Hamid Khan - Academia.edu (original) (raw)

Papers by Hamid Khan

American Journal of Gastroenterology, 2000

Search by Subject Search using Medical Subject Headings (< b&g... more Search by Subject Search using Medical Subject Headings (< b> MeSH</b>), a controlled vocabulary for indexing life sciences content.< br/> Note that some records do not have MeSH. These include Patents and the latest PubMed and PubMed Central records.

Skills in the cognitive domains of manufacturing engineering technologists are identified accordi... more Skills in the cognitive domains of manufacturing engineering technologists are identified according to Bloom's Taxonomy (Cronbach, 1983). Skills visible as behavioral outcomes of affect and psychomotor are stated in terms of progress toward the outcome as evidence of changed behavior. Previous researchers in manufacturing engineering have conducted broad based research in desirable skills outlining the specific competencies that are presently needed or will be needed by the year 2000. The professional society of manufacturing engineering called the Society of Manufacturing Engineers has produced a voluminous publication called Profile 2000 and Profile 2002 outlining such research. But these are only inputs to the curriculum. Effectiveness of a curriculum is judged by the outputs-reasonable performance of the program in terms of “behaviors as evidence”. Information gathered from published resources like Journal of Engineering Technology and Society of Manufacturing Engineers (SME) Profile 2000/2002 are used as “input information” from which the outcome statements are generated. They are categorized to a few outlined areas of importance as deemed proper by the Society of Manufacturing Engineers. The desirable outcomes as evidence are clear and concise expressions of behaviors that the successful student (as a stakeholder) must demonstrate at the close of his/her program. These are not the competencies required in each area of curricular endeavor because acquiring “competencies” acceptable as evidence does not guarantee that those competencies are used effectively. The administrators and the faculty also must evaluate the program as key stakeholders with the student perception of success. Outcome based program evaluation has the strength of being “interpretive” or “qualitative” as it occurs in social context, and is readily amenable to qualitative study. However the procedural steps outlined in the study are used for quantitative program evaluation by a study of different stakeholder perceptions

Journal of Comparative Neurology, 1998

Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Me... more Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Met-Arg-Phe-NH2 (FMRFamide)-related heptapeptides were identified with an antiserum specific for these substances in the central nervous system of the freshwater snail Helisoma duryi. Serotonergic neurons and their axons are present in all of the ganglia (paired buccal, cerebral, pedal, pleural, parietal, and single visceral) and major nerves of the central nervous system. Large neurons containing FMRFamide-related peptide immunoreactivity are located in the left parietal and visceral ganglia, whereas a few small neurons are located in the cerebral and pedal ganglia. Both serotonergic and FMRFamide-related peptide-immunoreactive dendrites and varicosities were observed in the kidney. A second antiserum with high affinity for FMRFamide-related heptapeptides was used to measure the levels of the immunoreactive material in various tissues, and such material was found in every tissue analyzed. When snails were exposed to a medium isosmotic to their hemolymph, the levels of immunoreactive FMRFamide-related peptides increased in the hemolymph, central nervous system, mantle, and kidney. Injection of dihydroxytryptamine, which is known to deplete serotonin content in the snail, also reduced the levels of FMRFamide-related-immunoreactive material in the above tissues. Therefore, serotonin may influence the levels of FMRFamide-related peptides in tissues by regulating the rate of their synthesis, axonal transport, or release. Both serotonin and FMRFamide-related peptides could be involved in osmoregulation.

Canadian Journal of Zoology-revue Canadienne De Zoologie, 1990

Page 1. The effects of mating on the fine structure of neurosecretory caudodorsal cells in Heliso... more Page 1. The effects of mating on the fine structure of neurosecretory caudodorsal cells in Helisoma duryi (Mollusca) HAMID R. KHAN, MARY LOU ASHTON, SPENCER T. MUKAI, AND ASM SALEUDDIN Department of Biology ...

