Cloning and sequence analysis of the VH and VL regions of an anti-myelin/DNA antibody from a patient with peripheral neuropathy and chronic lymphocytic leukemia

We have cloned and determined the nucleotide sequence of the Ig VH and VL region genes of an IgM kappa mAb that binds to denatured DNA and myelin from a patient (POP) with chronic lymphocytic leukemia and peripheral neuropathy. Sequence analysis indicates that the V region of the kappa L chain gene (PopVK) has 99% homology to a V kappa IIIa germ-line gene and the V region of the mu H chain gene (PopVH) has 96% homology to the VH26 germ-line gene that is a member of the VH3 gene family. It is likely the V kappa and VH genes arose from these respective germ-line genes via somatic mutation or from closely related genes. V kappa III genes have frequently been used by other IgMk mAb especially those with rheumatoid factor activity, and the VH26 gene with no somatic mutation has been used by several anti-DNA antibodies, suggesting the possibility of preferential association of these or related germ-line genes with autoantibodies. The minor differences between the sequences of POP's VH and V kappa genes and sequences used by other autoantibodies, may be responsible for this antibody's crossreactivity with myelin and, as a result, the autoimmune neuropathy.

Molecular cloning of a human immunoglobulin heavy chain variable (VH) region with anti-myelin-associated glycoprotein activity

A cDNA clone that encodes the heavy chain variable region (VH) of an IgM M-protein with anti-myelin-associated glycoprotein (MAG) activity secreted by chronic lymphocytic leukemia cells (B-C11) from a patient with peripheral neuropathy was cloned and sequenced. The JH region was identical to the germline JH4 sequence except for deletion of a thymidine residue at the site of D-JH recombination, and the D region showed greatest homology to DM2. Sequence analysis of the VH region revealed greatest homology to VH26, a member of the VH3 gene family, but homology was only 83.7% over 326 bases, suggesting that it was derived from as yet an unidentified member of the VH3 gene family.

School eye health appraisal

School children form an important large target group which must be screened adequately for early detection of eye diseases and prevention of blindness. A total approach in a school eye health programme must include teacher orientation and health education of children in addition to screening for eye diseases. The ocular morbidity pattern in 5135 school children of Jodhpur is discussed in this paper and it is hoped that it will be an indicator to all eye care agencies to help plan their priorities in the delivery of school based eye care.

Assessment of elastin maturation by radioimmunoassay of desmosine in the developing human lung

Desmosine has been quantitated in the normally grown fetal and early infant lung by radioimmunoassay. Desmosine could first be detected at 22 weeks gestation: the concentration of desmosine expressed per milligram lung DNA increased in approximately linear form up to about 55 weeks postconceptional age. The concentration in peripheral lung was approximately half that in whole lung homogenates. Lungs of infants dying with acute HMD and lungs of growth retarded infants showed no significant differences from the normals, although there was a tendency for higher desmosine concentrations in prematurely born growth retarded infants.

Quantitative aspects of perinatal lung growth

Weight, DNA, protein, hydroxyproline and disaturated phosphatidylcholine (DSPC) content were investigated in lungs of 97 normally formed infants over an age range from 22 to 75 postconceptional weeks, including 25 cases of hyaline membrane disease (HMD) and 13 small-for-dates infants (SFD). Lung weight and lung DNA relative to body weight were markedly lower in infants who died at 37-41 weeks than in those who died at shorter gestations or in early infancy. Total lung DSPC and DSPC concentration had a narrow peak at 36-41 weeks. The DSPC concentration per milligram of lung DNA in the first few months of infant life was similar to that in infants at 24 weeks gestation. Lung protein concentrations increased steadily but were variable at all ages. SFD infants had significantly higher concentrations of hydroxyproline and showed a peak DSPC concentration at an earlier gestation than the normals. Lungs of HMD infants showed some increase in hydroxyproline concentration but little other quantitative evidence of difference from the normals. We suggest that the relatively small lung size in many infants who die near term may result from recurrent intrauterine stress. Lung changes in small for dates infants are compatible with an advance in lung maturation, while the increased hydroxyproline concentration in the lungs of cases of HMD implies an early proliferative response to lung injury.

