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Biomedical subjects

L A Baker

Publications and source records attributed to L A Baker.

61 records · Page 4Linked to original sources
PubMed1975

Inhibition of dihydrostreptomycin action on Mycobacterium smegmatis by monovalent and divalent cation salts.

We have examined and compared the effects of monovalent and divalent cation salts on dihydrostreptomycin (DSM) action against Mycobacterium smegmatis. The Sauton synthetic liquid medium used was supplemented with test salts on the basis of ionic strength (mu). Turbidimetric growth experiments showed that 0.02 M MgSO(4) (mu = 0.08) prevented growth inhibition by 0.1 mug of dihydrostreptomycin per ml, but 0.02 M NaCl (mu = 0.02) did not. However, at molarities equivalent to mu = 0.08, four monovalent cation salts, including NaCl, Na(2)SO(4), NH(4)Cl, and (NH(4))(2)SO(4), all prevented inhibition by dihydrostreptomycin. When magnesium and sodium salts were compared at mu = 0.02, 0.04, and 0.05, two distinct growth protective patterns were seen. These data were indicative of two different mechanisms of dihydrostreptomycin antagnosim by salts; the first being divalent cation and concentration dependent, and the second being nonspecific and ionic strength dependent. Viability studies supported the existence of two mechanisms.

Cations, Divalent↗
PubMedDate not supplied

Immunolocalisation of an anti-EMA monoclonal antibody to a renal carcinoma xenograft.

The monoclonal antibody 77-1 originally raised to a membrane extract of human bladder cancer reacted with a human renal carcinoma xenograft XK1 on immunoperoxidase staining. This suggested a potential role for its immunolocalisation to renal carcinoma, and prompted a localisation study of the I-125 and In-111 labelled 77-1 to the xenograft. The uptake of the radiolabelled antibody by the xenograft was measured as a tumour to blood ratio taken at 24 hour intervals for up to 72 hours. Four animals were used for each time point and the mean tumour to blood ratio obtained. A monoclonal antibody 48-1, non reactive with XK1, was similarly radiolabelled and administered to another group of animals bearing the xenografts to act as a control. Statistical analysis using the unpaired Student't' test showed that the uptake of the 1-125 and In-111 labelled 77-1 by the xenografts was significantly higher than the non-specific antibody 48-1 at all time points (p less than 0.002-0.018), demonstrating that a specific localisation to the xenograft XK1 by the radiolabelled 77-1 had occurred.

Animals↗
PubMedDate not supplied

Leydig cell function after experimental testicular torsion despite loss of spermatogenesis.

Little is known about specific testicular cell responses to periods of testicular torsion. In particular, the steroidogenic capacity of Leydig cells in the post-torsion testis is unknown. Male Sprague-Dawley rats (450-550 g) underwent no torsion (control) or a 720 degrees unilateral testicular torsion for either 0 (sham), or 1 or 2 Such torsions have previously been shown to cause progressive damage to the rat testis. One, 15, or 30 days after torsion repair all animals (n = 5-10/group) were prepared for testicular venipuncture and intravenous infusion of ovine luteinizing hormone (LH) via the femoral vein. Testicular venous blood was collected directly from the surface of the testis both 5 minutes prior to and 90 minutes after infusion of predetermined ED50 (0.1 microgram) or ED100 (0.5 microgram) doses of LH. Testicular venous serum (TVS) was assayed for testosterone (T) by radioimmunoassay. Control animal TVS T concentrations before LH infusion and 90 minutes after ED50 and ED100 LH stimulation were 103 +/- 25, 621 +/- 103, and 1,055 +/- 140 ng/ml, respectively. Testes having experienced a 1-hour torsion did not have a significantly (P < 0.05) reduced capacity to respond to ED50 and ED100 stimulation at either 15 and 30 days after the torsion. Testes having experienced a 2-hour torsion did have significantly reduced (P < 0.05) ED50 responses at both 1 hour and 30 days after torsion repair. More remarkably, significant steroidogenic reserve was still present in testes after torsion, which in previous studies had been shown to have permanent loss of spermatogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