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Biomedical subjects

R J Grand

Publications and source records attributed to R J Grand.

At least 19 recordsLinked to original sources
PubMed1992

Messenger RNA sorting in enterocytes. Co-localization with encoded proteins.

This study describes the intracellular compartmentalization of three different mRNAs in the polarized rat fetal enterocyte. They encode proteins that are known to be localized within different regions of the epithelial cell namely (i) the apical, membrane-bound glycoprotein, lactase-phlorizin hydrolase (lactase), (ii) the mitochondrially localized enzyme, carbamoylphosphate synthetase (CPS), and (iii) the cytoplasmically localized enzyme, phosphoenolpyruvate carboxykinase (PEPCK). These mRNAs are found in close proximity to their respective protein products, i.e. the apical membrane, mitochondria and cytoplasm, respectively. The significance of these observations is twofold; (i) they indicate that mRNAs are sorted into specific domains of the cytosol of intestinal epithelial cells; and (ii) they imply the presence of two distinct pathways of mRNA targeting one that allows transport of mRNAs that are translated on ribosomes associated with the rough endoplasmic reticulum (lactase mRNA), and the other that allows sorting of mRNAs that are translated on free polysomes (CPS and PEPCK mRNA).

Animals↗
PubMed1992

Vitronectin is the major serum protein essential for NGF-mediated neurite outgrowth from PC12 cells.

The rat pheochromocytoma cell line PC12 can be induced to differentiate in response to nerve growth factor (NGF) in the presence of 1% fetal calf serum (FCS). Using a novel assay procedure we have developed a purification protocol which has allowed the isolation of the protein in serum responsible for neurite outgrowth after NGF treatment. FCS has been fractionated using four chromatographic procedures and in each case the peak of biological activity copurified with vitronectin. We have concluded, therefore, that vitronectin is the protein present in FCS which can mediate NGF-dependent neurite outgrowth in PC12 cells. Vitronectin and fibronectin from FCS have been chromatographically separated and only the former is capable of inducing neurite outgrowth. We have also shown that vitronectin utilizes the RGD amino acid sequence in binding to the surface of PC12s.

Amino Acid Sequence↗
PubMed1992

Vitamin E deficiency and impaired cellular immunity related to intestinal fat malabsorption.

This report describes a patient in whom a severe vitamin E deficiency developed secondary to an intestinal malabsorptive disorder. In vivo and in vitro impairment of T-cell function, as well as a polyneuropathy, were observed in conjunction with this vitamin deficiency. Repletion of the vitamin deficiency was associated with marked improvement in the T-cell functions and modest improvement in the neuropathy. Observations in this patient suggest that severe vitamin E deficiency in humans may impair T-cell activity and that correction of the deficient state may reverse these T-cell abnormalities. Further studies will need to be performed to confirm these findings.

Fats↗
PubMed1992

Lactase gene expression during early development of rat small intestine.

Expression of lactase messenger (m) RNA and protein in rat small intestine during fetal and postnatal development was analyzed using in situ hybridization and immunohistochemistry. Lactase mRNA was first identified at 18 days of development, and lactase protein was first detected at day 20. Lactase mRNA and protein were present along the entire villus. Lactase mRNA increased, reaching a maximum at day 20. Just before birth a decrease in lactase mRNA was observed. In newborn intestine, lactase mRNA was present only from the base of the villus up to the mid-villus region and was undetectable up to the villus tips. Lactase protein continued to be expressed along the entire villus. These data show that expression of lactase mRNA and protein do not parallel, indicating a posttranscriptional control in fetal development. Lactase gene transcription is initiated late in gestation concomitant with villus formation and is exclusively seen in villus epithelial cells. The restriction after birth of lactase mRNA expression to cells at the villus base suggests the occurrence of a previously unknown step in postnatal differentiation of the enterocyte.

Age Factors↗
PubMed1992

Efficacy of cimetidine for gastric acid suppression in pediatric patients.

The efficacy of oral cimetidine for gastric acid suppression in pediatric patients was examined in a double-blind study. Twenty-seven patients with gastroesophageal reflux-related gastrointestinal symptoms, pulmonary symptoms, or both were given randomly determined doses of cimetidine. Response was evaluated by continuous intragastric monitoring with a pH probe. Twenty-three patients were given cimetidine doses of 5,7.5, and 10 mg/kg; eight of these patients were also given additional doses of 15 mg/kg. Four patients received only 10 and 15 mg/kg, because of previous poor clinical response to the lower dosages. The onset of gastric pH greater than 4 was delayed more than 2 hours in 50% of patients with responses to the 5 mg/kg dose. Of the patients with responses to the 10 mg/kg dose, 75% had showed a rise in gastric pH greater than 4 within 2 hours. With respect to the duration of gastric acid suppression, 70% of patients receiving 5 mg/kg doses and 52% of those receiving 7.5 mg/kg doses did not have a sustained a response for more than 2 hours, whereas 75% of patients receiving 10 mg/kg doses had gastric acid suppression for longer than 2 hours. Of the patients receiving 15 mg/kg doses, 75% had a response for more than 2 hours; 50% of these patients had a response for more than 3 hours. We conclude that recommended doses of cimetidine for children may not be optimal for adequate gastric acid suppression.