The effects of preterm delivery and mechanical ventilation on human lung growth

The effects of preterm birth and mechanical ventilation on growth of the alveolar region of the lung were assessed by morphometric and/or quantitative biochemical methods in the lungs from 104 perinatal and infant autopsies. The lungs of 4 preterm infants who died at 4-16 weeks age without having received mechanical ventilation were large relative to body weight but showed normal alveolar number and alveolar surface area. Infants treated by mechanical ventilation for hyaline membrane disease (HMD) and who died at ages from 1 week up to 14 months showed impairment in alveolar development evidenced by low alveolar number and a low alveolar surface area. Lung volume and total lung DNA values were relatively normal. Dilated alveolar ducts were a feature at all ages with emphysematous changes apparent in the longest surviving infants. Biochemical features included a high concentration of hydroxyproline, reflecting collagen, and a high desmosine concentration, reflecting elastin, in infants dying at less than 60 weeks postconceptional age. Changes in the lungs of infants ventilated at low pressures for conditions other than HMD were of a similar nature but less severe than those seen in the HMD group. These findings indicate that preterm birth alone may have little adverse influence on lung development but that conditions necessitating mechanical ventilation may lead to permanent impairment in alveolar development. We postulate that the standard technique of applying positive pressure ventilation may itself lead to impaired alveolar growth, although the effect is enhanced by concomitant HMD and BPD.

Fetal lung growth in congenital laryngeal atresia

Morphometric and biochemical indexes of lung growth were measured in 2 cases of uncomplicated laryngeal atresia at 27 and 30 weeks gestation and in 1 case of cryptophthalmos syndrome with anomalies including laryngeal atresia and renal agenesis. Findings were compared with those in normally formed fetuses and newborn infants. The cases of pure laryngeal atresia showed a marked increase in surface area and lung volume for age, associated with an increase in alveolar number and apparent advance in elastin maturation, but little increase in cell population as measured by lung DNA content. Alveolar walls were thin but there was no increase in disaturated phosphatidylcholine (DSPC) content. Similar features were observed in the case of cryptophthalmos in marked contrast to the lung hypoplasia expected to result from renal agenesis. The results give further support to the importance of lung liquid retention for normal fetal lung growth. Overdistention with lung liquid appears to promote alveolar development by redistribution of cells rather than increase in cell population.

Sex hormone levels in young Indian patients with myocardial infarction

The finding of abnormal levels of sex hormones in men with coronary artery disease has led to the hypothesis that alterations in sex hormones may represent an important risk factor for myocardial infarction. In this study, the sex hormone profile of 28 young men (aged less than 40 years) with myocardial infarction was compared with 28 age- and weight-matched normal men. Although the mean total serum estradiol levels and the free estradiol index of the patients and controls were similar, the mean serum total testosterone level and the free testosterone index were significantly lowered in the patients with myocardial infarction (p less than 0.01). The ratio of serum estradiol to testosterone was significantly increased in the patients (p = 0.0005) and correlated with serum cholesterol, triglycerides, and plasma glucose. A significant inverse correlation was also demonstrated between total testosterone and serum cholesterol and triglycerides. Hence, the results of this study support the hypothesis that low plasma testosterone and an increased estradiol-to-testosterone ratio may be important risk factors for myocardial infarction.

Prolactin secretion in Sheehan's syndrome. Responses to thyrotropin-releasing hormone and metoclopramide

The prolactin response to thyrotropin-releasing hormone (TRH) and metoclopramide was studied in 16 patients with Sheehan's syndrome and 16 matched controls in the follicular phase. Metoclopramide resulted in a greater prolactin response than TRH did in the controls. However, both stimuli failed to evoke any appreciable prolactin response in the patients with Sheehan's syndrome. Since metoclopramide is generally free of side effects and far cheaper than TRH, we recommend the prolactin response to metoclopramide as the preferred screening test in the diagnosis of Sheehan's syndrome.

