Production planning of a flexible manufacturing system in a material requirements planning environment

Early flexible manufacturing system (FMS) production planning models exhibited a variety of planning objectives; typically, these objectives were independent of the overall production environment. More recently, some researchers have proposed hierarchical production planning and scheduling models for FMS. In this article, we examine production planning of FMS in a material requirements planning (MRP) environment. We propose a hierarchical structure that integrates FMS production planning into a closed-loop MRP system. This structure gives rise to the FMS/MRP rough-cut capacity planning (FMRCP) problem, the FMS/MRP grouping and loading (FMGL) problem, and the FMS/MRP detailed scheduling problem. We examine the FMRCP and FMGL problems in detail and present mathematical programming models for each of these problems. In particular, the FMRCP problem is modeled as a generalized assignment problem (GAP), and a GAP-based heuristic procedure is defined for the problem. We define a two-phase heuristic for the FMGL problem and present computational experience with both heuristics. The FMRCP heuristic is shown to solve problems that exhibit a dependent-demand relation within the FMS and with FMS capacity utilization as high as 99 percent. The FMGL heuristic requires very little CPU time and obtains solutions to the test problems that are on average within 1.5 percent of a theoretical lower bound. This FMS/MRP production planning framework, together with the resulting models, constitutes an important step in the integration of FMS technology with MRP production planning. The hierarchical planning mechanism directly provides for system-level MRP planning priorities to induce appropriate production planning and control objectives on the FMS while simultaneously allowing for necessary feedback from the FMS. Moreover, by demonstrating the tractability of the FMRCP and FMGL problems, this research establishes the necessary groundwork upon which to explore systemwide issues pertaining to the coordination of the hierarchical structure.     

Ganglioside Composition of Normal and Mutant Mouse Embryos

The enrichment of gangliosides in neuronal membranes suggests that they play an important role in CNS development. We recently found a marked tetrasialoganglioside deficiency in twl/twl mutant mouse embryos at embryonic day (E)-11. The recessive twl/twl mutants die at embryonic ages E-9 to E-18 from failed neural differentiation in the ventral portion of the neural tube. In the present study, we examined the composition and distribution of gangliosides in twl/twl mutant mouse embryos at E-12. The total ganglioside sialic acid concentration was significantly lower in the mutants than in normal (+/-) embryos. The mutants also expressed significant deficiencies of gangliosides in the "b" metabolic pathway (GD3, GD1b, GT1b, and GQ1b) and elevations in levels of gangliosides in the "a" metabolic pathway (GM3, GM2, GM1, and GD1a). These findings suggest that the mutants have a partial deficiency in the activity of a specific sialyltransferase in the b pathway. Regional ganglioside distribution was also studied in E-12 normal mouse embryos. The ganglioside composition in heads and bodies was similar to each other and to whole embryos. Total ganglioside concentration and the distribution of b pathway gangliosides were significantly higher in neural tube regions than in nonneural tube regions. These findings suggest that b pathway gangliosides accumulate in differentiating neural cells and that the deficiency of these gangliosides in the twl/twl mutants is closely associated with failed neural differentiation.     

Regional Specificity in Alterations of Rat Brain Copper and Catecholamines Following Perinatal Copper Deficiency

Abstract: Perinatal copper deficiency was studied in 1-month-old female and male Sprague-Dawley rat offspring to investigate regional changes in brain copper and catecholamine levels. Offspring of dams given the low copper treatment beginning at day 7 of gestation exhibited signs characteristic of deficiency such as impaired growth and 10-fold lower liver copper levels compared with copper-adequate controls. Regional analysis of brain copper by graphite furnace atomic absorption spectroscopy revealed uniform and severe reduction of copper to levels 20 ± 3% of controls in all regions, except the hypothalamus, where reductions to 56 and 28% of those in copper-adequate females and males, respectively, were measured. HPLC analysis revealed significant reductions in norepinephrine levels in cerebrum, midbrain, corpus striatum, cerebellum, and medulla-pons of copper-deficient offspring ranging between 39 and 67% of control values. There were no significant differences in norepinephrine concentration in the hypothalamus. There was a significant, one-third reduction of dopamine in the corpus striatum of copper-deficient male rats. Consistent with altered in vivo dopamine β-monooxygenase activity, there were five-, three-, and twofold elevations of dopamine in cerebellum, medulla-pons, and hypothalamus of copper-deficient rats. Spectrophotometric measurement of in vitro dopamine β-monooxygenase activity of brain and adrenal homogenates was higher in copper-deficient rats, confirming prior work. An explanation for the in vitro data is unclear. Changes in copper and catecholamine levels were influenced by diet and were regionally selective, especially in the hypothalamus.     

The Regional Distribution of N-Acetylaspartylglutamate (NAAG) and Peptidase Activity Against NAAG in the Rat Nervous System

Abstract: N -Acetylaspartylglutamate (NAAG), a prevalent peptide in the vertebrate nervous system, may be hydrolyzed by extracellular peptidase activity to produce glutamate and N -acetylaspartate. Hydrolysis can be viewed as both inactivating the peptide after synaptic release and increasing synaptic levels of ambient glutamate. To test the hypothesis that NAAG and the peptidase activity that hydrolyzes it coexist as a unique, two-stage system of chemical neurotransmission, 50 discrete regions of the rat CNS were microdissected for assay. In each microregion, the concentration of NAAG was determined by radioimmunoassay and the peptidase activity was assayed using tritiated peptide as substrate. The NAAG concentration ranged from 2.4 nmol/mg of soluble protein in median eminence to 64 in thoracic spinal cord. Peptidase activity against NAAG ranged from 54 pmol of glutamate produced per milligram of membrane protein per minute in median eminence to 148 in superior colliculus. A linear relationship was observed between NAAG peptidase and NAAG concentration in 46 of the 50 areas, with a slope of 2.26 and a correlation coefficient of 0.45. These data support the hypothesis that hydrolysis of NAAG to glutamate and N -acetylaspartate is a consistent aspect of the physiology and metabolism of this peptide after synaptic release. The ratio of peptide concentration to peptidase activity was >0.3 in the following four areas: ventrolateral medulla and reticular formation where the peptide is concentrated in axons of passage, thoracic spinal cord, where NAAG is concentrated in ascending sensory tracts as well as motoneuron cell bodies, and ventroposterior thalamic nucleus.     

