Foreign serum-induced pancreatitis in mice. II. Secretory disturbances of acinar cells

As previously reported, pancreatic acinar cell necrosis and inflammation develop in mice a few hours after one intraperitoneal injection of foreign serum. However, sublethally injured acinar cells exhibited notable increases in both zymogen granule numbers and amylase activity, observed within 3 hours and increasing with time. These two changes were coupled with a progressive decrease in the secretory response to pilocarpine and were preceded by significant disturbances in pancreatic tissue concentrations of sodium and potassium. We conclude that (1) the granule increase results from an induced disturbance of the granule exocytosis mechanism while granule formation continues and, therefore, (2) the granule secretory process is more sensitive to the serum injury mechanism than is the zymogen synthesis process. Although the granule increases developed in acinar cells throughout most of the nonnecrotic gland and persisted for at least 24 hours, acinar cell necrosis was maximal in extent--approximately 25% of the gland in severest form--by 12 to 15 hours. We conclude, therefore, that the increase in granules is neither the primary determinant nor initiator of acinar cell death. The latter is likely caused by disturbed plasma membrane functions, sufficient in some cells to result in lethal changes in ion and fluid composition. The injury mechanism, which permits granule formation to go on in the face of impaired granule exocytosis, is yet to be worked out. The possibilities are discussed in relationship to the reactivity of foreign sera for target cell plasma membranes.     

The alpha subunit of toluene dioxygenase from Pseudomonas putida F1 can accept electrons from reduced FerredoxinTOL but is catalytically inactive in the absence of the beta subunit

The oxygenase component of toluene dioxygenase from Pseudomonas putida F1 is an iron-sulfur protein (ISPTOL) consisting of alpha (TodC1) and beta (TodC2) subunits. Purified TodC1 gave absorbance and electron paramagnetic resonance spectra identical to those given by purified ISPTOL. TodC1 was reduced by NADH and catalytic amounts of ReductaseTOL and FerredoxinTOL. Reduced TodC1 did not oxidize toluene, and catalysis was strictly dependent on the presence of purified TodC2.     

T helper 2-dominant antilymphoma immune response is associated with fatal outcome

The precise role of the endogenous immune system in modulating cancer development remains unclear. Tumor cells are generally thought to be nonimmunogenic because they are of 'self' origin. However, tumor-reactive lymphocytes can be isolated from patients with many types of cancer. It is unclear what role these lymphocytes play and why they fail to protect the host. Using a murine B-cell leukemia/lymphoma (BCL1) model, we showed the development of a vigorous antitumor T-cell response in the tumor-susceptible host. Specific T-cell responses against BCL1 developed as early as day 4. However, the nature of this nonprotective response is different from the protective response produced in a major histocompatibility complex-matched tumor-resistant host. Susceptible hosts developed a T helper 2 (Th2)-dominant response, whereas resistant hosts developed a Th1-dominant response to BCL1. Cytolytic activity against BCL1 developed in both resistant and susceptible hosts, but in the susceptible host, this response was weaker and delayed compared with that in the resistant host. Thus, tumor susceptibility does not necessarily mean the absence of an antitumor immune response. Rather, the nature of the antitumor immune response is critical in determining clinical outcome.     

Progress in protein structure prediction

If protein structure prediction methods are to make any impact on the impending onerous task of analyzing the large numbers of unknown protein sequences generated by the ongoing genome-sequencing projects, it is vital that they make the difficult transition from computational 'gedankenexperiments' to practical software tools. This has already happened in the field of comparative modelling and is currently happening in the threading field. Unfortunately, there is little evidence of this transition happening in the field of ab initio tertiary-structure prediction.     

CATH--a hierarchic classification of protein domain structures

BACKGROUND: Protein evolution gives rise to families of structurally related proteins, within which sequence identities can be extremely low. As a result, structure-based classifications can be effective at identifying unanticipated relationships in known structures and in optimal cases function can also be assigned. The ever increasing number of known protein structures is too large to classify all proteins manually, therefore, automatic methods are needed for fast evaluation of protein structures. RESULTS: We present a semi-automatic procedure for deriving a novel hierarchical classification of protein domain structures (CATH). The four main levels of our classification are protein class (C), architecture (A), topology (T) and homologous superfamily (H). Class is the simplest level, and it essentially describes the secondary structure composition of each domain. In contrast, architecture summarises the shape revealed by the orientations of the secondary structure units, such as barrels and sandwiches. At the topology level, sequential connectivity is considered, such that members of the same architecture might have quite different topologies. When structures belonging to the same T-level have suitably high similarities combined with similar functions, the proteins are assumed to be evolutionarily related and put into the same homologous superfamily. CONCLUSIONS: Analysis of the structural families generated by CATH reveals the prominent features of protein structure space. We find that nearly a third of the homologous superfamilies (H-levels) belong to ten major T-levels, which we call superfolds, and furthermore that nearly two-thirds of these H-levels cluster into nine simple architectures. A database of well-characterised protein structure families, such as CATH, will facilitate the assignment of structure-function/evolution relationships to both known and newly determined protein structures.     

