Biomedical subjects

Robert M Klein

Publications and source records attributed to Robert M Klein.

5 recordsLinked to original sources

PubMed2002

Ablation of the chemokine monocyte chemoattractant protein-1 delays retrograde neuronal degeneration, attenuates microglial activation, and alters expression of cell death molecules.

The mechanisms regulating retrograde neuronal degeneration and subsequent death of thalamic neurons following cortical injury are not well understood. However, the delay in the onset of retrograde cell death and observed morphological changes are consistent with apoptosis. Our previous studies demonstrated that monocyte chemoattractant protein-1 (MCP-1), a beta-chemokine that attracts cells of monocytic origin to sites of injury, is rapidly and specifically expressed in the lateral geniculate nucleus following visual cortical lesions. To determine the potential role of MCP-1 in retrograde degeneration, the present study examined the effect of genetic deletion of MCP-1 (MCP-1 KO or -/-) or its high affinity receptor CCR2 (CCR2 KO or -/-) on thalamic microglial activation and neuronal cell death following aspiration lesions of the visual cortex in adult mice. Deletion of the MCP-1 gene delayed microglial activation and transiently improved the survival of thalamic neurons. Deletion of the CCR2 receptor resulted in a significant increase in apoptosis as measured by nucleosomal fragmentation after injury compared to wild-type mice, but did not alter neuron survival, suggesting that glial apoptosis is increased in the receptor knockout mice. Investigation of Bcl-2, Bax, Fas, Fas ligand (FasL) and activated caspase-3, key regulators of apoptosis that can be modulated by cytokines, revealed complex alterations of mRNA and protein levels in MCP-1(-/-) and CCR2(-/-) mice. As examples, Bcl-2 protein was detected in wild-type, but not in MCP-1(-/-) mice. Caspase-3 activity was higher in MCP-1(-/-) mice compared to wild-type and CCR2(-/-) mice at 5 days after injury. High levels of activated caspase-3 correlate with the beginning of a period of delayed, but rapid cell death in the thalami of MCP-1(-/-) mice. In summary, our data strongly suggest that MCP-1 is involved in early microglial response to axotomy and that modulation of this chemokine could provide a novel strategy for improved neuronal survival following injury to the central nervous system.

Animals↗

PubMed2002

Lactose intolerance.

Persons with lactose intolerance are unable to digest significant amounts of lactose because of a genetically inadequate amount of the enzyme lactase. Common symptoms include abdominal pain and bloating, excessive flatus, and watery stool following the ingestion of foods containing lactose. Lactase deficiency is present in up to 15 percent of persons of northern European descent, up to 80 percent of blacks and Latinos, and up to 100 percent of American Indians and Asians. A sizable number of adults believe they are lactose intolerant but do not actually have impaired lactose digestion, and some persons with lactase deficiency can tolerate moderate amounts of ingested lactose. A diagnosis of lactose intolerance can usually be made with a careful history supported by dietary manipulation. If necessary, diagnosis can be confirmed by using a breath hydrogen or lactose tolerance test. Treatment consists primarily of avoiding lactose-containing foods. Lactase enzyme supplements may be helpful. The degree of lactose malabsorption varies greatly among patients with lactose intolerance, but most of them can ingest up to 12 oz of milk daily without symptoms. Lactose-intolerant patients must ensure adequate calcium intake.

Calcium, Dietary↗

PubMed2002

Cortical spreading depression and gene regulation: relevance to migraine.

Cortical spreading depression (CSD) may be the underlying mechanism of migraine aura. The role of CSD in initiating a migraine headache remains to be determined, but it might involve specific changes in gene expression in the brain. To examine these changes, four episodes of CSD at 5-minute intervals were induced in the mouse brain by application of 300mM KCl, and gene expression was examined 2 hours later using cDNA array and reverse transcriptase-polymerase chain reaction. Controls consisted of groups that received anesthesia only, attachment of recording electrodes only, and application of 0.9% NaCl. Of the over 1,180 genes examined in our experiments, those consistently regulated by CSD included vasoactive peptides; the vasodilator atrial natriuretic peptide was induced by CSD, while the vasoconstrictor neuropeptide Y was downregulated. Other genes specifically regulated by CSD were involved in oxidative stress responses (major prion protein, glutathione-S-transferase-5, and apolipoprotein E). L-type calcium channel mRNA was upregulated. In summary, CSD regulates genes that are intrinsic to its propagation, that identify accompanying vascular responses as a potential source of pain, and that protect against its potential pathological consequences. We believe these observations have strong relevance to the mechanisms of migraine and its outcomes.

Anesthetics↗

PubMed2002

Multiorgan mRNA misexpression in murine autosomal recessive polycystic kidney disease.

