NISCAIR Online Periodicals Repository Collection: IJEB Vol.45(12) [December 2007]

Thyroid status alters gill ionic metabolism and chloride cell morphology as evidenced by scanning electron microscopy in a teleost Anabas testudineus (Bloch): Short and long term in vivo study

Title: Thyroid status alters gill ionic metabolism and chloride cell morphology as evidenced by scanning electron microscopy in a teleost Anabas testudineus (Bloch): Short and long term in vivo study

Authors: Sreejith, P; Beyo, R S; Prasad, G; Sunny, F; Oommen, O V

Abstract: Gill is the main organ of osmotic regulation in teleosts and chloride cells are the sites of ion transport across gill epithelium. Thyroid hormones are implicated in the regulation of osmotic balance in teleosts also. Treatment with 6-propyl thiouracil (6-PTU) inhibited the membrane bound enzyme Na⁺K⁺ATPase in the gill while triiodothyronine (T₃) injection stimulated it in a short-term in vivo study in the teleost Anabas testudineus. Na⁺, K⁺ and Ca²⁺ ions were also decreased in the 6-PTU treated fish and the T₃ treatment increased their concentrations in the gill lamellae. The gill morphology also changed according to the thyroid status in the long term study. 6-PTU treatment altered the typical serrated morphology of the gill lamellae, while the T₃ treatment reversed it. T₃ injection increased the density of pavement and chloride cells as evidenced by scanning electron microscopy. The results demonstrate that physiological status of the thyroid influences gill Na⁺ pump activity and chloride cell morphological changes. Further, the study suggests a regulatory role of T₃ on gill ions (Na⁺, K⁺ and Ca²⁺), Na⁺K⁺and Ca²⁺ ATPase activity and the different gill cell types in A. testudineus.

Page(s): 1015-1021

Regeneration of β cells in islets of Langerhans of pancreas of alloxan diabetic rats by acetone extract of Momordica charantia (Linn.) (bitter gourd) fruits

Title: Regeneration of β cells in islets of Langerhans of pancreas of alloxan diabetic rats by acetone extract of Momordica charantia (Linn.) (bitter gourd) fruits

Authors: Singh, Neera; Gupta, Manushma

Abstract: Acetone extract of whole fruit powder of M. charantia (bitter gourd) in doses 25, 50 and 75 mg/100 g body weight lowered the blood glucose from 13.30 to 50% after 8 to 30 days treatment in alloxan diabetic albino rats, confirming antihyperglycemic effect of this plant in diabetic animals and humans. Histological observations with acetone extract showed different phases of recovery of β cells of the islets of Langerhans of pancreas, which in the untreated diabetic rats were less in number and showed varied degree of atrophy. The most important finding of the present study was observation of the presence of small scattered islets among the acinar tissue in some experimental animals, which may reflect neoformation of islets from pre-existing islet cells. The liver of alloxan diabetic rats showed hydropic degeneration, fatty change and necrosis at some places but liver of extract treated animals was normal. Glycogen localization in liver of diabetic rats was faint but after 30 days treatment with different doses of extract, normal to heavy glycogen localization was observed.

Page(s): 1055-1062

Reversible male sterility in transgenic tobacco carrying a dominant-negative mutated glutamine synthetase gene under the control of microspore-specific promoter

Title: Reversible male sterility in transgenic tobacco carrying a dominant-negative mutated glutamine synthetase gene under the control of microspore-specific promoter

Authors: Mamun, A N K

Abstract: Metabolic engineering was used to disrupt glutamine metabolism in microspores in order to block pollen development. We used a dominant-negative mutant (DNM) approach of cytosolic glutamine synthetase (GS1) gene under the microspore-specific promoter NTM19 to block glutamine synthesis in developing pollen grains. We observed partial male sterility in primary transgenic plants by using light microscopy, FDA, DAPI and in vitro pollen germination test. Microspores started to die in the early unicellular microspore stage, pollen viability in all primary transgenic lines ranged from 40-50%. All primary transgenics produced seeds like control plants, hence the inserted gene did not affect the sporophyte and was inherited through the female germline. We regenerated plants by in vitro microspore embryogenesis from 4 individual lines, pollen viability of progeny ranged from 12 to 20%, but some of them also showed 100% male sterility. After foliage spray with glutamine, 100% male-sterile plants were produced viable pollen and seed set was also observed. These results suggested that mutated GS1 activity on microspores had a significant effect on normal pollen development. Back-cross progenies (T2) of DH 100% male-sterile plants showed normal seed set like primary transgenics and control plants.

Page(s): 1022-1030

Antibacterial and toxicological evaluation of ß-lactams synthesized by immobilized ß-lactamase-free penicillin amidase produced by Alcaligenes sp.

Title: Antibacterial and toxicological evaluation of ß-lactams synthesized by immobilized ß-lactamase-free penicillin amidase produced by Alcaligenes sp.

Authors: Gayen, Jiaur R; Majee, Sutapa B; Das, Shuvendu; Samanta, Timir B

Abstract: Search for anti-ß-lactamase and synthesis of newer penicillin were suggested to overcome resistance to penicillin in chemotherapy. It was found that clavulanic acid, an ant-ß-lactamase was ineffective due to its structural modification by bacteria. Thus, there is a need for the synthesis of newer pencillins. Retro-synthesis was inspired by the success of forward reaction i.e.conversion of penicillin G to 6-aminopenicillanic acid (6-APA) by biological process. In the present study a better enzymatic method of synthesis of newer pencillin by a ß-lactamase-free penicillin amidase produced by Alcaligenes sp. is attempted. Antibacterial and toxicological evaluation of the enzymatically synthesized ß-lactams are reported. Condensation of 6-APA with acyl donor was found to be effective when the reaction is run in dimethyl formamide (DMF 50% v/v) in acetate buffer (25 mM pH 5.0) at 37°C. Periplasm entrapped in calcium alginate exihibited the highest yield (~34%) in synthesis. The minimum inhibitory concentration of the synthetic products against Staphylococcus aureus and Salmonella typhi varied between 20–80 µg/ml. Some of the products exhibited antibacterial activity against enteric pathogens. It was interesting to note that product A was potent like penicillin G. LD₅₀ value of three products (product A, B and C) was more than 12mg/kg. Furthermore, these synthetic ß-lactams did not exihibit any adverse effect on house keeping enzymes viz., serum glutamate oxalacetate-trans-aminase, serum glutamate pyruvate -trans-aminase, acid phosphatase, alkaline phosphatase of the test animals. The hematological profile (RBC and WBC) of the test animals also remained unaffected.

Page(s): 1068-1072