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Biomedical subjects

K Ramakrishnan

Publications and source records attributed to K Ramakrishnan.

At least 19 recordsLinked to original sources
PubMed2006

Hemoglobin level as a risk factor for lower respiratory tract infections.

OBJECTIVE: This prospective study was conducted to evaluate the role of hemoglobin level, as a risk factor for Lower Respiratory Tract Infections in children (LRTI). METHODS: 100 children who came to the outpatient department for LRTI were included in the study. Age and sex-matched 100 children, not having any respiratory illness, were taken as control. They were subjected to complete blood count (CBC),C-reactive protein estimation (CRP), Mantoux test and X-ray chest. Peripheral smear, serum ferritin and serum iron binding capacity were done for all anemic children. Results. Radiological evidence of pneumonia was present in 63 children(63%).Hyper inflated lungs were seen in 27 (27%). Mantoux was positive in 22 children (22%) of study group and none among control group. CRP > 6 mg/L was noted in 45 children (45%) of study group and 14 (14%) of control group. Seventy four of study group (74 %) and 33 of control group (33%) had anemia. Of the anemic children, 60 (60%) had iron deficiency,10 (10%) chronic inflammation and 4 (4%) had hemolytic anemia. These values were 30 (30%), 2 (2%) and 1 (1%)respectively for control group. Low hemoglobin level due to whatever etiology, was a risk factor (p=0.000). CONCLUSION: Anemic children were 5.75 times more susceptible to LRTI compared to the control group. Prevention of anemia, due to whatever etiology, will reduce the incidence of LRTI.

Adolescent↗
PubMed2005

In vitro somatic embryogenesis from cell suspension cultures of cowpea [Vigna unguiculata (L.) Walp].

We report, an efficient protocol for plantlet regeneration from the cell suspension cultures of cowpea through somatic embryogenesis. Primary leaf-derived, embryogenic calli initiated in MMS [MS salts (Murashige and Skoog 1962) with B5 (Gamborg et al. 1968) vitamins] medium containing 2,4-Dichlorophenoxyacetic acid (2,4-D), casein hydrolysate (CH), and L: -Glutamic acid-5-amide (Gln). Fast-growing embryogenic cell suspensions were established in 0.5 mg l(-1) 2,4-D, which resulted in the highest recovery of early stages of somatic embryos in liquid MMS medium. Embryo development was asynchronous and strongly influenced by the 2,4-D concentration. Mature monocotyledonary-stage somatic embryos were induced in liquid B5 medium containing 0.1 mg l(-1) 2,4-D, 20 mg l(-1) L: -Proline (Pro), 5 muM Abscisic acid (ABA), and 2% mannitol. B5 medium was found superior for the maturation of somatic embryos compared to MS and MMS media. The importance of duration (5 d) for effective maturation of somatic embryos is demonstrated. A reduction in the 2,4-D level in suspensions increased the somatic embryo induction and maturation with decreased abnormalities. Sucrose was found to be the best carbon source for callus induction while mannitol for embryo maturation and maltose for embryo germination. Extension of hypocotyls and complete development of plantlet was achieved in half-strength B5 medium supplemented with 3% maltose, 2500 mg l(-1) potassium nitrate, and 0.05 mg l(-1) thidiazuron (TDZ) with 32% regeneration frequency. Field-established plants were morphologically normal and fertile. This regeneration protocol assures a high frequency of embryo induction, maturation, and plantlet conversion.

Cells, Cultured↗
PubMed2005

Developmental pattern formation of somatic embryos induced in cell suspension cultures of cowpea [Vigna unguiculata (L.) Walp].

