Molecular biology of the channel catfish gonadotropin receptors: 2. Complementary DNA cloning, functional expression, and seasonal gene expression of the follicle-stimulating hormone receptor

Molecular cloning of the channel catfish FSH receptor is reported together with temporal changes in the gene expression throughout a reproductive cycle. A cDNA encoding the receptor was isolated from the testis using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) procedures. The cDNA coded for a 662-amino acid protein that was most identical (51%-59%) to salmon gonadotropin receptor I and the FSH receptors of higher vertebrates, and less identical to LH receptors and thyrotropin receptors (45%-49% and 46%-47%, respectively). In addition, PCR analysis of the genomic DNA showed the absence of the LH receptor-specific intron. Expression of the channel catfish FSH receptor gene was highly restricted to the testis and ovary, except for a low-level expression in the spleen. Transfected COS cells expressed an active recombinant receptor as determined by the ligand-specific activation of a cAMP-responsive reporter gene (luciferase). The recombinant receptor was activated by human FSH and, to a small extent, hCG. Seasonal changes in the ovarian expression of the FSH receptor gene, examined by measuring the transcript abundance by quantitative real-time RT-PCR, showed a rise around the time of onset of ovarian recrudescence and a decrease prior to spawning. This pattern of seasonal expression of FSH receptor differs significantly from that of the LH receptor, which we reported recently. The differential expression of the two gonadotropin receptor genes, in addition to the differential secretion of the gonadotropic hormones, seem to be critical for the regulation of steroidogenesis and other gonadal physiological processes.

Piscine glycoprotein hormone (gonadotropin and thyrotropin) receptors: a review of recent developments

Similar to the higher vertebrates, the pituitary in bony fishes express three glycoprotein hormones: thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In addition to the appropriate secretion of these hormones, the timely and quantitative expression of their specific receptors (TSHR, FSHR and LHR) in the target tissues is an essential requirement for their physiological action. In fishes that constitute a very diverse group of vertebrates, there are only a few published reports of primary structure of these receptors although other examples have been communicated briefly. This review will summarize these reports as well as to describe the insights gained from what is known about the mammalian receptors. The structural organization of the fish receptors (as deduced from the encoding cDNAs) is highly homologous to the higher vertebrate receptors in that there is a 7-pass transmembrane region and an N-terminal extracellular domain, which contributes to ligand specificity. In mammals, the FSHR and the TSHR genes are composed of 10 exons whereas the LHR gene is composed of 11 exons. The position of the 'extra intron' is conserved in the catfish LHR gene. In the mammals, the transmembrane domain of each of the three glycoprotein hormone receptors is encoded by a single exon, however, in the salmon genes and homologous invertebrate genes, this portion of the receptor is encoded by multiple exons. In general, the tissue-specific expression of these receptors is similar to that seen in mammals, however, the gonadal expression of TSHR in the striped bass and sunrise sculpin and the renal expression of LHR in the channel catfish are unique.

Recombinant perciform GnRH-R activates different signaling pathways in fish and mammalian heterologous cell lines

Perciforms have three forms of gonadotropin-releasing hormone (GnRH) in their brain. All three GnRHs are potent secretogogues for luteinizing hormone (LH) from the pituitary. The pivotal role of GnRH-R-GnRH interactions in reproductive homeostasis is well established; however, there is a paucity of information on how a GnRH-R responds to the three endogenous GnRH forms in a perciform species. In this study, a recombinant pituitary GnRH-R from striped bass (stb) was expressed in a mammalian cell line (COS-7) and a fish cell line (CHSE-214). Activation of the signaling pathways was monitored by reporter gene (luciferase) based assays, which were specific for cAMP-PKA or Ca 2+/calmodulin kinase (activated via c-fos promoter) signaling pathways. The stbGnRH-R expressed in two different cell lines triggered different downstream signaling in response to the treatments with chicken (c) GnRH II. Interestingly, when endogenous GnRHs were used in combinations, the luciferase activity was significantly attenuated in transfected CHSE-214 cells.

