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Biomedical subjects

S Saha

Publications and source records attributed to S Saha.

At least 163 records · Page 9Linked to original sources
PubMed1995

The influence of polyvinylpyrrolidone on freezing of bovine IVF blastocysts following biopsy.

A study was conducted to develop a better freezing protocol for in vitro developed biopsied bovine blastocysts. Biopsied blastocysts were exposed to 1.8 M ethylene glycol (EG) + 0.05 M trehalose (T) and different concentration (5, 10, and 20%) of polyvinylpyrrolidone (PVP). Exposure to the solutions alone did not affect their in vitro development (Experiment 1). Experiments 2, 3, and 4 tested the viability of biopsied blastocysts cryopreserved in 1.8 M EG + different concentrations of T (0, 0.05, 0.1, and 0.3 M), 1.8 M EG + different concentrations of PVP (0, 5, 10, and 20%), and 1.8 M EG + 0.05 M T + different concentrations of PVP (0, 5, 10, and 20%), respectively. The proportion of biopsied blastocysts that reexpanded following cryopreservation in 1.8 M EG + 0.05 M T (38.5%) and 1.8 M EG + 0.1 M T (36.1%) was significantly (P < 0.05) higher than the proportion that reexpanded in 1.8 M EG + 0.3 M T (13.9%) (Experiment 2). The viability and the percentage of embryos that developed to > 250 microns in diameter in the 5, 10, and 20% PVP groups (77.8 and 50.0%, 78.1 and 43.8%, 76.9 and 65.4%, respectively) were significantly higher than those that developed cryopreserved without PVP (55.1 and 20.7%) (Experiment 3). Optimum development of in vitro culture of frozen-thawed biopsied blastocysts was obtained using 1.8 M EG + 0.05 M T and 20% PVP. Analysis of blastocysts > 250 microns in diameter showed that the number of ICM cells of biopsied blastocysts cryopreserved in 1.8 M EG + 0.05 M T with or without PVP was not different from the number of unfrozen biopsied blastocysts. These results indicate that PVP has some beneficial effect on freezing of biopsied bovine blastocysts.

Animals↗
PubMed1995

Alpha 2-adrenergic stimulation counteracts glucose-induced rise of sodium in pancreatic islets exposed to ouabain.

The effects of alpha 2-adrenergic activation by clonidine on sodium handling were analysed in beta-cell-rich pancreatic mouse islets. In the steady-state situation, clonidine (1 microM) amplified lowering of sodium induced by 20 mM glucose, while the content remained unchanged in 3mM glucose. The loss of sodium in Na(+)-deficient medium was stimulated by glucose but was not affected by clonidine. This agonist also did not influence the ouabain-induced uptake of sodium at 3 mM glucose but partially counteracted additional uptake in response to 20 mM glucose. Although lacking effects of its own, 5 microM yohimbine completely counteracted the action of clonidine. The glucose amplification of the ouabain-induced uptake of sodium was suppressed also by 10 microM of the Ca(2+)-channel blockers methoxyverapamil and diltiazem. Both tolbutamide (100 microM) and dibutyryl cyclic AMP (1 mM) mimicked the action of glucose by promoting clonidine-sensitive uptake of sodium in the presence of ouabain. It is concluded that activation of alpha 2-adrenoceptors has profound effects on the sodium handling of pancreatic beta-cells exposed to glucose and other stimulators of insulin release.

Adrenergic alpha-2 Receptor Agonists↗
PubMed1995

Glutamate, gamma-aminobutyric acid and tachykinin-immunoreactive synapses in the cat nucleus tractus solitarii.