The sequence of events in the functional body pattern formation during the somatic embryo development in cowpea suspensions is described under three heads. Early stages of somatic embryogenesis were characterized by both periclinal and anti-clinal cell divisions. Differentiation of the protoderm cell layer by periclinal divisions marked the commencement of somatic embryogenesis. The most critical events appear to be the formation of apical meristems, establishment of apical-basal patterns of symmetry, and cellular organization in oblong-stage somatic embryo for the transition to torpedo and cotyledonary-stage somatic embryos. Two different stages of mature embryos showing distinct morphology, classified based on the number of cotyledons and their ability to convert into plantlets, were visualized. Repeated mitotic divisions of the sub-epidermal cell layers marked the induction of pro-embryogenic mass (PEM) in the embryogenic calli. The first division plane was periclinally-oriented, the second anti-clinally-oriented, and the subsequent division planes appeared in any direction, leading to clusters of pro-embryogenic clumps. Differentiation of the protoderm layer marks the beginning of the structural differentiation in globular stage. Incipient pro-cambium formation is the first sign of somatic embryo transition. Axial elongation of inner isodiametric cells of the globular somatic embryo followed by the change in the growth axis of the pro-cambium is an important event in oblong-stage somatic embryo. Vacuolation in the ground meristem of torpedo-stage embryo begins the process of histodifferentiation. Three major embryonic tissue systems; shoot apical meristem, root apical meristem, and the differentiation of pro-cambial strands, are visible in torpedo-stage somatic embryo. Monocotyledonary-stage somatic embryo induced both the shoot apical meristem and two leaf primordia compared to the ansiocotyledonary somatic embryo.

Cells, Cultured↗
PubMed2001

Performance of heterozygous brain-derived neurotrophic factor knockout mice on behavioral analogues of anxiety, nociception, and depression.

Evidence suggests that brain-derived neurotrophic factor (BDNF) may be important in the pathophysiology of depression, in addition to its role as a neurotrophic factor for sensory neurons. The authors conducted a series of experiments examining the behavioral profile of BDNF heterozygous knockout and wild-type mice. The heterozygous and wild-type mice did not differ on measures of activity, exploration, or hedonic sensitivity, or in the forced swim test. When assessed in the learned helplessness paradigm, heterozygous mice were slower to escape after training than were wild-type mice (p = .02). This effect may be accounted for by the fact that these mice demonstrate a reduced sensitivity to centrally mediated pain, apparent on the hot plate and Formalin injection tests of nociception. Overall, heterozygous mice were not more likely to display anxious or depressive-like behaviors and, consequently, may not constitute a murine model of genetic vulnerability to mood and anxiety disorders.

Affect↗
PubMed1999

Irregular shedding of Blastocystis hominis.

The shedding pattern of the protozoan parasite, Blastocystis hominis, is investigated in man and in experimental animal infections. The shedding pattern of the vacuolar and cystic forms of Blastocystis hominis in infected individuals have been shown in the present study to be irregular. The study shows that there is marked fluctuation in the shedding of the parasite from day to day, varying from as high as 17 to 0 per x40 microscopic field. The cystic stages when estimated in 8 Blastocystis-infected individuals ranged from as high as 7.4x10(5) cysts per gram of stool to 0. The shedding of cystic and vacuolar forms observed over a period of 20 days in experimentally-infected Wistar rats were not only shown to be irregular but the amount varied from host to host. The study has important diagnostic implications in that the stool samples must be collected more than once from patients showing clinical signs and symptoms to eliminate the cause of it to Blastocystis. The study also shows that there are asymptomatic individuals who pass a large amount of cysts as such individuals should be treated to prevent transmission to others.

Animals↗
PubMed1999

Field's stain--a rapid staining method for Acanthamoeba spp.

Acanthamoeba sp. is a free-living amoeba known to cause chronic central nervous system infection or eye infection in humans. Many cases remain undetected for want of a good detection system. We report for the first time a rapid staining method to facilitate the identification of Acanthamoeba sp. using the modified Field's staining technique. A. castellanii, which was used in the present experiment, is maintained in our laboratory in mycological peptone medium (Gibco). The cultures were pooled together and smears were made on glass slides for staining purposes. Different types of stains such as Field's stain, modified Field's stain, Wright's stain, Giemsa stain, Ziehl-Neelsen stain, and trichrome stain were used to determine the best stain for the identification of this amoeba. The concentration of various stains and the duration of staining were varied to provide the best color and contrast for each stain. Acanthamoeba was also obtained from the brain of experimentally infected mice and was stained with various stains as mentioned above to determine the best stain for use in identifying the presence of this parasite in experimentally infected animals. The modified Field's stain gives a very good color contrast as compared with other stains. Furthermore, it takes only 20 s to be carried out using the least number of reagents, making it suitable for both laboratory and field use.