Alveolar development in the human fetus and infant

The lungs from 29 infants aged from 29 weeks of gestation to 18 weeks postnatal age were studied using morphometric analysis; total DNA was estimated in 12 of these. Alveoli could first be counted and measured at 29 weeks gestation; with increasing age they became more mature in appearance as the walls elongated and thinned, and they gradually increased in diameter. Lung volume increased 4-fold between 29 weeks and term, and further doubled in the 4 months after birth. Lung volume, alveolar surface area and DNA all increased linearly with age and weight. Alveolar number showed a curvilinear increase with age and DNA, but a linear relationship to body weight. At birth the lungs had an average of 150 million alveoli, half of the expected adult number. There was a wide normal range. The surface area was between 3 and 5 m2 at birth, one twentieth of the adult value.

Intravenous glucose tolerance tests in women with twin pregnancy

Carbohydrate metabolism was evaluated in 20 twin gestations and 20 singleton pregnancies. The groups were matched for age, parity, weight, height, and gestational age. Intravenous glucose tolerance tests were performed on all women in the third trimester of pregnancy using a glucose load of 0.5 g/kg body weight. Venous plasma glucose and insulin level were measured and statistically compared. The glucose disappearance rates (K) were not different in the two groups. No significant differences in the mean insulin or glucose responses were found between singleton and twin pregnancies. Thus, twin gestations are not at higher metabolic risk of gestational diabetes than are singleton pregnancies.

Small calvarial bone scan foci--normal variations

In a series of 3,000 bone scans reviewed retrospectively 21 (0.7%) small calvarial foci were observed. Seventeen of these lesions were found along skull suture lines. No evidence for metastatic disease could be found. Skull radiographs were normal and follow-up bone scans demonstrated no change in the size or location of the lesion. These intense calvarial foci are thought to represent normal variations; among the possibilities are subradiographic cartilaginous rests, sutural foramina, or enlarged Pacchionian granulations.

Insulin secretion in healthy Indian volunteers

The insulin response to a 100 g oral glucose load was studied in 20 non-obese, healthy Indian females and 20 matched Indian males. There were no differences between the mean glucose responses of the two groups. However, early-phase (0-60 minutes) insulin release was significantly greater in the females. While there were no significant differences between the two groups when the total areas under the insulin and glucose curves were computed, the female volunteers had a significantly higher mean insulinogenic index. It therefore appears that healthy Indian females have significantly greater early-phase insulin release than their matched male counterparts.

A prospective study of intrapulmonary fat accumulation in the newborn lung following intralipid infusion

In order to assess the safety and stability of a parenteral fat emulsion (Intralipid) in total parenteral nutrition (TPN), 29 infants were infused Vamin glucose and Dextrose electrolyte solution as well as one of two isocaloric regimens; either 25% Dextrose (Group I) or 10% Intralipid (Group II). Regular biochemical monitoring was performed in all cases and no infants became lipaemic nor developed abnormally high levels of total free fatty acid. Eight infants died and only those who had received fat emulsion had lipid staining material distending the pulmonary vessels. One infant having low infusion rates of Intralipid had massive fat accumulation in the lungs, but biochemistry during life had been normal. We speculate that in ill infants the emulsion becomes less stable and agglomeration of fat particles occurs which are then fully filtered out by the lungs before metabolism of the exogenous fat can occur.

Low-dose streptokinase for occluded Hickman catheters

In 14 patients, 16 episodes of occluded Hickman catheters were evaluated by contrast venography. In 13 instances, a fibrin sheath occluding the distal catheter was observed. A mechanical problem was responsible for occlusion in three catheters. Low-dose streptokinase effectively restored lumen patency in 12 catheters (92%) occluded by a fibrin sheath.

