Relationship of foetal number and parity in Barbari goats to plasma profile of caprine pregnancy-associated glycoprotein (caPAG) during gestation and the early postpartum period

This study was conducted to characterise pregnancy-associated glycoprotein (caPAG) in peripheral plasma during gestation and postpartum periods of nulliparous and multiparous does with one or two foetuses using a caPAG specific two-step sandwich ELISA system. Earliest time-points for detection of pregnancy and foetal number with appropriate cut-off values were identified. Plasma samples from 15 pregnant (multiparous: n = 8; nulliparous: n = 7; during pregnancy and postpartum period) and six non-pregnant (during oestrous cycle) goats were collected and analysed. Mean caPAG concentration was greater than the threshold for pregnancy detection (S-N = 0.40) on d22, peaked on d45 and remained unchanged until parturition. From d45 until parturition, caPAG concentration in multiparous does with two foetuses was 1.4 to 1.8 fold greater (P < 0.001) than those with one foetus. For the ELISA, 0.83 (S-N) was the most appropriate cut-off to differentiate does with two from those with a single foetus with an overall sensitivity and accuracy of 88.9% and 84.7%, respectively. Circulating caPAG concentration in multiparous goats was greater (P < 0.05) compared with nulliparous goats during the early pregnancy and postpartum periods. After parturition, caPAG concentrations markedly decreased and were basal within 14 days postpartum. In conclusion, using the caPAG specific ELISA, results indicated there were unique gestational and postpartum profiles for caPAG concentrations that are affected by number of foetuses and parity of the doe. The marked decrease in concentration of caPAG following parturition indicates there would not be compromising of the detection of subsequent pregnancies in goats using this technique.

Interactive virtual 3D models of renal cancer patient anatomies alter partial nephrectomy surgical planning decisions and increase surgeon confidence compared to volume-rendered images

Purpose

To determine whether the interactive visualisation of patient-specific virtual 3D models of the renal anatomy influences the pre-operative decision-making process of urological surgeons for complex renal cancer operations.

Methods

Five historic renal cancer patient pre-operative computed tomography (CT) datasets were retrospectively selected based on RENAL nephrectomy score and variety of anatomy. Interactive virtual 3D models were generated for each dataset using image segmentation software and were made available for online visualisation and manipulation. Consultant urologists were invited to participate in the survey which consisted of CT and volume-rendered images (VRI) for the control arm, and CT with segmentation overlay and the virtual 3D model for the intervention arm. A questionnaire regarding anatomical structures, surgical approach, and confidence was administered.

Results

Twenty-five participants were recruited (54% response rate), with 19/25 having > 5 years of renal surgery experience. The median anatomical clarity score increased from 3 for the control to 5 for the intervention arm. A change in planned surgical approach was reported in 19% of cases. Virtual 3D models increased surgeon confidence in the surgical decisions in 4/5 patient datasets. There was a statistically significant improvement in surgeon opinion of the potential utility for decision-making purposes of virtual 3D models as compared to VRI at the multidisciplinary team meeting, theatre planning, and intra-operative stages.

Conclusion

The use of pre-operative interactive virtual 3D models for surgery planning influences surgical decision-making. Further studies are needed to investigate if the use of these models changes renal cancer surgery outcomes.

Electronic supplementary material

The online version of this article (10.1007/s11548-019-01913-5) contains supplementary material, which is available to authorized users.

Identification of heat stress-susceptible and -tolerant phenotypes in goats in semiarid tropics