Neurophysiological and pharmacological evidence suggests that glutamate, gamma-aminobutyric acid and tachykinins (substance P and neurokinin A) each have a role in cardiovascular regulation in the nucleus tractus solitarii. This study describes the ultrastructural relationships between nerve terminals immunoreactive for these substances in the nucleus tractus solitarii of the cat using post-embedding immunogold (single and double) labelling techniques on sections of tissue embedded in LR White resin. The technique combines a high specificity of labelling with good ultrastructural and antigenic preservation. Glutamate-immunoreactive terminals, recognized by their high density of gold particle labelling compared to the mean tissue level of labelling, accounted for about 40% of all synaptic terminals in the region of the nucleus tractus solitarii analysed (medial, dorsal, interstitial, gelatinosus and dorsolateral subnuclei). They appeared to comprise several morphological types, but formed mainly asymmetrical synapses, most often with dendrites of varying size, and contained spherical clear vesicles together with fewer dense-cored vesicles. Substance P- and neurokinin A-immunoreactive terminals were fewer in number (9% of all terminals) but similar in appearance, with the immunoreaction restricted to the dense-cored vesicles. Analysis of serial- and double-labelled sections showed a co-existence of substance P and neurokinin A-immunoreactivity in 21% of glutamate-immunoreactive terminals. Immunoreactivity for gamma-aminobutyric acid was found in 33% of all terminals in the nucleus tractus solitarii. These predominantly contained pleomorphic vesicles and formed symmetrical synapses on dendrites and somata. Possible sites of axo-axonic contact by gamma-aminobutyric acid-immunoreactive terminals onto glutamate-or tachykinin-immunoreactive terminals were rare, but examples of adjacent glutamate and gamma-aminobutyric acid-immunoreactive terminals synapsing on the same dendritic profile were frequent. These results provide an anatomical basis for a gamma-aminobutyric acid mediated inhibition of glutamatergic excitatory inputs to the nucleus tractus solitarii at a post-synaptic level.

Animals↗
PubMed1995

Post-translational modifications of tubulin suggest that dynamic microtubules are present in sensory cells and stable microtubules are present in supporting cells of the mammalian cochlea.

Post-translational modifications to tubulin in the sensory and supporting cells of the cochlea were studied using antibodies specific to the tyrosinated, detyrosinated, acetylated and polyglutamylated isoforms. In the sensory cells, microtubules which label intensely with antibodies to tyrosinated tubulin are found in networks within the cytoplasm. Microtubules which label with antibodies to detyrosinated tubulin and polyglutamylated tubulin, but not acetylated tubulin, form a small component of the microtubules found in the cytoplasm only in the region below the cuticular plate. Microtubules in the supporting cells (inner and outer pillar cells and Deiters cells) are arranged in bundles and contain little tyrosinated tubulin. They are composed instead of predominantly post-translationally modified isoforms which include detyrosinated, acetylated and polyglutamylated tubulin. The findings suggest that microtubules in the sensory cells form dynamic structures, since microtubules that undergo cyclic polymerization and depolymerization predominantly contain tubulin that has not yet had its carboxy-terminal tyrosine residue removed. The presence of microtubules in the supporting cells in which the tubulin has been polymerized into microtubules long enough to be post-translationally modified, provides evidence that these microtubules are stable, long-lived and could contribute to the structural support of the sensory organ of Corti.

Acetylation↗
PubMed1995

Development in vitro and in vivo of aggregated parthenogenetic bovine embryos.

Mature bovine oocytes were activated with 7% ethanol followed by cytochalasin B or D treatment. Most oocytes extruded a second polar body and formed one pronucleus when treated with 7% ethanol alone [35/43 (81%)]. With ethanol followed by cytochalasin B or D, overall activation frequency was 70% (309/441), with activated oocytes containing two pronuclei. The cleavage rate was not significantly different between treatment with ethanol alone and ethanol followed by 5 micrograms mL-1 cytochalasin B, but it was significantly lower than in fertilized oocytes (P < 0.01). However, the blastocyst production rate was significantly different (P < 0.01) among the treatments. The incidence of parthenogenetic embryos with normal (diploid) complements and with chromosome anomalies (2N/4N) was 68% (17/25) and 32% (8/25) respectively, and this was not affected by cryopreservation treatment. The longitudinal diameter of aggregated-four embryos cultured in vitro was greater (P < 0.01) than aggregated-two or single embryos. One of the aggregated-four parthenogenetic embryos was further cultured in vitro and developed up to Day 27 after activation, with a diameter of 2980 microns. The aggregated-four parthenogenetic embryos were transferred to five recipients. The oestrus was prolonged in three recipients and they returned to oestrus on Day 57, 62 and 67 after the previous oestrus. These results indicate that aggregating parthenogenetic embryos can prolong their survival in vitro and in vivo.

