Hyperthyroxinemia with a non-suppressed TSH: how to confidently reach a diagnosis in this clinical conundrum

Disorders of thyroid function are among the commonest referrals to endocrinology. While interpretation of thyroid function testing is usually straightforward, accurate interpretation becomes significantly more challenging when the parameters do not behave as would be expected in normal negative feedback. In such cases, uncertainty regarding further investigation and management arises. An important abnormal pattern encountered in clinical practice is that of high normal or raised free thyroxine (fT4) with inappropriately non-suppressed or elevated thyroid-stimulating hormone (TSH). In this short review using two clinical vignettes, we examine the diagnostic approach in such cases. A diagnostic algorithm is proposed to ensure that a definitive diagnosis is reached in these challenging cases.

Allyl piperidine-1-carbodiothioate and benzyl 1H-imidazole 1 carbodithioate: two potential agents to combat against mycobacteria

AIMS

The emergence of multidrug resistant strains of Mycobacterium tuberculosis has made tuberculosis more difficult to manage clinically. With the aim of obtaining new and effective anti-mycobacterial agent(s), this study investigated the anti-mycobacterial activity of several imidazole and piperidine derivatives.

METHODS AND RESULTS

Towards obtaining new anti-mycobacterial agents, Mycobacterium smegmatis cells were treated with different compounds for their growth inhibitory activity. Among these, benzyl 1H-imidazole-1-carbodithioate and allyl piperidine-1-carbodiothioate exhibited better inhibition than the others. Thereafter, anti-biofilm property of these two was examined by treating M. smegmatis with these agents before and after the formation of biofilm. The result showed that both the compounds at their sublethal dose inhibited the formation of biofilm as well as dispersed preformed biofilm. Consistently, they augmented the activity of isoniazid or rifampicin against biofilm-encapsulated cells. MTT assay was performed to examine the toxic effects of this combinatorial therapy on different cell lines. Results exhibited a low cytotoxicity for this combinatorial treatment. The activity of these two was also verified against dormant mycobacterial cells and was found to be effective.

CONCLUSION

The present study identified two compounds that exhibited anti-mycobacterial activities against both planktonic and dormant cells. These two also exhibited anti-biofilm activity at their sublethal dose and augmented the activity of isoniazid and rifampicin against biofilm encapsulated cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

The current study provides two new agents that have the potential to be used in anti-mycobacterial therapy and may help in public health management.

Cytohistological correlation in pituitary tumor and immunological assessment with the help of Ki-67

Background:

Tumors of the pituitary gland and sellar region represent approximately 10–15% of all brain tumors. Pituitary adenoma (PA), the most common pathology of the pituitary gland, can be effectively subclassified only with the help of immunohistochemistry (IHC). This is important and needed for individual patient management.

Aims and Objectives:

The objective of the study was to analyze the importance of intraoperative imprint smear cytology and correlating with final histopathological diagnosis. Furthermore, to classify the different types of PA with the help of IHC, prolactin (PRL), adrenocorticotropic hormone (ACTH), and growth hormone (GH) and to predict the benign, atypical, or malignant nature of the tumor with the help of prognostic marker Ki-67.

Materials and Methods:

A prospective study was done in 34 cases. The patients whose pituitary gland samples are referred from the endocrine and the neurosurgery department to the pathology department for histopathological examinations were selected. We have studied the clinical features, radiology and touch imprint cytology, histopathology, and IHC with the help of PRL, ACTH, GH, and Ki-67 of PA over 2 years.

Results:

In our study, we had 32 cases of PA of 34 cases over a span of 2 years. We have seen that there is a correlation between cytological and histological diagnosis of the subtypes of PA in 62% cases, and the Kappa statistics show a moderate extent of agreement (Kappa - 0.320, 95% confidence interval = 0.031–0.609). Ki-67 when compared to the radiological grading showed a high degree of comparability (Chi-square test: P < 0.001). All cases with invasion had a higher Ki-67. On using the Fisher's exact test, we found that the Ki-67 expression with GH-producing adenomas and ACTH-producing adenomas was comparable (P = 1.000) while in PRL-producing adenomas too this was not significant (P = 0.269).

Conclusion:

PA can be effectively classified with the help of IHC. Intraoperative cytology is important in diagnosing PA, but histopathology remains the gold standard in diagnosing and differentiating PA from other pathologies of the pituitary gland. The radiological grading together with immunological classification and the prognostic markers of Ki-67 is important in deciding the benign or atypical nature of the adenomas thus helping in better patient management.