The production performance of livestock is influenced by short-term variation in weather pattern. Goat adapts to varied ecological conditions and maintains productivity; however, wide variation has been observed among individual animals in response to environmental stimuli in a population. The objective of the present study was to identify the contrasting phenotypes on the basis of the physiological response in goats during heat stress. The study utilised 138 Jamunapari and 242 Barbari goats during peak heat-stress period and 82 Jamunapari and Barbari goats under thermo-neutral conditions. The physiological response of goats to different environmental conditions was evaluated by recording various parameters such as rectal temperature (RT), respiration rate (RR) and heart rate (HR). The temperature humidity index varied from 85.36 to 89.80 and from 65.32 to 73.12 during heat-stress and thermo-neutral assessments respectively. There was direct increase in HR and RR (>25%) due to heat stress in the animals, as compared with those in thermo-neutral conditions. On the basis of the distribution of RR and HR values across the breed in the population, the individuals having a RR of ≥50 and a HR of ≥130 are recognised as heat stress-susceptible phenotypes and those having a RR of ≤30 and a HR of ≤100 are recognised as heat stress-tolerant individuals. Different biomarkers were analysed in plasma, while heat-shock proteins and leptin were analysed in tissue extracts by ELISA. C-reactive protein and HSP90 concentrations were significantly (P < 0.05) different between heat stress-susceptible and heat stress-tolerant individuals. Heat-shock proteins HSP70, HSP 90, and C-reactive protein and triiodothyronine were reliable indicators of long-term heat stress. Identification of contrasting phenotypes in regard to heat stress is necessary so as to evaluate the expression pattern at a cellular level, as well as physiological and biochemical parameters.

Differential expression pattern of heat shock protein 70 gene in tissues and heat stress phenotypes in goats during peak heat stress period

It has been established that the synthesis of heat shock protein 70 (Hsp70) is temperature-dependent. The Hsp70 response is considered as a cellular thermometer in response to heat stress and other stimuli. The variation in Hsp70 gene expression has been positively correlated with thermotolerance in Drosophila melanogaster, Caenorhabditis elegans, rodents and human. Goats have a wide range of ecological adaptability due to their anatomical and physiological characteristics; however, the productivity of the individual declines during thermal stress. The present study was carried out to analyze the expression of heat shock proteins in different tissues and to contrast heat stress phenotypes in response to chronic heat stress. The investigation has been carried out in Jamunapari, Barbari, Jakhrana and Sirohi goats. These breeds differ in size, coat colour and production performance. The heat stress assessment in goats was carried out at a temperature humidity index (THI) ranging from 85.36-89.80 over the period. Phenotyping for heat stress susceptibility was carried out by combining respiration rate (RR) and heart rate (HR). Based on the distribution of RR and HR over the breeds in the population, individual animals were recognized as heat stress-susceptible (HSS) and heat stress-tolerant (HST). Based on their physiological responses, the selected animals were slaughtered for tissue collection during peak heat stress periods. The tissue samples from different organs such as liver, spleen, heart, testis, brain and lungs were collected and stored at -70 °C for future use. Hsp70 concentrations were analyzed from tissue extract with ELISA. mRNA expression levels were evaluated using the SYBR green method. Kidney, liver and heart had 1.5-2.0-fold higher Hsp70 concentrations as compared to other organs in the tissue extracts. Similarly, the gene expression pattern of Hsp70 in different organs indicated that the liver, spleen, brain and kidney exhibited 5.94, 4.96, 5.29 and 2.63-fold higher expression than control. Liver and brain tissues showed the highest gene expression at mRNA levels as compared to kidney, spleen and heart. HST individuals had higher levels of mRNA level expression than HSS individuals in all breeds. The Sirohi breed showed the highest (6.3-fold) mRNA expression levels as compared to the other three breeds, indicating the better heat stress regulation activity in the breed.

Awareness and Attitudes toward Organ Donation in Rural Puducherry, India

BACKGROUND

For many of the end-stage organ diseases, organ transplantation is the most preferred treatment. The need for the organ transplantation is higher than the availability. For the transplantation program to be successful, awareness regarding organ donation is needed and people must have a positive attitude toward donating organs.

AIM

This study aims to assess the awareness and attitudes regarding organ donation among the rural population and to evaluate the sociodemographic factors associated with their awareness.

SUBJECTS AND METHODS

This community-based cross-sectional study was conducted among 360 people living in 4 villages of Puducherry. Face-to-face interviews were carried out using pretested questionnaire, which included the sociodemographic data. Data were entered into Excel and analyzed using Statistical Package for Social Sciences.

