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Biomedical subjects

S Kumar

Publications and source records attributed to S Kumar.

At least 199 records · Page 11Linked to original sources
PubMed1990

Tumorigenicity of EJ-ras oncogene transformed NIH 3T3 cells and expression of plasminogen activators.

A number of clonal cell lines have been isolated from NIH 3T3 cells transfected with the plasmid, pSV2 gpt-EJ-ras. The plasmid expresses Val12 instead of Gly12 in p21 ras protein and can be selected for the expression of E. coli XGPRT gene in mammalian cells. Southern analyses of the Eco R1 and Bam H1 digests of chromosomal DNA shows that multiple copies of the plasmid are integrated in a tandem sequence in the clones used in this study. The transfectants showed refractile appearance and criss-crossed pattern of growth, exhibited elevated expression of ras mRNA and formed tumors in nude mice commensurate with the copy number of the integrated EJ-ras gene. The increased propensity to form tumors did not correlate with the expression of urinary or tissue plasminogen activators (u-PA or t-PA). The cellular and secreted activity of u-PA in fact decreased as the ras gene expression increased. These data show that the enhanced tumorigenicity of transformed murine cells is related to the tandem integration and expression of human EJ-ras. The overexpression of ras has very little effect on t-PA but appears to suppress u-PA activity.

Animals↗
PubMed1990

Aneurysmal form of aortoarteritis (Takayasu's disease): analysis of thirty cases.

The clinical and radiological features, and outcome of 30 patients including 22 females, with the aneurysmal form of aortoarteritis were analysed. The average age at diagnosis was 27.4 +/- 7.2 years. Features which indicated the diagnosis of aneurysmal aortoarteritis included young age, female sex, characteristic location, associated stenotic lesions and the presence of multiple aneurysms. There were 41 fusiform and 18 saccular aneurysms, mostly located in the descending aorta. Diffuse dilatation (n = 24) was seen mainly in the ascending aorta. Two patients had dissecting aneurysms, while one patient had an aneurysm of the left main coronary artery. Both these lesions are rare in aortoarteritis. The aneurysmal form was associated with a higher incidence of aortic incompetence (P less than 0.01) and elevated ESR (P less than 0.001) as compared to the more common non-aneurysmal form. The average follow-up period was 59.7 (+/- 48.1) months. The event-free survival rate was 82.9% at 5 years, similar to that seen in the non-aneurysmal form. These data should be useful to the clinician in the diagnosis and management of the aneurysmal form of aortoarteritis.

Adolescent↗
PubMed1990

Reverse coitus: mechanism of urethral injury in male partner.

Reverse coitus, a rarely used sexual position, makes the male urethra more vulnerable to injury from the pubic arch and symphysis pubis of the female partner. Severe pain, bleeding and immediate detumescence were observed in 3 patients. The lesion usually occurred at the fossa navicularis, responded well to conservative management and did not hinder micturition. Potency has been well preserved in all 3 patients.

Adult↗
PubMed1990

Pulp calcifications in primary teeth.

Information regarding the prevalence of pulp calcifications in primary teeth is lacking. The occurrence of pulp calcifications in 120 primary maxillary and mandibular extracted teeth was evaluated radiographically. Twenty-five percent of second molars presented evidence of pulp calcifications; approximately 3% of central incisors were calcified. No other categories of teeth displayed pulp involvement. The low occurrence of pulp calcifications in primary teeth support the view that the occurrence of pulp calcification increases with age.

Age Factors↗
PubMed1990

Improvement of computer screen viewing in elderly patients.

Patients with early cataracts or cloudy posterior capsules often have problems with the reflected glare from the protective glass surface over the computer screen. This report describes a device which surrounds the computer screen and (a) decreases glare by shading the screen, thus increasing screen contrast, and (b) creates a new image of the computer screen at a lower position. This allows the bifocal wearer to read without tipping his or her head backward.

Aged↗
PubMed1990

Effect of intraocular lens decentration on retinal image contrast.

We describe an optical model of the eye that allowed the effect of intraocular lens (IOL) decentration on retinal image contrast to be photographically studied. Decentrations of varying degrees of severity were modeled to correlate the amount of aphakic pupillary area with the contrast of the resulting images as measured by a digital photometer. Image contrast was found to decrease linearly as the proportion of aphakic pupillary area increased. Human clinical correlates are discussed.

Contrast Sensitivity↗
PubMed1990

Spinal stresses in simulated raking with various rake handles.

Five young male subjects performed a simulated raking task by pushing and pulling 14 different rake handles at 60 N and 110 N simulated soil resistance in a random order. The raking action was performed at a self-selected uniform pace over a 60 cm stroke length with initial, middle and final phases marked. During this action the raking force and angle of the rake was measured by a load cell and a potentiometer respectively. The posture was recorded with a video cassette recorder. The posture and force values were used for the determination of the spinal compression load. In rake pulling the 13 modified rake handles generated a spinal compression of only 20% to 50% of the straight handle, whereas in rake pushing the modified handles generated compression up to five times that of the straight handle. The compression generated with the straight handle never reached the action limit, whereas those of the 13 modified handles rarely stayed within the action limit. Therefore, a straight handle is considered the handle of choice.