A delay-diffusion model of marine plankton ecosystem exhibiting cyclic nature of blooms

The cyclic nature of blooms is a very interesting characteristic of marine plankton ecosystem. Release of toxins by some phytoplanktons has an important role on planktonic interactions and hence on regulating the blooms. A mathematical model describing the phytoplankton-zooplankton interaction with these characteristics is studied. The time needed for liberation of toxins by phytoplanktons is considered. To account for the spatial heterogeneity of an aquatic environment, diffusivity of different plankton populations is also incorporated into the system. Stability and bifurcation behaviour of different steady states are analysed.

Effects of deterministic and random refuge in a prey-predator model with parasite infection

Most natural ecosystem populations suffer from various infectious diseases and the resulting host-pathogen dynamics is dependent on host's characteristics. On the other hand, empirical evidences show that for most host pathogen systems, a part of the host population always forms a refuge. To study the role of refuge on the host-pathogen interaction, we study a predator-prey-pathogen model where the susceptible and the infected prey can undergo refugia of constant size to evade predator attack. The stability aspects of the model system is investigated from a local and global perspective. The study reveals that the refuge sizes for the susceptible and the infected prey are the key parameters that control possible predator extinction as well as species co-existence. Next we perform a global study of the model system using Lyapunov functions and show the existence of a global attractor. Finally we perform a stochastic extension of the basic model to study the phenomenon of random refuge arising from various intrinsic, habitat-related and environmental factors. The stochastic model is analyzed for exponential mean square stability. Numerical study of the stochastic model shows that increasing the refuge rates has a stabilizing effect on the stochastic dynamics.

Postoperative intussusception following repair of eventration of diaphragm--two case reports

Two patients of postoperative intestinal obstruction following repair of eventration of diaphragm, subsequently diagnosed as postoperative intussusception managed successfully, are reported. Absence of common features of intussusception led to delay in the diagnosis. Rarity of this phenomenon and incidentally two consecutive cases of postoperative intussusception occurring after repair of eventration of diaphragm prompted to report these two cases.

Congenital duodenal obstruction with preduodenal portal vein and situs inversus totalis: report of two cases and literature review

Preduodenal portal vein is a rare congenital anomaly that causes high intestinal obstruction. The authors report two interesting cases of preduodenal portal vein that were diagnosed as having congenital duodenal obstruction. As there is a high potential for surgical risk, this anomaly is of special interest to the surgeon and should be kept in mind. Here, we discuss the clinical presentation, diagnosis and management along with a review of the literature.

Pyloric and antral strictures following corrosive acid ingestion: A report of four cases

This study reports four children who developed complete stricture of pylorus and antrum of the stomach following accidental ingestion of corrosive agent (toilet cleaner).

Simultaneous presentation of type 1 diabetes and Graves' disease

The association between type 1 diabetes mellitus and autoimmune thyroid disease is well documented in the literature. Both can coexist although one endocrinopathy usually precedes the other. The simultaneous new onset of both diseases is rarely seen. Hyperthyroidism can precipitate and complicate the management of diabetic ketoacidosis by masking its classical clinical features. Persistent tachycardia after correction of acidosis and dehydration, may be the only suggestion of another coexisting illness such as thyrotoxicosis. We describe the case of a previously healthy woman who developed new onset type 1 diabetes mellitus and Graves' disease, and presented with diabetic ketoacidosis.

Gastric teratoma in a female infant

Gastric teratoma is a rare lesion seen most often in male infants. This patient, aged one year, female was having a massive benign gastric teratoma. The size of the tumour was 22 cm x 10 cm x 8 cm and weighted 2.250 kg making it one of the largest gastric teratoma. The tumour was removed by surgery. Histopathology revealed presence of all 3 elements in the form of skin, cartilage, fibrofatty tissue, blood vessels and gland with tall columnar epithelium. Postoperative period was uneventful.

Outcome of colostomy closure with different skin closure techniques in a developing country

BACKGROUND

Colostomy site, which is a potentially contaminated wound, is traditionally closed with interrupted skin stitches and placement of intraperitoneal or parietal or both drains; often with poor cosmetic outcome in our country. This study aims at prospective evaluation of colostomy closure wounds by different techniques.

PATIENTS AND METHODS

This study was carried out in all infants and children with colostomy (for different pathologies) admitted for colostomy closure in our institute from August 1, 2006 to February 29, 2008. Patients were divided into two groups: Group A with colostomy closure without any drain and subcuticular skin closure and Group B with colostomy closure with both intraperitoneal and parietal drain and interrupted skin closure. Patient's details, including age, sex, body weight, diagnosis, preoperative bowel preparation, peroperative antibiotics, postoperative wound infection, anastomotic leaks, duration of hospitalisation and postoperative follow-up for wound assessment, were recorded. By the end of February 2008, 151 cases of colostomy closure were recorded, 70 in Group A and 81 in Group B.

