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Biomedical subjects

S Shankar

Publications and source records attributed to S Shankar.

At least 73 records · Page 4Linked to original sources
PubMed1995

Polyamines exert regulatory control on mycobacterial transcription: a study using RNA polymerase from Mycobacterium phlei.

We have used purified RNA polymerase from Mycobacterium phlei to study the role of polyamines in mycobacterial transcription. Both initiation and elongation phases of the process were affected biphasically by polyamines. Interaction of polyamines with DNA template plays an important role in transcription modulation. Our studies emphasize that polyamines can exert a regulatory control on mycobacterial transcription.

DNA-Directed RNA Polymerases↗
PubMed1995

The 'Rastelli' operation--results at the Singapore General Hospital.

Reconstruction of the right ventricular outflow tract in patients with right ventricle-pulmonary artery discontinuity with a valved conduit is well established. The aim of this study was to review our results at the Singapore General Hospital. Between October 1989 and May 1993, 13 patients underwent the 'Rastelli' operation. The mean age at definitive repair was 68 months. Ten patients had pulmonary atresia with ventricular septal defect, two patients truncus arteriosus (one patient each with type 3 and type 2) and one patient had tetralogy of Fallot with absent pulmonary valve syndrome. In 12 patients cryo-preserved pulmonary artery homografts with a mean diameter of 21mm (19-23mm) were used, and a 11mm composite Hancock dacron valved conduit in one patient. There were no operative deaths. The mean duration of follow-up is 37 months (23-48 months). All patients were well and in NYHA class I on recent follow-up. On echocardiographic assessment 12 patients had trivial or no gradient across the right ventricular outflow tract, while one patient had a gradient of 25mmHg. The "Rastelli" operation can be undertaken with low mortality and morbidity and early results are encouraging.

Blood Vessel Prosthesis↗
PubMed1995

Cancer prevention behaviors among African-American adults: a survey of wards 7 and 8 in Washington, DC.

A telephone survey of knowledge, attitude, and health practices regarding cancer was undertaken in wards 7 and 8, Washington, DC in 1988. These wards have the highest cancer rates in the city and are predominantly African American. Of the 670 randomly selected persons over 18 years of age, 243 were males and 427 were females. Among females, 84% believed cigarette smoking causes cancer, and 48% thought alcohol causes cancer; 31% smoked cigarettes and 38% consumed alcoholic beverages. Among males, 91% and 52% thought cigarettes and alcohol causes cancer respectively; 41% smoked and 54% consumed alcoholic beverages. Only 6% of the males over age 40 practiced all eight recommended cancer prevention behaviors, while 2% of the females over age 40 practiced all preventive health behaviors. Cancer preventive behavior was examined in relation to socioeconomic status. This study indicates that preventive health behaviors were not associated with socioeconomic status. Data suggest that cancer prevention and control programs and services targeted to this Washington, DC population should be increased and intensified.

Adolescent↗
PubMed1994

Energy metabolism and alginate biosynthesis in Pseudomonas aeruginosa: role of the tricarboxylic acid cycle.

Infection with mucoid, alginate-producing strains of Pseudomonas aeruginosa is the leading cause of mortality among patients with cystic fibrosis. Alginate production by P. aeruginosa is not constitutive but is triggered by stresses such as starvation. The algR2 (also termed algQ) gene has been previously identified as being necessary for mucoidy; an algR2 mutant strain is unable to produce alginate when grown at 37 degrees C. We show here that the levels of phosphorylated succinyl coenzyme A synthetase (Scs) and nucleoside diphosphate kinase (Ndk), which form a complex in P. aeruginosa, are reduced in the algR2 mutant. We were able to correlate the lower level of phosphorylated Scs with a decrease in Scs activity. Western blots (immunoblots) also showed a decreased level of Ndk in the algR2 mutant, but the presence of another kinase activity sensitive to Tween 20 provides the missing Ndk function. The effect of AlgR2 on tricarboxylic acid (TCA) cycle enzymes appears to be specific for Scs, since none of the other TCA cycle enzymes measured showed a significant decrease in activity. Furthermore, the ability of the algR2 mutant to grow on TCA cycle intermediates, but not glucose, is impaired. These data indicate that AlgR2 is responsible for maintaining proper operation of the TCA cycle and energy metabolism.

Alginates↗
PubMed1993

MchAI and MchAII, two class-II restriction endonucleases from Mycobacterium chelonei.

We have purified and characterized two class-II restriction endonucleases from the saprophyte Mycobacterium chelonei AMB 82. MchAI was an isoschizomer of NotI recognizing and cleaving at 5'-GC/GGCCGC. MchAI did not require Triton X-100 for activity and was fully active at concentrations over 10-200 mM KCl and MgCl2. MchAII was an isoschizomer of HaeIII recognizing and cleaving at 5'-GG/CC. MchAII was active in 10 mM Tris.HCl pH 8.0 containing MgCl2 at 10-200 mM, was strongly inhibited by NaCl at concentrations higher than 10 mM and was inactive at KCl concentrations lower than 250 mM.

