SUMMARYWe have isolated 38 viruses capable of infecting Caulobacter crescentus. Twentyeight of these isolates were DNA phages with a prolate cylindrical head and a long flexible tail. Each of them infected only one of the Caulobacter cell types, the swarmer cell, and many proved to be capable of establishing a lysogenic relationship with their host. Despite structural similarity and host cell specificity, the majority of these DNA phages appeared to be genetically distinct as shown by EcoRI restriction patterns of their DNA and by host range on phage resistant and lysogenic strains. Two isolates were small RNA phages, structurally similar to the Escherichia coli RNA phages, which specifically adsorbed to pili on the Caulobacter swarmer cell. The remaining eight isolates were DNA phages with polyhedral heads ranging from 60 to 16o nm in diameter. Six had contractile tails ranging from 50 to I6O nm in length, while two had long flexible non-contractile tails. Each of these isolates was capable of attaching to all Caulobacter cell types and two were capable of mediating generalized transduction between strains of Caulobacter (Ely & Johnson, I977).

Expression of interrelated gene products regulating cell proliferation and apoptosis may be disordered in squamous cell carcinoma (SCC) of the larynx compared with normal squamous mucosa. Certain of these abnormalities, alone or in combination, may be of prognostic significance in low-stage carcinomas of the larynx. A retrospective study of archival material was made. Expression of the Bcl-2 family of apoptosis-related genes (bcl-2, bcl-X, mcl-1, and bax) and the proliferation- and apoptosis-related genes p53 and cyclin D-1 were determined in 40 low-T-stage laryngeal carcinomas and in uvular epithelium from patients without SCC. Among the antiapoptotic members of the Bcl-2 family, Bcl-X and Mcl-1 showed more intense and widespread staining than Bcl-2 itself in both normal squamous mucosa and SCC. The well-ordered expression patterns of Bcl-2-related proteins found in normal epithelium were lost in SCC, and patterns of expression varied widely among individual tumors. Also, mean expression levels for Bax and cyclin D-1 were significantly lower than in normal epithelium (P = .036 and P = .009, respectively), whereas expression of p53 was higher in tumors (P = .034). Expression of Bcl-X and Mcl-1 was greater in poorly differentiated than in well-differentiated tumors (P = .014 and P = .031, respectively). No associations were seen between marker expression patterns and clinical outcome in this group of patients. Bcl-x and Mcl-1 appear to be the most abundantly expressed antiapoptotic proteins of the Bcl-2 family in both normal squamous mucosa and SCC of the larynx. Multiple genes regulating proliferation and apoptosis are expressed abnormally in laryngeal SCC compared with normal epithelium. In particular, loss or measurable decrease in expression of the proapoptotic protein Bax in tumors may contribute to the deranged growth control of SCC. Further study is needed to evaluate the prognostic significance of particular patterns of disordered expression of proteins regulating proliferation and apoptosis in SCC of different head and neck sites.

Rapid proliferation of squamous cell carcinomas of the head and neck (SCCHN) during therapy may contribute to treatment failure. We have investigated the presence of p53 abnormalities in patients with SCCHN as a correlate of proliferation rate and other pathologic and clinical variables. p53 Mutation, as determined by polymerase chain reaction and single-strand conformation polymorphism analysis of microdissected frozen sections of tumor biopsies, was significantly associated with a high labeling index, as determined by in vivo infusion of IUdR and BrdU (P = 0.017). p53 Protein expression was detected by immunohistochemistry with two different antibodies, followed by quantitative image analysis. Many cases exhibited strong p53 protein expression in the absence of mutations within the conserved region of the gene, and expression was not related to proliferation. The presence of p53 mutations was related to tumor differentiation in this group of patients.