Journal of Experimental Zoology, 1989

The hermaphrodite snail Helisoma duryi reproduces preferentially by cross-fertilization. Virgin a... more The hermaphrodite snail Helisoma duryi reproduces preferentially by cross-fertilization. Virgin and castrated snails lay an insignificant number of egg masses. The fine structure of its endocrine dorsal bodies (DB), which regulate reproduction, has been studied in reproductively inactive virgin and castrated snails and in reproductively active mated snails, using tannic acid staining and autoradiography after injection of [3H]leucine. The DB cells of the mated snails appear synthetically active, containing scattered rough endoplasmic reticulum (RER) and probably smooth endoplasmic reticulum (SER), many Golgi complexes, and putative DB hormone-containing granules. On the other hand, the DB cells of the virgin and castrated snails appear synthetically inactive, containing RER in circular stacks, few Golgi complexes, many lipid droplets, and scattered glycogen. Mitochondria appear slender in mated snails, whereas those in virgin and castrated snails appear large and spherical. With tannic acid treatment, the processes of the DB cells of mated snails exhibited more released granules than those of virgin and castrated snails. Many silver grains were seen on RER, Golgi complexes, and mitochondria in the autoradiographs of the DB cells of mated snails. It is suggested that the DB cells of the reproductively active snails are synthetically more active than those in virgin and castrated snails and that the DB cells may produce peptide hormone as well as a steroid hormone.

Cell and Tissue Research, 1992

The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma... more The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma duryi were studied in fast-growing virgin snails and in slow-growing reproducing snails. There are about 60 mediodorsal cells in clusters on each side of the cerebral commissure of the central nervous system, and they contain dense-cored granules which are 100–200 nm in diameter. The cells of virgin snails have dense Golgi bodies, scattered ER cisternae, and few granules, while those of reproducing snails have pale Golgi bodies, stacked ER cisternae, and numerous granules. Thus the mediodorsal cells of the virgin snails appear to be more active synthetically than those of the reproducing snails. The cells near the endocrine dorsal bodies contain many dorsal body precesses in their membrane interdigitations. There are junction-like interactions between some of the interdigitations. Gap junction-like contacts are seen between mediodorsal cells and glial cells. The axon endings of the mediodorsal cells at the neurohemal area in the labial nerve show more release profiles in virgin snails than in reproducing snails. A daily pattern of release has been observed in reproducing snails, and rates of release are higher in the evening than in the morning.

Tissue & Cell, 1992

The distribution of FMRFamide-immunoreactive neurons in the central nervous system of the freshwa... more The distribution of FMRFamide-immunoreactive neurons in the central nervous system of the freshwater pulmonate, Helisoma duryi is described. All parts of the central nervous system except the two pleural and the right parietal ganglia, contain immunoreactive neurons. By immunogold techniques, only one kind of neurosecretory FMRFamide-immunoreactive cell (previously identified as the type-3 cell) was localized in the visceral and left parietal ganglia. This cell type has been previously implicated in an antidiuretic role. FMRFamide-immunoreactive material is found in the whole mount of the kidney as well as in kidney sections. Electron microscopic examination shows that the axons innervating either the smooth muscles of the kidney or the kidney itself contain neurosecretory granules morphologically similar to type-3 cells of the visceral and left parietal ganglia. When incubated in saline containing nanogram quantities of FMRFamide, the wet weight of the kidney increased. It is suggested that FMRFamide-like substance may function as an antidiuretic factor and that the kidney is a target organ of this peptide for osmoregulation.

Journal of Comparative Neurology, 1998

Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Me... more Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Met-Arg-Phe-NH2 (FMRFamide)-related heptapeptides were identified with an antiserum specific for these substances in the central nervous system of the freshwater snail Helisoma duryi. Serotonergic neurons and their axons are present in all of the ganglia (paired buccal, cerebral, pedal, pleural, parietal, and single visceral) and major nerves of the central nervous system. Large neurons containing FMRFamide-related peptide immunoreactivity are located in the left parietal and visceral ganglia, whereas a few small neurons are located in the cerebral and pedal ganglia. Both serotonergic and FMRFamide-related peptide-immunoreactive dendrites and varicosities were observed in the kidney. A second antiserum with high affinity for FMRFamide-related heptapeptides was used to measure the levels of the immunoreactive material in various tissues, and such material was found in every tissue analyzed. When snails were exposed to a medium isosmotic to their hemolymph, the levels of immunoreactive FMRFamide-related peptides increased in the hemolymph, central nervous system, mantle, and kidney. Injection of dihydroxytryptamine, which is known to deplete serotonin content in the snail, also reduced the levels of FMRFamide-related-immunoreactive material in the above tissues. Therefore, serotonin may influence the levels of FMRFamide-related peptides in tissues by regulating the rate of their synthesis, axonal transport, or release. Both serotonin and FMRFamide-related peptides could be involved in osmoregulation.