RESULTS

Of 360 participants, 88% (317/360) were aware of organ donation. Among these 317 participants, awareness was highest in the age group 18-30 years 98.8% (87/88), male 91% (147/161), higher secondary and above 100% (58/58), and Class 1 socioeconomic status 92% (13/14). Source of awareness about organ donation was primarily through media 83% (263/317). The majority of the participants 88% (281/317) felt that the purpose of organ donation was to save life. Most of the participants 91% (290/317) said that all healthy adults are eligible organ donors and 87% (275/317) of the participants said that monetary benefits could not be accepted for organ donation. Most of the participants 70% (223/317) were willing to donate their organs after death. Among the participants who refused to donate their organs, family refusal 57% (25/44) was the most common reason.

CONCLUSION

This study shows that there is a high level of awareness about organ donation among rural people and most of the participants are willing to donate their organs.

Multiparametric MRI for detection of radiorecurrent prostate cancer: added value of apparent diffusion coefficient maps and dynamic contrast-enhanced images

BACKGROUND

Multiparametric magnetic resonance imaging (mp-MRI) is increasingly advocated for prostate cancer detection. There are limited reports of its use in the setting of radiorecurrent disease. Our aim was to assess mp-MRI for detection of radiorecurrent prostate cancer and examine the added value of its functional sequences.

METHODS

Thirty-seven men with mean age of 69.7 (interquartile range, 66-74) with biochemical failure after external beam radiotherapy underwent mp-MRI (T2-weighted, high b-value, multi-b-value apparent diffusion coefficient (ADC) and dynamic contrast-enhanced (DCE) imaging); then transperineal systematic template prostate mapping (TPM) biopsy. Using a locked sequential read paradigm (with the sequence order above), two experienced radiologists independently reported mp-MRI studies using score 1-5. Radiologist scores were matched with TPM histopathology at the hemigland level (n=74). Accuracy statistics were derived for each reader. Interobserver agreement was evaluated using kappa statistics.

RESULTS

Receiver-operator characteristic area under curve (AUC) for readers 1 and 2 increased from 0.67 (95% confidence interval (CI), 0.55-0.80) to 0.80 (95% CI, 0.69-0.91) and from 0.67 (95% CI, 0.55-0.80) to 0.84 (95% CI, 0.76-0.93), respectively, between T2-weighted imaging alone and full mp-MRI reads. Addition of ADC maps and DCE imaging to the examination did not significantly improve AUC for either reader (P=0.08 and 0.47 after adding ADC, P=0.90 and 0.27 after adding DCE imaging) compared with T2+high b-value review. Inter-reader agreement increased from k=0.39 to k=0.65 between T2 and full mp-MRI review.

CONCLUSIONS

mp-MRI can detect radiorecurrent prostate cancer. The optimal examination included T2-weighted imaging and high b-value DWI; adding ADC maps and DCE imaging did not significantly improve the diagnostic accuracy.

Using custom protein microarrays to identify autoantibody biomarkers for the early detection of breast cancer

