A.M. Yazid^1*, A.M. Ali², V. Kalaivani¹ and M. Shuhaimi¹

¹Department of Food Technology, ²Department of Biotechnology, Faculty of Food Science and
Biotechnology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

(Received 19 January 1998 / Accepted 24 July 1998)

Abstract.
Eighteen strains of bifidobacteria obtained from ATCC were tested for their inhibitory activity against selected pathogenic microorganisms by using double layer assay method. The results show that bifidobacteria were able to inhibit Pseudomonas aeruginosa, Bacillus megaterium, B. licheniforms, B. subtilis, B. sphaericus, Escherichia coli, Listerm monocytogenes and Salmonella enteritidis, All the tat get organisms showed different sensitivity to different strains of bifidobacteria. The ability of Bifidobacterium strains to grow in milk and their viability in acidified milk during storage were studied by culturing the bifidobacteria. into sterile reconstituted skim milk. The growth was observed by recording the pH and curd formation. B. bifidum, B. breve, B. infantis; and B. longum grew well in milk, forming curd in less than 24 hours. Whereas, B. adolescentis, B. pseudocatenulatum B. asteroides, B. angulatum and B. indicum showed very poor growth in milk. Four strains (B. adolescentis ATCC 11146, B. breve ATCC 15698 and 15701, and B. infantis ATCC 17920) had survival of more than 90% of the initial inoculum after 5 weeks of storage in acidified milk. Strains of B. asteroides ATCC 25909 and 25910 (isolated from honeybees) had survival of 83.2% and 87.8% respectively whereas the survival of B.bifidum was 73%. Only seven out of fourteen strains tested survived low temperature storage in acidified milk.

Keywords: bifidobacteria, probiotic, antibacteria growth, storage

Garcia, R., Pimentel, E., Somonte, D., Mena, J., Zaldua, Z., Lopez, A., Moran, R., and Garcia*, M.

Centro de lngenieria Genetica y Biotecnologia. P.O. Box 387, C.P. 70100. Camaguey, CUBA

(Received 2 February 1998 / Accepted 16 July 1998)

Abstract.
Isolation of sweet potato protoplasts from different organs has been very difficult to develop, due to the recalcitrant behavior of this crop when it is manipulated in-vitro. An efficient protocol for protoplast isolation from leaf and stem tissues was established. Different enzyme combinations and concentrations were tested, as well as several digestion conditions. A hard enzymatic treatment, combined with mechanical separation of the cells from the digested tissue, led to a high protoplast yield. Other factors, such as the osmotic solution used in the different washing steps, and the starch concentration in the medium, were evaluated for their influence on the final protoplast recovery and viability. The transformation of isolated protoplasts was mediated by polyethylene glycol (PEG). The plasmid transient expression was detected by a spectrophotometrical P glucoronidase (GUS) assay.

Keywords: sweet potato, protoplast isolation, PEG mediated transformation

Salmaan H. Inayat Hussain*, Gerald A Cohen' and Kelvin Cain'

Department of Biomedical Science, Faculty of Allied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia.
'MRC Toxicology Unit, Centre for Mechanisms of Human Toxicity, Hodgkin Building, PO Box 138, Lancaster Rd., Leicester, LE1 9HN, UK

(Received 7 August 19981 Accepted 6 October 1998)

Abstract.
The characteristic DNA cleavage patterns observed in apoptotic nuclei in vivo can be reproduced in isolated nuclei where it has been shown that initially the DNA is degraded into 'large fragments'of >700, 200-300 and 30 -0 kilobase pairs (kbp) by a Mg²⁺ dependent process which is potentiated by Ca²⁺ . These large fragments are subsequently cleaved to mono/ oligonucleosomes by Ca²⁺/Mg²⁺ activated endonuclease(s). In this study, Mn²⁺ alone can substitute for Mg²⁺ and Ca²⁺, thereby activating both 'large fragment' formation and internucleosomal cleavage in isolated rat liver nuclei. The effect of Mn²⁺ is concentration dependent in that low concentrations (<200 µM) of Mn²⁺ stimulate 'large fragment' formation only whereas higher concentrations also activate internucleosomal cleavage. The cleavage of DNA induced by either Mn²⁺, Mg²⁺ or Ca²⁺/Mg²⁺ was equally susceptible to inhibition by Zn²⁺ , N ethylmaleimide and 3,4 dichloroisocoumarin, a serine protease inhibitor. These results suggest that the multi step DNA cleavage is catalysed by a single endonuclease or a class of endonucleases which have multicationic binding sites.

Keywords: apoptosis, DNA cleavage, liver nuclei, Mn²⁺

A.K.M. Mohiuddin¹, M. K. U. Chowdhury ²,a, Zaliha C. Abdullah³, K. Harikrishna¹ and Suhaimi Napis^1*

¹GENTECT, Department of Biotechnology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia;
²PORIM, P.O. Box 10620, 50720 Kuala Lumpur, Malaysia and ³CRAUN, Land Custody and Development
Authority, Jln. Santubong, Petra Jaya, 93055 Kuching, Sarawak, Malaysia.

(Received 12 December 1997 / Accepted 11 February 1998)

Abstract.
An improved in vitro direct shoot organogenesis plant regeneration system has been developed by culturing proximal cotyledon, distal cotyledon and petiole segments from muskmelon (Cucumis melo, L) cv. Birdie seedlings on MS medium containing BA. BA at 1 and 2 mg^-1 was found to improve induction of shoot primordia production significantly from explants of proximal cotyledon, distal cotyledons as well as petiole segments. Shoot primordia was produced after 9-11 days of culture and the elongation of 15 day old shoot primordia was significantly improved when subcultured onto MS medium containing BA at 0.1, 0.3, and 0.5 mgl^-1 for prox-1imal cotyledon, petiole and distal cotyledon derived regenerants, respectively. No morphological abnormalities were observed with regenerants produced using these BA concentrations. Significantly improved rooting frequencies of 88%, 80% and 92% were obtained with MS medium containing NAA at 0.01, 0.03 and 0.01 mg1^-1, from proximal cotyledon, distal cotyledon and petiole derived shoots respectively. Dark treatment of non rooted regenerants derived from all three explants of muskmelon was sufficient to promote rooting

Keywords: Shoot Regeneration, Muskmelon, Cucumis Melo L.