With recent improvements in the commercial feasibility of high pressure pasteurization units, the technology is gaining rapid acceptability across various sectors of food manufacturing, thus requiring extensive validation studies for effective adoption. Various times (1 min to 10 min) and intensity levels (0 MPa to 380 MPa) of elevated hydrostatic pressure were investigated for decontamination of mesophilic background microflora and inoculated Salmonella in orange juice. Results were analyzed by GLM procedure of SAS using Tukey- and Dunnett-adjusted ANOVA, additionally the Kmax and D-values were calculated using best-fitted (maximum R2) model obtained by GInaFit software. At 380 MPa, for treatments of 1 min to 10 min, D-value of 1.35, and inactivation Kmax of 3.34 were observed for Salmonella serovars. D-values were 5.90 and 14.68 for treatments of 241 MPa and 103 MPa, respectively. Up to 1.01 and >7.22 log CFU/mL reductions (p < 0.05) of habituated Salmonella serovars at planktonic stages were achieved using application of pressure at 380 MPa for 1 min and 10 min, respectively. Mesophilic background microflora counts were reduced (p < 0.05) by 1.68 to 5.29 log CFU/mL after treatment at 380 MPa for 1 min and 10 min, respectively. Treatments below two minutes were less efficacious (p ≥ 0.05) against the pathogen and background microflora, in vast majority of time and pressure combinations.

Dividing nuclei from the giant ameba Pelomy~a carolinensis were fixed in osmium tetroxide solutions buffered with vcronal acctate to pH 8.0. If divalent cations (0.002 M calcium, magnesium, or strontium as chlorides) were added to the fixation solution, fibrils that arc 14 m/z in diameter and have a dense cortex are observed in the spindle. If thc divalent ions wcre omitted, oriented particles of smallcr size are present and fibrils are not obvious. The stages of mitosis were observed and spindle components compared. Fibrils fixed in the presence of calcium ions are not so well defined in early metaphase as later, but othcrwise have the samc diameter in the late mctaphase, anaphase, and early telophase. Fibrils are surroundcd by clouds of fine material except in early telophase, when they are formed into tight bundles lying in the cytoplasm unattached to nuclei. Metaphase and anaphase fibrils fixed without calcium ions are less well defincd and are not .observably different from each othcr. The observations are consistent with the concept that spindle fibrils arc composed of polymerized, oriented protein molecules that are in equilibrium with and bathed in nonoriented molecules of the same protein. Partially formed spindle fibrils and ribosome-like particlcs were observed in the mixoplasm when the nuclear envelope had only small discontinuities. Remnants of the envelope arc visible throughout division and arc probably incorporated into the new envelope in the tclophase. Ribosome-like particles arc numcrous in the metaphase and anaphase spindle but are not seen in the telophase nucleus, once the envelope is recstablishcd, or in the interphase nucleus.

Individual organisms of Amoeba proteus have been fixed in buffered osmium tetroxide in either 0.9 per cent NaC1 or 0.01 per cent CaC12, sectioned, and studied in the electron microscope in interphase and in several stages of mitosis. The helices typical of interphase nuclei do not coexist with condensed chromatin and thus either represent a DNA configuration unique to interphase or are not DNA at all. The membranes of the complex nuclear envelope are present in all stages observed but are discontinuous in metaphase. The inner, thick, honeycomb layer of the nuclear envelope disappears during prophase, reappearing after telophase when nuclear reconstruction is in progress. Nucleoli decrease in size and number during prophase and re-form during telophase in association with the chromatin network. In the early reconstruction nucleus, the nucleolar material forms into thin, sheet-like configurations which are closely associated with small amounts of chromatin and are closely applied to the inner, partially formed layer of the nuclear envelope. It is proposed that nucleolar material is implicated in the formation of the inner layer of the envelope and that there is a configuration of nucleolar material peculiar to this time. The plasmalemma is partially denuded of its fringe-like material during division.

SYNOPSIS. An electron microscope study has been made of the spores of a microsporidian, Thelohania californica, parasitic in Culex tarsalis. Fresh spores measure 7–9 × 5–6 μ and contain a polar filament which when extruded may reach a length of 150 μ or more. Thus, this is a typical microsporidian spore. The spore is enveloped in a resistant outer membrane. The polar filament is attached to this membrane at the narrow anterior end, runs inward for a distance and is coiled spirally close to the inner surface of the outer membrane. There are 12–14 spiral turns in the majority of the spores. In the anterior five turns the filament is distinctly larger in diameter than in the seven or more posterior coils. The polar filament appears to be tubular, but the lumen is filled partially or completely with material of high electron density. A laminated polaroplast surrounds the basal portion of the filament and extends into the middle and posterior regions of the intrasporal cavity. The sporoplasm is uninucleate and lies in close contact with the polar filament and the polaroplast. There is no polar capsule.