Biomedical subjects

J K Rao

Publications and source records attributed to J K Rao.

At least 19 recordsLinked to original sources

PubMed1995

The role of antineutrophil cytoplasmic antibody (c-ANCA) testing in the diagnosis of Wegener granulomatosis. A literature review and meta-analysis.

PURPOSE: To summarize the literature on the clinical utility of antineutrophil cytoplasmic antibody (c-ANCA) as a diagnostic marker for Wegener granulomatosis. DATA SOURCES: A structured literature search was done using MEDLINE; this search, combined with a manual search, yielded 747 articles for potential inclusion. These articles passed through a 4-stage review. Studies were included if they had a specified reference standard and a systematic method of patient selection and if a 2 x 2 contingency table could be constructed from their results. Fifteen articles met these criteria. DATA EXTRACTION: 3 physicians reviewed all selected articles. Detailed data abstraction was done, and the quality of the study methods was assessed. Items abstracted included the method of patient selection, the study design, the reference standard, the c-ANCA testing technique, disease activity, and the test results. Disagreements among reviewers were resolved by consensus. Contingency tables were used to calculate the operating characteristics for Wegener granulomatosis overall and for active and inactive Wegener granulomatosis. RESULTS: The sensitivities of c-ANCA testing for overall Wegener granulomatosis ranged from 34% to 92%, and the specificities ranged from 88% to 100%. The pooled sensitivity was 66% (95% CI, 57% to 74%), and the pooled specificity was 98% (CI, 96% to 99.5%). Four articles provided data on disease activity. For active disease, the pooled sensitivity was 91% (CI, 87% to 95%), and the pooled specificity was 99% (CI, 97% to 99.9%). For inactive disease, the pooled sensitivity and specificity were 63% and 99.5%, respectively. CONCLUSIONS: Although c-ANCA test results may serve clinicians as adjunct evidence for the diagnosis of Wegener granulomatosis, these results must be viewed in the context of the patient's clinical picture and disease activity and the prevalence of Wegener granulomatosis in the clinical setting in which the patient is seen.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed1995

A prospective study of antineutrophil cytoplasmic antibody (c-ANCA) and clinical criteria in diagnosing Wegener's granulomatosis.

Antineutrophil cytoplasmic antibody (c-ANCA) has a reported sensitivity and specificity greater than 90% for active Wegener's granulomatosis in selected patients with previously-defined disease. Because of these reports, some clinicians believe that a positive c-ANCA result provides strong circumstantial evidence for the diagnosis of Wegener's granulomatosis in patients with compatible clinical symptoms. However, this approach has not been examined prospectively. We prospectively studied 346 consecutive patients suspected of having vasculitis; those with previously established Wegener's granulomatosis (n = 29) or receiving immunosuppressives other than corticosteroids (n = 65) at baseline were excluded. Measures included a baseline c-ANCA, blinded chart reviews to record symptoms, physical findings, and corticosteroid use at baseline, and 2 to 8 months later to record final diagnoses and biopsy results. Wegener's granulomatosis was defined using the 1990 American College of Rheumatology (ACR) criteria, which does not require a biopsy. Follow-up information was available for 212 (84%) of the 252 patients eligible for this study (no corticosteroids: n = 174; corticosteroids: n = 78). 25 patients with compatible symptoms were classified with Wegener's granulomatosis by ACR criteria; only 6 of the 25 had biopsy-proven disease. 14 of these 212 patients had positive c-ANCA results. The overall sensitivity and specificity of c-ANCA for ACR-defined Wegener's granulomatosis were 28% (95% CI, 10%-46%) and 96% (93%-99%) respectively. The positive and negative predictive values were 0.50 and 0.91. The specificity remained greater than 90% regardless of baseline corticosteroid use or disease activity; however, the sensitivity and positive predictive value remained poor. For Wegener's granulomatosis defined by biopsy criteria and compatible clinical symptoms, the sensitivity was 83% (53%-100%); however, the positive predictive value was 36%. These results raise serious questions about the use of positive c-ANCA tests in diagnosing Wegener's granulomatosis in patients with clinical symptoms alone.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed1995

Systems for data analysis.

A system for data analysis is the end product of study planning, form design, data entry, data verification, and statistical analysis. This article reviews these steps and considers the fundamental choices in software for data entry and analysis. The appendix includes a listing of general and specialized software for data management and statistical analysis.

Data Interpretation, Statistical↗

PubMed1994

Implantable controlled delivery systems for proteins based on collagen--pHEMA hydrogels.