Effects of chrysotile on a lysosomal enzyme preparation and on the hydrolytic enzyme activity of cultured alveolar macrophages

The interaction between chrysotile and three lysosomal enzymes (acid phosphatase, acid RNase and acid protease) in isolated lysosomal enzyme-rich preparations (LEP), from sheep alveolar macrophages maintained in the presence and absence of serum components or pulmonary surfactant at pH 5.0 and pH 7.0 for up to 22 days, is investigated. It is concluded that chrysotile does not inhibit or enhance lysosomal enzyme activity at either pH but may preferentially absorb specific enzymes and that the binding reaction between any given enzyme and mineral can be dependent on the presence of other organic compounds. The release of three hydrolytic enzymes (beta-galactosidase, acid RNase and protease) from cultured rabbit alveolar macrophages, in the presence of different concentrations of bovine serum (5-20%) and in the presence and absence of chrysotile for 72 hr, was also studied. Chrysotile enhances early differential release of each hydrolytic enzyme, but after 72 hr both control and chrysotile-treated cultures (maintained in 10-20% serum) have very similar intra- and extracellular levels of hydrolytic activity. The apparent differential release of lysosomal enzymes by untreated macrophages, which is dependent on serum concentration and time in vitro, is discussed.

beta-hemolytic streptococcal infection appearing as persistent fetal circulation

Sixty neonates who were transferred to a neonatal intensive care unit during a four-year period had diagnoses of persistent fetal circulation (PFC). Six of these 60 neonates had beta-hemolytic streptococcal infection. The clinical appearance of these six neonates included respiratory distress, cyanosis, and/or apnea. The chest roentgenograms showed mild to moderate lung disease. All six neonates had progressive acidosis with hypoxemia. The diagnosis of PFC was made by cardiac catheterization or contrast echoangiography. The neonates were treated with mechanical ventilation, antibodies, and supportive therapy, including tolazoline hydrochloride. Mortality was high; only one of the six neonates survived. Streptococcal infection should be added to the growing list of conditions associated with PFC.

High prevalence of symptomatic bradyarrhythmias due to atrioventricular node-fascicular and sinus node-atrial disease in patients with mitral anular calcification

Mitral anular calcification (MAC) is associated with high frequency of conduction defects. To delineate this association in patients with symptomatic bradyarrhythmias, 68 consecutive patients requiring pacemakers (group I) and 56 matched controls (group II) were studied. The patients comprised 41 men and 27 women, whose ages ranged from 24 to 92 years (mean 68). The control group consisted of 56 subjects without bradyarrhythmias, whose ages ranged from 30 to 86 years (mean 70); there were 36 men and 20 women. MAC was detected in 59 patients (87%) with symptomatic bradyarrhythmias compared with 8 subjects (14%) in the control group. In group I, 15 patients (22%) had complete atrioventricular block, 23 patients (34%) had atrial fibrillation with slow ventricular response, and 30 patients (44%) had intermittent sinus arrest. The incidence of MAC was similar among these subgroups (93%, 83%, and 87%, respectively). Thus the present study confirms the strong association of MAC with symptomatic bradyarrhythmias.

Is fetal respiratory function a major determinant of perinatal survival?

A high proportion of infants who die in the perinatal period have undersized lungs of reduced weight and DNA content relative to body weight. Failure of formation or leakage of amniotic fluid causes a spectrum of changes varying from severe failure of growth and maturation of the lung to a predominantly maturational deficiency. The changes are associated with narrow airways suggesting a failure to secrete or retain lung liquid. Conditions in which there is reduction of thoracic volume, or certain neural and muscular abnormalities, are associated with failure of lung growth without impaired maturation. Studies in animals indicate that liquid secretion into the fetal airways and breathing movements are essential for normal lung growth. Such functions are readily inhibited by operations, drugs, or non-specific forms of stress. The success or failure of adaptation to extrauterine respiration may often be determined by the balance of actors influencing respiratory function in early fetal life.

