diagnosis and may be curative.

Two rat mononuclear cell-derived slow reacting substances: kinetic evidence that the peripheral airways-selective spasmogen is derived from a nonselectively acting precursor

The purpose of this study was to extend our knowledge of two slow reacting substances that are formed in rat mononuclear cells upon stimulation by the ionophore A 23187. Slow reacting substance (SRS) preparations were further purified through the sequential high performance liquid chromatographic procedures starting with exudates from cells that had been prelabeled with tritiated arachidonate. Approximately 2% of the released radioactivity (0.3% of the radioactivity that was taken up by the cells) cochromatographed with biologic activity in both preparations. Kinetic studies revealed that one of the SRSs was formed more rapidly than the other and analysis by nonlinear computer modeling techniques suggests a possible product-precursor relationship between the two substances. Activity of the preparations on guinea pig lung parenchyma and trachea was compared using a histamine standard; only the more slowly formed substance had the selective activity on the parenchyma that we associate with slow reacting substance of anaphylaxis (SRS-A). Taken together, these findings suggest that a material which may be a precursor of SRS-A, if it is also formed and accumulated in vivo, may contribute to the more central airway constriction which is seen in some asthmatics.