Search PubMed⌕ Search

Biomedical subjects

S Saha

Publications and source records attributed to S Saha.

At least 181 records · Page 10Linked to original sources
PubMed1994

Influence of day-0 and day-7 superovulated cow serum during development of bovine oocytes in vitro.

Oocytes were matured in medium supplemented with 5% serum collected from superovulated cows at oestrus (Day-0 SCS) or at the time of embryo collection (Day-7 SCS), or in medium supplemented with fetal calf serum (FCS). After insemination using frozen-thawed sperm, oocytes were cultured in vitro with medium supplemented with 5% Day-0 SCS or 5% Day-7 SCS or 5% FCS. The proportions of embryos that cleaved were not significantly different among treatments, whereas development of the embryo to a blastocyst was significantly higher in the presence of SCS than FCS. When the four possible combinations of Day-0 SCS and Day-7 SCS were used in the maturation and culture media, there were no differences among treatments, except that the cleavage rate was significantly higher (P < 0.05) with Day-0 SCS in the maturation medium and Day-7 SCS in the culture medium than with Day-7 SCS in the maturation medium and Day-0 SCS in the culture medium. The proportions of embryos that cleaved and developed to blastocysts were not related with the level of progesterone and luteinizing hormone in the serum added to the maturation and culture media. However, the use of serum with low concentrations of glucose, fatty acids and cholesterol in the maturation medium and the culture medium tended to be associated with a higher rate of cleavage and blastocyst development.

Animals↗
PubMed1994

Management of medial collateral ligament laxity.

Assessment of axial alignment with 3-foot radiographs and valgus-varus stress radiographs is important when managing symptomatic MCL instability. Realignment of the anatomical axis to 0 degrees to reduce the stress on the MCL reduces the symptomatic laxity. The assessment of MCL laxity is important when considering valgus HTO for medial compartment arthritis. A combined opening and closing wedge osteotomy reduces the size of the fragment needed and tensions the MCL at the same time. Interposition proximal tibial allografts may be used to retention combined MCL/LCL laxity as well as to correct associated deformities. As one would expect, defunctioning of the MCL in patients with valgus is best achieved using a varus distal femoral osteotomy.

Bone Malalignment↗
PubMed1993

New eukaryotic transcriptional repressors.

Transcriptional activating sequences have been described that are encoded by parts of the genome of Escherichia coli. These acidic peptides, fused to a DNA-binding fragment of the yeast transcriptional activator GAL4, activate transcription of a gene in a wide array of eukaryotes, provided that gene bears GAL4-binding sites nearby. Here we describe an E. coli-encoded sequence that, when attached to the same DNA-binding fragment (GAL4(1-147)), converts that fragment into a repressor. Thus, as assayed in yeast or in vitro in yeast extracts, this molecule represses transcription when bound upstream of a variety of different activators. Two additional repressing regions that work when tethered upstream, a multiple mutant derivative of the original isolate and a synthetic peptide are, like the original isolate, highly basic. At least one activator can be inhibited by the mutant but not by the parental repressing region. These and other findings suggest that these repressing regions interact with and inhibit the activity of activating regions bound nearby on DNA.

Amino Acid Sequence↗
PubMed1993

Studies of bacteriophage P2 DNA replication. The DNA sequence of the cis-acting gene A and ori region and construction of a P2 mini-chromosome.

A self-replicating plasmid was constructed from the 76.7 to 91.6% region of bacteriophage P2, which contains the P2 origin or replication (ori) and the genetically defined replication genes B and A. The sequence of the 76.7 to 80.2% has been determined previously, and the sequence of the 80.2 to 91.6% region is now reported. The sequenced region contained gene A, which predicts a 761 amino acid residue polypeptide known to induce a single-strand cut at or near ori, and ori, which has been located by electron microscopy to about 89% from the left end of the phage genome. Analysis of plasmid-encoded proteins in minicells indicated that the A gene product was about 78 kilodaltons. Five previously unknown open reading frames (orf-80, orf-81, orf-82, orf-83 and orf-91) were discovered. They have been cloned and their respective products were identified. The products of orf-80, orf-82 and gene A were found to be lethal to the host when overexpressed. The predicted amino acid sequences of the orf-82 and orf-83 gene products were similar to two early gene products of phage 186; the orf-91 product resembled the hypothetical protein of orfd of retron Ec67. Similarities between the products of P2 gene A, 186 gene A and orf2 and orf3 of Ec67 were also found. A P2 mini-chromosome has been constructed that contains only the P2 A gene and the beta-lactamase gene as a marker.

Amino Acid Sequence↗
PubMed1993

Dual effects of Na/K pump inhibition on cytoplasmic Ca2+ oscillations in pancreatic beta-cells.