Chemistry and hypoglycemic activity of benzimidoylpyrazoles

A series of benzimidoylpyrazoles was synthesized and evaluated as hypoglycemic agents. Methyl 1-(N-cyclohexylbenzimidoyl)-5-methyl-3-pyrazolecarboxylate (13) and methyl 1-[N-(4-methoxyphenyl)benzimidoyl]-5-methyl-3-pyrazolecarboxylate (33) are two of the more interesting compounds. A comparison of these benzimidoylpyrazoles with classical standards (tolazamide, phenformin, and buformin) in several experimental models show that these compounds seem to combine in one molecule some of the biological activities of the beta-cytotrophic sulfonylureas and some of the activities of the biguanides. A synthetic scheme for the preparation of the benzimidolypyrazoles and a preliminary structure-activity relationship are presented.

Use of DNA estimation for growth assessment in normal and hypoplastic fetal lungs

Total DNA was estimated in the lungs of 80 fetuses and newborn infants varying in gestation from 14 weeks to term. In fetuses of appropriate weight for gestational age total lung DNA increased at a constant rate from about 35 mg at 17 weeks' gestation to 480 mg at term. The lungs of immature fetuses were heavier and contained more DNA relative to body weight than did those of mature infants. Small-for-dates infants had lower lung DNA levels for gestation than infants with weights appropriate for gestational age, but there was no difference when lung DNA was corrected for body weight. Lung hypoplasia defined in terms of lung/body weight ratio was associated with low lung DNA content for gestation, even when corrected for body weight. The total lung DNA at 34-40 weeks' gestation in infants with lung hypoplasia associated with fetal anuria or urinary outflow obstruction was equivalent to that seen in normal fetuses at 20-22 weeks' gestation. We conclude that the early second trimester is a critical period for human fetal lung growth.

Fetal lung hypoplasia: biochemical and structural variations and their possible significance

Quantitative biochemical criteria for lung growth and maturation were compared with the histological appearances in hypoplastic lungs from 20 fetuses and newborn infants. Cases associated with oligohydramnios showed a characteristic series of changes with narrow airways, retardation of epithelial and interstitial growth, delay in development of blood-air barriers, and low concentrations of phospholipid phosphorus, lecithin phosphorus, total palmitate, and lecithin palmitate. The growth and maturation arrest appeared to affect the peripheral part of the acinus. Examples of other types of lung hypoplasia showed different features. Hypoplastic lungs from infants with normal or increased amniotic fluid were of mature structure with phospholipid concentrations similar to those of infants with normally developed lungs at term. The hypoplastic left lung in 2 cases of congenital diaphragmatic hernia had an immature structure with low phospholipid concentrations, whereas the right lung has structurally and biochemically more mature. It is suggested that fetal lung growth may be impaired by any influence which reduces thoracic volume but that maturation arrest is due specifically to loss of the ability to retain lung liquid.

Pulmonary fat accumulation after intralipid infusion in the preterm infant

Eight preterm infants who died after 'Intralipid' infusion had fat accumulation in the lungs. The rate of infusion in six of the infants was below the recommended maximum for preterm infants and in no case was the plasma lipaemic on regular visual inspection. Histological examination revealed varying degrees of lung involvement. The commonest finding was distension of empty pulmonary capillaries, but specific staining techniques for fat showed that the capillaries were engorged with large lipid globules. Removal of accumulated fat by histiocytes was seen in infants dying some time after cessation of intralipid infusion. Analysis of homogenised lung showed that those who died after intralipid infusion had a significantly greater (p < 0.001) concentration of lioleic acid, a marker for intralipid, than infants who died without receiving parenteral fat solution. Fat accumulation after intralipid infusion may be common but unrecognised and may seriously exacerbate ventilation/perfusion inequalities.

The induction of lysosomal enzyme release from leucocytes of normal and emphysematous subjects and the effects of tobacco smoke upon phagocytosis

1. The lysosomal enzymes of circulating polymorphonuclear leucocytes contain a potent elastase; release of this enzyme within the lung is thought to be responsible for the destruction of elastic tissue in pulmonary emphysema.