RESULTS

Statistical analysis of the data showed no statistically significant difference in wound infection and anastomotic leak between the two groups. On postoperative follow-up, wound assessment showed significantly better cosmesis in the no drain subcuticular group.

CONCLUSION

This study shows that closing colostomies without any drain and subcuticular skin closure does not result in any increased incidence of wound infection and has better cosmetic results.

Emergency separation of a xipho-omphalopagus twin in a developing country

Female conjoined twins (thoraco-omphalopagus) were delivered by emergency caesarean section in a private nursing home. On examination, one of the twins was dead and was threatening the survival of the surviving twin (twin A). An emergency separation was performed to salvage the surviving twin.

Metastatic breast cancer deluding as a papular skin rash

Dermatological metastases from internal malignancies are relatively less common than other sites. We describe an interesting case of an elderly lady who initially presented with symptomatic normocytic anaemia, and then developed a widespread papular rash over a period of ten days. The rash was found to be metastatic breast cancer.

A prospective observational clinical study involving an alternative cancer treatment, psorinum therapy, in treating stomach, gallbladder, pancreas, and liver cancers

3050

Background: The prospective observational clinical study was conducted to know the efficacy of an alternative cancer treatment, ‘psorinum therapy,‘ in treating liver, gall bladder, pancreatic, and stomach cancers. The primary outcome measures of the study were (1) to assess the radiological tumor response; (2) to assess how many participants survived at least 1 year, 2 years, 3 years, 4 years, and finally, 5 years after the beginning of the study. The secondary outcome measure of the study was to assess the side effects of the investigational anti-cancer drug (psorinum) if any. Methods: The drug psorinum (an alcoholic extract of scabies, scrub, slough, and pus cells) was administered orally at 0.01ml-0.02 ml/Kg body weight as a single dose in empty stomach per day and ongoing to all the participants along with allopathic and homeopathic supportive cares. Results: 158 histopathology or cytopathology proved participants (42 of stomach, 40 of gallbladder, 44 of pancreas, and 32 of liver cancers) were included in the final analysis at the end of the study. According to the AJCC/UICC TNM staging system, 7 (4.43%) of them diagnosed at stage II, 39 (24.68%) of them diagnosed at late stage II or early stage III and 112 (70.87%) of them diagnosed at late stage III or stage IV. According to the RECIST criteria, complete tumor response occurred in 28 (17.72%) cases and partial tumor response occurred in 56 (35.44%) cases. 126 (79.75%) of them survived at least 1 year, 99 (62.66%) of them survived at least 2 years, 87 (55.06%) of them survived at least 3 years, 76 (48.10%) of them survived at least 4 years, and 62 (39.24%) of them survived at least 5 years. These participants did not receive any other conventional or investigational cancer treatments. The participants report no side effects from the drug psorinum. Conclusions: Psorinum therapy is effective in treating stomach, gallbladder, pancreas, and liver cancers. Double-blinded randomized controlled clinical trial should be done for further investigation of this alternative cancer treatment.

No significant financial relationships to disclose.

Acquired tracheo-oesophageal fistula: a case report

This is a case report of a girl aged 4 years who presented with repeated attacks of chocking and dysphagia. She was diagnosed to be having an acquired tracheo- oesophageal fistula caused by fish bone impaction. She was treated successfully. In this report, the literature was reviewed of this rare condition.

Assessment of noise level in Burdwan town, West Bengal

Cities and towns of the world are now facing enormous rise of noise pollution problem due to very high population rise, transport congestion and associated commercial and industrial activities. Burdwan, a district headquarter (100 km away from Kolkata) is one such town where noise pollution is very frequent. In order to assess noise level, noise data were collected from various places of the town by sound level meter with a duration of 30 minutes/location during specified time like 6.00 am, 10.00 am, 1.00 pm, 4.00 pm and 6.00 pm. Most of the monitoring places either belongs to silence category or commercial category areas. From the tabulated data, it was found that sound level lies within the range of 64-85 dB or above in different time at different places. The locations that belong to the silence zone have the noise level up to 90 dB. Statistically noise level in all these zones differ significantly at their peak hours. Noise pollution adversely affects our environment as well as human beings. Sound causes both pathological and psychological disorders in human beings. Implementation of rules and regulations under section 20, 21J, 41, 68(I), 70, 90, 111A of Environment Protection Act, 1986 and of course various technological methods and public awareness are very essential to check noise pollution in Burdwan town.