Abstract #2003

Background: Cancer patients make antibodies to tumor-derived proteins that are potential biomarkers for early detection. To detect autoantibodies to tumor antigens in patient sera, we have adapted novel high-density custom protein microarrays (NAPPA) expressing 6,500 candidate tumor antigens for biomarker detection. These arrays are probed with sera from patients with early stage breast cancer and healthy women. Using this approach, we identified antibodies in the sera of breast cancer patients.&#x2028; Methods: 6,500 full-length human antigens were expressed using mammalian reticulocyte lysate and captured onto NAPPA protein microarrays. Protein expression (&gt;90%) was confirmed with anti-GST antibodies. Patient sera were added, and bound IgG detected with secondary antibodies. Serum samples were obtained from 103 patients with stages I-III breast cancer, and 103 age-matched control women, all undergoing routine mammography.&#x2028; Results: Using high-density protein microarrays, sera from breast cancer patients (n=53) and healthy donor sera (n=53) were screened for autoantibodies to 6,500 protein antigens. Antigens were selected for further analysis if the 95th percentile of signal of cases and controls were significantly different (p&lt;0.05) and if the number of cases with signals above the 95th percentile of controls was larger than the number expected due to random chance (p&lt;0.05). Known tumor antigens, such as p53, were detected, as well as novel antigens such as DCC1, Rab7L and USP44. In total, 768 unique antigens were selected for further analysis with an independent set of breast cancer patient (n=50) and healthy donor sera (n=50).&#x2028; Conclusions: Custom in-situ protein microarrays can be used to detect serum tumor antigen-specific antibodies and enables the rapid, simultaneous detection of immunogenic tumor antigens from patient sera. These autoantibodies are being evaluated as potential biomarkers for the early diagnosis of breast cancer.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2003.

Prospective Study of Elective Bilateral Versus Unilateral Femoral Arterial Puncture for Uterine Artery Embolization

The purpose of this study was to assess the effect of elective bilateral femoral arterial punctures for uterine artery embolization (UAE) of symptomatic fibroids on fluoroscopy and procedural time, patient dose, and ease of procedure. We conducted a prospective study of UAE with either the intention to catheterize both uterine arteries using a single femoral puncture (n = 12) or elective bilateral arterial punctures from the outset (n = 12). The same two operators undertook each case. Main outcome measures were total procedure time, fluoroscopy time, dose-area product (DAP), and total skin dose. A simulation was then performed on an anthropomorphic phantom using the mean in vivo fluoroscopy parameters to estimate the ovarian dose. Bilateral UAE was achieved in all patients. None of the patients with initial unilateral arterial puncture required further contralateral arterial puncture. The mean fluoroscopy time in the group with elective bilateral punctures was 12.8 min, compared with a mean of 16.6 min in patients with unilateral puncture (p = 0.046). There was no significant difference in overall procedure time (p = 0.68). No puncture-site complications were found. Additional catheters were required only following unilateral puncture. The simulated dose was 25% higher with unilateral puncture. Although there was no significant difference in measured in vivo patient dose between the two groups (DAP, p = 0.32), this is likely to reflect the wide variation in other patient characteristics. Allowing for the small study size, our results show that the use of elective bilateral arterial punctures reduces fluoroscopy time, requires less catheter manipulation, and, according to the simulation model, has the potential to reduce patient dose. The overall procedure time, however, is not significantly reduced.

Current status of transrectal ultrasound-guided prostate biopsy in the diagnosis of prostate cancer

In contemporary practice, most prostate cancers are either invisible on ultrasound or indistinguishable from concurrent benign prostatic hyperplasia. Diagnosis therefore rests on prostate biopsy. Biopsies are not simply directed at ultrasonically visible lesions, as these would miss many cancers; rather the whole gland is sampled. The sampling itself is systematic, using patterns based on prostate zonal anatomy and the geographical distribution and frequency of cancer. This review explains the evolution of the prostate biopsy technique, from the classical sextant biopsy method to the more recent extended biopsy protocols (8, 10, 12, >12 and saturation biopsy protocols). Extended protocols are increasingly being used to improve diagnostic accuracy, especially in those patients who require repeat biopsy. This trend has been facilitated by the ongoing improvement in safety and acceptability of the procedure, particularly with the use of antibiotic prophylaxis and local anaesthesia. The technical details of these extended protocols are discussed, as are the current data regarding procedure-related morbidity and how this may be minimized.