2. The release of lysosomal enzymes from blood leucocytes of normal and emphysematous subjects during phagocytosis of particulate material was studied In vitro. Acid phosphatase and acid ribonuclease were used as markers of lysosomal enzyme release, no sufficiently sensitive assay for elastase being available. Cigarette smoke was separated into ‘particulate’ and ‘soluble’ fractions. In a preliminary study, the particulate fraction stimulated enzyme release; in the experiments reported here, latex particles were used to produce this effect.

3. Approximately one-third of the total lysosomal enzyme content was released to the exterior of the cell during phagocytosis of latex particles. In this respect there was no difference between normal and emphysematous subjects.

4. The effects of the non-particulate soluble fraction of cigarette smoke on phagocytosis-induced enzyme release were studied. This fraction inhibited enzyme release from polymorphonuclear leucocytes of normal subjects but not from those of emphysematous patients. When the ‘cigarette-smoke solution’ was replaced by the respiratory inhibitor, antimycin A, a similar inhibition of enzyme release occurred. The inhibition of phagocytosis in cells of normal subjects is presumed to be due to a respiratory inhibitor such as carbon monoxide in the soluble fraction of the smoke. We postulate that the polymorphonuclear leucocytes of emphysematous patients are adapted to hypoxic conditions so that inhibition of enzyme release does not occur.

Effect on lung growth of cervical cord section in the rabbit fetus

Experiments were performed to clarify the mechanism by which cervical cord transection retards lung growth in the fetal rabbit. In 10 sets of fetuses operated on at 24 1/2 days gestation and studied 3--4 days later, cord section at C1--C3 (high section) caused a significantly greater reduction in lung weight and lung DNA than cord section at C5--C8 (low section) as compared with control littermates. Comparison with the lungs of additional control fetuses removed at the time of operation showed that high section had reduced lung growth by 70% and low section had reduced growth by 40% relative to sham-operated controls. The hypoplastic lungs of the high-section group had poorly expanded, thick-walled terminal sacs, while those of the low section group more nearly resembled the controls. Fetal weights and weights of liver, kidneys, thymus and diaphragm did not differ significantly between the groups, but the hearts of the low-section group were unduly large. In a separate 6 sets of fetuses tracheal ligation at the time of high-cord section was found to result in large fluid-filled lungs with a normal DNA content. The results indicate that preservation of an upper motor neurone supply to the phrenic nucleus is of critical importance for fetal lung growth, and confirm the growth-promoting effects of liquid distension of the fetal lungs. We conclude that normal fetal lung growth depends on development and maintenance of a sophisticated form of function involving integration of respiratory movements and lung lipid secretion. This functional control of fetal lung growth has important implications for perinatal medicine.

Studies on the fate of pulmonary surfactant in the lung

1. Radioactively labelled pulmonary surfactant was prepared in an isolated perfused lung system provided with [14C]hexadecanoate. 2. After intratracheal administration of pulmonary surfactant radioactively labelled components were rapidly distributed into different lung fractions, including macrophages (free cells), but most of the radioactive label was accumulated by the lung tissue. 3. Alveolar macrophages, maintained in a variety of culture media in the presence and absence of mineral particles, incorporated a low percentage (11%) of radioactively labelled components when incubated with the surfactant, although evolution of labelled CO2 (6% of the original total activity) suggested that some breakdown of the components had taken place. 4. In similar cultures little intracellular accumulation or extracellular release of non-esterified fatty acids was demonstrated, indicating minimal catabolism of the high-molecular-weight lipid components of surfactant (particularly phosphatidylcholine). 5. However, experiments in vitro designed to simulate the lysosomal degradation of endocytosed surfactant indicated that the macrophage had enzymes capable of releasing non-esterified fatty acids, particularly hexadecanoate, from the lipoprotein complex. 6. It is argued that lung cells, other than alveolar macrophages, may also have a role in surfactant turnover.

