Inhibition of human renal cancer by monoclonal-anti-body-linked methotrexate in an ascites tumor model

Summary The monoclonal antibody DAL K29 against a cell-surface antigen associated with a human renal cell carcinoma was covalently linked to the antifolate methotrexate with full retention of antibody activity and partial retention of drug activity. Using an ascites tumor model, developed after intraperitoneal (i.p.) inoculation of 5 × 10⁶ cells of the human kidney cancer line Caki-1 per pristane-primed nude mouse, we showed that the methotrexate-Dal-K29 conjugate was a more potent tumor inhibitor (P <0.0005) of human renal cell carcinoma (which is resistant to currently available modalities including chemotherapy) than the drug or mAb alone, the drug linked to an isotype-matched nontumor-specific IgG or a mixture of the drug and the mAb. Only the conjugate could produce tumor-free survival in a proportion of the mice during the period of observation (i.e. 150 days after tumor inoculation).     

Stabilization of restriction endonuclease Bam HI by cross-linking reagents

Bacillus amyloliquefaciens H produces a restriction endonuclease enzyme BamHl which is heat labile even at low temperatures. Studies were conducted to enhance thermal stability of BamHl using cross-linking reagents, namely, glutaraldehyde, dimethyl adipimidate (DMA), dimethyl suberimidate (DMS), and dimethyl 3,3'-dithiobispropionimidate (DTBP). Reaction with glutaraldehyde did not result in a preparation with enhanced thermal stability. However, the DMA-, DMS-, and DTBP-cross-linked preparations of BamHI exhibited significant improvement in thermal stability. Studies on thermal denaturation of the cross-linked enzyme preparations revealed that these do not follow a true first-order kinetics A possible deactivation scheme has been proposed in which the enzyme has been envisaged to go through a fully active but more susceptible transient state which, on prolonged heat exposure, exhibits a first-order decay kinetics. At 35 degrees C, which is close to the optimum reaction temperature of 37 degrees C for BamHl activity, the half-line of DMA-, DMS-, and DTBP-cross-linked preparations were 4.0, 5.25, and 5.5 h, respectively, whereas the native enzyme exhibited a half-line of 1.2 h only. The apparent values of deactivation rate constants for native, DMA-, DMS-, and DTBP-cross-linked BamHl were 1.13, 0.39, 0.29, and 0.26 h(-1), respectively, at the same temperature, and the apparent values of activation energies for denaturation of native, DMA-, DMS-, and DTBP-cross-linked BamHl were 2.63, 5.24, 6.55, and 9.2 kcal/mol, respectively. The DTBP-cross-linked Bam HI was, therefore, the best heat-stable preparation among those tested. The unusually low values of activation energies for denaturation of Bam Hl represent their highly thermolabile nature compared to other commonly encountered enzymes such as trypsin, having activation energies of more than 40 kcal/mol for their denaturation.     

Immunochemotherapy of Cancer with Chlorambucil-carrying Antibody

Cell-surface localizing heterologous antibodies against the mouse EL4 lymphoma and a human malignant melanoma could be bound to chlorambucil without causing the loss of the alkylating activity of chlorambucil or interfering with the reactivity of the antibodies with their respective tumour cells. When given to mice preinoculated with tumour cells 2, 24, 72, and 120 hours before the beginning of treatment the chlorambucil-bound antibody was a much more effective tumour inhibitor than chlorambucil or the antibody alone. In a patient with disseminated malignant melanoma injection of the chlorambucil-bound anti-melanoma antibody first locally into a few metastatic nodules and then by the intravenous route was followed by the regression of all the metastatic nodules.     

A Highlights from MBoC Selection: Exploratory polarization facilitates mating partner selection in Saccharomyces cerevisiae

Yeast decode pheromone gradients to locate mating partners, providing a model for chemotropism. How yeast polarize toward a single partner in crowded environments is unclear. Initially, cells often polarize in unproductive directions, but then they relocate the polarity site until two partners’ polarity sites align, whereupon the cells “commit” to each other by stabilizing polarity to promote fusion. Here we address the role of the early mobile polarity sites. We found that commitment by either partner failed if just one partner was defective in generating, orienting, or stabilizing its mobile polarity sites. Mobile polarity sites were enriched for pheromone receptors and G proteins, and we suggest that such sites engage in an exploratory search of the local pheromone landscape, stabilizing only when they detect elevated pheromone levels. Mobile polarity sites were also enriched for pheromone secretion factors, and simulations suggest that only focal secretion at polarity sites would produce high pheromone concentrations at the partner’s polarity site, triggering commitment.     

Serology of Aspergillus granuloma

A total of 21 cases of granuloma caused by Aspergillus species were encountered during the period 1972–79. The organs involved were nasal and paranasal sinuses, brain, orbit, subcutaneous tissue of cheek, lungs and endocardial valve in the decreasing order of their frequency. Aspergillus flavus was the main etiological agent. Immunodiffusion tests with various Aspergillus species as antigen showed a positivity of 17 out of 18 (94.4 per cent) cases. The role of precipitins in diagnosis and prognosis of the disease has been discussed.     

Foraging strategies of black kites (<Emphasis Type="Italic">Milvus migrans govinda</Emphasis>) in urban garbage dumps

Large numbers of black kites (Milvus migrans govinda) forage with house crows (Corvus splendens) at garbage dumps in many Indian cities. Such aggregation of many individuals results in aggressiveness where adoption of a suitable behavioral approach is crucial. We studied foraging behavior of black kites in dumping sites adjoining two major corporation markets of Kolkata, India. Black kites used four different foraging tactics which varied and significantly influenced foraging attempts and their success rates. Kleptoparasitism was significantly higher than autonomous foraging events; interspecific kleptoparasitism was highest in occurrence with a low success rate, while ‘autonomous-ground’ was least adopted but had the highest success rate.