Neuroendo 9/11

Andrew Wakefield (1998)

Published fraudulent study claiming MMR vaccine caused autism; led to drop in vaccination rates and rise in measles cases.

Research bias

When study design, data collection, or interpretation is influenced by expectations or external pressures, leading to misleading or harmful conclusions.

MMR vaccine fraud consequence

Caused vaccine hesitancy, decreased immunization rates, and resurgence of preventable diseases.

Peptide hormones

Short chains of amino acids (e.g., oxytocin, vasopressin); usually under 50 amino acids.

Protein hormones

Longer amino acid chains (e.g., growth hormone).

Nonapeptides

Peptides with 9 amino acids; oxytocin and vasopressin are nearly identical nonapeptides.

Oxytocin (OT)

A nonapeptide hormone from magnocellular neurons; involved in milk letdown and uterine contractions.

Vasopressin (AVP, antidiuretic hormone)

A nonapeptide hormone from magnocellular neurons; regulates blood pressure and water retention in kidneys.

Peptide hormone properties

Polar, hydrophilic, lipophobic; soluble in blood without carriers; cannot cross cell membranes; act via cell surface receptors.

Peptide hormone synthesis

DNA → mRNA → ribosome translates prepropeptide (signal peptide + hormone + copeptides).

Prepropeptide

Inactive precursor containing a signal peptide, hormone sequence, and copeptides.

Signal peptide

Directs the prepropeptide into the endoplasmic reticulum for processing.

Propeptide

Intermediate product after signal peptide is removed; requires further enzymatic cleavage.

Convertases (prohormone convertases)

Enzymes in secretory vesicles that cleave propeptides into active hormones and copeptides.

Copeptides

By-products of propeptide cleavage, released along with the active hormone.

Secretory vesicles

Intracellular storage granules containing peptide hormones and enzymes; release contents by exocytosis when calcium levels rise.

Regulated secretion

Hormone release controlled by signals such as calcium influx; ensures hormones are secreted only when needed.

Exocytosis

Process where vesicles fuse with the plasma membrane to release stored hormones into extracellular space.

Specificity in blocking vasopressin

Must target vasopressin receptors, gene, or processing enzymes without affecting oxytocin, since they are structurally similar.