Molecular biology of channel catfish gonadotropin receptors: 1. Cloning of a functional luteinizing hormone receptor and preovulatory induction of gene expression

There is little known about the molecular biology of piscine gonadotropin receptors, and information about gene expression during reproductive development is particularly lacking. We have cloned the LH receptor (LHR) in the channel catfish (cc), and examined its gene expression throughout a reproductive cycle. A cDNA encoding the receptor was isolated from the testis using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends procedures. It encoded a 696-amino acid protein that showed the greatest homology (46-50% identity) with the known LHRs and lesser similarity with FSH receptors and thyroid-stimulating hormone receptors (44-47% and 42-44% identity, respectively). In addition, two characteristics unique to the LHRs were conserved in the cloned receptor and the encoding gene: presence of an intron corresponding to intron 10 in mammals and turkey and occurrence of a double cysteine residue in the cytoplasmic tail for potential palmitoylation. The ccLHR gene was well expressed in the gonads and kidney and merely detectable in the gills, muscle, and spleen. The isolated cDNA encoded an active ccLHR protein, as the recombinant receptor expressed in COS7 cells activated a cAMP response element-driven reporter gene (luciferase) upon exposure to hCG in a dose-dependent manner. Seasonal changes in the ovarian expression of the ccLHR gene, as examined by measuring the transcript abundance by quantitative real-time RT-PCR, remained rather low during most of the reproductive cycle but was acutely induced around the time of spawning. This pattern of expression correlates well with the reported expression of its ligand (LH) in fishes and concurs with the notion that LH is a key regulator of the periovulatory maturational events.

Lipid peroxidation and diabetic retinopathy

The high level of glucose in blood for a long duration is the main cause of the development of retinopathy. So yearly screening of patients newly diagnosed with NIDDM diabetes is recommended because rare cases of treatable diabetic retinopathy have occurred early in one course of NIDDM diabetes. Hyperglycaemia leads to non-enzymatic glycosylation of proteins and HbA1C was found increased. Antioxidants such as GSH and SOD level is found decreased in retinopathy conditions due to the higher lipid peroxidation, which is evident from high MDA and DC values. So it can be clearly stated that increase in the free radical by hyperglycaemia, lipid peroxidation and advanced glycosylation endproducts along with decreased antioxidants are the causative agents for the development of retinopathy.

Cloning and functional expression of a thyrotropin receptor from the gonads of a vertebrate (bony fish): potential thyroid-independent role for thyrotropin in reproduction

The thyroid stimulating hormone receptor (TSHR) mediates the pituitary control of the development, growth and function of the thyroid. The expression of the gene encoding this receptor is known only in the thyroid, lymphocytes, fibroblasts, retro-orbital tissue and fat cells. We have cloned a TSHR from the gonads of a non-mammalian vertebrate, a bony fish (striped bass, Morone saxatilis) in the course of our search for gonadotropin receptors (follicle stimulating hormone receptor, FSHR and luteinizing hormone receptor, LHR). RT-PCR analysis demonstrated that the striped bass TSHR (stbTSHR) transcripts were abundant in both the thyroid and gonads and detectable in skeletal muscle, heart and brain tissues. The stbTSHR cDNA encoded a 779-amino acid glycoprotein hormone receptor with much higher homology (57-59%) to the mammalian TSH receptors than the mammalian LH receptors (47-49%) and FSH receptors (47%), and salmon and catfish gonadotropin receptors (42-45%). There was a TSHR-specific insertion in the extracellular domain as seen in mammalian receptors. Moreover, PCR analysis of genomic DNA indicated the absence of the LHR-specific intron in the striped bass TSHR gene. Recombinant stbTSHR expressed in COS1 cells activated reporter genes (luciferase) driven by either a cAMP response element or the c-fos promoter in response to bovine TSH, stbLH or hCG, but not human FSH. In situ hybridization studies revealed the presence of stbTSHR transcripts in the gametes but not in the follicular cells. This pattern of expression is unique and suggests a direct, albeit unknown, role for TSH in gamete physiology.

Dienophilic behavior of the vinylic (C=C) and the carbonyl (C=O) bonds of ketenes in reactions with 1,3-diazabuta-1,3-dienes

[reaction: see text] Ab initio and density functional studies (DFT) on cycloaddition reactions of 1,3-diazabuta-1,3-dienes with ketenes are reported. The vinylic (C=C) and the carbonyl (C=O) units of the ketenes are found to participate in concerted asynchronous [4 + 2] cycloaddition reactions. The transition states (3t, 4t, and 7t) for these paths have been located on the PE surface at the correlated levels of ab initio calculations. A reasonable mechanism for the formation of [4 + 2] and [2 + 2] adducts is presented.