Inhibition of the Na/K pump by ouabain or removal of K+ resulted in gradual increase of intracellular sodium in beta-cell-rich pancreatic islets from ob/ob-mice exposed to 3 mM glucose. In individual beta-cells this action of ouabain was paralleled by closure of ATP-regulated K+ channels and a slow elevation of the cytoplasmic Ca2+ concentration ([Ca2+]i). In most beta-cells an increase of the glucose concentration to 11-20 mM induced large amplitude oscillations of [Ca2+]i with a frequency of 0.2-0.5/min. Ouabain had dual actions on these glucose-induced oscillations in promoting their appearance and at higher concentrations transforming them into a sustained increase of [Ca2+]i. At 100 microM ouabain reduced the frequency of the glucose-induced oscillations but nevertheless raised the time-average [Ca2+]i by increasing the amplitudes and half-widths of the Ca2+ peaks. When high concentrations of ouabain or removal of K+ transformed the oscillations into a sustained increase of [Ca2+]i, the level reached exceeded that obtained in response to rise of glucose alone. By favoring Ca2+ entry and counteracting removal of the cation from the cytoplasm, Na/K pump inhibition perturbs the balance between the processes determining glucose-induced oscillations of [Ca2+]i.

Animals↗
PubMed1993

Survival rate of frozen-thawed bovine IVF embryos in relation to exposure time using various cryoprotectants.

The relationship between cryoprotectant and exposure time on the development of IVF-derived embryos in culture after freezing and thawing was examined. Good to excellent quality Day 7 to 8 blastocysts and expanded blastocysts were suspended in 1.6 M propylene glycol (PG), 1.8 M ethylene glycol (EG), 1.1 M diethylene glycol, and 1.3 M ethylene glycol monomethyl ether (EME). In Experiment I, after 30 and 120 min of exposure, embryos were placed directly into culture medium and washed three times. Embryos were cocultured with cumulus cells in culture medium. After a 48-h culture, there were no significant differences in fully expanded, hatching, and hatched rates between the 30- and 120-min exposure to all four cryoprotectants except for the fully expanded rate with PG (55 vs 83%). In Experiment II, to compare the cryoprotective effects of the four cryoprotectants, embryos were exposed to each cryoprotectant for variable times from 10 to 120 min, seeded, and cooled to -30 degrees C at 0.3 degree C/min, plunged into liquid nitrogen for storage, and then thawed. Survival was measured by coculturing the embryos with cumulus cells in culture medium. There were no significant differences in development to hatched blastocysts of embryos exposed to either PG (27-42%) or EG (37-56%). The number of embryos developing after exposure to EME was similar to that in PG or EG when exposure time did not exceed 40 min (43-49%). Our findings suggest that the toxicity of different cryoprotectants is related to the exposure time and that PG and EG were relatively nontoxic as is exposure to EME for short periods.

Animals↗
PubMed1993

Pregnancy rate and survival in culture of in vitro fertilized bovine embryos frozen in various cryoprotectants and thawed using a one-step system.

Bovine oocytes surrounded with compact cumulus cells were cultured for 20 to 22 hours (38.5 degrees C, 5% CO(2)) in modified TCM-199 medium supplemented with 5% superovulated cow serum (SCS) and inseminated by in vitro capacitated spermatozoa. Day 7 to 8 embryos were equilibrated for 10 minutes in 1.3 M methyl cellosolve (MC), 1.1 M diethylene glycol (DEG), 1.8 M ethylene glycol (EG), 1.6 M propylene glycol (PG) and 1.1 M 1, 3-butylene glycol (BG) solutions. They were then loaded into 0.25-ml straws, placed into an alcohol bath freezer at 0 degrees C, cooled from 0 degrees C to -6 degrees C at -1 degrees C/minute, seeded, held for 10 minutes, and cooled again at -0.3 degrees C or -0.5 degrees C/minute to -30 degrees C. Straws were then plunged and stored in liquid nitrogen. After thawing in 30 degrees C water, the embryos were rehydrated in TCM-199 medium and then cultured for 48 hours in TCM-199 plus 5% SCS. Embryos were considered viable if they progressed to later developmental stages with good morphology. Some of the embryos frozen in each cryoprotectant were thawed and transferred nonsurgically without removing the cryoprotectant. Hatched embryos survived freezing and one-step dilution as follows: EG (50.0%), MC (53.6%), DEG (56.9%), PG (58.0%) and BG (11.5%). The survival rate of embryos cooled at -0.3 degrees C vs -0.5 degrees C/minute was not significantly different (P>0.05), however, blastocysts hatched most often (P<0.01) in vitro when cooled at a rate of -0.3 degrees C/minute (64.6%, 31/48) than at -0.5 degrees C/minute (22.6%, 12/53). Pregnancy rates resulting from embryos frozen in the different cryoprotectants were as follows: MC (48%, 10/21); DEG (30%, 3/10); EG (74%, 20/27); and PG (40%, 4/10). These results indicate that MC, DEG, EG and PG have utility as cryoprotectants for the freezing and thawing of IVF bovine embryos.

Journal Article↗
PubMed1993

Biomechanical study of C1-C2 posterior arthrodesis techniques.

Fifteen cervical spines from cadavers were used to compare the rotational and translational stability of the Brooks fusion, a fusion construct using Halifax interlaminar clamps, and the Gallie fusion. The Brooks and Halifax clamp constructs exhibited significantly greater rotational and translational stiffness than the Gallie construct (P < 0.001). The Halifax clamp construct exhibited greater rotational stiffness and equal translational stiffness when compared with the Brooks construct (P < 0.05). The Brooks and Halifax fixation constructs provided superior fixation but presented technical challenges. The Gallie construct is less technically demanding but provides less stable fixation.