Acanthamoeba↗
PubMed1999

Blastocystis in animal handlers.

The present study investigated whether people working closely with animals were at higher risk of getting infected with Blastocystis hominis. The prevalence of the parasite was determined in two population groups, i.e., animal handlers and normal healthy individuals who did not work with animals. In all, 105 stool samples were collected from animal handlers from 2 local research institutions, a local zoo, and a local abattoir and 163 stool samples were collected from normal healthy individuals residing in high-rise flats in the city. The in vitro culture method used in the study detected that 41% of 105 animal handlers and 17% of 163 flat-dwellers in the city were positive for Blastocystis. This statistically significant finding (P = 0.0000313) shows that people who work closely with animals do stand at risk of acquiring Blastocystis infection.

Animal Technicians↗
PubMed1995

Patterns of colorectal liver metastases according to Couinaud's segments.

PURPOSE: It is commonly believed that the right lobe of the liver is the most frequent site of colorectal liver metastases. However, direct evidence for this is lacking in the literature. This study was designed to document and evaluate the pattern of liver metastases according to liver segments. METHODS: A retrospective medical records review of 270 patients with hepatic metastases from colorectal adenocarcinoma was performed to determine the pattern of metastases according to Couinaud's segments. There was operative confirmation of liver metastases in 202 patients (75 percent). A total of 1,166 segments were involved with liver metastases and were used in this analysis. Segment I was excluded from calculations because of its dual blood supply. When groups contained different numbers of Couinaud's segments an appropriate correction was made in the statistical comparison. RESULTS: There were 736 (63 percent) right lobe segments (V, VI, VII, VIII) and 430 (37 percent) left lobe segments (II, III, IV) involved with metastases (P < 0.001). Of 430 left lobe segments, 298 (69 percent) involved the left lateral segment (II, III) and 132 (31 percent) involved the medial segment (IV) of the left lobe (P = 0.25). When evaluating patients with 4 or less segments involved, there were 258 right lobe segments (75 percent) and 88 left lobe segments (25 percent) involved with metastases (P < 0.0001). Of 88 left lobe segments with 4 or less segments involved, there were 68 segments (77 percent) involving the left lateral segment and 20 segments (23 percent) involving the medial segment of the left lobe (P = 0.035). All of these relationships were statistically independent of the primary tumor site. CONCLUSIONS: We have documented an overall predominance of right hepatic lobe metastases independent of site of the primary colorectal carcinoma. However, when metastases occurred in the left lobe, the left lateral segment (II, III) was more commonly affected than the medial segment (IV), but this difference was statistically significant only when there were four or less segments involved with liver metastases.

Adenocarcinoma↗
PubMed1995

Associated atrial septal defects increase perioperative morbidity after ventricular septal defect repair in infancy.

Although closure of ventricular septal defects (VSDs) is currently associated with a relatively low risk, infants with associated atrial septal defects (ASDs) seem to have a higher perioperative morbidity. To clarify this impression, we reviewed our entire experience (since 1977) with closure of simple VSDs in 163 infants (age, < or = 12 months). Of these, 57 had significant ASDs (ASD-VSD subgroup). Hospital mortality was 3.7% (6/163) overall and 1.4% (2/145) since 1980. Actuarial survival at 10 years was 92% +/- 5%. Significant morbidity occurred in 15.5% (16/103) of the VSD subgroup versus 48.1% (26/54) of the ASD-VSD subgroup (p < or = 0.001). Multivariate analysis identified the presence of multiple VSDs and early date of operation as risk factors for hospital death, and younger age, an associated ASD, the size of the VSD, and use of hypothermic circulatory arrest as risk factors for significant perioperative morbidity. Compared with the VSD subgroup, the ASD-VSD subgroup had a higher hospital mortality (5.3% [3/57] versus 2.8% [3/106]), were younger (5.1 +/- 2.9 versus 7.2 +/- 2.9 months; p = 0.001), had a higher preoperative pulmonary artery pressure (70.2 +/- 19.0 versus 62.7 +/- 21.8 mm Hg; p = 0.08), needed more inotropic support (12.3% versus 3.7%; p = 0.07), needed more prolonged ventilation (3.3 versus 1.8 days; p = 0.02), and had longer postoperative hospital stays (11 versus 8 days; p = 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1994