Modeling the Role of Diffusion Coefficients on Turing Instability in a Reaction-diffusion Prey-predator System

The paper is concerned with the effect of variable dispersal rates on Turing instability of a non-Lotka-Volterra reaction-diffusion system. In ecological applications, the dispersal rates of different species tends to oscillate in time. This oscillation is modeled by temporal variation in the diffusion coefficient with large as well as small periodicity. The case of large periodicity is analyzed using the theory of Floquet multipliers and that of the small periodicity by using Hill's equation. The effect of such variation on the resulting Turing space is studied. A comparative analysis of the Turing spaces with constant diffusivity and variable diffusivities is performed. Numerical simulations are carried out to support analytical findings.

A comparison of glycaemic and metabolic control over time among South Asian and European patients with Type 2 diabetes: results from follow-up in a routine diabetes clinic

AIMS

Although South Asians have a higher prevalence of diabetes which develops at a younger age, data on change in metabolic parameters post-diagnosis are relatively sparse. We therefore wished to determine whether South Asians with diabetes had similar or greater year-on-year deterioration in metabolic parameters compared with Europeans.

METHODS

We analysed longitudinal change in metabolic parameters [glycated haemoglobin (HbA(1c)), blood pressure, body mass index (BMI), lipids] among South Asian (n = 210) and European (n = 1557) patients consecutively attending the same diabetes clinic over a mean period of 5.3 years.

RESULTS

South Asians were younger than Europeans at first recorded diagnosis of diabetes (mean age 45.9 vs. 57.3 years, P < 0.001) and had significantly lower ( approximately 1.2 units) BMI and blood pressure. Mean HbA(1c) was not different across ethnic groups at first visit, but with time glycaemic control was worse in South Asians than Europeans, with average deterioration 1.31% (= 0.23%/year) in Asians vs. 0.82% (0.16%/year) in Europeans, P = 0.003. This ethnic difference in mean change in HbA(1c) persisted after adjustment for age, sex, baseline HbA(1c), and weight change in linear regression analysis (beta = 0.46, 95% CI 0.24-0.69, P < 0.001), and with additional adjustment for time to referral and duration of diabetes (P = 0.01). Moreover, South Asians had significantly smaller improvements in blood pressure (P < 0.001) and cholesterol (P = 0.044) over the follow-up period in keeping with fewer prescriptions of anti-hypertensive agents and lipid-lowering agents.

CONCLUSIONS

These data suggest the need to be more aggressive in the management of diabetes and related risk factors in South Asians.

Normoglycaemia in acute renal failure--a difficult diagnosis of diabetes

We report diagnostic difficulties in a case of diabetes mellitus presenting as acute on chronic renal failure with normoglycaemia. A renal biopsy indicated diabetic nephropathy; she developed hyperglycaemia following the institution of haemodialysis. It is important to remember that diabetic patients may have normal blood glucose concentrations in renal failure. In a patient with undiagnosed diabetes mellitus presenting with acute on chronic renal failure, choice of diagnostic biochemical test for diabetes may be difficult.

DNA sequence variation and haplotype structure of the ICAM1 and TNF genes in 12 ethnic groups of India reveal patterns of importance in designing association studies

We have examined the patterns of DNA sequence variation in and around the genes coding for ICAM1 and TNF, which play functional and correlated roles in inflammatory processes and immune cell responses, in 12 diverse ethnic groups of India. We aimed to (a) quantify the nature and extent of the variation, and (b) analyse the observed patterns of variation in relation to population history and ethnic background. At the ICAM1 and TNF loci, respectively, the total numbers of SNPs that were detected were 28 and 12. Many of these SNPs are not shared across ethnic groups and are unreported in the dbSNP or TSC databases, including two fairly common non-synonymous SNPs at positions 13487 and 13542 in the ICAM1 gene. Conversely, the TNF-376A SNP that is reported to be associated with susceptibility to malaria was not found in our study populations, even though some of the populations inhabit malaria endemic areas. Wide between-population variation in the frequencies of shared SNPs and coefficients of linkage disequilibrium have been observed. These findings have profound implications in case-control association studies.

