Respirator fitting: the key to protecting workers

How can you be sure that workers are being properly fitted with respirators? For now8 quantitative fit tests are the best way, unless hazards are minimal.

Purification of the fusion protein of Sendai virus: analysis of the NH2-terminal sequence generated during precursor activation

The two glycoproteins of Sendai virus, the hemagglutinin-neuraminidase and the fusion protein (F), were separated and purified by affinity chromatography on a Lens culinaris lectin-Sepharose column. F was shown to consist of two disulfide-bonded glycopolypeptide chains, F1 and F2, of molecular weights 51,000 and 11,000, each of which contained 15% carbohydrate by weight. Amino-terminal sequence analysis showed that F2 was blocked and that the hydrophobic sequence NH2-Phe-Phe-Gly-Ala-Val-Ile-Gly-Ile-Ile-Ala-Leu-Gly-Pro-Ala-Thr- was at the amino terminus of F1. This sequence shows identity at six positions with the hydrophobic amino-terminal sequence of the smaller glycopolypeptide chain, HA2, of the hemagglutinin of influenza virus. Both F1 and HA2 are formed by proteolytic cleavage of precursor glycoproteins (Fo, Sendai virus; HAo, influenza virus). Since these cleavages confer infectivity upon both Sendai and influenza viruses and the ability to induce cell-to-cell fusion upon Sendai virus, the hydrophobic NH2-terminal sequences on F1 and HA2 may play a role in fusion of viral and host-cell membranes.

Serum-alpha-hydroxybutyrate dehydrogenase levels in sickle-cell disease and sickle-cell crisis

In patients with sickle-cell disease (Hb S/S disease) who are not in crisis, the serum-level of alpha-hydroxybutyrate dehydrogenase (alpha-H.B.D.) is significantly above normal. The degree of elevation correlates with the severity of the disease. During infarctive crises the level increases still further by a factor of 2 to 3, and it returns to the patient's normal level on recovery. The level of alpha-H.B.D. thus provides an index of the severity of the disease. Also, it allows distinction between true infarctive crisis, infection, and fake symptoms. In 5 patients a rise in the level of alpha-H.B.D. above the patient's normal level was detected several days before the onset of symptoms, which suggests that there may be a "prodromal" phase.

Plasmapheresis in Raynaud's disease

Understanding of the pathogenesis, clinical course, and treatment of Raynaud's disease is confused and unsatisfactory, and no success in treatment can be promised. Five patients with severe Raynaud's disease, who had not responded to other forms of treatment, were treated by plasmapheresis, which produced a striking improvement. Ultrasonic velocimetry showed that segments of digital arteries which had been thought to be permanently occluded became patent and remained patent after plasmapheresis.

Serum cholesterol, activity, feed intake, and body weight in lines of mice selected for growth

Feed intake, growth and serum cholesterol (SC) were recorded on 102 male mice, and voluntary physical activity and SC were recorded on 113 male mice from lines selected for maximum 21- to 42-day weight gain (H), for minimum 21- to 42-day weight gain (L), and from a random-bred unselected control line (C). Voluntary physical activity in a revolving wheel was recorded for a 22-h period every sixth day from 3 to 10 weeks of age. Growth and feed intake on two different diets (diet 1 containing 4.5% fat and 23.4% protein; diet 2 containing 11% fat and 17% protein) were measured three times per week and rate of weight gain was calculated on a weekly basis. Blood samples were obtained by sinus orbital bleeding at 5 and 10 weeks of age after six hours fasting and analyzed for SC by gas chromatography. A least squares analysis of variance of the SC data using a model including lines, diets, ages and all possible interactions indicated highly significant differences in the main effects and in most of the interactions. SC and growth were higher and feed intake was lower in mice on diet 2. SC values (mg/100 ml) were 143.3, 124.1 and 132.2 at 10 weeks of age for H, C and L line animals fed diet 1 and 220.3, 178.1 and 180.4 for animals fed diet 2. An analysis of variance in the activity data resulted in highly significant differences in the main effects (line and age) but revealed no significance in the interaction. Activity scores (revolutions) for the H, C and L lines were 79234, 107987 and 124409, respectively for eight 22-h periods. Activity reached maximum levels at 56 days of age, then declined slightly. Within line phenotypic correlations between SC and activity and between SC and feed intake were significant throughout ages of testing only in the high line.

Diagnosis of alpha-thalassemia trait from Coulter Counter 'S' indices

A number of patients of Mediterranean and Asian origins were found to have unexplained microcytic hypochromic red blood cells. Iron deficiency and beta-thalassaemia trait were both satisfactorily excluded in all of them. The haematological indices of these patients, obtained on a Coulter Model 'S' Counter, were found to be very similar to those seen in obligatory heterozygotes for alpha-thalassaemia. It is postulated that these patients were also carriers for alpha-thalassaemia. Subsequent investigation of some of these patients showed the characteristically reduced rates of alpha-chain synthesis seen in this condition. The discriminant function of England and Fraser (1973) may be of help in diagnosing this state. alpha-Thalassaemia trait should be considered in all patients of 'high-risk' ethnic origins with a blood picture suggestive of beta-thalassaemia trait but in whom the levels of Hb A2 and Hb F are within normal limits.