Chaperone-like activity of a synthetic peptide toward oxidized gamma-crystallin

alphaA-Crystallin can function like a molecular chaperone. We recently reported that the alphaA-crystallin sequence, KFVIFLDVKHFSPEDLTVK (peptide-1, residues 70-88) by itself possesses chaperone-like (anti-aggregating) activity during a thermal denaturation assay. Based on the above data we proposed that the peptide-1 sequence was the functional site in alphaA-crystallin. In this study we investigated the specificity of peptide-1 against gamma-crystallin aggregation in the presence of H2O2 and CuSO4. Peptide-1 was able to completely protect against the oxidation-induced aggregation of gamma-crystallin. Removal of N-terminal Lys or the replacement of Lys with Asp (DFVIFLDVKHFSPEDLTVK, peptide-2) did not alter the anti-aggregation property of peptide-1. However, deletion of KF residues from the N-terminus of peptide-1 resulted in a significant loss of its anti-aggregation property. Bio-gel P-30 size-exclusion chromatography of gamma-crystallin incubated with peptide-2 under oxidative conditions revealed that a major portion of the peptide elutes in the void volume region along with gamma-crystallin, suggesting the binding of the peptide to the protein. Peptide-1 and -2 were also able to prevent the UV-induced aggregation of gamma-crystallin. These data indicate that the same amino acid sequence in alphaA-crystallin is likely to be responsible for suppressing the heat-denatured, oxidatively modified and UV-induced aggregation of proteins.

Synthesis and characterization of a peptide identified as a functional element in alphaA-crystallin

Eye lens alpha-crystallin is a member of the small heat shock protein (sHSP) family and forms large multimeric structures. Earlier studies have shown that it can act like a molecular chaperone and form a stable complex with partially unfolded proteins. We have observed that prior binding of the hydrophobic protein melittin to alpha-crystallin diminishes its chaperone-like activity toward denaturing alcohol dehydrogenase, suggesting the presence of mutually exclusive sites for these proteins in alpha-crystallin. To investigate the mechanism of the interaction between alpha-crystallin and substrate proteins, we determined the melittin-binding sites in alpha-crystallin by cross-linking studies. Localization of melittin-binding sites in alpha-crystallin resulted in the identification of RTLGPFYPSR and FVIFLDVKHFSPEDLTVK of alphaA-crystallin and FSVNLDVK of alphaB-crystallin as the chaperone sites. Of these sites, FVIFLDVKHFSPEDLTVK and FSVNLDVK were identified earlier as 1,1'-bi(4-anilino) naphthalene-5,5'-disulfonic acid (bis-ANS)-binding hydrophobic sites. Here we also report the synthesis and characterization of the peptide, KFVIFLDVKHFSPEDLTVK, having the melittin as well as bis-ANS-binding sequence of alphaA-crystallin. We show that this peptide has characteristics similar to that of alphaA-crystallin by in vitro thermal aggregation assay, gel filtration study, CD spectroscopy, and bis-ANS interaction studies. The peptide sequence corresponds to the beta3 and beta4 region present in the alpha-crystallin domain of sHSP 16.5. We hypothesize that the alpha-crystallin domain in other sHSPs may have a similar function and would likely possess the anti-aggregation property even when separated from the native protein.

Serotyping of Streptococcus pneumoniae by coagglutination with 12 pooled antisera

We report on the performance of a recently introduced commercial chessboard method using 12 antisera, in comparison with that of the 55-antiserum panel used in determining the serogroups and types (SGTs) of Streptococcus pneumoniae, both of which were carried out by a coagglutination technique. Of a total of 150 strains of S. pneumoniae studied, 135 (90%) belonged to the SGTs represented in the 23-valent pneumococcal vaccine; of these, 130 (96.3%) were identified as the same SGTs by both typing methods. The remaining five strains showed cross-reactivity with more than two pools by the chessboard method, but could be assigned to a single SGT by the Quellung test. The 96.3% concordance of the chessboard method suggests it can be adopted for determination of the SGTs of S. pneumoniae in laboratories.