Journal of Experimental Zoology, 1991

The metabolic origin of hypertonically induced intracellular free amino acid (FAA) accumulation i... more The metabolic origin of hypertonically induced intracellular free amino acid (FAA) accumulation in the freshwater pulmonate snail, Helisoma trivolvis was examined. The changes in FAA patterns in response to hypertonic stress were common in haemolymph and tissues; but FAA concentrations were much lower in the former. Transport experiments with 3H-glycine and detection by high-performance liquid chromatography (HPLC) showed that isolated kidneys in vitro took up FAA against a concentration gradient. Fluorography demonstrated that injected 14C-amino acids were incorporated into haemolymph protein significantly less in hypertonically stressed snails than in control snails. These results suggest that, in H. trivolvis, reduction in synthesis of haemolymph protein and FAA transport from haemolymph into cells contribute to intracellular FAA increase during the initial stage of hypertonic stress.

Journal of Morphology, 1990

The morphology and the organization of the endocrine dorsal bodies (DB) of non-reproducing virgin... more The morphology and the organization of the endocrine dorsal bodies (DB) of non-reproducing virgin and castrated, and reproducing mated Helisoma duryi have been examined using serial sectioning. The DB cells occur in two masses on the mid-dorsal side of the cerebral commissure, each of which has a cortical zone containing the cell bodies and a medulla where cell processes terminate. The cell bodies measure 10–15 μm in diameter, and are arranged in lobules of 6–12 cells. The complex cell processes are winding and terminate at various distances from their cell bodies in both reproducing and non-reproducing snails. Few 70–90-nm membrane-bound granules are found in the cell bodies and many are seen in the cell processes, which seem to penetrate the perineurium of the cerebral ganglia and make close contacts with neurosecretory cells. In reproducing snails the DB cells display a significantly larger amount of plasma membrane sproutings in the form of loops and circles compared to that in reproductively inactive virgin or castrated snails. Images of thin-sections and freeze-fracture replicas of these membranes suggest that they are gap junctions, which join the DB cells with each other. It is likely that gap junction-mediated cell to cell communication is involved in the activation of the DB cells for their role(s) in reproduction.

American Journal of Gastroenterology, 2000

Search by Subject Search using Medical Subject Headings (< b&g... more Search by Subject Search using Medical Subject Headings (< b> MeSH</b>), a controlled vocabulary for indexing life sciences content.< br/> Note that some records do not have MeSH. These include Patents and the latest PubMed and PubMed Central records.

Skills in the cognitive domains of manufacturing engineering technologists are identified accordi... more Skills in the cognitive domains of manufacturing engineering technologists are identified according to Bloom's Taxonomy (Cronbach, 1983). Skills visible as behavioral outcomes of affect and psychomotor are stated in terms of progress toward the outcome as evidence of changed behavior. Previous researchers in manufacturing engineering have conducted broad based research in desirable skills outlining the specific competencies that are presently needed or will be needed by the year 2000. The professional society of manufacturing engineering called the Society of Manufacturing Engineers has produced a voluminous publication called Profile 2000 and Profile 2002 outlining such research. But these are only inputs to the curriculum. Effectiveness of a curriculum is judged by the outputs-reasonable performance of the program in terms of “behaviors as evidence”. Information gathered from published resources like Journal of Engineering Technology and Society of Manufacturing Engineers (SME) Profile 2000/2002 are used as “input information” from which the outcome statements are generated. They are categorized to a few outlined areas of importance as deemed proper by the Society of Manufacturing Engineers. The desirable outcomes as evidence are clear and concise expressions of behaviors that the successful student (as a stakeholder) must demonstrate at the close of his/her program. These are not the competencies required in each area of curricular endeavor because acquiring “competencies” acceptable as evidence does not guarantee that those competencies are used effectively. The administrators and the faculty also must evaluate the program as key stakeholders with the student perception of success. Outcome based program evaluation has the strength of being “interpretive” or “qualitative” as it occurs in social context, and is readily amenable to qualitative study. However the procedural steps outlined in the study are used for quantitative program evaluation by a study of different stakeholder perceptions