Co-polymeric hydrogels of collagen and poly(hydroxyethyl methacrylate) (pHEMA) were prepared using an ammonium persulphate-sodium metabisulphite redox initiation technique. Fluorescein isothiocyanate (FITC)-labelled bovine serum albumin (BSA) was entrapped into these hydrogels. These gels were modified differently by external cross-linking and made highly porous by incorporation of ethylene glycol. The morphological characteristics of the gels containing FITC-BSA before and after release were studied. The in vitro release of FITC-labelled BSA was studied in phosphate buffer, pH 7.4, at 37 degrees C. The results clearly indicated that collagen-pHEMA hydrogels release FITC-BSA in a zero-order fashion. In the case of uncross-linked hydrogels, the release of FITC-BSA was about 81% within 8 d, compared to 49% for the same period in the case of cross-linked hydrogels. It was also observed that in the case of porous hydrogels the release was very fast (19% in the first hour) and lasted for about 12 h, releasing 76% of FITC-BSA. These results clearly indicated that collagen-pHEMA hydrogels released BSA in a zero-order fashion and that the release rate can be programmed by appropriate modification of the hydrogel matrices.

Animals↗

PubMed1994

Controlled release systems for proteins based on gelatin microspheres.

The preparation and characterization of biodegradable gelatin microspheres for the controlled release of peptides and proteins has been investigated. Bovine serum albumin (BSA) was chosen for incorporation into the gelatin microspheres and the spheres were characterized for the in vitro release of BSA and other properties. BSA was labelled with fluorescein isothiocyanate (FITC) for easy analysis. FITC-BSA was entrapped into the gelatin microspheres using a polymer dispersion technique developed in our earlier studies. The morphological characteristics of microspheres were analysed by optical and scanning electron microscopy (SEM). The optical and SEM photographs of FITC-BSA microspheres showed the solid spherical nature of the spheres. The entrapment efficiency of FITC-BSA was about 62%. The in vitro release pattern of FITC-BSA showed that 51% of the entrapped drug was released during the first day and the release followed approximate zero order kinetics from day 2 onwards. The total release of FITC-BSA lasted for about 8 days. SDS-PAGE analysis revealed that BSA was not degraded by this preparation of microspheres.

Biodegradation, Environmental↗

PubMed1992

Genetic analysis of MRL-lpr mice: relationship of the Fas apoptosis gene to disease manifestations and renal disease-modifying loci.

In MRL mice, the mostly recessive lpr mutation results in both the accumulation of CD4-, CD8-, CD3+ T cells in lymphoid tissue and many features of generalized autoimmune disease, including immune complex glomerulonephritis. To positionally clone the lpr mutation and analyze the effects of background genes, backcross offspring were examined from the cross: (MRL/MpJ-lpr x CAST/Ei)F1 x MRL/MpJ-lpr. The lpr gene was found to be closely linked to a mouse chromosome 19 marker defined by a variation of a Fas gene restriction fragment. Our results identified differences in RNA expression and differences in the genomic organization of the Fas gene between normal and lpr mice, and confirm the recent report that a mutation in the Fas apoptosis gene is the lpr mutation. However, our results also indicate that the Fas gene is expressed in spleen cells from normal mice, and spleen and lymph node cells from mice with a second mutation at the lpr locus (lprcg). Together these results suggest that altered Fas transcription results in the failure of lymphocytes to undergo programmed cell death and may lead to an altered immune cell repertoire. This mechanism may explain certain central and peripheral defects in tolerance that are present in autoimmune disease. The current study also demonstrates the profound effect of background genes on the degree of nephritis, lymphadenopathy, and anti-DNA antibody production. Of major note, our studies suggest the identification of chromosomal positions for genes that modify nephritis. Analysis of the backcross mice for markers covering most of the mouse genome suggests that over 50% of the variance in renal disease is attributable to quantitative trait loci on mouse chromosomes 7 and 12. Moreover, this study provides a model for dissecting the complex genetic interactions that result in manifestations of autoimmune disease.

Animals↗

PubMed1992

Crystal structure of a complex of HIV-1 protease with a dihydroxyethylene-containing inhibitor: comparisons with molecular modeling.