Computer simulation of leachate quality by recirculation in a sanitary landfill bioreactor

Sanitary Landfills are the most widely used method of solid waste disposal around the world. Modern sanitary landfills are designed with impervious liners, and leachate collection, removal, and treatment systems to minimize the potential for groundwater contamination. Leachate recycle through the landfill is an effective method of leachate treatment, and to enhance solid waste stabilization. A mathematical model is developed to simulate the release of contaminants from solid wastes, and their movement into the percolating liquid. Two differential equations are used that express the mass balance of the contaminants in the percolating water and those in the solid wastes. These simultaneous linear differential equations are solved numerically using a fourth-order Runge-Kutta algorithm with many physical and process parameters. The model results are used to estimate the active life of landfill with and without leachate recirculation. Such information is valuable in the operation, maintenance, and closure plan of a sanitary landfill.

Pancreatic lesions in von Hippel-Lindau disease

OBJECTIVE

Von Hippel-Lindau disease is an inherited neoplasia syndrome. The main endocrine manifestations are phaeochromocytoma and paraganglioma. The presence of pancreatic disease has also been variably reported. This study was undertaken to describe the prevalence, nature, natural history and clinical associations of pancreatic lesions in von Hippel-Lindau disease.

PATIENTS AND DESIGN

A retrospective analysis of the case notes of 17 consecutive patients. Average duration of follow-up was 5.5 years. Clinical, biochemical, genetic and radiological testing was routinely performed.

RESULTS

Eleven (64.7%) patients had pancreatic lesions either on computed tomography or magnetic resonance imaging. Serous microcystic adenomas and multiple cysts were the commonest findings, but solid lesions were also found. The commonest clinical association was diabetes mellitus in patients with extensive serous microcystic adenomas. None of the pancreatic lesions showed evidence of biochemical function. All patients with pancreatic lesions also had renal lesions. Mutations were found at several points in the gene and there was no apparent association between pancreatic lesions and a particular mutation.

CONCLUSIONS

Pancreatic lesions are very common in von Hippel-Lindau disease and all patients had coexisting renal lesions. The main clinical correlate was diabetes mellitus, but otherwise the lesions were clinically and biochemically silent.

Obstetric morbidity and socio-demographic factors in rural West Bengal, India

The impact of selected socio-demographic factors on reported obstetric morbidity during antepartum and postpartum periods was studied through a cross-sectional retrospective survey carried out in rural areas of three districts of West Bengal, India. During their most recent live births, 56.6% of mothers reported at least one morbid condition. Mothers with higher levels of education reported fewer overall problems. Factors such as age and pregnancy order affect obstetric morbidity differently in different religious groups. More mothers reported postpartum than antepartum problems, and very few sought treatment. The present study provides an insight into various factors affecting obstetric morbidity in a developing country.

Oxaloacetate synthesis in the methanarchaeon Methanosarcina barkeri: pyruvate carboxylase genes and a putative Escherichia coli-type bifunctional biotin protein ligase gene (bpl/birA) exhibit a unique organization

Evidence is presented that, in Methanosarcina barkeri oxaloacetate synthesis, an essential and major CO(2) fixation reaction is catalyzed by an apparent alpha(4)beta(4)-type acetyl coenzyme A-independent pyruvate carboxylase (PYC), composed of 64.2-kDa biotinylated and 52.9-kDa ATP-binding subunits. The purified enzyme was most active at 70 degrees C, insensitive to aspartate and glutamate, mildly inhibited by alpha-ketoglutarate, and severely inhibited by ATP, ADP, and excess Mg(2+). It showed negative cooperativity towards bicarbonate at 70 degrees C but not at 37 degrees C. The organism expressed holo-PYC without an external supply of biotin and, thus, synthesized biotin. pycA, pycB, and a putative bpl gene formed a novel operon-like arrangement. Unlike other archaeal homologs, the putative biotin protein ligases (BPLs) of M. barkeri and the closely related euryarchaeon Archaeoglobus fulgidus appeared to be of the Escherichia coli-type (bifunctional, with two activities: BirA or a repressor of the biotin operon and BPL). We found the element Tyr(Phe)ProX(5)Phe(Tyr) to be fully conserved in biotin-dependent enzymes; it might function as the hinge for their "swinging arms."

Clinical appraisal of Ascaris lumbricoides, with special reference to surgical complications

Over a period of 4 years (January 1993-December 1997), 509 patients were treated for abdominal colic with or without intestinal obstruction and a history of passage of adult roundworms either in the stool or in vomitus. All patients were below the age of 10 years, the youngest 6 months old, and were treated successfully with antispasmodics and normal saline enemas. When the pain subsided, an anthelminthic drug was given. Of 209 patients admitted to the hospital, 105 responded to conservative management and 104 (50%) required surgical intervention. The procedures included squeezing out of worms, resection and anastomosis, and treatment of other pathologies like acute appendicitis, tubercular stricture of the small intenstine, etc. Five patients died in the postoperative period due to various complications. There were no deaths among those treated by conservative management. Early recognition of the condition can prevent serious surgical complications and morbidity.