Adult↗
PubMed1990

Effects of stimulus degradation on letter-matching performance of left and right hemispheric stroke patients.

Performance on a letter-matching task involving conditions of perceptual degradation was tested on 18 Right CVA patients, 18 Left CVA patients and 18 control subjects. Letter stimuli were presented in three conditions: Clear, Line-Masked, and Blurred. Subjects judged whether two letters of a pair were the same in name or different in name. Right CVA patients performed significantly less accurately than did Left CVA patients and control subjects when letters were perceptually degraded with a line mask overlay or by blurring. No significant differences were found between the two patients groups when the letters were presented without perceptual degradation (the Clear condition), but both patient groups were significantly less accurate than control subjects. The results are similar to findings reported in visual half-field studies with neurologically normal subjects and indicate right-hemisphere superiority for the processing of perceptually degraded visual information.

Adult↗
PubMed1990

Molecular recognition and binding of a GC site-avoiding thiazole-lexitropsin to the decadeoxyribonucleotide d-[CGCAATTGCG]2: 1H-NMR evidence for thiazole intercalation.

The structural and dynamic aspects of the interaction of the thiazole containing lexitropsin (1) with an oligodeoxyribonucleotide were studied by high field 1H-NMR spectroscopy. Complete assignment of the 1H-NMR resonances of lexitropsin 1 was accomplished by 2D-NMR techniques. The complexation-induced chemical shifts and NOE cross peaks in the NOESY map of the 1:1 complex of lexitropsin (1) and d-[CGCAATTGCG]2 reveal that the thiazole ring of the lexitropsin (1) intercalates between dA4.A5 bases and the rest of the ligand resides in the minor groove of the AT rich core of decamer, thus occupying the 5'-AATT sequence on the DNA. Intercalation of the thiazole moiety of the drug has been detected by the presence of intermolecular NOEs both in the major and the minor groove of the decamer helix. The absence of intranucleotide NOEs between base protons and H1'/H2' protons suggested local unwinding of the binding site on the DNA. From COSY and NOESY methods of 2D-NMR, it was established that the N-formyl (amino) terminus of the thiazole lexitropsin (1) is projecting into the major groove towards A5H8 while the amidinium terminus lies in the minor groove towards the T7G8 base pairs of the opposite strand. The expected intranucleotide NOEs confirmed that the decadeoxyribonucleotide in the 1:1 complex exists in a right handed B-conformation. The presence of exchange signals along the binding site 5'-AATT indicated an exchange of the bound drug process wherein the rate of exchange between the two equivalent sites was estimated to be congruent to 130 s-1 at 30 degrees C and with delta G degrees of 62.4 kJ mol-1. Force field and Pi calculations permitted a rationalization of the experimentally observed binding mode in terms of preferred conformation of the ligand and repeat length in lexitropsins compared with the DNA receptor.

Base Composition↗
PubMed1990

Sequence specific molecular recognition and binding by a GC recognizing Hoechst 33258 analogue to the decadeoxyribonucleotide d-[CATGGCCATG]2: structural and dynamic aspects deduced from high field 1H-NMR studies.

The non-exchangeable and imino proton NMR resonances have been assigned of the 1:1 complex of an analogue 2 of Hoechst 33258 1 bound to the decadeoxyribonuycleotide d-[CATGGCCATG]2 by a combination of NOE difference, COSY and NOESYPH techniques. In contrast to Hoechst 33258 which recognizes 5'-AATT sequences exclusively, analogue 2 possesses structural features designed to permit the recognition of GC sites. The NOESY and 1D-NOE experiments place the drug in the minor groove and it is located on the 5'-CCAT sequence. The orientation of the drug in the groove is such as to place the N-methylpiperazine terminus at a GC site. Cross-correlation peaks in the NOESY experiment show that the DNA duplex retains its right-handed B form, similar to that in the free decamer. Specific NOEs locate the benzoxazole moiety on the 5'-CCAT and are consistent with the pyridine nitrogen forming a new hydrogen bond to G(4)-2NH2 at 5'-CCAT. The drug appears to undergo rotation around the C9-C10 bond, at a rate comparable with NMR time scale, even after binding. Variable temperature 1H-NMR studies established that the DNA is thermally stabilized as a result of the drug binding. The drug binding is a dynamic process involving exchange between the equivalent 5'-CCAT sites at approximately 60s-1 with delta G degree of 65 kJ mol-1 at 308K. The experimental evidence is in accord with a slide-swing mechanism for this process.

Base Sequence↗
PubMed1990

A comparison of the sensitivity to photodynamic treatment of endothelial and tumour cells in different proliferative states.

Bovine aorta endothelial and human colon adenocarcinoma (WiDr) cells were exposed to haematoporphyrin derivative plus light. Cell survival was determined using a [3H]thymidine incorporation and a clonogenic assay for both cell types. The endothelial cells were more sensitive to photodynamic treatment. This could be explained in terms of increased drug uptake into the endothelial cells despite there being no difference in cell volume between the cells. For both tumour and endothelial cells, exponentially growing cells were more sensitive to photodynamic treatment than plateau-phase cells. This was associated with a reduction in drug uptake into plateau-phase endothelial cells. However, there was no difference in uptake into exponentially growing and plateau-phase WiDr cells.