Long-term humoral and cellular immunity after vaccination with cell culture rabies vaccines in man.

To determine the duration of anti-rabies immunity, peripheral blood of 18 vaccinees was obtained between 2 and 14 years after immunization. Peripheral blood mononuclear cells (PBMC) and serum were tested for the presence of either rabies virus-specific antibodies or rabies antigen-specific proliferation. Neutralizing immunoglobulin class G anti-rabies virus antibodies could be detected in sera of all vaccinees, but not in 18 age- and sex-matched controls. Rabies antigen-induced proliferation of PBMCs from vaccinees was significantly higher than that of controls. The anti-rabies T and B cell response showed no time-dependent pattern. These results suggest the induction of a long-term immunity after rabies immunization according to pre- and post-exposure schedules with inactivated cell culture vaccines against rabies.

Adult↗
PubMed1994

Typing of hepatitis C virus isolates by DNA enzyme immunoassay.

Recently, at least six types of hepatitis C viruses (HCV) have been identified. Different types of HCV appear to possess different pathogenic properties and a different sensitivity to interferon treatment. Typing of HCV isolates may therefore be an important diagnostic procedure. We report on a new method for identification of HCV types 1a, 1b, 2a, 2b and 3a which are most prevalent in Europe, North America and Japan. The assay is based on a combination of two well established techniques, the polymerase chain reaction (PCR) and DNA enzyme immunoassay (DEIA). In the first step of the method a cDNA of about 250 bp corresponding to the HCV core-region is amplified by nested PCR. The target cDNA is then hybridized to type-specific oligonucleotides fixed to a solid phase through an avidin-biotin bridge. The formed hybrids are detected by a standard ELISA using monoclonal antibodies reacting with double-stranded DNA. Typically, signal-to-noise (S/N) ratios between 18.2 and 48.6 could be observed when different HCV types/subtypes were analyzed by this method. The test was evaluated using cloned HCV cDNAs of known types and by sequence determination of some of the typed cDNAs. Typing of 115 isolates from Germany, Russia and Turkey revealed that subtype 1b (59-100%) and 1a (24-32%) are most prevalent in these countries.

Antibodies, Monoclonal↗
PubMed1990

The aetiology of bleeding peptic ulcer--as observed in a district general hospital.

A review was made of the hospital case notes of 124 patients admitted with symptoms of upper gastrointestinal haemorrhage due to bleeding peptic ulcer over a five-year period. A high proportion of the patients were found to be elderly and female, as observed by Walt et al 1986. This finding was more pronounced if the source of the bleed was a gastric ulcer. Many of these elderly patients had been on anti-inflammatory drugs at the time of presentation. Concomitant treatment with cimetidine or demulcents did not seem to prevent episodes of bleeding. Many patients on anti-inflammatory drugs bled repeatedly after apparently adequate medical or surgical treatment.

Adult↗
PubMed1989

Standardization of an enzyme immunoassay for the in vitro potency assay of inactivated tissue culture rabies vaccines: determination of the rabies virus glycoprotein with polyclonal antisera.