Animals↗
PubMed1995

Glutamate-immunoreactivity in identified vagal afferent terminals of the cat: a study combining horseradish peroxidase tracing and postembedding electron microscopic immunogold staining.

Using electron microscopic immunohistochemistry we have shown that strong glutamate-immunoreactivity (glutamate-ir) is present in neuronal cell bodies of the nodose ganglion, axons in the tractus solitarius and afferent terminals in the nucleus tractus solitarii. Vagal afferent fibres were specifically labelled by transganglionic retrograde transport of horseradish peroxidase (HRP). Fifty-seven per cent of the HRP-labelled terminals in the dorsomedial medulla were found to contain a high level of glutamate-ir, suggesting that a population of vagal afferent fibres uses glutamate as a neurotransmitter substance. There were no apparent ultrastructural differences between glutamate-ir and non-glutamate-ir vagal afferent terminals, both classes mainly containing rounded vesicles and forming asymmetric synapses. However, some difference in their preference for postsynaptic target was noted. The great majority (83%) of non-glutamate-ir vagal afferent terminals made axodendritic synapses, but only just over half (57%) of the glutamate-ir vagal terminals made synaptic contact with dendrites. Approximately 13% of the HRP-labelled terminals were found to make synaptic contact with HRP-labelled dendrites or soma of motoneurones of the dorsal vagal motor nucleus, confirming the existence of monosynaptic connections between vagal afferent fibres and vagal motoneurones.

Afferent Pathways↗
PubMed1995

Effect of thyroxine on experimental bronchospasm in guinea pigs.

Effect of Thyroxine was studied in histamine induced bronchospasm in guinea pigs. Chronic treatment with the drug significantly protected against experimental bronchospasm. Thyroxine also potentiated salbutamol evoked bronchodilation in this experimental model. Up-regulation of beta-2 adrenoceptors in bronchial smooth muscle may be the probable mechanism of action of thyroxine.

Albuterol↗
PubMed1995

Influence of dietary protein on DDT-induced immune responsiveness in rats.

The influence of protein deficiency was evaluated on immune responsiveness after subchronic DDT exposure in albino rats. Rats were given 20%, 12% and 3% protein diets and exposed to DDT (20, 50 or 100 ppm) for 4 weeks. DDT (50 and 100 ppm) induced humoral and cellular immune suppression only in rats fed on 3% protein diet. There was (a) an increase in the albumin/globulin ratio, (b) suppression in IgM and IgG levels, and (c) attenuation in the tetanus toxoid-induced antibody responses. Further, in rats immunized with tetanus toxoid, the leucocyte and macrophage migration inhibition were also attenuated. Moreover, these animals maintained on 3% protein diet showed depression in humoral and cellular immune responses to antigen in a dose-dependent pattern after exposure to DDT at dose levels which were not immunosuppressive for rats on 12% or 20% protein diet. These results suggest that dietary protein content may predispose to the immunotoxic effects of DDT exposure, and also be a crucial determinant in DDT detoxification.

Animals↗
PubMed1995

Predatory aggression induced by hypothalamic stimulation: modulation by midbrain periaqueductal gray (PAG).

Adequate electrical stimulation of extreme lateral hypothalamic regions of healthy, non-aggressive male cats was employed to produce aggression on live but anaesthetized rats. Stimulus response (S-R) curves based on scoring systems for both somatic and affective display components of behaviour were used to assess how manipulation of midbrain PAG by electrocoagulative lesions or drug microinjections affected the sensitivity of attack producing hypothalamic loci. Anodal lesions of dorsal PAG and adjoining tectum increased the excitability of hypothalamic loci producing predatory attack. Microinjection of 250 ng of delta-alanine-methionine enkephalin (DAME) in dPAG completely suppressed the somatomotor components of attack behaviour and markedly inhibited the affective display components. Administration of naloxone, an opioid antagonist (1 microgram) at the same sites facilitated the hypothalamically induced attack behaviour and annulled the inhibitory effect of DAME. These findings indicate the involvement of midbrain enkephalinergic mechanisms in the modulation of predatory attack behaviour elaborated by hypothalamic stimulation.

Aggression↗
PubMed1994

Sulfonylureas mimic glucose in stimulating the uptake of Na+ in pancreatic islets exposed to ouabain.

