The relative activities attributable to the three phosphoglucomutase loci (PGM1, PGM,2 PGM3) in human tissues

1. The isozymes attributable to the three phosphoglucomutase loci, PGM_1;PGM₂ and PGM₃, have been separated by agarose-acrylamide gel electrophoresis and their relative activities have been measured in a range of human tissues. 2. In most tissues except red cells and fibroblasts, 85–95 % of the total PGM activity is determined by the PGM₁ locus, 2–15 % is contributed by the PGM₂ locus and 1–2 % is determined by the third locus PGM₃. 3. In fibroblasts the PGM₃ isozymes are relatively much more active and account for nearly 7 % of the total PGM activity. 4. In red cells approximately equal amounts of the PGM₁ and PGM₂ isozymes occur but no PGM₃ isozymes are found. 5. The atypical PGM isozyme pattern observed in red cells is probably a reflexion of in vivo stability differences between the three forms of PGM. In other tissues the PGM isozyme patterns are probably consequent upon differences in rates of synthesis or differences in the specific activities of the gene products.     

Identification of human phosphoglucomutase 3 (PGM3) as N-acetylglucosamine-phosphate mutase (AGM1)

We performed phenotyping of human phosphoglucomutase 3 (PGM₃) and screening for mutations in the human N‐acetylglucosamine‐phosphate mutase gene (AGM₁) to identify PGM₃ as AGM₁. By sequencing the coding region of AGM₁, two alleles containing a G or A base at nucleotide 1396, that can respectively encode aspartic acid or asparagine at codon 466, were identified. Cell extracts of COS7 cells after transfection with the pcDNA 3·1(+) plasmid containing an AGM₁ allele with 1396G or 1396A showed similar electrophoretic patterns to the PGM₃ 1 or PGM₃ 2 protein, respectively, with the isozyme detection method used for PGM₃ phenotyping. The genotypes determined by the two alleles of AGM₁ coincided exactly with the PGM₃ phenotypes in 20 individuals. We also investigated the allele frequency of the AGM₁ nucleotide polymorphism in a Japanese population by DNA sequencing and found that the frequencies of alleles 1396G and 1396A were similar to previously reported PGM₃*1 and PGM₃*2 frequencies. Overall, the facts that the AGM₁ gene product shows PGM activity, AGM₁ is polymorphic, the electrophoretic mobility is similar between AGM₁ allele‐specific products and PGM₃ 1 and 2 proteins, PGM₃ phenotypes and AGM₁ genotypes completely coincide in 20 individuals, and AGM₁ allele frequencies are similar to those of PGM₃*1 and PGM₃*2 in Japanese populations, suggest that PGM₃ is identical to AGM₁.     

Rare phosphoglucomutase phenotypes

1. PGM phenotypes have been determined by starch-gel electrophoresis in more than 2000 unrelated ‘ English’ people and several smaller samples from other populations. 2. Besides the three common phenotypes (PGM 1, 2–1 and 2), eleven rare phenotypes have been identified, and their genetical basis investigated. 3. Nine of the new phenotypes, PGM 3–1, 3–2, 4–1, 4–2, 5–2, 6–1, 6–2, 7–1 and 7–2, appear to represent heterozygous combinations of one or another of a series of rare alleles, PGM³₁, PGM⁴₁, PGM⁵₁, PGM⁶₁ and PGM⁷₁, with either PGM¹₁ or PGM²₁. Each of these alleles probably determines the formation of two new isoenzyme components which are homologous with components a and c determined by PGM¹₁ and components b and d determined by PGM²₁. 4. The ‘Atkinson’ and ‘Palmer’ phenotypes are thought to represent heterozygotes for alleles at a different locus, PGM₂. The common allele at this locus is designated PGM¹₂ and the postulated genotype for the ‘Atkinson’ phenotype is PGM¹₂PGM²₂ and for the ‘Palmer’ pheno-type is POM¹₂PGM³₂. It is suggested that PGM¹₂ determines isoenzyme components e, f and g and that PGM²₂ and PGM³₂ each determine three isoenzyme components which are electrophoretically different from but homologous with e, f and g. 5. The ‘Atkinson’ phenotype appears to have an appreciable incidence in Negro populations and has so far not been observed in any non-Negro group.     