Studies on proteases and alpha-macroglobulin activity in amphibian blood plasma

Frog plasma effectively hydrolysed the synthetic chromogenic substrates, H-D-Glu-Gly-Arg-p-nitroanilide (S-2444), benzoyl-Ile-Glu-Gly-Arg-p-nitroanilide (S-2222) and acetyl-Ile-Glu-Gly-Arg- p-nitroanilide (S-2423), all sensitive substrates for trypsin. Moderate hydrolytic activities was observed with H-D-Phe-Pip-Arg-p-nitroanilide (S-2238, substrate for thrombin) and H-D-Pro-Phe-Arg-p-nitroanilide (S-2302, substrate for plasma kallikrein). Frog plasma contained moderate alpha-macroglobulin activity. When plasma was incubated at 37 degrees C, the macroglobulin activity decreased in a time dependent manner while only a moderate decrease in the protease activity was observed. Ten fold dilution of plasma with 0.1 M phosphate buffer, pH 7.6 prevented the inherent loss of macroglobulin activity but it had no effect on protease activity. Dye ligand chromatography of the plasma on red Sepharose revealed that bulk of alpha-macroglobulin activity along with minor proteolytic activity (S-2222 hydrolysis) was present i the washings. On the other hand, about one third of the alpha-macroglobulin activity and bulk of the protease activity was bound to the column and were eluted with 1.5 M NaCl. alpha-Macroglobulin activity in red Sepharose washings and elutions on chromatography on Sephadex G-200, was eluted in two regions with Ve/Vo value of 1.33 and 1.08, respectively.

Peritoneal dialysis for acute renal failure in infants: a comparison of three types of peritoneal access

Peritoneal access for peritoneal dialysis (PD) poses a significant problem in infants due to their small size and can result in considerable morbidity and occasional mortality. This study was carried out to compare the complications associated with three different types of PH catheters for intermittent PD. A total of 79 session of PD were given to 51 infants with acute renal failure. Twenty-nine infants received 1, 18 received 2 and 2 infants received 3 and 4 sessions of PD, respectively. For PD access an intravenous cannula was used in 36, stylet catheter in 18, and guide wire inserted femoral vein catheter in 25 procedures. Percentage reduction of serum creatinine per PD session was comparable in infants being dialysed with different types of PD access. Local puncture site and intraperitoneal bleed were associated with the use of a stylet catheter during 4 procedures each (22.2%). Catheter blockade was commonest with the intravenous cannula (22.2%), followed by guide wire inserted femoral vein catheter (16%), and was least with the stylet catheter (5.5%). Total mechanical complications were lower with guide wire inserted femoral vein catheter (16%) as compared to intravenous cannula (25%) and stylet catheter (66%) (p < 0.05). There were 4 episodes of peritonitis (5.0%), 3 bacterial and 1 fungal. Although peritonitis was more common with intravenous cannula (8.3%) than guide wire inserted catheter (4%) and stylet catheter (nil), the difference was not statistically significant. Total complications including mechanical and infective were least with guide wire inserted femoral vein catheter (20%), followed by intravenous cannula (33%) and stylet catheter (66%) (p < 0.05). Of 51 infants, 20 died (39.0%). The PD procedure per se resulted in mortality in 2 cases, 1 because of massive intraperitoneal bleed due to stylet induced injury of an intra abdominal blood vessel and the other due to fungal peritonitis. To conclude, of the three types of access for intermittent PD, complications related to the PD procedure are the least with guide wire inserted femoral vein catheter.

Bidirectional Glenn shunt: a step in the right direction

Bidirectional Glenn (BDG) shunt was carried out in 14 patients (age range 1.5-22 years; mean 9.3 years) for a variety of congenital cyanotic heart diseases with decreased pulmonary blood flow. Postoperative cardiac catheterisation was carried out in 10 patients including successful balloon angioplasty of the shunt and LPA in one patient. There was a significant improvement in oxygen saturation and a drop in haematocrit level at follow-up. Doppler echocardiography studies in 13 patients revealed functioning shunts in all cases with low velocity continuous flow. Thus BDG is a useful palliative procedure and could be undertaken as the first stage of total cavopulmonary connection in high-risk Fontan groups where biventricular repair is not feasible.

