Cell biology

Septum

A septum is a wall or partition that a dividing cell builds between itself and its daughter cell, made of peptidoglycan in bacteria and of cell wall material in fungi.

seqFISH

seqFISH (sequential fluorescence in situ hybridization) is an imaging-based spatial transcriptomics method that localizes RNA in fixed cells; its seqFISH+ variant images 10,000 genes per cell.

Sequential fluorescence in situ hybridization

Sequential fluorescence in situ hybridization (seqFISH) is a multiplexed RNA imaging method that repeatedly hybridizes, images, and strips probes to barcode transcripts in fixed cells.

Serial block-face electron microscopy

Serial block-face electron microscopy (SBEM, also SBF-SEM) is a volume electron microscopy method that repeatedly images and slices resin-embedded tissue, producing 3D datasets of cellular ultrastructure.

Serial passage

Serial passage is a bench technique that repeatedly transfers cells or microbes into fresh environments, selecting variants adapted to them, which often means loss of virulence.

Serous membrane

Serous membrane (serosa): mesothelium plus connective tissue lining closed body cavities; pleura, pericardium, peritoneum; parietal and visceral layers; secretes friction-reducing serous fluid; transports fluid, aids repair, inflammation, and tumor adhesion.

Serous secreting cell

Serous secreting cell (serous cell, CL:0000313) is an exocrine gland cell secreting watery, protein-rich, mucin-free fluid; found in salivary, pancreatic, lacrimal, and airway glands, it secretes most salivary fluid plus antimicrobials like lysozyme and lactoferrin.

SGC-7901

SGC-7901 (SGC7901, CVCL_0520) is a human cell line established in China in 1982 as a gastric adenocarcinoma model but shown by STR profiling to be a HeLa derivative, registered as misidentified (ICLAC-00577) yet still widely used.

SH-SY5Y

SH-SY5Y (CVCL_0019, ATCC CRL-2266, ECACC 94030304) is a human neuroblastoma cell line, a thrice-cloned subline of SK-N-SH from a 1970 pediatric bone marrow biopsy, used as a differentiable neuronal model in neuroscience and toxicology research.

Sheath cell (sensu Nematoda)

Sheath cell (sensu Nematoda): glial cell of nematode sensilla that ensheaths sensory neuron dendritic tips, paired with a socket cell; exemplified by C. elegans AMsh glia, which secrete extracellular matrix and are required for sensory ending structure and function.

Shiga toxin

Shiga toxin (Stx, verotoxin, Shiga-like toxin): AB5 cytotoxin of Shigella dysenteriae type 1 and STEC that cleaves adenine 4324 in 28S rRNA after Gb3 binding and retrograde transport, causing HUS; Stx1 and Stx2 subtypes differ in potency.

Signal peptide

Signal peptide: N-terminal peptide directing protein secretion via SRP, Sec, or Tat pathways; tripartite N-H-C structure, 15-30 residues, cleaved by signal peptidase; Tat type carries twin-arginine motif.

Signal transduction

Signal transduction, also known as cell signaling, is the process by which a cell converts signals such as hormones and growth factors into specific responses via receptors and second messengers.

Oct 20, 2026

SiHa

SiHa (CVCL_0032, ATCC HTB-35) is an HPV16-positive human cervical squamous cell carcinoma cell line established in 1970 from a 55-year-old Japanese patient, widely used in cervical cancer research.

Silver Staining

Silver staining: metal-impregnation technique introduced by Golgi in 1873 (black reaction) and shared by Golgi and Cajal's 1906 Nobel Prize; detects low-ng proteins in gels, fungi (GMS), spirochetes (Warthin-Starry), and tau pathology, but has narrow dynamic range and MS incompatibility.

Single-cell proteomics

Single-cell proteomics measures the identity and abundance of proteins in individual cells, using mass spectrometry or antibody-based assays; protein abundances span one to ten million copies per cell.

Oct 15, 2026

Single-molecule fluorescence in situ hybridization

Single-molecule fluorescence in situ hybridization (smFISH) is a molecular biology method that counts individual RNA molecules in fixed cells using many short fluorescent probes, making each transcript a visible spot.

Oct 20, 2026

Sister chromatid cohesion protein Pds5

Pds5 (precocious dissociation of sisters 5; PDS5A/PDS5B in vertebrates) is a conserved cohesin-associated regulator that stops loop extrusion by displacing NIPBL, promotes Smc3 acetylation, protects replication forks, and shapes 3D genome organization.

SJNB-10

SJNB-10 (SJ-NB-10, NB10, NB90-9; CVCL_1441) is a human neuroblastoma cancer cell line from a 2-year-old male with an adrenal primary and liver metastasis, characterized by homozygous NF1 deletion, loss of neurofibromin, and retinoic acid resistance.

SJNB-12

SJNB-12 is a human neuroblastoma cell line derived from a bone marrow metastasis in a female infant sampled at 10 months of age, with high BCL-2 expression.

SJSA-1

SJSA-1 (OsA-CL, OSA; ATCC CRL-2098, RRID CVCL_1697) is a human osteosarcoma cell line established in 1982 from a 19-year-old male's femur tumor, distinguished by ~20-fold MDM2 amplification with wild-type TP53.

SK-BR-3

SK-BR-3 (SKBR3), ATCC HTB-30, Cellosaurus CVCL_0033: human breast adenocarcinoma cell line established 1970 from a pleural effusion; HER2-positive, ER/PR-negative standard model for HER2-targeted therapy research.

SK-ES-1

SK-ES-1 (SK-ES-01, CVCL_0627) is a human Ewing sarcoma cell line established in 1971 from an 18-year-old male's bone biopsy at Memorial Sloan Kettering; it carries an EWSR1-FLI1 type 2 fusion and TP53 C176F.

SK-HEP-1

SK-HEP-1 (CVCL_0525, ATCC HTB-52) is a human cancer cell line established in 1971 from ascites of a 52-year-old man with liver adenocarcinoma; long used as a hepatocellular carcinoma model but now shown to be of endothelial origin.

SK-LU-1

SK-LU-1 (SKLU01, ATCC HTB-57, Cellosaurus CVCL_0629) is a human lung adenocarcinoma cell line established in 1969; KRAS G12D, CDKN2A-deleted, telomerase-negative and ALT-positive, non-tumorigenic in immunocompromised mice.

SK-MEL-2

SK-MEL-2 (CVCL_0069, ATCC HTB-68) is a human melanoma cell line from a 60-year-old male, established at Memorial Sloan Kettering; NRAS Q61R-mutant, TP53 G245S, NCI-60 panel member.