Administration, Oral↗
PubMed1992

Molecular basis of lactase levels in adult humans.

The molecular basis of adult human "lactase deficiency" has long been a subject of controversy. To address this issue, small intestinal biopsies from orienta, black, and white patients were analyzed. Adjacent samples were assayed for lactase and sucrase specific activities and the sucrase/lactase ratio (high ratio signifies lactase deficiency), and the results were compared to lactase steady-state mRNA levels detected in Northern blots probed with a human lactase mDNA. All oriental patients had high ratios and no detectable lactase mRNA. Four black patients had a similar pattern; two with low ratios had detectable mRNA. The group of white patients displayed a range of findings, from high ratio/no mRNA to low ratio/considerable mRNA. Elevated levels of lactase mRNA always correlated with the presence of elevated levels of lactase enzyme activity, suggesting that the difference in levels of adult human intestinal lactase activity among racial groups may be regulated at the level of gene transcription.

Adult↗
PubMed1992

Cellular localization and T antigen binding of the retinoblastoma protein.

Mutation of the retinoblastoma (Rb) gene is found frequently in human sarcomas, lung, bladder and breast carcinomas and is the molecular basis for hereditary predisposition to retinoblastoma. The Rb protein is a nuclear phosphoprotein that is differentially phosphorylated during the cell cycle. Its precise function is unknown but it has been suggested that it may act as a transcriptional regulator or as a regulator of cellular DNA synthesis. The Rb protein forms specific complexes with the oncogenes of three different groups of DNA tumour viruses. We have prepared a new monoclonal antibody to the Rb protein and used it to establish sensitive immunoassays for Rb complexed to T antigen. In SV40-infected and transformed cells these assays showed that Rb enters a trimolecular complex containing p53, Rb and T. A large panel of human tumour cell lines was tested for expression, cellular localization and T-binding activity of Rb using the new antibody.

Antibodies, Monoclonal↗
PubMed1991

Cortisone and thyroxine modulate intestinal lactase and sucrase mRNA levels and activities in the suckling rat.

Glucocorticoids and thyroxine modulate postnatal intestinal sucrase and lactase activities. Whether changes in enzyme activity are accompanied by changes in enzyme mRNA levels were determined in day 6 rats given thyroxine, cortisone, or thyroxine plus cortisone and killed 3 days later. Cortisone induced precocious expression of jejunal sucrase activity which was enhanced when cortisone plus thyroxine was administered; sucrase mRNA changed in parallel. Jejunal lactase activity was unaffected by thyroxine and was increased after cortisone, but not after thyroxine plus cortisone. Jejunal lactase mRNA levels increased equally after cortisone or after cortisone plus thyroxine. Thus, cortisone induces coordinated increases in sucrase and lactase activities and in corresponding mRNA levels. Thyroxine only enhances cortisone induced sucrase expression and antagonizes cortisone by depressing lactase activity post-translationally.

Animals↗
PubMed1991

The human intestinal response to enteral nutrients: a review.

This review identifies the factors which influence mucosal integrity during enteral nutrition. These include biliary and pancreatic secretions, trophic influences of endocrine and gastrointestinal polypeptides, intestinal blood flow, and innervation. Fiber, bacterial fermentation products, purines, and glutamines are potential essential nutrients which may not be provided by parenteral nutrition. However, contrary to experience in animal models, the specific advantages of intraluminal delivery of nutrients for the maintenance of mucosal integrity and structure remain unproven in the human. Current evidence in the human suggests that changes in small bowel structure and function when enteral nutrients are excluded are minor and rapidly reversible as long as general nutritional status is maintained.

Animals↗
PubMed1991

Lactose intolerance and the genetic regulation of intestinal lactase-phlorizin hydrolase.

Lactase-phlorizin hydrolase, which hydrolyzes lactose, the major carbohydrate in milk, plays a critical role in the nutrition of the mammalian neonate. Lactose intolerance in adult humans is common, usually due to low levels of small intestinal lactase. Low lactase levels result from either intestinal injury or (in the majority of the world's adult population) alterations in the genetic expression of lactase. Although the mechanism of decreased lactase levels has been the subject of intensive investigation, no consensus has yet emerged. Recent studies have begun to define the cellular and molecular biology of this enzyme. In animals and humans, a glycosylated precursor is proteolytically cleaved to yield the mature enzyme on the microvillus membrane of the enterocyte, bound to the lipid bilayer only by a hydrophobic anchor sequence. The enzyme hydrolyzes lactose, phlorizin, and glycosylceramides. A decline in lactase specific activity occurs at the time of weaning in most mammalian species; in most humans who have low lactase activity as adults, the decline occurs at approximately 3-5 years of age. In a few human groups, the elevated juvenile level of lactase specific activity persists throughout adulthood. These developmental patterns of lactase expression are most likely regulated at the level of gene transcription.