Development of the Chitra tilting disc heart valve prosthesis

BACKGROUND AND AIMS OF THE STUDY

The high prevalence of rheumatic valvular disease in the young population and the high cost of imports necessitated the development of an Indian valve. The development of a tilting disc prosthesis was successfully concluded in February 1995, when the third model completed its clinical trial. The tilting disc valve has an integrally machined cobalt alloy cage, an ultra high molecular weight polyethylene disc and a polyester suture ring. The choice of design was based on its superior hydrodynamics and the age distribution of patients, the majority of whom were below 30 years. The polymer-metal combination was selected for its extremely low wear rate and proven durability in the human body.

MATERIALS AND METHODS

The hydrodynamic performance was tested under steady and pulsatile flow conditions. The accelerated durability of nine test valves was evaluated at 800-840 cycles/min for over 350 million cycles each. Size 23 mm valves mere implanted in the mitral position of five sheep. In a clinical trial, 306 patients with isolated mitral or aortic valve replacements were followed up for a total of 371 patient years (mean 1.37 years and range 0-4 years).

RESULTS

The hydrodynamic performance was comparable to that of proven clinical models. The accelerated testing indicated lifetimes in excess of 50 years and the animal trials showed the valve to be safe. In the clinical trial, there was no incidence of structural failure or paravalvular leak. The linearized rate of late thromboembolism was 6.2%/patient-year (pty), anticoagulant related hemorrhage 0.54%/pty and infective endocarditis 0.54%/pty. At two years, the total actuarial survival was 89.5%. The higher incidence of thromboembolism and the very low incidence of anticoagulant related hemorrhage illustrate the difficulty in the management of anticoagulant therapy in a developing country, while the low incidence of endocarditis reflects their greater resistance to infection.

CONCLUSION

These data clearly showed the valve to be safe and comparable to other similar valves in clinical use.

Open heart surgery in presence of hereditary spherocytosis

A patient with ostium secundum atrial septal defect was operated upon despite having hereditary spherocytosis, without any hemolytic effects of cardiopulmonary bypass. A short bypass time is safe in presence of this congenital hemolytic anemia.

Identification of positive and negative transcriptional regulatory elements of the rabbit angiotensin-converting enzyme gene

The two tissue-specific mRNAs encoding the isozymes of rabbit angiotensin-converting enzyme (ACE) are generated from the same gene by alternative choice of two transcription initiation sites 5.7 kb apart. In the current study, we have characterized the regulatory sites controlling the transcription of the larger pulmonary isozyme mRNA. For this purpose, reporter genes driven by varying lengths of upstream region of the ACE gene were transfected into ACE-producing cells. Our results demonstrated that the transcription of this gene is primarily driven by positive elements within the first 274 bp DNA upstream of the transcription initiation site. The reporter gene driven by this region was expressed in two ACE-producing cells but not in two ACE-non-producing cells thereby establishing its tissue specificity. Our experiments also revealed the existence of a strong negative element located between -692 and -610 positions. This element suppressed the expression of the reporter gene in a dose-dependent and position and orientation-independent fashion thus suggesting that it is a true silencer element. It could also repress the expression of a reporter gene driven by the heterologous strong promoter of the beta-actin gene. The repressing effects of the negative element could be partially overcome by cotransfecting the isolated negative element along with the reporter gene containing the negative element. This result was possibly due to the functional removal of a limiting trans-acting factor which binds to this element. Electrophoretic mobility shift assays revealed that the negative element can form several complexes with proteins present in the nuclear extract of an ACE-producing cell line. At least part of the negative element is strongly conserved in the upstream regions of the human and mouse ACE genes.

Recovery from paraplegia following aortic saddle embolism. Case report

An aortic saddle embolus causing paraplegia is rare and even rarer is a documentation of neurological recovery from this event. A 47 year old male presented with absent pulsations in the lower limbs and paraplegia, both of sudden onset. He underwent immediate bilateral transfemoral embolectomy. The postoperative period was stormy. The paraplegia recovered over a period of 2 months and he could walk to his place of work after 6 months. The rare combination of saddle embolus and paraplegia is discussed. An attempt has been made to verify the hypothesis of Dickson et al which states that a low origin of the great radicular artery (GRA) below T12 level may be responsible for paraplegia when obstructed by a saddle embolus. We found the GRA arising at L2 vertebral level in this patient. Postoperative selective spinal arteriogram and magnetic resonance imaging (MRI) of the spinal cord showed a patent GRA and normal spinal cord structure respectively. Early surgical intervention in restoring the blood flow into the GRA may prevent severe histological changes hitherto responsible for nonrecovery from paraplegia in the earlier reports.

