Morphological analysis of female gametophyte development in the bel1 stk shp1 shp2 mutant

Abstract

In Arabidopsis thaliana, cell fate in developing ovules is determined by the action of the homeodomain factor BELL1 (BEL1) and of the MADS-box factors SEEDSTICK (STK), SHATTERPROOF1 (SHP1) and SHP2. The analysis of the bel1 and the stk shp1 shp2 mutants revealed that the functional megaspore is formed, however, it does not proceed into megagametogenesis. In the bel1 stk shp1 shp2, quadruple mutant megasporogenesis does not take place. In this article we describe a detailed morphological analysis of the quadruple mutant, and we discuss the possibility that BELL1, STK, SHP1 and SHP2 not only control integument identity determination and development, but that they might also play a role during megasporogenesis.     

Patterns of Sleeping Site and Sleeping Tree Selection by Black-and-Gold Howler Monkeys (Alouatta caraya) in Northern Argentina

International Journal of Primatology - The selection of sleeping sites and sleeping trees in nonhuman primates is related to social and ecological factors. We investigate the role of body...     

Effect of the lymphocytosis-stimulating factor from Bordetella pertussis on murine lymphoid and hemopoietic cells

Effect of B. pertussis lymphocytosis-promoting factor (LPF) on the lympho-hematopoietic system of mice was studied. The injection of LPF was shown to sharply enhance endogenous colony formation and to induce a severe depletion of thymus cells, reaching its maximum of day 4. Thymocytes obtained on day 2 or 3 after the injection of LPF produced a suppressive effect on endogenous colony formation. The proliferative activity of hematopoietic stem cells sharply increased under the influence of LPF, though it had no radioprotective action. On the following day after the injection of LPF a steep rise in the number of hematopoietic stem cells was observed in the blood of mice: their content increased 20-fold in comparison with the control level. These data may be important for the evaluation of the side effects of pertussis vaccine on the lympho-hematopoietic system.     

The cluster method in conducting epidemiological research

The Expanded Programme on Immunization (EPI) whose goal is to reduce morbidity and mortality by providing children with immunizations against diphtheria, pertussis, tetanus, poliomyelitis, measles, and tuberculosis continually faces the problem of documenting immunization coverage rates. Therefore the EPI seeks simple, effective, and inexpensive methods of evaluation which could be implemented in different countries. An example of such a method is a simplified cluster sampling technique of estimation of immunization coverage through the examination of 210 children, selected randomly as 30 groups of 7 children each. In 1978-1984 more than 1000 immunization coverage surveys were performed all over the world, mainly in developing countries. In a modified way this method is also used to collect data on morbidity and mortality of certain EPI target diseases as well as diarrhoeal diseases.     

Antibodies against calcium-regulating hormones in infectious-allergic forms of bronchial asthma

Antibodies to calcitonin, parathyroid hormone and cortisol are detected in acute stage of infection-caused bronchial asthma. The appearance of antibodies is paralleled by marked hypercalcaemia. The antibodies may bind excessive hormones in the blood, preventing further hormonal imbalance. Ten-day treatment with glucocorticoids decreased the amount of antibodies possibly due to normalization of hormonal secretion and restoration of their balance. As a result, calcium blood levels returned to normal.     

Metyrapone - reduced cytochrome P-450 complex: A specific method for the determination of the phenobarbital inducible form of rat hepatic microsomal cytochrome P-450

Using homogeneous cytochrome P-450, we have shown that the well-known metyrapone-dithionite reduced cytochrome P-450 complex is specific for the cytochrome P-450b induced by phenobarbital. A linear relationship was observed between the absorbance of metyrapone-reduced cytochrome P-450 complex and the one of CO-reduced cytochrome P-450 complex, the usual method for the determination of cytochrome P-450. A method has been proposed for the specific determination of the cytochrome P-450b.     

Molecular control of rabbit follicular testosterone production. Role of protein and RNA after stimulation with luteinizing hormone.

The time and dose dependence of the relationship between uptake of labelled precursors into protein and RNA and production of testosterone by rabbit follicles was examined. Although testosterone production was stimulated by luteinizing hormone at concentrations between 0.1 and 10 microgram/ml, the uptake of [3H]leucine into protein was significant only when the concentration of luteinizing hormone was greater than 2.5 microgram/ml. Increased production of testosterone was observed within 15 min of stimulation with luteinizing hormone whereas uptake of [3H]leucine was only significant at 90 min. Puromycin (40 microgram/ml) and cycloheximide (10 microgram/ml) in the presence of luteinizing hormone inhibited the synthesis of both testosterone and protein. However, lower concentrations of puromycin (0.1, 1 and 10 microgram/ml) and cycloheximide (1 microgram/ml) had no effect on luteinizing hormone-induced testosterone production but significantly inhibited protein synthesis by 58, 37, 31 and 71%, respectively. Actinomycin D (20, 80 and 160 microgram/ml) alone and in combination with 5 microgram luteinizing hormone/ml severely inhibited uptake of [3H]uridine into RNA without affecting testosterone production. However, with 1 microgram actinomycin/ml, testosterone production was significantly (P less than 0.01) greater than in the presence of luteinizing hormone alone. These results cast doubt on the obligatory role of RNA and protein synthesis in rabbit ovarian follicular steroidogenesis.     

Changes in the size and shape of the synaptic vesicles in the sensorimotor cortex of the rat brain in the initial phases of kindling

The sensorimotor area of rat cerebral cortex was subjected to repeated electrical stimulation at 10-min intervals, with resultant formation and progressive lengthening of self-sustained after-discharges (SSAD). One and 60 min after the third SSAD ended, we carried out an electron microscopy morphometric analysis of the agranular synaptic vesicles in type I synapses (after Gray) in the second cortical layer of the homotopic area of the unstimulated hemisphere. One minute after the seizure ended, 5.8% enlargement of the synaptic vesicles compared with the control was demonstrated in zone II of the synapse (0.1-0.2 micron from the active zone of the synapse). Neither the size nor the shape of the synaptic vesicles in the other parts of the synaptic apparatus altered. Sixty min after the seizure ended, a 5.5% enlargement of the synaptic vesicles in zone I (0.0-0.1 micron) and a 5.4% enlargement of those in zone II was found. The synaptic vesicles in zone I in the experimental animals were more oval than in the controls. Our findings support the vesicular theory and testify that hyperfunction, up to temporary exhaustion of the synaptic apparatuses, produces a change in the transmitter content of the synaptic vesicles. A raised amount of transmitter in the synaptic vesicles near the active zone could be one of the factors responsible for continued hyperexcitability of the tissue one hour after the seizure had ended. The results likewise support the concept of two mechanisms of synaptic vesicle formation, and hence of the existence of two different vesicle populations.