Mortality Patterns in Dairy Animals under Organized Herd Management Conditions at Karnal India

Mortality patterns of two Zebu cattle breeds, Sahiwal and Tharparkar, and two crossbred strains, Karan Swiss and Karan Fries, maintained at the National Dairy Research Institute, Karnal were studied. Nine-year (1989--90 to 1997--98) data on mortality were analysed for year, season, age and cause effects on mortality rate. The overall mortality was 14.17%. The mortality in Sahiwal, Tharparkar, Karan Swiss and Karan Fries averaged 14.35%, 7.21%, 17.12% and 13.46%, respectively. The breed mortality rate did not vary significantly between years, seasons, age categories and causes of disease. However, the trends indicated appreciable difference in mortality rates. The mortality was highest in the year 1994--95 (19.53%) and lowest in 1991--92 (8.56%). There was very little variation in seasonal mortality rate and mortality rate averaged 4.53%, 4.81% and 4.84% in hot-dry (March-June), hot-humid (July-October) and cold (November-February) seasons, respectively. The mortality up to 2 months of age accounted for a major share (50-60% or higher) in different breed groups. Digestive problems followed by respiratory disorders together accounted for 70-80% of total deaths.

Fluorophore-labeled S-nitrosothiols

A series of fluorophore-labeled S-nitrosothiols were synthesized, and their fluorescence enhancements upon removal of the nitroso (NO) group were evaluated either by transnitrosation or by photolysis. It was shown that, with a suitable alkyl linker, the fluorescence intensity of dansyl-labeled S-nitrosothiols could be enhanced up to 30-fold. The observed fluorescence enhancement was attributed to the intramolecular energy transfer from fluorophore to the SNO moiety. Ab initio density functional theory (DFT) calculations indicated that the "overlap" between the SNO moiety and the dansyl ring is favored because of their stabilizing interaction, which was in turn affected by both the length of the alkyl linker and the rigidity of the sulfonamide unit. In addition, one of the dansyl-labeled S-nitrosothiols was used to explore the kinetics of S-nitrosothiol/thiol transnitrosation and was evaluated as a fluorescence probe of S-nitrosothiol-bound NO transfer in human umbilical vein endothelial cells.

Mechanism of transfer of NO from extracellular S-nitrosothiols into the cytosol by cell-surface protein disulfide isomerase

N-dansylhomocysteine (DnsHCys) is quenched on S-nitrosation. The product of this reaction, N-dansyl-S-nitrosohomocysteine, is a sensitive, direct fluorogenic substrate for the denitrosation activity of protein disulfide isomerase (PDI) with an apparent K(M) of 2 microM. S-nitroso-BSA (BSA-NO) competitively inhibited this reaction with an apparent K(I) of 1 microM. The oxidized form of DnsHCys, N,N-didansylhomocystine, rapidly accumulated in cells and was reduced to DnsHCys. The fluorescence of DnsHCys-preloaded human umbilical endothelial cells and hamster lung fibroblasts were monitored as a function of extracellular BSA-NO concentration via dynamic fluorescence microscopy. The observed quenching of the DnsHCys fluorescence was an indirect measure of cell surface PDI (csPDI) catalyzed denitrosation of extracellular S-nitrosothiols as decrease or increase in the csPDI levels in HT1080 fibrosarcoma cells correlated with the rate of quenching and the PDI inhibitors, 5,5'-dithio-bis-3-nitrobenzoate and 4-(N-(S-glutathionylacetyl) amino)phenylarsenoxide inhibited quenching. The apparent K(M) values for denitrosation of BSA-NO by csPDI ranged from 12 microM to 30 microM. Depletion of membrane N(2)O(3) with the lipophylic antioxidant, vitamin E, inhibited csPDI-mediated quenching rates of DnsHCys fluorescence by approximately 70%. The K(M) for BSA-NO increased by approximately 3-fold and V(max) decreased by approximately 4-fold. These findings suggest that csPDI catalyzed NO released from extracellular S-nitrosothiols accumulates in the membrane where it reacts with O2 to produce N(2)O(3). Intracellular thiols may then be nitrosated by N2O3 at the membrane-cytosol interface.

