Histologic diagnoses in persistently swollen cervical lymph nodes.

BACKGROUND: Biopsy and histological examination of persistently enlarged cervical lymph nodes represent a major health care issue and have high impact on further clinical therapy. Tertiary health centers are faced with an increased demand for diagnostic workup to rule out malignancy. We performed a retrospective study from January 2000 to June 2008 to identify patients referred to us for diagnostic biopsy and to document the histopathological result. METHODS: Patients with a diagnostic biopsy, but neither clinical signs of head and neck cancer nor other malignancies, were identified within the records. Patient characteristics and histopathological diagnosis were retrieved. RESULTS: Three hundred twenty-six patients were identified (146 women, and 180 men). One hundred twenty-three patients (38%; 44 women, and 79 men) had a malignancy: 61 with metastatic disease and 62 with malignant lymphoma; the youngest was 15 years old and the oldest was 92 years old. CONCLUSION: Persistently swollen cervical lymph nodes should trigger a thorough clinical examination and prompt biopsy for histopathological workup.

Single amino acids in the lumenal loop domain influence the stability of the major light-harvesting chlorophyll a/b complex.

The major light-harvesting complex of photosystem II (LHCIIb) is one of the most abundant integral membrane proteins. It greatly enhances the efficiency of photosynthesis in green plants by binding a large number of accessory pigments that absorb light energy and conduct it toward the photosynthetic reaction centers. Most of these pigments are associated with the three transmembrane and one amphiphilic alpha helices of the protein. Less is known about the significance of the loop domains connecting the alpha helices for pigment binding. Therefore, we randomly exchanged single amino acids in the lumenal loop domain of the bacterially expressed apoprotein Lhcb1 and then reconstituted the mutant protein with pigments in vitro. The resulting collection of mutated recombinant LHCIIb versions was screened by using a 96-well-format plate-based procedure described previously [Heinemann, B., and Paulsen, H. (1999) Biochemistry 38, 14088-14093], enabling us to test several thousand mutants for their ability to form stable pigment-protein complexes in vitro. At least one-third of the positions in the loop domain turned out to be sensitive targets; i.e., their exchange abolished formation of LHCIIb in vitro. This confirms our earlier notion that the LHCIIb loop domains contribute more specifically to complex formation and/or stabilization than by merely connecting the alpha helices. Among the target sites, glycines and hydrophilic amino acids are more prominently represented than hydrophobic ones. Specifically, the exchange of any of the three acidic amino acids in the lumenal loop abolishes reconstitution of stable pigment-protein complexes, suggesting that ionic interactions with other protein domains are important for correct protein folding or complex stabilization. One hydrophobic amino acid, tryptophan in position 97, has been hit repeatedly in independent mutation experiments. From the LHCIIb structure and previous mutational analyses, we propose a stabilizing interaction between this amino acid and F195 near the C-proximal end of the third transmembrane helix.