The structure of a crystal complex of recombinant human immunodeficiency virus type 1 (HIV-1) protease with a peptide-mimetic inhibitor containing a dihydroxyethylene isostere insert replacing the scissile bond has been determined. The inhibitor is Noa-His-Hch psi [CH(OH)CH(OH)]Vam-Ile-Amp (U-75875), and its Ki for inhibition of the HIV-1 protease is < 1.0 nM (Noa = 1-naphthoxyacetyl, Hch = a hydroxy-modified form of cyclohexylalanine, Vam = a hydroxy-modified form of valine, Amp = 2-pyridylmethylamine). The structure of the complex has been refined to a crystallographic R factor of 0.169 at 2.0 A resolution by using restrained least-squares procedures. Root mean square deviations from ideality are 0.02 A and 2.4 degrees, for bond lengths and angles, respectively. The bound inhibitor diastereomer has the R configurations at both of the hydroxyl chiral carbon atoms. One of the diol hydroxyl groups is positioned such that it forms hydrogen bonds with both the active site aspartates, whereas the other interacts with only one of them. Comparison of this X-ray structure with a model-built structure of the inhibitor, published earlier, reveals similar positioning of the backbone atoms and of the side-chain atoms in the P2-P2' region, where the interaction with the protein is strongest. However, the X-ray structure and the model differ considerably in the location of the P3 and P3' end groups, and also in the positioning of the second of the two central hydroxyl groups. Reconstruction of the central portion of the model revealed the source of the hydroxyl discrepancy, which, when corrected, provided a P1-P1' geometry very close to that seen in the X-ray structure.

Amino Acid Sequence↗

PubMed1991

Structural and evolutionary relationships between retroviral and eucaryotic aspartic proteinases.

Three-dimensional crystal structures of the homologous retroviral proteinases from Rous sarcoma virus (RSV PR) and from human immunodeficiency virus (HIV-1 PR) are to a large extent similar and bear close resemblance to the six known structures of the bilobal fungal and mammalian aspartic proteinases. Systematic three-dimensional structural superpositions were carried out between the retroviral and the eucaryotic aspartic proteinases. Both retroviral enzymes were found to be similarly related to their fungal and mammalian counterparts. The most strongly conserved parts correspond to those regions in the N- and C-domains of the eucaryotic enzymes that are related by the interdomain dyad and consist of a combination of secondary structural elements that form the psi loop-alpha helix motif at the active sites of the aspartic proteinases. The retroviral proteinase monomer exhibits nearly the same degree of structural equivalence to the N- and C-domains of the eucaryotic enzymes. In light of the deduced structural relationships between HIV-1 PR and RSV PR, sequence alignments were performed for a number of retroviral proteinases from different subfamilies. There are three highly conserved amino acid sequence stretches, of which two belong to the psi loop-alpha helix motif, that bear moderate sequence similarity with the eucaryotic enzymes. The third conserved sequence stretch among the retroviral proteinases belongs to the flap and bears no resemblance to the flap sequences in the eucaryotic enzymes. The interdomain antiparallel beta sheet in the cellular enzymes differs from the intersubunit beta sheet in the number, arrangement, and directionality of strands, suggesting the possibility of convergent evolution.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1990

Structure of the aspartic protease from Rous sarcoma retrovirus refined at 2-A resolution.

The structure of Rous sarcoma virus protease has been solved by multiple isomorphous replacement in the crystal form belonging to space group P3(1)21, with unit-cell parameters a = 88.95 A and c = 78.90 A. The enzyme belongs to the family of aspartic proteases with two identical subunits composing the active homodimer. The noncrystallographic dyad relating these two subunits was identified after preliminary tracing in the MIR map and was used for phase improvement by electron-density averaging. Structure refinement resulted in a model that included 1772 protein atoms and 252 water molecules, with an R factor of 0.144 for data extending to 2 A. The secondary structure of a retroviral protease molecule closely resembles that of a single domain in pepsin-like aspartic proteases and consists of several beta-strands and of one well-defined and one distorted alpha-helix. The dimer interface is composed of the N- and C-terminal chains from both subunits which are intertwined to form a well-ordered four-stranded antiparallel beta-sheet. In each monomer, the catalytic triad (Asp-Ser-Gly) is located in a loop that forms a part of the psi-structure characteristic to all aspartic proteases. The position of a water molecule between the active-site aspartate residues and the general scheme of H bonding within the active site bear close resemblance to those in pepsin-like aspartic proteases and therefore suggest a similar enzymatic mechanism. The binding cleft over the active site is covered by two flap arms, one from each monomer, which are partially disordered. The retroviral protease dimer has been compared with several enzymes of cellular origin, with chains aligning to an rms deviation of 1.90 A or better.

Amino Acid Sequence↗

PubMed1990

Is the pseudo-dyad in retroviral proteinase monomers structural or evolutionary?