A non-competitive enzyme-linked immunoassay (ELISA) has been standardized to supplement the in vivo potency test used for the quality control of inactivated tissue culture vaccines against rabies. The essentials of the ELISA were: fixation of the virus in different dilutions of vaccine on the surface of microtitre plates; testing of the reference and up to six test vaccines on one plate; incubation with polyclonal antisera to rabies virus glycoprotein containing an excess of antibody; further incubation with a species-specific anti-IgG coupled to peroxidase; a final incubation with a substrate. The incubation periods were 1 h, 1 h and 30 min both at +37 degrees C. The relative potency determinations were made graphically or by a computer using a parallel line bioassay in which the potencies of the vaccines of unknown potency were tested against the reference preparation on a single microtitre plate. Under these conditions inactivated rabies vaccines of different types (virus strains, cell substrates, inactivation and concentration procedures) were tested for potency. Furthermore, it was possible with this in vitro method to assay adjuvanted vaccines, in process samples such as tissue culture supernatants with live or inactivated rabies virus, concentrates, and vaccines undergoing thermal stability tests. The rabies glycoprotein antigen-antibody reaction was highly specific according to the results and the glycoprotein content was measured quantitatively. The potency determined by the in vitro ELISA correlated with the in vivo NIH protection potency test. The lower limit of detection of the ELISA was 0.015 IU/ml. Quantitative antigen determination was possible with both homologous and heterologous antisera to rabies virus glycoprotein when vaccines of the same virus strain were tested. When the potencies of vaccines of different virus strain specificity were calculated, it was necessary to take into account the strain-specific antigenicity. Even so vaccines of high potency were found to give a stronger reaction with a heterologous serum than did weak vaccines with a homologous antiserum. Stability tests made on inactivated tissue culture vaccines such as vaccine from the human diploid cell strain (HDCS), from purified chicken embryo cell (PCEC) or from purified Vero cell rabies vaccine (PVRV), showed high stability of the glycoprotein antigen even after four months of storage at +37 degrees C or 24 h at +56 degrees C, provided that the vaccines were stored in a lyophilized state. The antigenicity of liquid vaccines was inactivated after a few hours at +56 degrees C. For tropical areas, therefore, only lyophilized vaccines should be considered.

Adsorption↗
PubMed1986

7-Deoxydaunomycinone quinone methide reactivity with thiol nucleophiles.

Under anaerobic conditions and with NADPH as a reducing agent, daunomycin is reduced in the presence of spinach ferredoxin: NADP+ oxidoreductase as the enzyme catalyst to its hydroquinone, from which intramolecular elimination of the C-7 glycoside proceeds to provide a quinone methide intermediate. This quinone methide is capable of bimolecular reaction with the thiolate nucleophiles N-acetyl-L-cysteine, N-(tert-butoxycarbonyl)-L-cysteine, and 1-thio-beta-D-glucose, providing a pair of C-7 diastereomers, when the reaction is carried out under the autocatalytic conditions offered by substoichiometric quantities of NADPH. With 0.4 equiv of NADPH, optimal yields of the adducts are obtained of approximately 65%. In each case, the 7S adduct is the major product, with the observed stereoselectivities (7S to 7R) ranging from 2.6 to 1 for N-acetyl-L-cysteine to 4 to 1 for both the N-(tert-butoxycarbonyl)-L-cysteine and 1-thio-beta-D-glucose as nucleophiles. By standard blocking and deblocking procedures, the complete set of complementary functionalized (7S)- and (7R)-N-acetyl and O-methyl 7-L-cysteinyl-7-deoxydaunomycinones is prepared. All efforts to extend this quinone methide trapping reaction to additional nucleophiles (such as I- or N3-), including the use of Fe(III) chelation, are unsuccessful. The Fe(III) chelate of daunomycin is however reduced by ferredoxin reductase and NADPH to the Fe(III) chelate of 7-deoxydaunomycinone, suggesting that quinone reduction of the chelate to the quinone methide has occurred. Of the new compounds prepared, only (7R)-7-S-(beta-D-glucopyranosyl)-7-thio-7-deoxydaunomycinone has biological activity. As an in vitro inhibitor of P388 cell growth, it has a 50% inhibitory concentration 25 times greater than that of daunomycin.

Animals↗