Genetic parameters of serum cholesterol levels, activity and growth in mice

Heritabilities (h2) of, and phenotypic and genetic correlations among, serum cholesterol (SC), levels of physical activity, growth, and body moisture content were estimated from data on 466 sire-son pairs of random-bred, ICR albino mice. Heritability estimates of SC and body moisture content were 0.31 +/- 0.07 and 0.29 +/- 0.11, respectively. Estimates of h2 for activity measured by standard exercise wheels at 28, 49 and 70 days of age were 0.31 +/- 0.17, 0.50 +/- 0.11 and 0.27 +/- 0.14 and for weight at 21, 44 and 67 days of age, were 0.11 +/- 0.09, 0.33 +/- 0.09 and 0.42 +/- 0.08, respectively. The estimates of h2 for weight gain ranged from 0.22 +/- 0.07 to 0.27 +/- 0.08. Significant negative phenotypic correlations occurred between activity and rate of body weight gain. A negative genetic correlation of -0.70 +/- 0.11 between SC and body moisture implied that SC and percent body fat are positively correlated. Genetic correlations among SC values and activity scores and between SC values and body weight gains were near zero.

Compensatory mechanisms for the severe anaemia caused by haemoglobin Hammersmith

A severely anaemic, but asymptomatic patient, who is a heterozygous carrier of haemoglobin Hammersmith (beta42 (CD1) phenylalanine - Serine), has been studied to elucidate the mechanisms resulting in physiological compensation for the anaemia. Four factors have been investigated: the oxygen affinity of her blood, the cardiac output at rest and during exercise, the blood gas indices, and pulmonary function. It was found that due to the presence of Heinz bodies within the erythrocytes, the level of functional, haemoglobin was considerably less (50 g/l) than that measured by standard methods (87 g/l). In addition a moderate degree of arterial hypoxaemia (arterial oxygen tension = 10.7 kPa (80.4 mmHg) was present which could not be explained on the basis of abnormal pulmonary function. Both of these factors would result in tissue hypoxia, but the finding of consistently normal oxygen tensions ('mixed' venous oxygen tension = 5.4 kPa (40.3 mmHg) in blood obtained from the right atrium, suggested that hypoxia was not present. This was explained by a decreased whole blood oxygen affinity (P50 = 4.6 kPa (34.5 mmHg) at pH 7.4) and an increase in the cardiac index (5.3 L.min.-1m-2). The latter was the result of an increased stroke volume (125 - 135 ml), the heart rate being normal (63/min.). During moderate exercise, further increases at cardiac output were brought about by a change in heart rate alone. It has been calculated that the decrease in whole blood oxygen per se could not account for adequate tissue oxygenation. This is confirmed by the finding of an increased cardiac output in this patient. It is suggested that in any severe haemolytic anaemia, even if the whole blood oxygen affinity is low, cardiac output is probably increased to achieve complete physiological compensation.

Increasing whole blood oxygen affinity during rapid exchange transfusion: a potential hazard

Whole blood cell separators are being used to achieve partial exchange transfusions in patients with hemoglobin S. The rate and extent of the alteration of whole blood oxygen affinity, incurred by this procedure, has been determined in a patient with Hb S/C disease. The implications in terms of oxygen delivery to the tissues are described for this patient and also for patients with the more severe disease associated with Hb S/S. It is concluded that whole blood cell separators should be used with an awareness of the possible detrimental effects of acute increases of whole blood oxygen affinity in these patients.

Optical waveguide refractive index profiles determined from measurement of mode indices: a simple analysis

The WKB approximation is used to derive simple equations that predict the shape of the index profile from measured mode indices of a planar optical waveguide. This nondestructive test is a useful tool in the study of diffused guides. The index profile is assumed either to decrease monotonically from the surface or to be symmetrical in the case of a buried guide. The approximation uses straight line segments to connect the measured points. Results are compared with mathematical solutions for exponential, Fermi, and step distributions and with other independent experimental observations of the profile in a nickel-diffused LiNbO(3) guide.

Heterosis, sex and maternal interactions in crosses among inbred lines of mice

All possible crosses and reciprocals were made among four inbred lines (F = 92%) developed from 12 generations of full-sib mating. All lines originated from a common outbred base population of ICR-albino mice. Data were obtained from 356 litter containing 2,734 mice to evaluate heterosis, reciprocal effects, sex effects and their interactions as they affect body weight and weight gain. Heterosis was significant for most of the postweaning traits (42- and 56-day weight and gain from 21 to 42 days). Nonadditive gene action may have included overdominance and epistasis since both reciprocal linecrosses were generally heavier than those of the better inbred lines. Although significant differences in reciprocals and inbred lines were not frequent, there were sufficient differences to indicate that lines varied in the fixation of loci during inbreeding. Sex-heterosis interactions were significant for 12 of 30 possible cases. However, eight of the 12 significant interactions occurred in crosses involving only one of the lines. The interactions were of the divergent type and arose from males exhibiting more heterosis than females. Overdominance in genes on the sex chromosomes modified by other loci (epistasis) was proposed as a possible explanation for these results. Some sex-linkage affecting growth was evident from the interaction of sex with reciprocal effects.