Biomechanical Phenomena↗
PubMed1993

The use of one compared with two distal screws in the treatment of femoral shaft fractures with interlocking intramedullary nailing. A clinical and biomechanical analysis.

The torsional and compressive biomechanical characteristics of a system for intramedullary fixation with a slotted locking nail and either one or two distal locking screws were evaluated in sixteen femora obtained from eight cadavera. No significant difference was found in the torsional rigidity or axial load to failure when one as opposed to two distal screws had been used. We also managed twenty-seven patients who had a fracture of the femoral shaft with interlocking fixation, using only a single distal screw for distal fixation. The average duration of follow-up was nine months (range, three to twenty-five months). The average time to radiographic healing was three months (range, two to six and one-half months). There were no non-unions or failures of the implant. Clinically unimportant migration of the distal screw occurred in five patients. We concluded that one distal screw provides adequate distal fixation of fractures of the femoral shaft treated with interlocking intramedullary nailing.

Adolescent↗
PubMed1993

The application of new composite materials for total joint arthroplasty.

The material and design issues for the composite hip stem development are examined. The development of the "isoelastic" hip is based on the hypothesis that the matching of the material modulus to that of cortical bone will result in an optimal stress transfer to the bone, resulting in a minimal bone loss. The biomechanical data showed no statistical difference in strain transfer in the bone before or after implantation of low modulus stems. The clinical reports of a number of earlier "isoelastic" devices showed evidence of loosening and lack of stability. The current interest has been in the development of femoral components made from carbon fiber reinforced polyaryletherketone, polysulfone, and carbon/carbon composites. As these materials are optimized, it is important to look into matching the rigidity of bone. Moreover, the unsupported neck area needs to be as strong as metal, like Ti6-Al4-V, to prevent failure, whereas the femoral component inside the bone needs to have lower rigidity. Therefore, monolithic composite material from neck area to the distal stem will not withstand the loading needs and a material optimization scheme is required to come up with a long-lasting composite device. Lastly, the price vs. patient benefits for these composite material stems need to be established.

Cost-Benefit Analysis↗
PubMed1993

Midbrain adrenergic mechanism modulating predatory attack behaviour induced by hypothalamic stimulation.

The present study was carried out in ten cats which did not attack the rats spontaneously. Predatory attack on a rat was produced by lateral hypothalamic stimulation using mean current strength of 340-690uA. This attack was accompanied by minimal affective display and culminated in neck biting. It was found that norepinephrine (NE) when microinjected into dorsal periaqueductal gray (dPAG) region in doses of 2, 4 and 10ug significantly lowered the mean current strength required for the elicitation of predatory attack by hypothalamic stimulation. Microinjection of propranolol (Prop), a beta-blocker, within the same region in similar doses significantly blocked the response as indicated by the increase in current strength required to produce the response. Control injections of normal saline and propylene glycol failed to produce any change. These findings indicate that hypothalamically induced aggressive responses involves beta adrenoceptive mechanisms located in the dPAG.

Adrenergic alpha-Agonists↗
PubMed1993

Midbrain adrenergic mechanisms modulating flight behaviour induced by hypothalamic stimulation.

The present study was carried out in ten cats of either sex. Flight response was obtained by electrical stimulation of dorsomedial regions of preoptic area (A13-14.5, L3.5 V-3.5 to -3.7) and lateral hypothalamic regions (A12.5, L2.5-3.5, V-3.7). It consisted of a goal directed attempt to get out of the cage with a vigorous leaping to foot. Norepinephrine when microinjected in 10 micrograms doses into pretectal area of midbrain (A3.5, 3.0, V+1.0 to +1.5 mm) significantly lowered the mean current strength from 640uA to 420uA; clonidine, an alpha-2 agonist in 5 micrograms dose when microinjected into the same locus also significantly lowered the mean current strength to the same level. On the other hand yohimbine, an alpha-2 blocker in 5 micrograms dose when microinjected in to the same locus significantly increased the mean current strength from 640 to 970 uA. These results indicate that hypothalamically induced flight response is mediated via the alpha-2 adrenoceptive mechanism operating at the midbrain level. Control microinjection of normal saline and propylene glycol in similar volumes failed to produce any changes in current strength.

Adrenergic alpha-Agonists↗
PubMed1993

Difficulties in the management of superior vena caval obstruction in young adults.

Case records of 50 patients of superior vena caval obstruction in young adults treated and followed-up at Radiotherapy Department, Medical College Hospitals, Calcutta have been looked into. Twenty-eight out of these 50 patients had disease confined to mediastinum only during presentation. In consideration of the fact that the optimum management of superior vena caval obstruction depends upon a balance between just adequate pretreatment investigation and early institution of treatment, the various difficulties in the management discussed. With the existing infrastructural facilities, the institutional policy for the management of superior vena caval obstruction in young adults whose disease is confined to mediastinum only, during presentation, is described.

Adolescent↗