N-dansyl-S-nitrosohomocysteine a fluorescent probe for intracellular thiols and S-nitrosothiols

The fluorescence emission spectrum of N-dansyl-S-nitrosohomocysteine was enhanced approximately 8-fold upon removal of the NO group either by photolysis or by transnitrosation with free thiols like glutathione. The fluorescence enhancement was reversible in that it could be quenched in the presence of excess S-nitrosoglutathione. Attempts were then made to utilize N-dansyl-S-nitrosohomocysteine as an intracellular probe of thiols/S-nitrosothiols. Fluorescence microscopy of fibroblasts in culture indicated that intracellular N-dansyl-S-nitrosohomocysteine levels reached a maximum within 5 min. N-Dansyl-S-nitrosohomocysteine fluorescence was directly proportional to intracellular GSH levels, directly determined with HPLC. N-Dansyl-S-nitrosohomocysteine preloaded cells were also sensitive to S-nitrosoglutathione uptake as the intracellular fluorescence decreased as a function of time upon exposure to extracellular S-nitrosoglutathione.

A distinct subgroup of small DRG cells express GDNF receptor components and GDNF is protective for these neurons after nerve injury

Several lines of evidence suggest that neurotrophin administration may be of some therapeutic benefit in the treatment of peripheral neuropathy. However, a third of sensory neurons do not express receptors for the neurotrophins. These neurons are of small diameter and can be identified by the binding of the lectin IB4 and the expression of the enzyme thiamine monophosphatase (TMP). Here we show that these neurons express the receptor components for glial-derived neurotrophic factor (GDNF) signaling (RET, GFRalpha-1, and GFRalpha-2). In lumbar dorsal root ganglia, virtually all IB4-labeled cells express RET mRNA, and the majority of these cells (79%) also express GFRalpha-1, GFRalpha-2, or GFRalpha-1 plus GFRalpha-2. GDNF, but not nerve growth factor (NGF), can prevent several axotomy-induced changes in these neurons, including the downregulation of IB4 binding, TMP activity, and somatostatin expression. GDNF also prevents the slowing of conduction velocity that normally occurs after axotomy in a population of small diameter DRG cells and the A-fiber sprouting into lamina II of the dorsal horn. GDNF therefore may be useful in the treatment of peripheral neuropathies and may protect peripheral neurons that are refractory to neurotrophin treatment.

Expression of the mature and the pro-form of human sterol carrier protein 2 in Escherichia coli alters bacterial lipids

Sterol carrier protein 2 (SCP2) is a protein that is believed to be involved in the intracellular transport of cholesterol and phospholipids. Expression in mammalian COS cells of a cDNA encoding SCP2 revealed that the mature protein is synthesized as a pro-form containing a 20-residue amino-terminal leader sequence. The function of this presequence is currently not known, and pro-SCP2 is generally not detected in tissues. In order to obtain large quantities of pro-SCP2 as well as the mature form of human SCP2, Escherichia coli expression plasmids were constructed. Both proteins were produced in high yield (10-30% of the total cell protein) and were found in the supernatant fraction after cell lysis. Recombinant human SCP2 and pro-SCP2 were purified to homogeneity by acid precipitation followed by ion-exchange chromatography. Both recombinant human SCP2 and pro-SCP2 had sterol exchange activity similar to that seen with SCP2 purified from rat liver. In addition, the lipid content of SCP2- and pro-SCP2-producing E. coli was analyzed. Acidic lipids were significantly increased in the transfected cells. Specifically, fatty acids were increased 2-3-fold, phosphatidylglycerol was increased 2-fold, and lipid A was increased 3-4-fold, while neutral lipids were decreased 2-3-fold as compared to control cells. This alteration of the lipid composition of E. coli expressing SCP2 or pro-SCP2 is consistent with the proposed role for SCP2 in intracellular lipid movement.