A third phosphoǵlucomutase locus in man

1. Investigation of human tissue extracts by starch gel electrophoresis has vevealed three groups of isozymes with PGM activity. 2. Previous studies on red cell lysates have established that two of these groups of isozymes, PGM₁ and PGM₂ are determined by two separate autosomal loci, PGM₁ and PGM₂ respectively. 3. The new series of isozymes, designated PGM₃, are electrophoretically faster than the other PGM components, constitute only a small fraction of the total PGM activity, and exhibit person-to-person differences in electrophoretic patten which are independent of te PGM₁ and PGM₂ variants. Three commonly occuring phenotypes have been recognized : PGM₃ 1, PGM₃ 2-1 and PGM₃ 2. 4. The genetics of this polymorphism have been studied using plancentae derived from pairs of non-identical twins. The reult suggest the occurence of two common alleles PGM1/3 and PGM2/3 at an atosomal locus, with frequencies of 0.74 and 0.26 respectively in the English population and 0.34 and 0.66 respectively in the Nigerian population. 5. Tests for linkage using the twin data indicate that the PGM₁ and PGM₃ loci are not closely linked. 6. The possibility of structural homologies between the various PGM isozymes is noted.     

Thermostability studies on the isozymes of human phosphoglucomutase

1. A new method for investigating the heat-stabilities of isozymes is described. Using this method it has been shown that the relative thermostabilities of the isozymes determined by the separate phosphoglucomutase (PGM) loci are PGM₂ > PGM₁ > PGM₃. This conclusion has been confirmed by conventional heat-stability experiments. 2. No interallelic or intra allelic stability differences were detected between the isozymes determined by the two common alleles PGM¹₂ and PGM²₁at the PGM₁ locus, between PGM¹₂ and PGM²₂at the second locus or between PGM¹₃ and PGM²₃ at the third locus. The isozymes determined by a very rare allele (PGM⁴₁) appear to be relatively less stable than the isozymes determined by either PGM¹₁or PGM²₁^. 3. Comparison of the PGM isozyme patterns in red cells and other tissues suggests that the in vitro differences in thermostabilities between the isozymes of the separate loci are a true reflexion of the in vivo stabilities of PGM. 4. Promising results obtained with other enzymes suggest that the new method used in the heating experiments on PGM may be a useful general procedure for the investigation of other genetically determined differences in isozyme thermostability.     

Further genetic heterogeneity of human red cell phosphoglucomutase-1: a non-electrophoretic polymorphism

The electrophoretic patterns of human red cell phosphoglucomutase (PGM) were determined by standard starch-gel electrophoresis on two aliquots of haemolysate, one of which was previously heat-treated. Samples from 67 families and 417 unrelated healthy subjects were examined. Heat denaturation studies combined with electrophoresis showed a greater heterogeneity of phosphoglucomutase-1 (PGM₁) isozymes than that revealed by electrophoresis alone. Both the PGM} and the PGM? isozymes turned out to be either heat-resistant (tr) or heat-sensitive (ts) and this new phenotypic property segregated along with the electrophoretic allele with which it was originally associated. Comparison of red cell PGM₁ patterns of 217 PGM₁2-l heterozygous individuals, analysed both as described in this paper and by acid starch-gel electrophoresis, which also distinguishes two common PGM¹¹ (PGM₁^1S and PGM₁^1F) and two common PGM₁²(PGM₁^2Sand PGM₁^2F) allelic products, has shown that the two sets of four alleles do not coincide. Thus eight different PGM₁ alleles were identified. The PGM₁^1Str, PGM₁^1Sts, PGM₁^1Ftr, PGM₁^1Fts, PGM₁^2Str, PGM₁^2Sts and PGM₁^2Ftsgene frequencies were estimated as 0523,0–066,0099, 0–029, 0–224, 0–012, 0–043, 0–004, respectively. Three polymorphic sites are hypothesized within the PGM₁ structural gene and the observed frequencies of the eight alleles discussed in terms of ‘disequilibrium’ among these sites. This is the second example of a human enzyme isoelectrophoretic polymorphism revealed by research specifically aimed at detecting electrophoretically cryptic genetic variations. The technique used in this study appears to offer a reliable means of detecting isoelectrophoretic variants for proteins already known to be electrophoretically polymorphic.     