Intracerebral polyposis. Case report

A 25-year-old man presented with nontraumatic cerebrospinal fluid rhinorrhea and meningitis. On investigation, he was found to have a multiloculated intracerebral cystic lesion of the right frontal lobe with a bony lesion inside the cyst, just above the right cribriform plate. Surgery revealed multiple grape-like cystic pedunculated lesions with narrow stalks attached to a bony outgrowth which was adherent to the right cribriform plate. Macroscopically and microscopically, the excised lesions were similar to nasal polyps.

Use of alternative polyadenylation sites for tissue-specific transcription of two angiotensin-converting enzyme mRNAs

The pulmonary isozyme of rabbit angiotensin-converting enzyme (ACE) is encoded by an mRNA of about 5 kb. cDNA clones corresponding to different parts of this mRNA have been isolated and the complete nucleotide sequences of both the coding and non-coding regions of the mRNA have been determined. The encoded protein has 1309 residues with a 33 amino acids-long signal peptide at the amino terminus and a potential membrane-anchoring domain near the carboxyl terminus. There is a strong sequence homology between two regions of the rabbit cDNA and between the rabbit, human, and mouse cDNAs. Comparison of the nucleotide sequences of the 3' untranslated regions of rabbit pulmonary and testicular ACE cDNAs revealed that the testicular cDNA is nested within the pulmonary cDNA at the 3' end. A rabbit genomic clone encompassing this region was isolated and partially sequenced. It was shown that the gene contains two potential polyadenylation sites 628 bp apart within one exon. Northern analyses with an appropriate oligonucleotide probe confirmed that the proximal polyadenylation site is used exclusively for terminating the testicular mRNA whereas the distal one is used exclusively for the pulmonary mRNA. These results demonstrated that the transcription of the two mRNAs encoding the two ACE isozymes not only initiates at two alternative tissue-specific sites which are 5.7 kb apart but the mRNAs also get polyadenylated at two alternative sites which are 628 bp apart.

The mRNAs encoding the two angiotensin-converting isozymes are transcribed from the same gene by a tissue-specific choice of alternative transcription initiation sites

The two tissue-specific isozymes of angiotensin-converting enzyme are encoded by two mRNAs. The 5-kilobase pulmonary mRNA (mRNAP) and the 2.5-kilobase testicular mRNA (mRNAT) have identical sequences near their 3'-ends, whereas each has a unique sequence toward its 5'-end. Here we report that the two mRNAs originate from the same gene by initiation of transcription at two alternative sites. We have isolated a rabbit genomic clone which encodes these mRNAs. The sequence organization of the genome is such that the unique sequence of mRNAP precedes that of mRNAT, which in turn precedes the sequence common to both species. For generation of mRNAP, the mRNAT-specific sequence is eliminated as an intron from the primary transcript by splicing. Transcription of mRNAT, on the other hand, initiates within this intron at the middle of the gene. The exact initiation sites of mRNAT and mRNAP have been determined by DNA sequencing; DNA, oligonucleotide, and antisense RNA protection assays; and primer extension assays. Analyses of the sequence upstream of the transcription initiation sites revealed the presence of putative binding sites of several known transcription factors including SP-1, AP-2, and IID.

Structure of testicular angiotensin-converting enzyme. A segmental mosaic isozyme

The complete amino acid sequence of rabbit testicular angiotensin-converting enzyme has been deduced from the sequence of the corresponding cDNA clone. A protein of the expected molecular weight of 84,000 was translated in vitro from the mRNA encoded by this cDNA. All of the previously determined sequences of seven tryptic peptides from the enzyme are present in the deduced sequence, thus confirming the identity of the protein. From the deduced sequence it appears that the protein contains a signal peptide at the amino terminus and a hydrophobic anchoring domain near the carboxyl terminus. Northern analysis with oligonucleotide probes, whose sequences represented different regions of the cDNA, revealed not only the regions of extensive homology between the mRNAs encoding the testicular and the pulmonary isozymes but also a stretch of sequence near the 5' end unique to the testicular mRNA.