Surface changes in chimpanzee sperm during epididymal transit

Intact chimpanzee caput and cauda epididymal sperm, sperm cell lysates, and caput and cauda epididymal fluid were radiolabeled by enzymatic iodination with lactoperoxidase and Na125 I and were compared by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Caput epididymal sperm showed nine labeled macromolecular components of 90, 64, 56, 48, 38, 31, 20, 18 and 16 Kd and cauda epididymal sperm showed eleven macromolecular components of 90, 64, 55, 47, 42, 33, 27, 18, 17, 15 and 11 Kd. Six of the components labeled on caput sperm (90, 64, 56, 48, 18 and 16 Kd) were detected in equal amounts of cauda sperm and two (38 and 20 Kd) were detected at greatly reduced labeling intensities. In the cauda epididymidis, four new components (33, 27, 17 and 11 Kd) became prominent features of the sperm surface. Analysis of labeled caput and cauda sperm cell lysates resolved components distinct from those detected on sperm surfaces. Electrophoresis of caput epididymal fluid showed five labeled components of 66, 56, 47, 41 and 37 Kd, while electrophoresis of cauda epididymal fluid showed eight labeled components of 92, 66, 56, 48, 31, 27, 24 and 11 Kd. Three components (66, 56 and 47 Kd) were present in both caput and cauda fluid, two (41 and 37 Kd) in caput fluid only, and five (92, 31, 27, 24 and 11 Kd) in cauda fluid only. Components of 37 Kd were labeled in caput fluid and on caput sperm but not on cauda sperm, whereas components of 27 Kd and 11 Kd were labeled in cauda fluid and on cauda sperm but not on caput sperm. These data show that chimpanzee sperm undergo extensive surface modifications during epididymal maturation and that some of these modifications may be related to exogenous proteins/glycoproteins in epididymal fluids.     

The ecology of Escherichia coli in market calves fed a milk-substitute diet

Dynamic changes in the Escherichia coli population in the calf gut were studied over 21 days in a group of 18 intensively-reared market calves. Isolates were identified by O-serogrouping, biotyping and resistogram patterns. Seventy O-serogroups were identified among nearly 3000 E. coli isolates examined and these were subdivided into 416 strains by means of their biotype and resistogram. Seventy-five per cent of these strains were detected only once or twice, which points to the continual replacement of the E. coli flora with strains that showed low persistence in the gut. The rise in the frequency of antibiotic resistance observed during the study was not due to a change in the proportion of resistant to sensitive strains in the gut flora. It was a consequence of the displacement of the original flora by multiply-resistant strains, which presumably originated from the calves' environment.     

Changes in binding of a 27-kilodalton chimpanzee cauda epididymal protein glycoprotein component to chimpanzee sperm

Motility patterns of caput epididymal chimpanzee sperm, caput epididymal chimpanzee sperm incubated in vitro with chimpanzee cauda epididymal fluid, and cauda epididymal chimpanzee sperm were assessed quantitatively. Sperm recovered from the caput epididymis showed no motility, whereas sperm recovered from cauda epididymis showed progressive forward motility. After incubation in cauda fluid, approximately 25% of caput epididymal sperm showed some motile activity. Electrophoretic analysis of ¹²⁵I-labeled sperm plasma membrane preparations revealed that the surface of caput epididymal sperm, incubated in cauda fluid, was modified by the appearance of a major protein-glycoprotein surface component with an apparent molecular weight of 27 kilodaltons (kD). THis 27-kD component was not detected on caput epididymal sperm incubated in buffer or in caput fluid. However, it was present in cauda fluid and on cauda epididymal sperm. Binding to caput epididymal sperm was cell specific in that chimpanzee erythrocytes incubated in cauda fluid did not bind this 27-kD cauda fluid component. Motility patterns of ejaculated chimpanzee sperm and of ejaculated chimpanzee sperm incubated in the uterus of adult female chimpanzees also were assessed quantitatively. Ejaculated sperm showed progressive forward motility, whereas in utero incubated ejaculated sperm showed hyperactivated motility typical of capacitated sperm. Electrophoretic analysis of ¹²⁵I-labeled sperm plasma membrane preparations revealed the loss of a 27-kD component from the surface of ejaculated sperm after in utero incubation. No significant change in the ¹²⁵I-distribution pattern was detectable when ejaculated sperm were incubated in buffer. These results suggest that the lumenal fluid component, which becomes adsorbed to the surface of chimpanzee sperm during maturation in the epididymis and which is removed from the surface of mature chimpanzee sperm in the female reproductive tract, affects sperm motility.     