Molecular size estimates of the human phosphoglucomutase isozymes by gel filtration chromatography

1. Molecular sizes of the three sets of the human phosphoglucomutase isozymes attributable to the loci PGM₁, PGM₂ and PGM₃ have been studied by gel nitration. 2. The PGM₂ isozymes (M.W. C. 61,000) appear to be significantly larger than the PGM₁ and PGM₃ isozymes and the PGM₃ isozymes (M.W. C. 53,000) appear to be slightly larger than the PGM₁ isozymes (M.W. C. 51,000). 3. No inter-allelic or intra-allelic differences in molecular size were detected. 4. The estimated molecular size for rabbit muscle PGM by the same method is similar to that obtained for the human PGM₁ isozymes. This is somewhat lower than previously reported estimates obtained by ultra centrifugation.     

PGM3 LOCUS AND ITS GENETIC POLYMORPHISM IN LYMPHOCYTES OF THE PIG

PGM₃ activity was investigated by means of horizontal starch gel electrophoresis. In the pig of the German Landrace three different phenotypes have been recognized: F, S and FS. Family studies suggest the occurrence of at least two alleles –PGM₃^F and the PGM₃^S at an autosomal locus.     

PGM3 LOCUS AND ITS GENETIC POLYMORPHISM IN LEUCOCYTES OF GOATS

PGM₃ activity was investigated in 150 ‘Boerbok’ goats and 132 Angora goats by means of horizontal starch gel electrophoresis. In ‘Boerbok’ goats no polymorphism was found. In Angora goats three different phenotypes have been recognized: F, S, and FS. The results suggest the occurrence of two common alleles: PGM₃-^F and PGM₃-^S at an autosomal locus with frequencies of 0.6176 and 0.3824, respectively.     

The detection and differentiation of the products of the human carbonic anhydrase loci, CAI and CAII using fluorogenic substrates

1. The carbonic anhydrase isozymes of human red cells have been investigated by starch-gel electrophoresis using the fluorogenic substrates, 4-methyl-umbelliferyl acetate and fluorescein diacetate, for the detection of the CA_I and CA_II locus isozymes respectively. 2. The previously described electrophoretic polymorphism at the CA_II locus was easily distinguished using fluorescein diacetate as the stain, thus reducing the need for a specific anti CA_II antiserum in future population and family tests. 3. The variant allele CA_II² (previously designated CA II-H) was found to occur with a frequency of 0·046 in a population sample of 196 Black Africans living in London. No electrophoretic variants of CA_II were detected in a survey of 434 Europeans and 304 Asiatic Indians living in London. 4. No electrophoretic variants of CA_I were detected in the three population groups tested.     

Differential distribution of γ-aminobutyric acidA, receptor subunit (α1, α2, α3, α5 and β2+3) immunoreactivity in the medial prefrontal cortex of the rat

A detailed mapping of the γ-aminobutyric acid (GABA)_A receptor subunits (α₁, α₂, α₃ and β₂₊₃) in the infralimbic/ventral prelimbic region (IL/vPL) of the rat frontal cortex was carried out using subunit-specific antibodies. The α₁ and β₂₊₃ subunit antibodies immunostained all layers of the IL/vPL region. Layers II and III displayed immunostaining of cell bodies whereas I, V and VI showed predominantly neuropil staining. The size of the α₁-positive cell bodies corresponded to that of small interneurons (range, 20–55 μm²; mean ± SEM, 37 ± 5.5 μm²) as well as pyramidal cells or large interneurons (range, 87–135 μm²; mean ± SEM, 103.4 ± 9.7 μm²). However, β₂₊₃ antibody immunostained only small cell bodies. Immunoreactivity for α₂ was restricted to layers I and II, whereas α₃ and α₅ subunit expression was seen only in layer VI. The antibody to the α₂ subunit immunostained small cell bodies (range, 29–63 μm²; mean ± SEM, 32 ± 4.5 μm²) in layer II, resembling interneurons. Conversely, both α₃ and α₅ antibodies immunostained large cell bodies (range, 94–151 gmm²; mean ± SEM, 115.7 ± 13.4 μm²), consistent with pyramidal cell labelling in layer VI.     

