Fine structural observations of sperm resorption in the seminal vesicle of a marine snail, Littorina scutulata (Gould, 1849)

The fine structure of the spermatogonium, spermatocyte and spermatid of a marine snail, Littorina sitkana is described. The ring centriole (annulus) is formed from the distal centriole and it migrates to the base of the mitochondrial region where it lies in a joint-like structure which is formed by an area of invaginated plasma membrane. The distal and proximal centrioles are at first perpendicular to each other but the proximal centriole rotates to a position coaxial with the distal centriole and fuses with it. The peripheral doublet fibers are continuous between the two centrioles but the central fibers originate only in the distal centriole. The acrosome differentiates from the proacrosomal granule which is derived from a Golgi body. Microtubules, present at this stage, may assist acrosomal formation. Chromatin condensation begins with the formation of fibrous strands, then to lamellar plates which become folded and later twisted around the flagellar shaft. In the final stages the lamellae appear in cross section as concentric rings which eventually fuse to form a homogeneously dense nuclear tube.     

Theoretical explanation of the relationship between backscattered electron and x-ray linear attenuation coefficients in calcified tissues

Adverse reactions to seafood are common and may cause many types of symptoms that are difficult to define. The nature of these reactions are variable including allergic and toxic reactions as well as infectious diseases. The differentiation between these entities is essential in choosing therapy. We describe 9 patients with IgE mediated allergic reactions due to crustaceans and fish diagnosed from case history, clinical findings, skin tests and specific IgE antibodies. Most symptoms of a IgE mediated allergic reaction appear within 30 minutes after ingestion. Characteristics clinical features may include an urticarial rash, gastrointestinal symptoms and even anaphylaxis. In this case immediate therapy with intravenous glucocorticoids, antihistamine and perhaps subcutaneous epinephrine is required.     

Renovascular arterial hypertension. Importance of subtraction digital angiography in its diagnosis

The objective of this study is to contribute to the positioning of the intravenous digital subtraction angiography (IVDSA) in the detection of morphologic abnormalities of renal arteries (RAs), susceptible to originate renovascular hypertension (RVH). The authors focus on the prevalence of RVH in the broad spectrum of systemic arterial hypertension. The definition of RVH is given and its diagnostic criteria are revisited. The angiography methods used in the evaluation of RAs morphologic abnormalities are described.     

Artemisinin-derived sesquiterpene lactones as potential antitumour compounds: cytotoxic action against bone marrow and tumour cells

Epidemiologic and public health researchers frequently include several dependent variables, repeated assessments, or subgroup analyses in their investigations. These factors result in multiple tests of statistical significance and may produce type 1 experimental errors. This study examined the type 1 error rate in a sample of public health and epidemiologic research. A total of 173 articles chosen at random from 1996 issues of the American Journal of Public Health and the American Journal of Epidemiology were examined to determine the incidence of type 1 errors. Three different methods of computing type 1 error rates were used: experiment-wise error rate, error rate per experiment, and percent error rate. The results indicate a type 1 error rate substantially higher than the traditionally assumed level of 5% (p < 0.05). No practical or statistically significant difference was found between type 1 error rates across the two journals. Methods to determine and correct type 1 errors should be reported in epidemiologic and public health research investigations that include multiple statistical tests.