The relationship between Schistosoma mansoni and Biomphalaria glabrata: genetic and molecular approaches.

Biomphalaria glabrata is a major intermediate host for the helminth parasite Schistosoma mansoni. Beginning in the mid-20th century, studies were carried out with this snail species to identify the immunological and genetic components that might be involved in controlling schistosome development. A number of genetically well-defined snail stocks were derived as a direct result of these studies and have since played major roles in helping investigators to identify important cellular and humoral components in the snail/schistosome relationship. This review will explore the historical development of these stocks and describe some of the major advances in several areas of medical malacology that hawe been made possible be their use.

The identification of markers segregating with resistance to Schistosoma mansoni infection in the snail Biomphalaria glabrata.

Both snail and parasite genes determine the susceptibility of the snail Biomphalaria glabrata to infection with the trematode Schistosoma mansoni. To identify molecular markers associated with resistance to the parasite in the snail host, we performed genetic crosses between parasite-resistant and -susceptible isogenic snails. Because resistance to infection in adult snails is controlled by a single locus, DNA samples from individual F2 and F1 backcross progeny, segregating for either the resistant or susceptible phenotypes, were pooled (bulked segregant). Genotypes for both parents were determined with 205 arbitrary decamer primers by random amplified polymorphic DNA-PCR. Of the 205 primers, 144 were informative, and the relative allele frequencies between the pools for these primers were determined. Two primers, OPM-04 and OPZ-11, produced fragments in the resistant parent of one cross that were inherited in a dominant fashion in the resistant F2 and backcross-bulked segregant progeny. Subsequent typing of DNA samples of individual progeny snails showed that the 1.2-kb marker amplified by primer OPM-04 and the 1.0-kb marker produced by primer OPZ-11 segregated in the same dominant fashion with the resistant phenotype. Sequence analysis of the 1.2-kb marker showed that it corresponds to a repetitive sequence in the snail genome with no homology to existing DNA sequences in the public databases. Analysis of the 1. 0-kb marker showed that it also corresponds to a repetitive sequence in the B. glabrata genome that contains an imperfect ORF, with homology to retrovirus-related group-specific antigens (gag) polyprotein.

Surgery of the crooked nose.

The approach to surgery of the crooked nose has changed significantly in the last two decades due in a large measure to a better understanding of the growth, anatomy, and physiology of the nose. The crooked nose often presents a challenging problem to the surgeon because of the multiplicity of deformities. In most cases, deformities of the external bony and cartilaginous nose, septum and turbinates must all be corrected simultaneously in order to obtain a satisfactory and lasting restoration of the nasal airway as well as the external nasal configuration.

The aging nose: characteristics and correction.

The effects of aging are particularly manifested in the face. The vertical dimension of the lower third of the face decreases but the same dimension increases in the nose. The chin moves up; the nose droops down. In order to restore normal nasal physiologic function in persons who present with this type of nose, correction of the cartilaginous and occasionally the bony external nose is necessary. This produces an improved physiologic and cosmetic result.

Evaluation of sclera as a homograft in facial plastic and reconstructive surgery.

Augmentation of deficient soft tissue contours accounts for a large part of facial plastic and reconstructive surgery. An attempt to use homograft sclera in the feline animal model is presented. Augmentation of nasal dorsum and the chin contours was carried out in the cat model with preserved homograft sclera. Serial soft tissue radiographs and histologic study of the homografts demonstrated complete resorption of the grafts by six months. Further physical and chemical alterations of homograft sclera appear to be necessary prior to its implantation for the purpose of soft tissue augmentation.

Parasympathetic nerve section for control of sialorrhea.

Twenty mentally retarded patients with a considerable drooling problem underwent transtympanic sectioning of selected preganglionic parasympathetic nerve fibers to the major salivary glands. Following surgery, cessation of trouble-some sialorrhea occurred in 15 to 20 patients; but by six months postoperatively, only ten patients remained controlled. The best results obtained were in a subgroup of five patients who underwent bilateral Jacobson nerve and chorda tympani nerve section. In four of these patients, sialorrhea was controlled after a minimum follow-up of two years. Parasympathetic denervation of the major salivary glands via a transtympanic approach is offered as a primary modality of therapy in those mentally retarded patients judged to have considerable sialorrhea. Sacrifice of both chorda tympani nerves appears to enhance the surgical results.

Symposium: the supra-tip in rhinoplasty: a dilemma. I. Theories and causes of supra-tip convexities.

Supratip convexities following rhinoplasty present a challenge to the surgeon. The correct diagnosis as to cause is necessary for proper correction. The pertinent anatomy of this area -- the theories, causes, suggested methods of prevention and correction -- are presented.

Infectious mononucleosis, mastoiditis, and facial paralysis.

To our knowledge this is the first report of a patient with infectious mononucleosis associated with a mononuclear granulomatous mastoiditis and facial paralysis. Pathologic examination of tissue from this patient, removed at the time of radical mastoidectomy, provides a basis for further speculation about the relationship between facial paralysis and infectious mononucleosis.