Blood pressure and its biocultural correlates among the Lepchas of Sikkim, India: a microlevel epidemiological study

The present study evaluates the blood pressure profile among the Buddhist Lepchas, a tribal population, indigenous to the Sikkim Himalaya, in relation to selected biological, behavioral and sociocultural factors. The study subjects (aged 16 years and older) have been chosen from urban (Gangtok town, the capital of the State of Sikkim) and rural (Dzongu villages, about 75 km north of Gangtok) areas. The subjects inhabiting the urban area are engaged primarily in service sector, while those inhabiting the rural area are practicing agri-horticulture. The results reveal that significant age effect exists on logarithmically transformed blood pressures; sex effect is not significant. Among the anthropometric variables considered, calfgirth and height are found to be significantly correlated with systolic and diastolic blood pressures, respectively. While disease status significantly affects systolic pressure, a significant effect of alcohol intake is discernible only on diastolic pressure. Furthermore, significant effects of rural/urban residence and educational level are found on blood pressures, both systolic and diastolic. Mean systolic and diastolic blood pressures of the urban Lepchas are found to be significantly higher compared to their rural counterparts. An increase in both mean systolic and diastolic pressures is noticed with increasing level of education, although the trend is not absolutely uniform.

A GTP-dependent vertebrate-type phosphoenolpyruvate carboxykinase from Mycobacterium smegmatis

This is the first report on a bacterial verterbrate-type GTP-dependent phosphoenolpyruvate carboxykinase (PCK). The pck gene of Mycobacterium smegmatis was cloned. The recombinant PCK was overexpressed in Escherichia coli in a soluble form and with high activity. The purified enzyme was found to be monomeric (72 kDa), thermophilic (optimum temperature, 70 degrees C), very stable upon storage at 4 degrees C, stimulated by thiol-containing reducing agents, and inhibited by oxalate and by alpha-ketoglutarate. The requirement for a divalent cation for activity was fulfilled best by Mn(2+) and Co(2+) and poorly by Mg(2+). At 37 degrees C, the highest V(m) value (32.5 units/mg) was recorded with Mn(2+) and in the presence of 37 mm dithiothreitol (DTT). The presence of Mg(2+) (2 mm) greatly lowered the apparent K(m) values for Mn(2+) (by 144-fold in the presence of DTT and by 9.4-fold in the absence of DTT) and Co(2+) (by 230-fold). In the absence of DTT but in the presence of Mg(2+) (2 mm) as the co-divalent cation, Co(2+) was 21-fold more efficient than Mn(2+). For producing oxaloacetate, the enzyme utilized both GDP and IDP; ADP served very poorly. The apparent K(m) values for phosphoenolpyruvate, GDP, and bicarbonate were >100, 66, and 8300 micrometer, respectively, whereas those for GTP and oxaloacetate (for the phosphoenolpyruvate formation activity) were 13 and 12 microm, respectively. Thus, this enzyme preferred the gluconeogenesis/glycerogenesis direction. This property fits the suggestion that in M. smegmatis, pyruvate carboxylase is not anaplerotic but rather gluconeogenic (Mukhopadhyay, B., and Purwantini, E. (2000) Biochim. Biophys. Acta. 1475, 191-206). Both in primary structure and kinetic properties, the mycobacterial PCK was very similar to its vertebrate-liver counterparts and thus could serve as a model for these enzymes; examples for several immediate targets are presented.

An aminoacyl tRNA synthetase whose sequence fits into neither of the two known classes

Aminoacyl transfer RNA synthetases catalyse the first step of protein synthesis and establish the rules of the genetic code through the aminoacylation of tRNAs. There is a distinct synthetase for each of the 20 amino acids and throughout evolution these enzymes have been divided into two classes of ten enzymes each. These classes are defined by the distinct architectures of their active sites, which are associated with specific and universal sequence motifs. Because the synthesis of aminoacyl-tRNAs containing each of the twenty amino acids is a universally conserved, essential reaction, the absence of a recognizable gene for cysteinyl tRNA synthetase in the genomes of Archae such as Methanococcus jannaschii and Methanobacterium thermoautotrophicum has been difficult to interpret. Here we describe a different cysteinyl-tRNA synthetase from M. jannaschii and Deinococcus radiodurans and its characterization in vitro and in vivo. This protein lacks the characteristic sequence motifs seen in the more than 700 known members of the two canonical classes of tRNA synthetase and may be of ancient origin. The existence of this protein contrasts with proposals that aminoacylation with cysteine in M. jannaschii is an auxiliary function of a canonical prolyl-tRNA synthetase.