A pseudo-dyad was found to exist in the monomers of the crystal structures of the proteinases from Rous sarcoma virus and the human immunodeficiency virus. This dyad, also discovered earlier in pepsin-like aspartic proteinases and considered to be of probable evolutionary origin, has been shown to arise as a result of the topology and the folding of the proteinase monomers and may not therefore have much evolutionary significance.

Avian Sarcoma Viruses↗

PubMed1989

Crystal structure of a retroviral protease proves relationship to aspartic protease family.

Retroviral gag, pol and env gene products are translated as precursor polyproteins, which are cleaved by virus-encoded proteases to produce the mature proteins found in virions. On the basis of the conserved Asp-Thr/Ser-Gly sequence at the putative protease active sites, and other biochemical evidence, retroviral proteases have been predicted to be in the family of pepsin-like aspartic proteases. It has been suggested that aspartic proteases evolved from a smaller, dimeric ancestral protein, and a recent model of the human immunodeficiency virus (HIV) protease postulated that a symmetric dimer of this enzyme is equivalent to a pepsin-like aspartic protease. We have now determined the crystal structure of Rous sarcoma virus (RSV) protease at 3-A resolution and find it is dimeric and has a structure similar to aspartic proteases. This structure should provide a useful basis for the modelling of the structures of other retroviral proteases, such as that of HIV, and also for the rational design of protease inhibitors as potential antiviral drugs.

Amino Acid Sequence↗

PubMed1988

Distribution pattern of cell bodies and fibers with neurotensin-like immunoreactivity in the cat hypothalamus.

Neurotensin is widely distributed in the central and peripheral nervous systems. Extensive radioimmunoassay and immunohistochemical studies in rats show that the neurotensin immunoreactive perikarya and fibers are most prominent in the hypothalamus. Radioimmunoassay studies have suggested that the levels of neurotensin in the hypothalamus of cats may be six times higher than that of rats. We studied the distribution pattern of neurotensin immunoreactivity within the hypothalamus of the cat by avidin-biotin modification immunohistochemical methods: (1) to define its distribution pattern within the hypothalamus, and (2) to compare our findings with the patterns that have been described in rats. Results show that neurotensin immunoreactive cell bodies and fibers are most prominent in the rostral and intermediate regions of the cat hypothalamus. Cell bodies with neurotensin-like immunoreactivity are seen maximally in the medial preoptic region, the infundibular nucleus, and the lateral hypothalamus. The neurotensin positive fibers are dense in the periventricular regions of the entire rostro-caudal extent of the hypothalamus. This pattern of distribution of neurotensin immunoreactivity is similar to that described in rats. The suprachiasmatic nuclei of the cat hypothalamus, however, contained a significant number of neurotensin immunoreactive cell bodies, an observation not noted in the rat hypothalamus. The neurotensin immunoreactive neurons were more numerous in the lateral hypothalamus than has been reported in rats, but the paraventricular nucleus of the hypothalamus in cats contained fewer neurotensin immunoreactive perikarya. The presence of neurotensin immunoreactive perikarya in the suprachiasmatic nucleus and the apparent increase in the number of neurotensin immunoreactive neurons in the lateral hypothalamus may account for the increased levels of neurotensin reported in cats. Neurotensin has been speculated to play a role in nociception, thermoregulation, and control of arterial pressure by acting as a hormone or a neurotransmitter. Details of the pattern of colocalization of neurotensin with that of other neuropeptides and neurotransmitters will aid in our understanding of its role in these functions.

Animals↗

PubMed1987

Thyrotropin-releasing hormone and cyclo (His-Pro)-like immunoreactivities in the cerebrospinal fluids of 'normal' infants and adults, and patients with various neuropsychiatric and neurologic disorders.

Levels of thyrotropin-releasing hormone (TRH) - and cyclo(His-Pro) (CHP)-like immunoreactivities and the activity of enzyme Pyroglutamate aminopeptidase (PAPase) were measured in cerebrospinal fluid (CSF) of over 100 normal adults (NA) and infants, and adult patients with various neurologic and neuropsychiatric disorders (NNDA). Levels of TRH and CHP in CSF of over 70% of the NA group were below 50 and 500 pg/ml respectively. The TRH- and CHP-like immunoreactivities in the remainder of the 30% of NA specimens exhibiting higher peptide concentrations were enzymatically and chromatographically characterized and were found to behave like authentic peptides. The levels of both of these peptides were significantly elevated in the CSF of most of the NNDA patients. An elevation in the CSF level of CHP was significantly correlated with the level of TRH, but not PAPase. Results from this study suggest that CSF elevation of TRH level may be due to a nonspecific response to stress that may be associated with hospitalization, myelogram procedure, and/or the neurologic and neuropsychiatric diseases for which the patients were admitted.