Animals↗
PubMed1991

Crohn's disease associated with autoimmune neutropenia.

We report a 29-year-old woman with a 20-year history of Crohn's disease and neutropenia. Because of repeated complications of Crohn's disease, she has undergone three intestinal resections and also has had recurrent skin abscesses, sinusitis, and pneumonia. Persistent neutropenia has been noted throughout the course of her disease, and antineutrophil antibodies have been detected in her serum and that of her younger brother, who also has Crohn's disease and neutropenia. We discuss autoimmune neutropenia in the context of other autoimmune manifestations of Crohn's disease and speculate as to its possible contributory role in the pathogenesis of Crohn's disease.

Adult↗
PubMed1991

The use of beta-galactosidase fusion proteins encoding the early region 1 transforming proteins of adenovirus type 12 to examine the humoral response in tumour-bearing animals.

Sera from 26 rats bearing tumours induced by wild-type (wt) and mutant human adenovirus type 12 (Ad12), or by cells transformed with these viruses, were analysed for antibodies against the early region 1 (E1) transforming proteins. Six Ad12-beta-galactosidase fusion proteins encoding different regions of the Ad12 E1 proteins were constructed. The sera from the tumour-bearing animals reacted most strongly with the fusion protein encoding the N terminus of the E1A protein. Tumour-bearing rats exposed to the E1B 54K and 19K proteins showed strong reactions with the N terminus of the 54K protein and the C terminus of the 19K protein. Monospecific polyclonal antisera were raised against five of the fusion proteins by immunization of rats and rabbits; these sera cross-reacted with the purified native protein. No antibodies could be obtained which recognized a fusion protein containing amino acids 136 to 268 of the 54K protein. The fusion proteins were also used to purify monospecific antisera from tumour-bearer sera using affinity chromatography.

Adenoviridae Infections↗
PubMed1991

Induction of Epstein-Barr virus lytic cycle by tumor-promoting and non-tumor-promoting phorbol esters requires active protein kinase C.

Exposure to the tiglian 12-O-tetradecanoylphorbol-13-acetate (TPA) represents one of the most efficient and widely used protocols for inducing Epstein-Barr virus (EBV)-infected cells from latent into lytic cycle. Since TPA is both a potent tumor promoter and a potent activator of the cellular protein kinase C (PKC), we sought to determine whether either of these activities was closely linked to EBV lytic cycle induction. A panel of TPA structural analogs, encompassing tiglians with different spectra of biological activities, was assayed on a number of EBV-positive B-lymphoid cell lines. Lytic cycle induction correlated with the capacity to activate PKC, not with tumor promoter status; some nonpromoting tiglians were as efficient as TPA in inducing lytic cycle antigen expression. We then sought more direct evidence for an involvement of PKC in the induction process. In initial experiments, 1-(5-isoquinolinyl sulphonyl)-2-methylpiperazine (H-7), the best available pharmacological inhibitor of PKC, completely blocked the induction of the lytic cycle by TPA and its active analogs. This is consistent with, but does not prove, a requirement for active PKC in the induction process, since H-7 targets PKC preferentially but also has some effects on other kinases. We therefore turned to the synthetic pseudosubstrate peptide PKC(19-36) as a means of specific PKC inhibition and to the closely related but inactive peptide PKC(19-Ser-25-36) as a control. Using the technique of scrape loading to deliver the peptides into cells of an adherent EBV-positive target line, we found that the pseudosubstrate peptide PKC(19-36) completely and specifically blocked tiglian-induced entry of the cells into the lytic cycle. The evidence both from TPA analogs and from enzyme inhibition studies therefore indicates that the pathway linking TPA treatment to lytic cycle induction involves active PKC. Interestingly, inhibition of PKC had no effect upon the spontaneous entry into lytic cycle which occurs in naturally productive cell lines, suggesting that spontaneous entry is signalled by another route.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Clinical aspects of lactose intolerance in children and adults.

The principal carbohydrate of human milk is the disaccharide lactose. In human and all mammalian species, lactose is hydrolyzed in the small intestine by lactase-phlorizin hydrolase, also abbreviated as lactase. The absence of lactase results in the passage of undigested lactose into the large intestine and is associated with a well-known clinical syndrome: lactose intolerance. Low lactase levels result either from intestinal injury or, as in the majority of world's adult population, from alterations in the genetic expression of lactase. In this review terminology, pathophysiology, symptoms, diagnostic procedures, and therapy of lactose intolerance will be discussed.

Adult↗