Base Sequence↗
PubMed1992

Can consultants resuscitate?

Twenty-four of 53 hospital consultants responded to an offer to attend a resuscitation training course. Fourteen of them had never had resuscitation training. Their performance of basic life-support was assessed before and after training according to the Resuscitation Council UK recommendations. Their initial performance of basic life-support on a manikin was extremely poor. One hour of training and practice resulted in statistically significant improvements.

Cardiopulmonary Resuscitation↗
PubMed1991

Dietary fiber and cancer prevention.

A large body of literature suggests that eating a variety of foods containing high fiber has a protective effect against colon cancer. Evidence also indicates that a high fiber-containing diet may be protective against breast, ovary, endometrial, and gastrointestinal cancer. The focus of this review is the epidemiologic data for an inverse association between a high-fiber diet and risk for the previously mentioned cancers. Epidemiologic studies are categorized as international, within country, metabolic, time trend, case control, and cohort. Since 1980, 32 studies have assessed the role of fiber-containing foods in relation to colon cancer. Among these studies, 25 showed an inverse association. Of the seven case-control studies, which evaluated the relationship between the fiber-rich diet and breast cancer, six demonstrated an inverse association. For cancers of the esophagus, mouth, pharynx, stomach, rectum, endometrium, and ovary, there are only a limited number of studies, most showing a protective effect from eating a diet high in fiber-containing foods. The epidemiologic studies reviewed previously focus on dietary patterns in which fiber-rich foods usually occur as a complex mixture with other foods and food components, thus making it difficult to assess at this time if the protection is clearly from fiber per se or some other dietary component, such as low fat. For cancer prevention, the emphasis for dietary recommendation should be on a dietary pattern rather than on an isolated dietary fiber supplement.

Animals↗
PubMed1991

Ciliary beat frequency and structure of recipient and donor epithelia following lung transplantation.

To investigate possible changes following lung transplantation, the structure and in vitro ciliary beat frequency (CBF) of airway epithelium from the cytology brushings of 9 heart-lung (HLT) and 5 single-lung (SLT) transplant recipients were examined. The CBF of brushings taken proximal and distal to the anastomosis was measured 2-10 months following transplant. There was no difference between the measured mean CBF at the two sites or between the two groups; HLT CBF: distal 11.0 +/- 0.5 Hz (standard error of mean), proximal 10.5 +/- 0.4 Hz, SLT CBF: distal 11.7 +/- 0.9 Hz, proximal 12.0 +/- 0.6 Hz. Mean CBF of bronchial brushings (except distal brushings from SLT patients) was significantly lower than that from controls: 13.6 +/- 0.3 Hz (n = 7) (p less than 0.05). Transmission electron microscopy of epithelial brushings from 4 patients (3 HLT, 1 SLT) revealed epithelial abnormalities both proximal and distal to the anastomosis, particularly ciliary depletion, mitochondrial abnormalities and death of cells. No significant ciliary ultrastructural abnormalities were seen in any tissue. We conclude that epithelial abnormalities were observed both proximal and distal to the anastomosis following lung transplantation. These may contribute to impairment of mucociliary clearance.

Bronchi↗
PubMed1990

Management of the stump of the pancreas after distal pancreatic resection.

The optimal management of the stump of the pancreas following distal resection remains controversial. To determine whether there was an advantage in draining the stump of the pancreas into a Roux-en-Y loop of jejunum, a retrospective survey of 113 patients who had a distal pancreatectomy for chronic pancreatitis or complications of acute pancreatitis in the non-acute phase was undertaken. The decision to perform a drainage procedure was determined on the basis of the pancreatogram, the size of the pancreatic duct and technical factors at the time of the operation. Sixty-seven patients had no drainage procedure and 46 patients had a drainage procedure. The two groups were comparable in all respects before surgery. The postoperative outcome in the short- and long-term was similar in both groups. It is concluded that caudal pancreatic drainage confers no benefit following distal pancreatic resection.

Adolescent↗
PubMed1990

The effect of the progression of vitamin A deficiency on glucose, galactose and mannose incorporation into sugar phosphates and sugar nucleotides in hamster liver.