Antiplatelet efficacy and specificity of DMP728, a novel platelet GPIIb/IIIa receptor antagonist

The present study was undertaken to define the platelet GPIIb/IIIa affinity and specificity of DMP728, the cyclic [(D-2-aminobutyrate-N-methyl-L-arginyl-glycyl-L-aspartyl)-3-aminomethyl- benzoic acid] methane sulfonate. DMP728 demonstrated similar potency (IC50 = 0.046 +/- 0.002 microM) in inhibiting human platelet aggregation induced by various agonists or combination of agonists as assessed either by light transmittance aggregometry or impedance techniques. Similarly, DMP728 inhibited (IC50 = 2.3 +/- 0.8 nM) with equipotency in inhibiting 125I-fibrinogen binding to human gel-purified platelets regardless of the agonist used. In purified human GPIIb/IIIa ELISA, DMP728 demonstrated a competitive high affinity binding (Ki = 0.4 nM). Additionally, a high binding affinity (Kd = 0.1 nM) of 3H-DMP728 was demonstrated in human platelets. Furthermore, a platelet deaggregatory efficacy was shown. DMP728 demonstrated a high degree of specificity for platelet GPIIb/IIIa (alpha 2/beta 3) as compared to other integrins on endothelial cells (vitronectin receptors), platelets GPIb/1X, alpha v/beta 3, and other integrins on leukocytes or nonintegrin-related systems. In conclusion, DMP728 is a novel antiplatelet agent with high affinity and specificity for platelet GPIIb/IIIa.

Re-evaluation of molecular weight of pig heart NAD-specific isocitrate dehydrogenase

NAD-specific pig heart isocitrate dehydrogenase was earlier reported, on the basis of gel filtration experiments, to have a molecular weight of approximately 340,000. In the present study, the enzyme is shown by equilibrium ultracentrifugation to have a weight average molecular weight of approximately 224,000 which can be attributed to a rapidly associating-dissociating protein system. The results of light-scattering measurements are consistent with the lower value of molecular weight. The enzyme exhibits an average frictional ratio, f/f0, of 1.39 as determined from ultracentrifuge experiments, and this deviation from typical proteins may account for the previous high molecular weight estimates. An average Stokes radius of 6.0 nm was calculated from the present gel filtration experiments. By use of this value and a sedimentation coefficient of 9.1 S, an average molecular weight of 245,000 has been calculated. Previous studies (Ramachandran, N., and Colman, R. F. (1980) J. Biol. Chem. 255, 8859-8864) have indicated that the enzyme is composed of three different subunits, present in the ratio 2:1:1, each of which has a molecular weight of about 40,000. These results, together with the present observations, lead to the conclusion that, under stabilizing conditions in solution, the NAD-dependent isocitrate dehydrogenase predominantly exhibits a minimum, molecular weight of 160,000 but behaves as a mixture of oligomeric species with an average Mr of about 224,000.

Chemical characterization of distinct subunits of pig heart DPN-specific isocitrate dehydrogenase

Pig heart DPN-dependent isocitrate dehydrogenase is heterogeneous on isoelectric focusing in 6 M urea. Under these conditions, three types of subunits (termed alpha, beta, and gamma), which have isoelectric points of about 5.7, 6.6, and 7.2, respectively, can be separated. On the basis of densitometric scans of analytical isoelectric focused gels stained with Coomassie blue, it is estiated that the subunits are present in the whole enzyme in the approximate ratio of 2 alpha:1 beta: 1 gamma. The three isolated subunits have distinct amino acid compositions and the amino acid composition of the total enzyme, when expressed as residues per average polypeptide chain of 40,000 daltons, is consistent with contributions of alpha, beta, and gamma subunits in the ratio of 2:1:1. Each isolated subunit yields a readly distinguishable tryptic peptide map which is much simpler than that of the total enzyme, and is consistent with the number of peptides expected from the lysyl plus arginyl residues for the subunit. The alpha and beta chains both have alanine as the NH2-terminal amino acid, whereas phenylalanine is the NH2-terminal residue of the gamma subunit. Since the alpha subunit exhibits a molecular weight of 39,000 and the beta and gamma subunits have indistinguishable molecular weights of 41,000, the two-band pattern observed on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate is understandable. These results suggest that a complete DPN-specific isocitrate dehydrogenase would have a minimum molecular weight of 160,000.