Declining sperm counts in the United States? A critical review

PURPOSE: Recent reports suggest declining sperm counts in the United States. These reports did not include all available data and did not account for geographic variations noted in prior studies. We examined all available data on U.S. sperm counts and evaluated whether geographic variations account for the decline suggested. MATERIALS AND METHODS: We reviewed all 29 U.S. studies from 1938 to 1996 reporting manually counted semen analyses of 9,612 fertile or presumably fertile men. We determined mean sperm concentrations by geographic location with weighted analysis of variance, and assessed any changes with time by linear regression analysis. RESULTS: Mean sperm concentrations from New York were significantly higher than from all other U.S. cities (98.6 versus 71.6 x 10(6) sperm per cc, respectively, p = 0.006). There has been no statistically significant change with time for mean sperm concentrations reported from New York (p = 0.49) or from U.S. cities other than New York (p = 0.62). Analysis without separating by location revealed a decline (p = 0.047). CONCLUSIONS: Sperm concentrations are highest in New York compared to other U.S. cities. When accounting for this geographic difference and examining all available data, there appears to be no significant change in sperm counts in the U.S. during the last 60 years. Further studies addressing the causes of geographic variations are needed.     

Association of human leucocyte antigen phenotype with vaccine efficacy in patients receiving vaginal mucosal immunization for recurrent urinary tract infection

CONTEXT: One or both commercial tuberculin skin test reagents (Aplisol and Tubersol) may have a high rate of false-positive reactions. OBJECTIVE: To compare the reaction size and specificity of skin testing with Aplisol, Tubersol, and the standard purified protein derivative (PPD-S1). DESIGN: Double-blind trial, conducted between May 14, 1997, and October28, 1997, in which each individual received 4 tuberculin skin reagents at sites assigned at random. SETTING: Health departments and universities in 6 US cities. PARTICIPANTS: A total of 1555 persons at low risk of latent tuberculosis infection. INTERVENTION: Simultaneous skin tests with Aplisol, Tubersol, PPD-S1, and either a second PPD-S1 or PPD-S2 (a proposed new standard). MAIN OUTCOME MEASURE: Reaction size at each injection site measured by 2 investigators blinded to type of reagent. RESULTS: Aplisol produced slightly larger reactions than Tubersol, but this difference did not significantly change skin test interpretation. The mean +/- SD reaction sizes were 3.4+/-4.2 mm with Aplisol, 2.1+/-3.2 mm with Tubersol, and 2.5+/-3.6 mm with PPD-S1. Assuming that all participants were uninfected and using a 10-mm cutoff, the specificities of the tests were high: Aplisol, 98.2%; Tubersol, 99.2%; and PPD-S1, 98.9%. Significant variability was not detected in interobserver, host, and lot-to-lot reagent comparisons. CONCLUSION: Using a cutoff of at least 10 mm, testing with 3 different PPD reagents resulted in similar numbers of uninfected persons being correctly classified.     

Maternal regulation of embryonic growth: the role of vasoactive intestinal peptide

Vasoactive intestinal peptide (VIP) is an important growth regulator of the embryonic day (E)9-E11 mouse. In comparably aged rat embryos, VIP messenger RNA (mRNA) is not detectable; however, peak concentrations of VIP in maternal rat serum indicate a nonembryonic source. In the current study, mouse maternal and embryonic tissues were examined from E6-E12. Although RT-PCR revealed VIP mRNA in E6-E7 conceptuses, by E8 (when extraembryonic tissues could be separated from the embryo), VIP mRNA was detected only in the decidua/trophoblast. Decidual/trophoblastic VIP mRNA decreased until E10, after which it was not detectable. VIP mRNA was not apparent in the embryo until E11-E12. At E9, VIP immunoreactivity was localized to abundant, diffuse cells in the decidua basalis, which were also immunoreactive for T cell markers. VIP binding sites were dense in the decidua/trophoblast at E6, but gradually decreased until E10, after which they were not apparent. VIP binding sites were detected in embryonic neuroepithelium by E9. The transient presence of VIP binding sites and mRNA in the decidua/trophoblast correlate with the critical period of VIP growth regulation, when VIP mRNA is absent in the embryo. These findings suggest that maternal lymphocytes are the source of VIP's regulating early postimplantation embryonic growth.