Journal of Comparative Neurology, 1998

Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Me... more Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Met-Arg-Phe-NH2 (FMRFamide)-related heptapeptides were identified with an antiserum specific for these substances in the central nervous system of the freshwater snail Helisoma duryi. Serotonergic neurons and their axons are present in all of the ganglia (paired buccal, cerebral, pedal, pleural, parietal, and single visceral) and major nerves of the central nervous system. Large neurons containing FMRFamide-related peptide immunoreactivity are located in the left parietal and visceral ganglia, whereas a few small neurons are located in the cerebral and pedal ganglia. Both serotonergic and FMRFamide-related peptide-immunoreactive dendrites and varicosities were observed in the kidney. A second antiserum with high affinity for FMRFamide-related heptapeptides was used to measure the levels of the immunoreactive material in various tissues, and such material was found in every tissue analyzed. When snails were exposed to a medium isosmotic to their hemolymph, the levels of immunoreactive FMRFamide-related peptides increased in the hemolymph, central nervous system, mantle, and kidney. Injection of dihydroxytryptamine, which is known to deplete serotonin content in the snail, also reduced the levels of FMRFamide-related-immunoreactive material in the above tissues. Therefore, serotonin may influence the levels of FMRFamide-related peptides in tissues by regulating the rate of their synthesis, axonal transport, or release. Both serotonin and FMRFamide-related peptides could be involved in osmoregulation.

Canadian Journal of Zoology-revue Canadienne De Zoologie, 1990

Page 1. The effects of mating on the fine structure of neurosecretory caudodorsal cells in Heliso... more Page 1. The effects of mating on the fine structure of neurosecretory caudodorsal cells in Helisoma duryi (Mollusca) HAMID R. KHAN, MARY LOU ASHTON, SPENCER T. MUKAI, AND ASM SALEUDDIN Department of Biology ...

Journal of Experimental Zoology, 1989

The hermaphrodite snail Helisoma duryi reproduces preferentially by cross-fertilization. Virgin a... more The hermaphrodite snail Helisoma duryi reproduces preferentially by cross-fertilization. Virgin and castrated snails lay an insignificant number of egg masses. The fine structure of its endocrine dorsal bodies (DB), which regulate reproduction, has been studied in reproductively inactive virgin and castrated snails and in reproductively active mated snails, using tannic acid staining and autoradiography after injection of [3H]leucine. The DB cells of the mated snails appear synthetically active, containing scattered rough endoplasmic reticulum (RER) and probably smooth endoplasmic reticulum (SER), many Golgi complexes, and putative DB hormone-containing granules. On the other hand, the DB cells of the virgin and castrated snails appear synthetically inactive, containing RER in circular stacks, few Golgi complexes, many lipid droplets, and scattered glycogen. Mitochondria appear slender in mated snails, whereas those in virgin and castrated snails appear large and spherical. With tannic acid treatment, the processes of the DB cells of mated snails exhibited more released granules than those of virgin and castrated snails. Many silver grains were seen on RER, Golgi complexes, and mitochondria in the autoradiographs of the DB cells of mated snails. It is suggested that the DB cells of the reproductively active snails are synthetically more active than those in virgin and castrated snails and that the DB cells may produce peptide hormone as well as a steroid hormone.

Cell and Tissue Research, 1992

The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma... more The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma duryi were studied in fast-growing virgin snails and in slow-growing reproducing snails. There are about 60 mediodorsal cells in clusters on each side of the cerebral commissure of the central nervous system, and they contain dense-cored granules which are 100–200 nm in diameter. The cells of virgin snails have dense Golgi bodies, scattered ER cisternae, and few granules, while those of reproducing snails have pale Golgi bodies, stacked ER cisternae, and numerous granules. Thus the mediodorsal cells of the virgin snails appear to be more active synthetically than those of the reproducing snails. The cells near the endocrine dorsal bodies contain many dorsal body precesses in their membrane interdigitations. There are junction-like interactions between some of the interdigitations. Gap junction-like contacts are seen between mediodorsal cells and glial cells. The axon endings of the mediodorsal cells at the neurohemal area in the labial nerve show more release profiles in virgin snails than in reproducing snails. A daily pattern of release has been observed in reproducing snails, and rates of release are higher in the evening than in the morning.