The incorporation of [2-3H]mannose into dolichyl phosphate mannose and glycoproteins is markedly reduced in livers of vitamin A-deficient hamsters. To determine whether vitamin A deficiency selectively alters the level of mannose incorporation into sugar phosphates and sugar nucleotides, we studied the in vivo incorporation of [2-3H]mannose, [5-3H]glucose, and [4,5-3H]galactose into sugar phosphates and sugar nucleotides. Male hamsters fed either a vitamin A-depleted or a retinoic acid-supplemented (3 micrograms/g) diet were used at 4, 6 and 8 wk of age; the animals were killed at various time points after an intraperitoneal injection of the radiolabeled sugar. A two- to threefold increase in the amount of [2-3H]mannose was found in liver of hamsters fed a vitamin A-depleted diet for 4 wk, resulting in enhanced incorporation into mannosyl-phosphate and guanosine diphosphate (GDP) mannose. As deficiency progressed, there was a smaller increase in [2-3H]mannose and a significant decrease in [3H]mannose-phosphate and GDP-[3H]mannose, suggesting a decreased mannose kinase activity. [5-3H]Glucose-labeled livers showed no difference in the total uptake of the label or its incorporation into uridine diphosphate glucose and galactose-phosphate during the 8-wk study. However, the synthesis of glucosyl-phosphate was reduced by 50 to 90% at 6 and 8 wk of deficiency, suggesting an impaired gluco-kinase activity. In hamsters injected with [4,5-3H]galactose only [3H]glucose was found within 5 min in the free sugar fraction. In contrast, as much as 70% of the label in the sugar phosphate and sugar nucleotide fraction remained as [3H]galactose even at 60 min. These effects on sugar, sugar phosphate and sugar nucleotide formation in part may explain the effects of vitamin A deficiency on glycoconjugate biosynthesis.

Animals↗
PubMed1990

Elective resection of tumours of the trachea and main carina after endoscopic laser therapy.

In our patients with tumour affecting the trachea or carina elective surgery was carried out after endoscopic laser treatment. Laser treatment was performed as an emergency procedure in three of the patients, who presented with impending asphyxia; the improvement provided time in which to assess the disease, withdraw corticosteroids, and treat infection. The fourth patient was treated with the laser for life threatening haemoptysis, but further bleeding made it necessary to tamponade the tumour with a cuffed endotracheal tube for 24 hours. Elective resections of the trachea (three cases) and carina (one case) were performed successfully four to eight weeks after laser treatment. Frozen sections of the resection margins were clear in all cases and paraffin sections subsequently confirmed the localised nature of the lesions. All patients are alive and well with no evidence of tumour recurrence after 18 months to 4 years. Laser therapy appears to be an ideal preoperative treatment for patients with impending asphyxia but it may be of limited value in controlling very brisk haemorrhage.

Aged↗
PubMed1989

Haemorrhage in pancreatic disease.

Haemorrhage is a life-threatening complication in pancreatic disease. Twenty-five patients with this complication are described; 15 had major bleeding, nine had minor bleeding and one patient had a pseudoaneurysm identified at operation. Of the 15 patients with major bleeding, six presented with this complication and in nine cases it followed pancreatic resection. Of the six patients who presented with major bleeding, five underwent resection with one death while the patient managed conservatively died. The nine patients who had major bleeding after pancreatic resection were managed by ligation of the bleeding artery in six cases with one death, and one patient who rebled after ligation of the bleeding artery was successfully managed by further resection. Three patients with postresection major bleeding were managed conservatively with one death. All minor haemorrhages were managed conservatively without mortality. Deaths after major bleeding were a result of sepsis in three cases and respiratory failure in one. The severity of the underlying pancreatitis was an important factor in two patients. Pseudocysts and pancreatic fistulae were important underlying factors leading to the complication. It is recommended that patients with sepsis, a pancreatic fistula or severe underlying pancreatitis should have their haemorrhage treated by pancreatic resection, while those patients with bleeding following pancreatic resection without such complications can be managed by ligation.

Aged↗
PubMed1989

Changes in the myoelectric signal (MES) power spectra during dynamic contractions.

Power spectra of surface myoelectric signals (MES) have been estimated during dynamic contractions of the biceps brachii. The effect of applied torque, velocity of contraction and muscle length have been studied with respect to median frequency and total spectral power. The results of the investigation carried out thus far can be summarised as follows: (1) The median frequency is observed to vary with the applied torque and the muscle length but not with the velocity of contraction. (2) The expected dependence of the MES power with the applied torque, velocity and muscle length was confirmed. These results suggest that the power spectrum could be used to reveal changes in the electrophysiological characteristics of a muscle during dynamic contractions as is the case with static contractions.

Adult↗
PubMed1989

Serum and tissue levels of teicoplanin during cardiac surgery: the effect of a high dose regimen.

Two prospective trials suggested that teicoplanin was less effective in preventing Gram-positive wound infections after cardiac surgery than a combination of flucloxacillin and an aminoglycoside. The initial dose of 400 mg was associated with a subinhibitory concentration of teicoplanin in fat at the end of operation. In this study, the behaviour of a higher initial dose (12 mg/kg) was investigated in ten patients during coronary artery surgery. As in the earlier trials, a second dose (400 mg) was given after 24 h. The mean concentration at the end of cardiopulmonary bypass was 15 mg/l in serum, 6 mg/kg in fat and 9 mg/kg in skin, all in excess of the expected break-point for staphylococci (4 mg/l). The higher dose regimen might be more successful in surgical prophylaxis.

Adult↗