A stable archaeal pyruvate carboxylase from the hyperthermophile Methanococcus jannaschii

The pyruvate carboxylase (PYC) of the hyperthermophilic, strictly hydrogenotrophic, autotrophic and marine methanarchaeon Methanococcus jannaschii was purified to homogeneity. Optimal activity was at pH 8.5, > or = 80 degrees C, and a KCl concentration of 0.175 M. This enzyme is the most thermophilic PYC so far studied. Unlike the Methanobacterium thermoautotrophicum enzyme, Mc. jannaschii PYC was expressed in cells grown without an external source of biotin and in the purified form was stable during storage at 4, -20 and -80 degrees C. However, it was rapidly inactivated at 80 degrees C. The enzyme was insensitive to aspartate and glutamate, mildly inhibited by alpha-ketoglutarate, and was strongly inhibited by ATP and ADP (apparent Km, for ATP, 0.374 +/- 0.039 mM; apparent Ki for ATP, 5.34 +/- 2.14 mM; Ki for ADP, 0.89 +/- 0.18 mM). It was also strongly inhibited when the Mg2+ concentration in the assay exceeded that of ATP. Thus, this stable PYC could serve as a model for mechanistic studies on archaeal PYCs. It was apparently an alpha4beta4-type PYC composed of a non-biotinylated 55.5-kDa subunit (PYCA) and a 64.2-kDa biotinylated subunit (PYCB). The determined NH2-terminal sequences for these subunits provided additional support for our earlier proposal to rename the ORFs MJ1229 and MJ1231 in the NCBI Mc. jannaschii genome sequence database as PYCA and PYCB, respectively; even very recently, these have been misidentified as a subunit of acetyl-CoA carbxoylase (AccC) and the alpha-subunit of ion-pumping oxaloacetate decarboxylase (OADalpha), respectively.

A novel pH2 control on the expression of flagella in the hyperthermophilic strictly hydrogenotrophic methanarchaeaon Methanococcus jannaschii

The methanarchaeon, Methanococcus jannaschii, a hyperthermophilic, autotrophic, and strictly hydrogenotrophic inhabitant of submarine hydrothermal vents, was cultivated in a reactor at two hydrogen partial pressure (p(H(2))) values, 178 kPa (high) and 650 Pa (ultralow), and the cells were subjected to a comparative proteome analysis. From these studies, it was discovered that, when p(H(2)) was high and the cell density was low (a combination representing a hydrogen-excess condition), the cells possessed very low or undetectable levels of four flagella-related polypeptides (FlaB2, FlaB3, FlaD, and FlaE); electron microscopic examination showed that most of these cells were devoid of flagella. Flagella synthesis occurred when hydrogen became limiting either at high cell density under high p(H(2)) or at low cell density under low p(H(2)). The results from a p(H(2))-shift experiment corroborated the above observations. The p(H(2))-dependent changes in the levels of two methanogenic enzymes (MTD and HMDX) were as expected, and thus they served as internal controls. To our knowledge, this is the first example for the regulation of expression of flagella by hydrogen in any domain of life and for a control of any kind on flagella synthesis in the archaea. Our work also provides the only known example for each of the following: (i) the pure culture cultivation of a methanogen at an ultralow, near ecologically relevant p(H(2)); (ii) experimental functional genomics for M. jannaschii; and (iii) the use of proteomics with M. jannaschii.

Pyruvate carboxylase from Mycobacterium smegmatis: stabilization, rapid purification, molecular and biochemical characterization and regulation of the cellular level

This is the first report on the purification and characterization of an anaplerotic enzyme from a Mycobacterium. The anaplerotic reactions play important roles in the biochemical differentiation of mycobacteria into non-replicating stages. We have purified and characterized a pyruvate carboxylase (PYC) from Mycobacterium smegmatis and cloned and sequenced its gene. We have developed a very rapid and efficient purification protocol that provided PYC with very high specific activities (up to 150 U/mg) that remained essentially unchanged over a month. The enzyme was found to be a homomultimer of 121 kDa subunits, mildly thermophilic, absolutely dependent on acyl-CoAs for activity and inhibited by ADP, by excess Mg(2+), Co(2+), and Mn(2+), by aspartate, but not by glutamate and alpha-ketoglutarate. Supplementation of minimal growth medium with aspartate did not lower the cellular PYC level, rather doubled it; with glutamate the level remained unchanged. These observations would not fit the idea that the M. smegmatis enzyme fulfills a straightforward anaplerotic function; in a closely related organism, Corynebacterium glutamicum, PYC is the major anaplerotic enzyme. Growth on glucose provided 2-fold higher cellular PYC level than that observed with glycerol. The PYCs of M. smegmatis and Mycobacterium tuberculosis were highly homologous to each other. In M. smegmatis, M. tuberculosis and M. lepra, pyc was flanked by a putative methylase and a putative integral membrane protein genes in an identical operon-like arrangement. Thus, M. smegmatis could serve as a model for studying PYC-related physiological aspects of mycobacteria. Also, the ease of purification and the extraordinary stability could make the M. smegmatis enzyme a model for studying the structure-function relationships of PYCs in general. It should be noted that no crystal structure is available for this enzyme of paramount importance in all three domains of life, archaea, bacteria, and eukarya.