Tissue & Cell, 1992

The distribution of FMRFamide-immunoreactive neurons in the central nervous system of the freshwa... more The distribution of FMRFamide-immunoreactive neurons in the central nervous system of the freshwater pulmonate, Helisoma duryi is described. All parts of the central nervous system except the two pleural and the right parietal ganglia, contain immunoreactive neurons. By immunogold techniques, only one kind of neurosecretory FMRFamide-immunoreactive cell (previously identified as the type-3 cell) was localized in the visceral and left parietal ganglia. This cell type has been previously implicated in an antidiuretic role. FMRFamide-immunoreactive material is found in the whole mount of the kidney as well as in kidney sections. Electron microscopic examination shows that the axons innervating either the smooth muscles of the kidney or the kidney itself contain neurosecretory granules morphologically similar to type-3 cells of the visceral and left parietal ganglia. When incubated in saline containing nanogram quantities of FMRFamide, the wet weight of the kidney increased. It is suggested that FMRFamide-like substance may function as an antidiuretic factor and that the kidney is a target organ of this peptide for osmoregulation.

Journal of Comparative Neurology, 1998

Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Me... more Serotonergic neurons were studied by specific histological methods, and neurons containing Phe-Met-Arg-Phe-NH2 (FMRFamide)-related heptapeptides were identified with an antiserum specific for these substances in the central nervous system of the freshwater snail Helisoma duryi. Serotonergic neurons and their axons are present in all of the ganglia (paired buccal, cerebral, pedal, pleural, parietal, and single visceral) and major nerves of the central nervous system. Large neurons containing FMRFamide-related peptide immunoreactivity are located in the left parietal and visceral ganglia, whereas a few small neurons are located in the cerebral and pedal ganglia. Both serotonergic and FMRFamide-related peptide-immunoreactive dendrites and varicosities were observed in the kidney. A second antiserum with high affinity for FMRFamide-related heptapeptides was used to measure the levels of the immunoreactive material in various tissues, and such material was found in every tissue analyzed. When snails were exposed to a medium isosmotic to their hemolymph, the levels of immunoreactive FMRFamide-related peptides increased in the hemolymph, central nervous system, mantle, and kidney. Injection of dihydroxytryptamine, which is known to deplete serotonin content in the snail, also reduced the levels of FMRFamide-related-immunoreactive material in the above tissues. Therefore, serotonin may influence the levels of FMRFamide-related peptides in tissues by regulating the rate of their synthesis, axonal transport, or release. Both serotonin and FMRFamide-related peptides could be involved in osmoregulation.

Journal of Experimental Zoology, 1991

The metabolic origin of hypertonically induced intracellular free amino acid (FAA) accumulation i... more The metabolic origin of hypertonically induced intracellular free amino acid (FAA) accumulation in the freshwater pulmonate snail, Helisoma trivolvis was examined. The changes in FAA patterns in response to hypertonic stress were common in haemolymph and tissues; but FAA concentrations were much lower in the former. Transport experiments with 3H-glycine and detection by high-performance liquid chromatography (HPLC) showed that isolated kidneys in vitro took up FAA against a concentration gradient. Fluorography demonstrated that injected 14C-amino acids were incorporated into haemolymph protein significantly less in hypertonically stressed snails than in control snails. These results suggest that, in H. trivolvis, reduction in synthesis of haemolymph protein and FAA transport from haemolymph into cells contribute to intracellular FAA increase during the initial stage of hypertonic stress.

Journal of Morphology, 1990

The morphology and the organization of the endocrine dorsal bodies (DB) of non-reproducing virgin... more The morphology and the organization of the endocrine dorsal bodies (DB) of non-reproducing virgin and castrated, and reproducing mated Helisoma duryi have been examined using serial sectioning. The DB cells occur in two masses on the mid-dorsal side of the cerebral commissure, each of which has a cortical zone containing the cell bodies and a medulla where cell processes terminate. The cell bodies measure 10–15 μm in diameter, and are arranged in lobules of 6–12 cells. The complex cell processes are winding and terminate at various distances from their cell bodies in both reproducing and non-reproducing snails. Few 70–90-nm membrane-bound granules are found in the cell bodies and many are seen in the cell processes, which seem to penetrate the perineurium of the cerebral ganglia and make close contacts with neurosecretory cells. In reproducing snails the DB cells display a significantly larger amount of plasma membrane sproutings in the form of loops and circles compared to that in reproductively inactive virgin or castrated snails. Images of thin-sections and freeze-fracture replicas of these membranes suggest that they are gap junctions, which join the DB cells with each other. It is likely that gap junction-mediated cell to cell communication is involved in the activation of the DB cells for their role(s) in reproduction.