Bioavailability of sodium cyanate in patients with sickle cell disease and the lack of inhibition in vitro of globin synthesis at in vivo concentrations of cyanate

Studies have been made on the bioavailability in blood of sodium cyantate administered orally in gelatin capsules, in gelatin capsules plus antacid, in enteric-coated capsules and in cocoa butter suppositories administered rectally to patients with sickle cell disease. Maximal blood concentrations of cyanate did not exceed 0.4 mM. Sodium cyanate taken orally in gelatin capsules yielded the highest blood concentrations of the drug, but the peak concentrations and curve areas were not necessarily dose-related. The duration of the drug in the circulation was about 210 minutes. Administration of sodium cyanate in the gelatin capsules, taken with an antacid, improved the dose-response relationship within a given patient. Enteric-coated capsules and suppositories were found to show variable and low bioavailability profiles, respectively. Variability in bioavailability between patients with a given dosage form requires further study. Since the concentration of cyanate attainable in vivo does not inhibit synthesis of either the alpha- or beta-chain of hemoglobin in vitro, previous reports on the inhibitory effects of 10 to 100 mM cyanate on globin synthesis in vitro do not appear to be relevant.

The effect of lead on the red cell membrane

Conformational changes have been shown in the proteins of the red blood cell membrane, induced by lead poisoning. Evidence that the change in spatial arrangement of proteins is believed to be responsible for inhibition of the sodium (Na⁺)/potassium (K⁺) ATPase of the RBC membrane is presented.

Diallel analysis of growth traits in mice

Two replications of a complete diallel cross experiment were performed among four partially inbred lines of mice. These inbred lines originated from a random-bred ICR strain and were produced by 12 generations of full sibbing (F congruent to 92%). Individual body weight was recorded for each animal at 12, 21, 42 and 56 days of age. Body weight gain traits were examined for intervals 12-21, 21-42 and 42-56 days. Simultaneous least squares analyses of inbred and linecrossed groups were used. Sex differences were highly significant for all traits. Replicate differences were significant but made a small contribution to the total variation. Inbred lines differed greatly. Crosses showed growth trends similar to their contemporary maternal and paternal inbreds. Heterosis was highly significant for all traits except 21-day weight. Inbreds were heavier at 12 days of age, but linecrossed progeny were superior to inbreds for all postweaning weights. General combining ability was highly significant for 12- and 56-day weights and 21-42-day gain. Specific combining ability was highly significant for 21-day weight, 12-21- and 42-56-day gain. Significant maternal effects were found for all individual weights but not for 12-21- and 21-42-day gain. Residual reciprocal effects were significant for all traits. Estimated variances among linecrossed groups contained a large maternal component, a fluctuating additive genetic component and consistent non-additive genetic influence on all growth parameters measured.

Thalassaemia, iron, and pregnancy

Haematological values of 35 pregnant women with beta-thalassaemia trait were followed during pregnancy. The discriminant function, calculated from haematological indices, was of no value in diagnosing beta-thalassaemia trait during pregnancy. Initially patients were given iron supplements only if the serum iron and total iron binding capacity levels indicated iron deficiency, but bone marrow biopsies performed in the first 22 patients at 32 weeks indicated deficient iron stores. These patients were therefore given iron irrespective of their serum iron level. All subsequent patients with beta-thalassaemia were also put on iron routinely at booking. Retrospectively the patients were divided into two groups. Patients in group 1 (18 patients) had received iron for less than 12 weeks, and their haemoglobin levels fell significantly during pregnancy (P less than 0-001). Haemoglobin levels in 16 patients who had received iron for more than 12 weeks (group 2), however, did not fall significantly during pregnancy (P less than 0-6). It is suggested (contrary to common practice) that patients with beta-thalassaemia trait should be given iron supplements during pregnancy. Serum folate and vitamin B12 levels did not change significantly in these patients and there was no increase in the incidence of maternal or fetal complications.

Milk yield in lines of mice selected for growth or maternal ability

Two experiments were conducted to measure milk yield as a correlated response to selection for increased 12-day litter weight (maternal lines) for 13 generations and increased and decreased body weight gain from 21 to 42 days of age (postweaning gain lines) for 12 to 14 generations. Milk yield was measured from day 6 to day 21 of lactation by separating litters from their dams for 6 h, then weighing litters before and after a 1.5 h suckling period. Average total milk production was 30.3 +/- 0.9 g and 28.6 +/- 1.1 g in maternal and control lines, respectively. This difference was not significant (P greater than 0.05). Differences among gain lines were significant (P less than 0.01) in the second experiment with average production of 44.1 +/- 1.4 g for increased gain lines, 22.5 +/- 0.9 g for the decreased gain line and 31.2 +/- 1.0 g for the control. These results indicated that response to selection for increased 12-day litter weight was not associated with increases in milk yield, but sizable changes inmilk yield accompanied bi-directional selection for early postweaning gain.