BACKGROUND: BALB/c mice homozygous for the cpk mutation develop a form of polycystic kidney disease (PKD) with multiorgan pathology similar to human autosomal recessive PKD. Messenger RNA expression in multiple affected organs was analyzed to determine if common gene cascades were misexpressed in the cystic kidney and extrarenal sites of disease. In cystic kidneys, misexpressed mRNAs were found in one of four general groups: proliferation/cell growth, apoptosis, differentiation or extracellular matrix. METHODS: RNA was isolated from kidney, liver and pancreas of cystic and normal BALB/c-cpk mice. Using Northern blot hybridization and ribonuclease protection assays (RPA), the expression of several genes thought to be associated with PKD, namely c-myc, epidermal growth factor receptor (EGF-R) and PKD-1, were evaluated. RPAs were used to assess mRNA expression of cyclins and members of the bax/bcl-2 family. In addition, kidney, liver and pancreas were immunostained for c-Myc and PCNA. RESULTS: Cystic kidney, liver and pancreas all exhibited similar patterns of mRNA misexpression of c-myc, EGF-R and PKD-1. In addition, a number of cell proliferation and apoptosis-related mRNAs also were elevated in cystic kidney and pancreas. Renal epithelial cells expressing proliferation-associated proteins [c-Myc and proliferating cell nuclear antigen (PCNA)] were nearly absent in normal kidney; however, cells of cystic and non-cystic renal tubules plus liver and pancreatic cyst exhibited an increased number of nuclei labeled with antibodies to these proteins. CONCLUSIONS: These data suggest that similar pathologic mechanisms (including the expression of c-myc, EGF-R, PKD-1, cyclin, and bax/bcl-2 family mRNAs) may be responsible for the development of cystic changes in kidney, liver and pancreas in murine autosomal recessive PKD. Treatments targeting these similarly misexpressed mRNAs may be efficacious in ameliorating the cystic pathology in the kidney as well as the other affected organs in ARPKD.

Animals↗

PubMed2002

A thematic approach to enhance clinical content in a cell and tissue biology course.

OBJECTIVE: (1) To integrate clinical problem solving into freshman cell and tissue biology (CTB) and (2) to enhance understanding of diabetes using CTB principles to explain the etiology, management, and development of complications in terms of cell, tissue, and organ structure and function. DESCRIPTION: First-year medical students often question the need to learn detailed basic science material. Although clinical content has increased throughout basic science courses, little attempt has been made to link clinical correlations to one another or to enhance use of basic science material in clinical problem solving. The CTB course applies pertinent cell biology concepts such as cell proliferation, differentiation, migration, adhesion, and morphogenesis to tissue and organ function. Diabetes mellitus was chosen as a theme for CTB as diabetes has devastating effects on multiple tissues, and the disease has reached epidemic proportions in the United States, affecting individuals of every age and population group. Type I diabetes, presenting as ketoacidosis in a ten-year-old boy, was introduced by generalist physicians using a "grand rounds" approach. This format challenged students on the first day of medical school to diagnose a patient's problem and to explain the clinical findings in terms of anatomic, biochemical, and physiologic changes. The role of the blood/bicarbonate buffering system was the main focus of faculty-led discussion. The patient was then presented at age 25 with many diabetic complications. This stimulated discussion of the etiology of diabetes (type I versus type II), glycation, and the use of hemoglobin (Hb) A1c to monitor blood sugar control. Compliance and other aspects of diabetes management were added to the discussion. Faculty provided scientific information as necessary, and summary materials were distributed after the sessions. The interaction of a cell biologist with two generalist physicians optimized the integration of basic science with clinical problem solving. During the two semesters of CTB, the diabetes case is frequently referenced. Insulin synthesis provides the model for protein synthesis. Glycation, advanced glycation end products (AGE), and receptors (RAGE) are discussed. Other diabetes-related topics include wound healing (epithelium), basement membrane thickening (connective tissue), insulin regulation of muscle metabolism, diabetic neuropathy (neurohistology), platelet adhesiveness, glycation and HbA1c (blood), osteoporosis and Charcot joints (skeletal system), autoimmune mechanisms (cellular immunology), atherosclerosis and high blood pressure (blood vessels), diabetic nephropathy (renal), altered hepatic and gastrointestinal function, impotence (male reproductive system), and a comparison of type I and type II diabetes (endocrine system). DISCUSSION: Students have provided very positive feedback. The initial case enhanced interest in CTB, established clinical relevance, and has motivated learning and integration of materials from different parts of CTB and other courses. Other courses are now formally linking to the theme. For example, neuroscience will revisit diabetic neuropathy and retinopathy, physiology will relate ketoacidosis to acid-base balance, a human anatomy clinical correlation is being designed for transplantation surgeons to "cure" our diabetic patient with a renal-pancreas transplant. Uses of the case for introduction to clinical medicine, aspects of medical ethics, preventive medicine, and courses in pharmacology and pathology are contemplated.

Biology↗