Reactor-scale cultivation of the hyperthermophilic methanarchaeon Methanococcus jannaschii to high cell densities

For the hyperthermophilic and barophilic methanarchaeon Methanococcus jannaschii, we have developed a medium and protocols for reactor-scale cultivation that improved the final cell yield per liter from approximately 0.5 to approximately 7.5 g of packed wet cells ( approximately 1.8 g dry cell mass) under autotrophic growth conditions and to approximately 8.5 g of packed wet cells ( approximately 2 g dry cell mass) with yeast extract (2 g liter(-1)) and tryptone (2 g liter(-1)) as medium supplements. For growth in a sealed bottle it was necessary to add Se to the medium, and a level of 2 microM for added Se gave the highest final cell yield. In a reactor M. jannaschii grew without added Se in the medium; it is plausible that the cells received Se as a contaminant from the reactor vessel and the H(2)S supply. But, for the optimal performance of a reactor culture, an addition of Se to a final concentration of 50 to 100 microM was needed. Also, cell growth in a reactor culture was inhibited at much higher Se concentrations. These observations and the data from previous work with methanogen cell extracts (B. C. McBride and R. S. Wolfe, Biochemistry 10:4312-4317, 1971) suggested that from a continuously sparged reactor culture Se was lost in the exhaust gas as volatile selenides, and this loss raised the apparent required level of and tolerance for Se. In spite of having a proteinaceous cell wall, M. jannaschii withstood an impeller tip speed of 235.5 cms(-1), which was optimal for achieving high cell density and also was the higher limit for the tolerated shear rate. The organism secreted one or more acidic compounds, which lowered pH in cultures without pH control; this secretion continued even after cessation of growth.

Purification, regulation, and molecular and biochemical characterization of pyruvate carboxylase from Methanobacterium thermoautotrophicum strain deltaH

We discovered that Methanobacterium thermoautotrophicum strain DeltaH possessed pyruvate carboxylase (PYC), and this biotin prototroph required exogenously supplied biotin to exhibit detectable amounts of PYC activity. The enzyme was highly labile and was stabilized by 10% inositol in buffers to an extent that allowed purification to homogeneity and characterization. The purified enzyme was absolutely dependent on ATP, Mg2+ (or Mn2+ or Co2+), pyruvate, and bicarbonate for activity; phosphoenolpyruvate could not replace pyruvate, and acetyl-CoA was not required. The enzyme was inhibited by ADP and alpha-ketoglutarate but not by aspartate or glutamate. ATP was inhibitory at high concentrations. The enzyme, unlike other PYCs, exhibited nonlinear kinetics with respect to bicarbonate and was inhibited by excess Mg2+, Mn2+, or Co2+. The 540-kDa enzyme of A4B4 composition contained a non-biotinylated 52-kDa subunit (PYCA) and a 75-kDa biotinylated subunit (PYCB). The pycB gene was probably monocistronic and followed by a putative gene of a DNA-binding protein on the opposite strand. The pycA was about 727 kilobase pairs away from pycB on the chromosome and was probably co-transcribed with the biotin ligase gene (birA). PYCA and PYCB showed substantial sequence identities (33-62%) to, respectively, the biotin carboxylase and biotin carboxyl carrier + carboxyltransferase domains or subunits of known biotin-dependent carboxylases/decarboxylases. We discovered that PYCB and probably the equivalent domains or subunits of all biotin-dependent carboxylases harbored the serine/threonine dehydratase types of pyridoxal-phosphate attachment site. Our results and the existence of an alternative oxaloacetate synthesizing enzyme phosphoenolpyruvate carboxylase in M. thermoautotrophicum strain DeltaH (Kenealy, W. R., and Zeikus, J. G. (1982) FEMS Microbiol. Lett. 14, 7-10) raise several questions for future investigations.