The increase of sodium in response to ouabain inhibition of the Na+/K+ pump was measured in beta-cell-rich pancreatic islets from ob/ob mice using integrating flame photometry. D-Glucose promoted the uptake of sodium when added at a concentration of 6 mM or above. The hypoglycemic sulfonylurea compound, tolbutamide, mimicked the action of D-glucose in stimulating the sodium uptake at concentrations of 10 microM or above. There was no stimulation beyond that obtained with 20 mM glucose during exposure to 100 microM tolbutamide. Other test substances also affected sodium uptake in a way reflecting known effects on insulin release. Accordingly, the sodium uptake was stimulated with glibenclamide, glipizide, HB 699 (4-[2-(5-chloro-2-methoxybenzamido)ethyl]benzoic acid) and high K+. Sulphonamides (sulfamethazole, sulfadiazine and sulfadoxine) had practically no effect when added at a concentration of 1 mM. Sodium uptake in response to glucose and tolbutamide was antagonized by 400 microM diazoxide or 4 microM tetrodotoxin. It is concluded that both glucose and hypoglycemic sulfonylureas stimulate Na+ entry into the pancreatic beta-cells, a process presumably involving depolarization.

Animals↗
PubMed1994

Molecular characterisation of red cell glucose-6-phosphate dehydrogenase deficiency in Singapore Chinese.

Sixty-two G6PD deficient Chinese males have been investigated for the presence of seven mutations of the coding region of the G6PD gene by natural and artificially created amplified restriction sites. The results show that the G to T substitution at nucleotide (nt) 1376 and G to A substitution at nt 1388 represent 24% and 21% of G6PD deficiency, respectively, in the Singapore Chinese; 37% of the sample could not be characterised. The remaining samples were identified as follows: 10% C-->T at nt 563, 5% A-->G at nt 95, and 3% C-->T at nt 1024. The G to A substitution (nt 487) and the substitution A-->G (nt 493) were not present in this sample. None of the subjects with the Mediterranean mutation (563 C-->T) had the silent mutation at 1311 (C-->T). This study confirms the extreme molecular heterogeneity of the G6PD gene in the Chinese.

Base Sequence↗
PubMed1994

Investigation of protein-protein noncovalent interactions in soybean agglutinin by electrospray ionization time-of-flight mass spectrometry.

Noncovalent interactions in soybean agglutinin (SBA) were studied on an electrospray ionization (ESI) time-of-flight mass spectrometer constructed recently at the University of Manitoba. The high m/z range and high sensitivity of the instrument together with mild ESI interface conditions turned out to be ideal for detecting this noncovalently bonded tetrameric protein (MW approximately 116,000 Da) in low charge states (z = 23 to 27). By altering the acetonitrile content of the SBA solutions it was shown that the observed SBA tetramers are due to structurally specific noncovalent associations in solution. Octamers and dodecamers (MW approximately 350,000 Da) were also detected. Information on the quaternary structure of the tetramers was obtained by analyzing the fragment-ion spectrum resulting from the collision-induced dissociation of the tetramer ions.

Lectins↗
PubMed1994

Prognostic evaluation of intracranial metastasis in malignant melanoma.

BACKGROUND: Malignant melanoma (MM) is often reported as the third most common cause of intracranial metastasis (IM) after carcinoma of the breast and lung. Most patients with advanced MM will have widespread extracranial disease, but the majority will die from intracerebral spread. METHODS: A retrospective review of 117 patients with documented IM from MM over the past 25 years was undertaken. Various factors (including age, race, sex distribution, primary lesions with Clark's level, Breslow's thickness, primary sites and staging at initial presentation, diagnosis of IM and its various treatment methods, survival data, and autopsy findings) were analyzed. Prognostic indicators were clarified from this analysis as a predictor of central nervous system (CNS) metastasis. An ideal treatment plan was also analyzed in order to predict a better survival. RESULTS: Fifty-eight percent of patients were male; 42% were female. Seventy-one percent of the primary lesions were of Clark's level IV and V, with mean Breslow's thickness of 3.5 mm. Median time interval between the initial diagnosis and development of IM was 3.5 years. Complete surgical resection of the intracranial lesion in the brain resulted in the longest mean survival of 10.3 months, whereas mean survival for the group with no treatment was only 3 weeks. Patients with primary lesions of the head and neck had the lowest mean survival of 3.3 months, whereas those whose primary sites were unknown had the longest mean survival of 7.5 months. One- and 2-year survival were 9% and 3%, respectively. All but one of the 30 patients at autopsy were found to have visceral metastasis, namely of the lung, liver, and bone. CONCLUSION: An aggressive search for metastasis should be undertaken in patients at high risk of developing CNS metastasis, e.g., male, head and neck primary, Clark's level IV and V, Breslow's thickness of > 3 mm, and presence of visceral metastases, mainly lung. A complete surgical resection should be attempted whenever possible, with adjunctive use of whole-brain irradiation, along with systemic chemotherapy for further control of recurrence and to prolong survival.