''Secondary'' isozymes derived from the three PGM loci

1. The isozymes derived from the human phosphoglucomutases - PGM₁, PGM₂, PGM₃ have been examined in three tissues (lymphocytoid cells, placentae and red blood cells) in which the average age of the constituent proteins may be expected to differ. The appearance of one or more more negatively charged isozymes would appear to be correlated with increasing overall protein age. It is suggested that these are ‘secondry’ isozymes formed in vivo from the least negatively chared form which presumed to be the primary post translational product of the particular gene. 2. Changes in the PGM₃, isozyme pattern have been observed on storage of the placental extracts. Both the primary and the secondary in vivo isozymes were similarly affected. The storage effects observed are possibly due to reaction with red cell oxidized glutathione contaminating the extract. They may lead to confusion in typing unless controlled. Similar changes were not observed with the PGM₁, and PGM₂, isozymes. 3. The effects of a number of thiol reagents on the three PGMs have been examined and various changes in isozyme pattern have been produced artificially. Both the primary and the secondary in vivo isozymes derived from each allele were similarly affected by any particular treatment. PGM₃, isozymes were more reactive with thiol reagents than PGM₁, or PGM₂, isozymes. These findings suggest that the primary and secondary isozymes derived from each of the three PGM loci each contain at least one reactive sulphydryl group. However, the in vivo changes by which secondary isozymes are generated do not appear to be due to such thiol effects.     

Reactivity to sodium tetrachloropalladate (Na2[PdCl4]) compared to PdCl2 and NiCl2 in lymphocyte proliferation tests

Background: For patch testing, replacement of the commonly used palladium dichloride (PdCl₂) by sodium tetrachloropalladate (Na₂[PdCl₄]) was recently demonstrated to improve test accuracy and show a significant correlation with nickel (Ni), supporting the concept of cross‐reactivity between Pd and Ni. A promising alternative to metal allergy patch testing is the in vitro lymphocyte proliferation test (LTT). Objectives: The aim of this study was to test whether Na₂[PdCl₄] is also more sensitive for diagnosing Pd allergy with a standardized LTT. Patients/methods: After determining optimal nontoxic and nonmitogenic concentrations for Na₂[PdCl₄], blood samples from 105 patients with clinical suspicion of metal allergy were tested with an LTT called memory lymphocyte immuno stimulation assay for Na₂[PdCl₄], PdCl₂ and NiCl₂. Reaction profiles were analysed for concordant positive reactions. Results: Using the conventional cut‐off of stimulation index ≥ 3, 74.3% showed a positive reaction to NiCl₂, 15.2% to PdCl₂ and 28.6% to Na₂[PdCl₄]. All positive results to PdCl₂ were covered by Na₂[PdCl₄]. From the 30 positive reactions to Na₂[PdCl₄], 26 (87%) were concordant for NiCl₂ reactivity. Conclusion: In LTT, the use of Na₂[PdCl₄] results in more positive reactions in Pd allergy testing which are in concordance with positive reactions to PdCl₂ and NiCl₂.     

Role of Ca2+ mobilization and Ca2+ sensitization in 8-iso-PGF2α-induced contraction in airway smooth muscle

Background Isoprostanes are prostaglandin (PG)-like compounds synthesized by oxidative stress, not by cyclooxygenase, and increase in bronchoalveolar lavage fluid of patients with asthma. The airway inflammation implicated in this disease may be amplified by oxidants. Although isoprostanes are useful biomarkers for oxidative stress, the action of these agents on airways has not been fully elucidated. Objective This study was designed to determine the intracellular mechanisms underlying the effects of oxidative stress on airway smooth muscle, focused on Ca²⁺ signalling pathways involved in the effect of 8-iso-PGF_2α. Methods Using simultaneous recording of isometric tension and F₃₄₀/F₃₈₀ (an indicator of intracellular concentrations of Ca²⁺, [Ca²⁺]_i), we examined the correlation between tension and [Ca²⁺]_i in response to 8-iso-PGF_2α in the fura-2 loaded tracheal smooth muscle. Results Augmented tension and F₃₄₀/F₃₈₀ by 8-iso-PGF_2α were attenuated by ICI-192605, an antagonist of thromboxane A₂ receptors (TP receptors). Moreover, D609, an antagonist of phosphatidylcholine-specific phospholipase C, markedly reduced both the tension and F₃₄₀/F₃₈₀ induced by 8-iso-PGF_2α, whereas U73122, an antagonist of phosphatidylinositol-specific phospholipase C, modestly inhibited them by 8-iso-PGF_2α. SKF96365, a non-selective antagonist of Ca²⁺ channels, markedly reduced both tension and F₃₄₀/F₃₈₀ by 8-iso-PGF_2α. However, diltiazem and verapamil, voltage-dependent Ca²⁺ channel inhibitors, modestly attenuated tension although their reduction of F₃₄₀/F₃₈₀ was not different from that by SKF96365. Y-27632, an inhibitor of Rho-kinase, significantly attenuated contraction induced by 8-iso-PGF_2α without reducing F₃₄₀/F₃₈₀, whereas GF109203X and Go6983, protein kinase C inhibitors, did not markedly antagonize them although reducing F₃₄₀/F₃₈₀ with a potency similar to Y-27632. Conclusion 8-iso-PGF_2α causes airway smooth muscle contraction via activation of TP receptors. Ca²⁺ mobilization by SKF96365- and D609-sensitive Ca²⁺ influx and Ca²⁺ sensitization by Rho-kinase contribute to the intracellular mechanisms underlying the action of 8-iso-PGF_2α. Rho-kinase may be a therapeutic target for the physiologic abnormalities induced by oxidative stress in airways.     