Purification of the heat-stable inhibitor protein of the Ca2+-activated cyclic nucleotide phosphodiesterase by affinity chromatography

The recently discovered heat-stable inhibitor protein of the Ca2+-activated cyclic nucleotide phosphodiesterase (Sharma, R. K., Wirch, E. & Warg, J. H. (1978) J. Biol. Chem., in press) has been purified 238 214-fold from bovine brain extract using an affinity column of the modulator protein--Sepharose 4B conjugate. The purified sample appears to be homogeneous as judged by sodium dodecyl sulphate (SDS) gel electrophoresis. The protein band has a mobility corresponding to that of a polypeptide of molecular weight 68 000. Since the heat-stable inhibitor protein has a molecular weight of 70 000 under nondenaturing conditions, it suggests that it is a monomeric protein. The protein has no inhibitory activity toward the cAMP-dependent protein kinase or protein phosphatase. The purified sample has been tested for various enzyme activities which include ATPase, GTPase, cAMP phosphodiesterase, cGMP phosphodiesterase, 5'-nucleotidase, and protein kinase. None of these activities are exhibited by the purified sample.

Catalytic and regulatory properties of two forms of bovine heart cyclic nucleotide phosphodiesterase

The soluble supernatant fraction of bovine heart homogenates may be fractionated on a DEAE cellulose column into two cyclic nucleotide phosphodiesterases (EC 3.1.4.-):PI and PII phosphodiesterases, in the order of emergence from the column. In the presence of free Ca2+, the PI enzyme may be activated several fold by the protein activator which was discovered by Cheung((1971) J. Biol. Chem. 246, 2859-2869). The PII enzyme is refractory to this activator, and is not inhibited by the Ca2+ chelating agent, ethylene glycol bis (beta-aminoethyl ether)-N, N'-tetraacetate (EGTA). The activated activity of PI phosphodiesterase may be further stimulated by imidazole or NH+4, and inhibited by high concentrations of Mg2+. These reagents have no significant effect on either the PII enzyme or the basal activity of PI phosphodiesterase. Although both forms of phosphodiesterase can hydrolyze either cyclic AMP or cyclic GMP, they exhibit different relative affinities towards these two cyclic nucleotides. The PI enzyme appears to have much higher affinities toward cyclic GMP than cyclic AMP. Km values for cyclic AMP and cyclic GMP are respectively 1.7 and 0.33 mM for the non-activated PI phosphodiesterase; and 0.2 and 0.007 mM for the activated enzyme. Each cyclic nucleotide acts as a competitive inhibitor for the other with Ki values similar to the respective Km values. In contrast with PI phosphodiesterase, PII phosphodiesterase exhibits similar affinity toward cyclic AMP and cyclic GMP. The apparent Km values of cyclic AMP and cyclic GMP for the PII enzyme are approx. 0.05 and 0.03 mM, respectively. The kinetic plot with respect to cyclic GMP shows positive cooperativity. Each cyclic nucleotide acts as a non-competitive inhibitor for the other nucleotide. These kinetic properties of PI and PII phosphodiesterase of bovine heart are very similar to those of rat liver cyclic GMP and high Km cyclic AMP phosphodiesterases, respectively (Russel, Terasaki and Appleman, (1973) J. Biol. Chem. 248, 1334).

Characterization of pulmonary surfactant from ox, rabbit, rat and sheep

1. Pulmonary surfactants from ox, rabbit, rat and sheep were isolated and analysed. 2. All preparations had a high anenoic phosphatidylcholine content and would produce stable surface tensions of 0.01 Nm-1 or less. 3. Protein content was 8-18% of the dry weights. A number of proteins were observed; their overall composition were high in hydrophobic amino acid residues. 4. Lipid content varied from 79% (ox) to 90% (rabbit) with phosphatidylcholine representing from 58% (sheep) to 83% (rabbit) of the total lipid. The surfactant preparations were rather similar in lipid composition except that sheep surfactant contained about 10% lysophosphatidylcholine. 5. Hexadecanoic acid was the principal fatty acid. It was particularly high in phosphatidylcholine. 6. Phosphatidylglycerol was a minor constituent of all surfactants but phosphatidyldimethylethanolamine was not detected.