Adult↗

PubMed1987

Is all cyclo(His-Pro) derived from thyrotropin-releasing hormone?

Cyclo(His-Pro), or histidyl-proline diketopiperazine, is an endogenous cyclic dipeptide that is ubiquitously distributed in tissues and body fluids of both man and animals. This cyclic dipeptide is not only structurally related to thyrotropin-releasing hormone (TRH, pGlu-His-ProNH2), but it can also arise from TRH by the action of the enzyme pyroglutamate amino-peptidase (pGlu-peptidase). The data on the distribution of TRH, cyclo(His-Pro), and pGlu-peptidase under normal and abnormal conditions are summarized and potential relationships analyzed. We conclude that all of the cyclo(His-Pro) cannot be derived from TRH. Two additional sources of cyclo(His-Pro) are suggested. It is proposed that 29,247 molecular weight TRH prohormone, prepro TRH, which contains 5 copies of TRH sequence, can be processed to yield cyclo(His-Pro). Thus, both TRH and cyclo(His-Pro) share a common precursor, prepro[TRH/Cyclo(His-Pro)].

Animals↗

PubMed1987

Pyroglutamate aminopeptidase activity in human cerebrospinal fluid decreases with age.

The activity of pyroglutamate aminopeptidase, the major enzyme catalyzing thyrotropin-releasing hormone (TRH) metabolism in human CSF, decreased with age. This decrement is not due to age-dependent appearance of any enzyme inhibitor in CSF. The results of these studies underline the importance of using age-matched controls in assessing abnormalities of TRH metabolism in CSF during disease states.

Adult↗

PubMed1987

Hypothalamo-pituitary-adrenal function in infantile spasms: effects of ACTH therapy.

The metyrapone test was used to study the hypothalamo-pituitary-adrenal function in ten children with infantile spasms, before and after ACTH treatment. The hypothalamo-pituitary-adrenal response was normal before ACTH treatment in almost all children. After ACTH, the responses of two children were suggestive of a diminished pituitary reserve; three were suggestive of decreased adrenal as well as decreased pituitary reserve, and one suggested either adrenal hyperplasia with normal pituitary reserve, or appropriate response to a developing medical stress. We suggest that, in children being treated with ACTH, the dosage of ACTH should be gradually tapered, AM cortisol levels should be monitored, and high-dose steroids should be included when treating medical stress.

Adrenocorticotropic Hormone↗

PubMed1986

The distribution pattern of adrenocorticotropin-like immunoreactivity in the cat central nervous system.

The distribution pattern of adrenocorticotropin-like immunoreactivity (ACTH-LI) in cats using the avidin-biotin modification of an immunocytochemical method shows cell bodies containing ACTH-LI in the medial basal hypothalamus, especially in the infundibular nucleus. The fibers from these neurons extended beyond the hypothalamus, into the paraventricular nucleus of the thalamus, rostral amygdala, periaqueductal gray, locus coeruleus, parabrachial nucleus and medial nucleus of the nucleus tractus solitarius. The distribution pattern of the cell bodies and fibers containing ACTH-LI bears several similarities to that seen in rats. The pattern differs from that of rats in the fact that the termination in the amygdala is more extensive and that ACTH-LI was not observed in cell bodies in any location other than the medial basal hypothalamus.

Adrenocorticotropic Hormone↗

PubMed1986

An analysis of the structure of the product of the rbsA gene of Escherichia coli K12.

The predicted amino acid sequence of rbsA, a gene from the high affinity ribose transport operon (rbs) of Escherichia coli K12, is homologous to the products of hisP, malK, and pstB, components of the histidine, maltose, and phosphate high affinity transport operons. The recent finding by Hobson et al. (Hobson, A. C., Weatherwax, R., and Ames, G.F.-L. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 7333-7337) that the hisP and malK products bind ATP suggests that these four gene products may be involved in coupling the energy from ATP to drive the active transport in their respective transport systems. Each gene product contains a sequence of glycine and basic residues which are characteristic of an ATP-binding site (Walker, J.E., Saraste, M., Runswick, M.J., and Gay, N.J. (1982) EMBO J. 1, 945-951). Interestingly the N- and C-terminal halves of rbsA are also homologous, suggesting that a primordial gene duplication and subsequent fusion of the products occurred.

Amino Acid Sequence↗