CO2 retention in lung disease; could there be a pre-existing difference in respiratory physiology

Some patients with lung disease retain CO₂, while others with similar lung function do not. This could be explained if CO₂ retainers had a pre-existing low hypercapnic ventilatory response (HCVR) and, from this, a tendency to retain CO₂. To test if such a phenomenon exists in healthy people, we determined the change in end-tidal P_CO2 (ΔPET_CO2) produced by the addition of a dead-space (DS), during wakefulness and sleep, and related this to the HCVR measured awake. The group mean (n=14) HCVR slope was 2.2±1.1 (S.D.) L min⁻¹ mmHg⁻¹. The ΔPET_CO2 with the application of DS was 1.6±1.6 mmHg awake and 2.6±2.2 mmHg asleep. During wakefulness the ?PET_CO2 with DS did not correlate with the HCVR slope. However, during sleep, four subjects had a marked increase in the ΔPET_CO2 (3.7, 4.3, 6.2, 8.0 mmHg) and a relatively low HCVR (slope 1.5, 1.7, 1.5, 1.7 L min⁻¹ mmHg⁻¹, respectively). We speculate that such individuals, should they develop lung disease, may be predisposed to retain CO₂.     

The distribution of some serum protein and red cell enzyme polymorphisms in the Koch ethnic group of west Bengal,India

Three populations (Poliya, Deshi, and Tiyor) of the Koch ethnic group have been studied for the distribution of three serum protein and four red cell enzyme polymorphisms. There was no significant difference in the allelic frequencies of these systems in the three populations of the Koch ethnic group. The overall gene frequencies were as follows:Hp ¹, 0.21;Gc ^1F, 0.34;Gc ^1s, 0.36;Gc ², 0.30;Tf ^C1, 0.66;Tf ^C2, 0.26;Tf ^C3, 0.001;Tf ^D, 0.06;GLO ¹, 0.21;PGI ², 0.04;AK ², 0.01;PGM ¹⁺, 0.80;PGM ^1–, 0.06;PGM ²⁺, 0.11 andPGM ^2–, 0.02. The phenotypic distribution at all the loci was at Hardy-Weinberg equilibrium.     

P1 incompatibility in pigeon breeders

Pigeon breeders of the P₂ blood phenotype may develop anti-P₁ haemagglutinins as a consequence of natural immunization to pigeon dust. The half-life of labelled P₁ erythrocytes was determined in two P₂ pigeon breeders otherwise compatible except for the presence of anti-P₁ antibodies and in four compatible controls without anti-P₁. The half-life of tagged cells was within the normal range in one breeder but significantly reduced in the other, indicating that P₁ incompatibility may occur in vivo. Since anti-P₁ antibodies are found in about 20% of P₂ pigeon breeders, it is suggested that this group may be prone to developing an incompatibility to transfused P₁ red cells.     