Adult↗
PubMed1994

Viability of frozen-thawed bovine IVM/IVF embryos in relation to aging using various cryoprotectants.

Bovine IVF embryos developed on Days 7, 8 and 9 were equilibrated with 1.6 M propylene glycol (PG), 1.8 M ethylene glycol (EG), 1.1 M diethylene glycol (DEG) or 1.3 M ethylene glycol monomethyl ether (EME) for 10 to 20 min in modified phosphate buffered saline. (mPBS) supplemented with 10% superovulated cow serum. The embryos were loaded into 0.25-ml plastic straws and were placed directly into a 0 degrees C alcohol bath chamber and held for 2 min. They were cooled from 0 degrees C to -5.5 degrees C at 1 degrees C/min and then seeded, followed by a 10-min holding period at -5.5 degrees C. The straws were then cooled to -30 degrees C at 0.3 degrees C/min before plunging into liquid nitrogen. Embryos were thawed and placed directly into the culture medium and washed 3 times. The survival rates of the Day-9 embryos based on reappearance of blastocoele, expansion, and hatching after 48 h of post-thaw culture were significantly lower (P<0.01) than those of the Day-7 and 8 embryos, in all of the cryoprotectants tested. On the other hand, while the reappearance of blastocoele and expansion of blastocysts after 48 h of post-thaw culture were not significantly different among each cryoprotectant, the percentage of hatching blastocysts were significantly different between DEG and EME (P<0.05), between DEG and EG (P<0.01) and between PG and EG (P<0.05). These findings demonstrate that the age of the embryo (Day 7 and 8) is very important for the successful freezing of IVF bovine embryos. Also, as to the hatching rates, EME and EG are superior as cryoprotectants than the other 2 cryoprotectants tested.

Journal Article↗
PubMed1994

Supramaximal decrease of sulphonylurea-induced accumulation of sodium in pancreatic islets.

Sodium was measured in beta-cell-rich pancreatic islets of mice under steady state conditions or after 6 min of exposure to 1 mM ouabain. The islet content of sodium increased when 100 microM tolbutamide or 1 microM glipizide were added to an albumin-containing (1 mg ml-1) medium, but remained unaffected at 10-fold higher concentrations. Both sulphonylurea compounds promoted the uptake of Na+ in the presence of ouabain. Whereas tolbutamide was stimulatory at 10 microM or above in a medium containing 10 mg ml-1 albumin, only 0.1 microM was required in the absence of albumin. In the latter situation there was a reduction of the stimulatory action with increase of the tolbutamide concentration from 100 to 1000 microM. The inhibitory component in the sulphonylurea action on the Na+ uptake was particularly impressive with glipizide, maximal stimulation being reached at 10 microM in the presence of 1 mg ml-1 albumin. Diazoxide (400 microM) modified the glipizide action on Na+ uptake, making 1000 microM stimulatory instead of 1 microM. The latter concentration of glipizide became inhibitory after removal of K+. Glipizide stimulated the Na+ uptake both at low and high concentrations in a medium deficient in Ca2+ or when the cotransport of Na+, K+ and Cl- was blocked by 20 microM bumetanide. The observation that the sulphonylurea-induced islet accumulation of sodium is diminished at supramaximal concentrations reinforces existing arguments for additional effects of high concentrations of hypoglycemic sulphonylureas.

Animals↗