Further evidence of a role for abscisic acid in conversion of somatic embryos ofDaucus carota

Summary Somatic embryogenesis has been shown to be an imperfect recapitulation of stages involved to form embryos from vegetative tissues. Although abscisic acid has been implicated in normalizing development, studies that specifically investigate conversion (vegetative leaf initiation) in somatic embryos are lacking. This report documents a follow-up of a study that implicated abscisic acid as a vital factor in allowing embryos ofDaucus carota to progress to the plantlet stage. Abscisic acid was determined to enhance conversion at doses ranging from 1 to 50 µM. Younger embryo stages were more responsive to abscisic acid application with regards to plantlet recovery. Pulses of abscisic acid were shown to elicit more rapid response with younger embryo stages, indicating more plastic development. Fluridone, an abscisic acid synthesis inhibitor, was shown to dramatically reduce conversion, even at low doses (<5µM). When abscisic acid was applied concurrently with fluridone, partial restoration of conversion was observed. Histologically, fluridone was seen to cause pronounced vacuolation in the shoot apical notch which resulted in the loss of meristematic cells, negating conversion capacity. Quantitation of total cytoplasmic area showed that abscisic acid reduced vacuolar intrusion into the apical notch, while fluridone caused a significant increase in vacuolation of cells in this region. This report documents further evidence of a role for abscisic acid in plantlet establishment from somatic embryos ofDaucus carota.     

Identification of a developmentally regulated sialidase inEimeria tenella that is immunologically related to theTrypanosoma cruzi enzyme

Sporozoites and merozoites of three species ofEimeria, E. tenella, E. maxima, andE. necatrix, that cause diarrhea in chickens worldwide, were examined for their expression of sialidase (SA) activity. The enzyme was found in three species, and the activity of merozoites was 10–20 times higher than that of sporozoites. The enzyme was resistant to degradation by proteases that are normally present in the intestine, a site inhabited by theEimeria parasites, and it was relatively resistant to heat, with optimum activity being at 40°C, which is within the range of temperature in the chicken intestine (40–43°C).E. tenella SA was immuniprecipitated by monoclonal and polyclonal antibodies raised against theTrypanosoma cruzi SA (TCSA), and enzyme activity was neutralized by these antibodies.E. tenella SA was identified by immunoblots as a doublet of molecular weight 190 000 and 180 000 using, as a probe, anti-TCSA antibodies and antibodies against a synthetic peptide (TR) derived from the long tandem repeat domain of TCSA. Binding of the monoclonal and polyclonal antibodies toE. tenella was completely blocked by TR, but not by an irrelevant peptide (BR). Therefore,E. tenella expresses a developmentally regulated SA that is structurally related to theT. cruzi counterpart. Because of the high SA activity in merozoites, and by analogy with other SA-producing microbes that inhabit mucin-rich epithelia, we suggest that theEimeria SA plays a role in desialylating intestinal mucins to reduce viscosity of the local environment and thereby facilitate parasite migration. The enzyme could also play a role in host cell-parasite interaction.Abbreviations SA sialidase (neuraminidase) - Neu5Ac N-acetylneuraminic acid - 4-MU-Neu5Ac 2-(4-methylumbelliferyl)--N-acetyl-d-neuraminic acid - BSA bovine serum albumin - PBS phosphate buffered saline - PMSF phenylmethylsulfonyl fluoride - PNA peanut agglutinin - Ab antibody - TCN-2 monoclonal antibody toT. cruzi sialidase, anti-Ars, monoclonal antibody top-azophenylarsonate - TCSA Trypanosoma cruzi sialidase     

Ultrastructure of human dermal mast cells in 29 different lysosomal storage diseases

The effect of lysosomal storage diseases on the ultrastructure of human mast cells has not previously been reported. Indeed, there has been little published evidence indicating that mast cells contain typical lysosomes. However, mast cell cytoplasmic granules contain hydrolases similar to those found in lysosomes, but which differ from lysosomal hydrolases in exhibiting optimal activity at higher pH. We therefore examined by transmission electron microscopy the dermal mast cells in 58 biopsies of patients exhibiting 1 of 29 different lysosomal storage diseases. We found mast cells containing abnormal lysosomes in 16 of these disorders. In 6 of these 16 diseases, the mast cells' cytoplasmic granules appeared normal. These observations indicate that human mast cells can contain lysosomes, and provide evidence that the enzymes affected by lysosomal storage diseases are active in mast cells.     

Isolation and properties of a soluble sialidase from the culture fluid of Chinese hamster ovary cells

A Soluble sialidase that can degrade recombinant glycoproteinsexpressed in Chinese hamster ovary (CHO) cells has been isolatedand purified to near homogeneity from the cell culture fluidof this host. Purification of