Autoradiographic mapping of serotonin 5-HT1A, 5-HT1D, 5-HT2A and 5-HT3 receptors in the aged human spinal cord

Quantitative autoradiography with selective radioligands was used to establish the respective distribution of serotonin 5-HT_1A, 5-HT_1D, 5-HT_2A and 5-HT₃ receptors at the cervical, thoracic and lumbar levels of the spinal cord from subjects who died at 81–94 years. A high density of 5-HT_1A receptors, labeled by [³H]8-hydroxy-2-(di-n-propylamino)tetralin ([³H]8-OH-DPAT), was found in the superficial layers of the dorsal horn, with a significant enrichment ( 20%) in the lumbar vs. the thoracic and cervical segments. In contrast, only very low specific labeling by [³H]8-OH-DPAT (i.e. less than 10% of that measured in the dorsal horn), was detected in the ventral horn. 5-HT_1D sites labeled by [¹²⁵I]serotonin-O-carboxymethyl-glycyl-iodo-tyrosinamide ([¹²⁵I]GTI) were also mainly located within the superficial layers of the dorsal horn, but no difference in their relative density was noted at the three levels of the spinal cord examined. 5-HT_2A sites labeled by [³H]ketanserin were found in the dorsal horn of the cervical segments but no specific binding of this radioligand could be detected at any other level of the spinal cord of such aged subjects. Finally, a high density of [³H]S-zacopride-labeled 5-HT₃ receptors was noted especially in the most superficial layer (lamina I) of the dorsal horn at all segments examined. These data provide anatomical support for a role of spinal serotonin especially in nociception processing.     

Ratio of myeloid and plasmacytoid dendritic cells and TH2 skew in CRS with nasal polyps

Background: The role of myeloid and plasmacytoid dendritic cells and its consequences for the T_H2 skew in chronic rhinosinusitis (CRS) with nasal polyps (CRSNP⁺) should be detailed. Methods: In 18 CRS patients without nasal polyps (CRSNP^?), 35 CRSNP⁺ patients and 22 patients with nasal structural abnormalities without rhinosinusitis (controls), dendritic cells (DC) were differentiated into myeloid (mDC) and plasmacytoid (pDC) subtypes using an antibody cocktail including CD1c (BDCA‐1) and CD303 (BDCA‐2) in peripheral blood mononuclear cells (PBMC) and single cell preparations of sinonasal mucosa by flow cytometry. Moreover, cells were analysed for expression of CD45, CD3, CD4, CXCR3 (T_H1) and CCR4 (T_H2) and IFN‐γ, IL‐5, TGF‐β1, TGF‐β2, ECP and total IgE in nasal secretions were determined. As a possible confounder, Staphylococcus aureus in nasal lavages was detected. Results: The tissue mDC/pDC‐ratio was 1.7 (1.0–2.4) in controls, 3.0 (1.8–4.0) in CRSNP^? and 0.8 (0.6–1.0) in CRSNP⁺ (P < 0.01). In tissue samples, the T_H1/T_H2 ratio was 12.6 (6.4–16.0) in controls, 12.5 (6.9–21.2) in CRSNP^? and 1.8 (1.3–3.6) in CRSNP⁺ (median and interquartile range, P < 0.001). Less pronounced differences were found in PBMC. S. aureus detection rates or TGF‐β levels did not differ between patient groups and S. aureus detection had no influence on the parameters investigated. Conclusion: A significant T_H2 skew in CRSNP⁺ could be confirmed on the cellular level. It was driven by low myeloid dendritic cell numbers. The T_H2 skew did not correlate with S. aureus detection. The data support the concept that CRSNP⁺ and CRSNP^? are pathophysiologically distinct.     

The genetic relationship between the human foetal acetylesterase ESA7 and the adult acetylesterase ESA5

• 1 There are very few clear examples among human enzymes of foetal isozymes which are the products of foetal specific gene loci. Earlier studies had pointed to the foetal brain esterase ESA₇, as a probable example.
• 2 Detailed biochemical investigation of partially purified human adult brain ESA₅ and the foetal esterase ESA₇ has revealed a close resemblance in the biochemical properties of these two isozymes. In addition to similarities in substrate specificity and inhibition sensitivity the two esterases have the same molecular size (c. 57000), are both relatively unstable at 37 d?C and show decreased anodal electrophoretic mobility after storage at 20 d?C. Furthermore there was suggestive evidence that ESA₇ and ESA₅ may be interconvertible.
• 3 A variant esterase isozyme pattern, which shows unusual features of both ESA₇ and ESA₅, was found in a survey of 120 foetal brains. This variant pattern is consistent with a monomeric structure for both esterases and points strongly to a common genetic determination.