Animals↗
PubMed1990

N,N-diethylphenylacetamide--a new repellent for Periplaneta americana (Dictyoptera: Blattidae), Blattella germanica, and Supella longipalpa (Dictyoptera: Blattellidae).

The residual repellency of N,N-diethylphenylacetamide (DEPA) was studied against American cockroach, Periplaneta americana (L.); German cockroach, Blattella germanica (L.); and brownbanded cockroach, Supella longipalpa (F.) at various concentrations. DEPA exhibited residual repellency for 4, 3, and 2 wk against American, German, and brownbanded cockroach, respectively, at a concentration of 0.5 mg/cm2.

Acetamides↗
PubMed1990

Cumulative load as a risk factor for back pain.

The association between cumulative load (biomechanic load and exposure time integral over the entire work experience) and back pain was investigated in a group of institutional aides with physically stressful jobs. A questionnaire/interview was conducted with 161 of these institutional aides. The point prevalence of back pain in this sample was 62%. Men had worked a mean duration of 14.3 years and women 11.6 years at the time of the onset of the first pain episode. Every job performed was analyzed by the use of a two-dimensional static mathematical model. The compression and shear at the thoracolumbar and lumbosacral discs were computed by the use of a biomechanic model. Cumulative compression and shear were significantly higher in institutional aides with pain compared with those without pain (P less than 0.05-0.01). The pain group was similar to the no-pain group in age, weight, and height.

Adult↗
PubMed1990

Molecular cloning and sequencing of an Australian isolate of proviral bovine leukaemia virus DNA: comparison with other isolates.

The molecular cloning and characterization of an EcoRI fragment, 8.26 kb in size, of an Australian isolate of bovine leukaemia virus (pBLV-A1) is described. This fragment includes most of the proviral genome as well as 340 bp of flanking bovine DNA sequence at the 5' end. Approximately 790 bp, including the 3' long terminal repeat, was missing from this clone. At the level of restriction enzyme mapping, this isolate could be distinguished from American, Belgian and Japanese isolates. DNA sequencing of the entire clone demonstrated some variation at the amino acid level between pBLV-A1 and the Japanese and Belgian isolates, particularly in the gag gene. In that gene there were 59 amino acid changes compared to the Japanese isolate and 24 compared to the Belgian isolate. The greater number in the case of the Japanese isolate was due to both single nucleotide changes and frameshift in a single region of the gene. This study also demonstrates that there are large tracts of amino acid sequence, particularly within the env and pol genes, that are highly conserved in different isolates. Some of these conserved sequences exist in regions containing epitopes important in virus infectivity.

Amino Acid Sequence↗
PubMed1990

Postoperative analgesia in children who have genito-urinary surgery. A comparison between caudal buprenorphine and bupivacaine.

A study conducted on 40 children, aged 1-11 years, who had genito-urinary surgery compared the quality and duration of analgesia after caudal blocks in two groups of patients. Group 1 (n = 20) received caudal bupivacaine 0.25% and group 2 (n = 20) caudal buprenorphine 4 micrograms/kg; each received 0.5 ml/kg body weight. Patients were operated on under general anaesthesia. Postoperative behaviour and severity of pain were measured on a 3-point scale. The results indicate that caudal buprenorphine provides excellent postoperative analgesia in children comparable to caudal bupivacaine in the early postoperative period. Buprenorphine proved better in the late postoperative period. Analgesia lasted from 20 hours to more than 24 hours after caudal buprenorphine with fewer side effects.

Analgesia↗
PubMed1990

A comparison of a short half-life marker (low-dose isoniazid), a long half-life pharmacological indicator (low-dose phenobarbitone) and measurements of a controlled release 'therapeutic drug' (metoprolol, Metoros) in reflecting incomplete compliance by volunteers.

1. Although, long half-life compounds appear to be more appropriate pharmacological indicators of compliance with treatment, short half-life markers or measurements of short half-life therapeutic drugs are frequently used. 2. We have compared the usefulness of low-dose phenobarbitone (a long half-life indicator), low dose isoniazid (a short half-life marker) and controlled release metoprolol (Metros) (a controlled release formulation of a short half-life 'therapeutic' drug) in seven volunteers with simulated partial (two thirds) compliance. 3. Detection of isoniazid metabolites in urine had an 83% sensitivity and 94% specificity for detecting ingestion within the previous 24 h and 100% sensitivity and 82% specificity for detecting ingestion within the past 6 h but gave no indication of the longer term pattern of compliance. 4. At 28 days (a time when steady-state would be obtained for all three drugs) phenobarbitone plasma levels were 70% (66-76%)--median and interquartile range--of the expected steady-state level if compliance had been complete. Corresponding figures for metoprolol were 82% (37-100%). 5. Measurement of phenobarbitone was much superior to isoniazid or metoprolol measurements in reflecting partial compliance over the previous 1 to 4 weeks.

Administration, Oral↗