The effect of ampicillin and tylosin on the faecal enterococci of healthy young chickens

Enterococcal isolates from young chickens were differentiated into one of three species, namely Enterococcus faecalis, Ent. faecium and Ent. gallinarum . The proportion of each species among the enterococcal population changed with time in birds not dosed with antibiotics. This pattern of change was modified in birds dosed with either tylosin or ampicillin even though ampicillin did not select for ampicillin resistance among the enterococcal population. A gradual increase in tylosin resistance was recorded with time among the enterococci of the 'undosed' control birds. This was associated with an increase in the proportion of Ent. faecium , a species commonly resistant to tylosin, among the enterococci of the birds as they grew older.     

Preparation of a low-density species of endocytic vesicle containing immunoglobulin A.

Immunoglobulin A is transported across hepatocytes in specialized vesicles. A population of endocytic vesicles of approx. 140 nm diameter, containing immunoglobulin A, has now been separated from all other major cytoplasmic organelles, including plasma membrane and lysosomes, by sequential centrifugation on Ficoll/sucrose and Metrizamide gradients.     

Inhibition of Salmonella typhimurium by the products of tartrate metabolism by a Veillonella species

The inhibition of the growth of Salmonella typhimurium by a Veillonella species grown on media supplemented with tartrate was examined. Growth of Salmonella typhimurium was not inhibited by the concentrations of products metabolized by Veillonella cultures on media supplemented with 0 or 50 mmol 1^-1 of tartrate, but was inhibited on media supplemented with 100 or 150 mmol 1^-1 of tartrate. Inhibition of Salm. typhimurium was correlated with the increased production of acetate and propionate from tartrate by the Veillonella species.     

Limited proteolysis of native proteins: the interaction between avidin and proteinase K.

Avidin is a tetramer of 16-kDa subunits that have a high affinity for biotin. Proteolysis of native apoavidin by proteinase K results in a limited attack at the loop between beta-strands 3 and 4, involving amino acids 38-43. Specifically, sites of proteolysis are at Thr 40-Ser 41 and Asn 42-Glu 43. The limited proteolysis results in an avidin product that remains otherwise intact and which has enhanced binding for 4'-hydroxyazobenzene-2-benzoic acid (HABA), a chromogenic reporter that can occupy the biotin-binding site. Saturation of the biotin-binding site with the natural ligand protects avidin from proteolysis, but saturation with HABA enhances the rate of proteolysis of the same site. Analysis of the three-dimensional structures of apoavidin and holoavidin reveals that the 3-4 loop is accessible to solvent and scores highly in an algorithm developed to identify sites of proteolytic attack. The structure of holoavidin is almost identical to the apoprotein. In particular, the 3-4 loop has the same structure in the apo and holo forms, yet there are marked differences in proteolytic susceptibility of this region. Evidence suggests that the 3-4 loop is rather mobile and flexible in the apoprotein, and that it becomes constrained upon ligand binding. In one crystal structure of the apoprotein, this loop appears constrained by contacts with symmetry-related molecules. Structural analyses suggest that the "lid" to the biotin-binding site, formed by the 3-4 loop, is displaced and made more accessible by HABA binding, thereby enhancing its proteolytic susceptibility.     

Controlled formaldehyde fumigation system.

A comparative study of formaldehyde (HCHO) fumigation was carried out by controlled vaporization, using an electric vapor generator, and by the Formalin-permanganate method. Determination of vapor levels as well as bactericidal action showed the generator to be more effective. Maximum achievable fumigant levels were temperature dependent and related to the equilibrium vapor concentration of HCHO. At a room temperature of 21 degrees C, vaporization of more than 2,000 micrograms of HCHO per liter resulted in conversion of HCHO to paraformaldehyde, which condensed on surfaces and contributed to prolonged residual vapor levels. An electronic monitor is described which is capable of detecting HCHO levels as low as 10 microgram/liter and can be used to monitor the complete fumigation process.     

Measurement of the motility of rat spermatozoa collected by micropuncture from the testis and from different regions along the epididymis.

Spermatozoa from the testis and various regions along the epididymis of the rat were collected by micropuncture and their motility after dilution was estimated over a 15-min period by using a Quantimet image analyser. The motility of sermatozoa from the rete testis and seminiferous tubules was too low to be measured. The estimate of motility of spermatozoa from the proximal caput epididymidis was much lower than that of spermatozoa from the other regions. Spermatozoa from the distal part of the caput showed sustained motility for 15 min, whereas those from the caudal region and ductus deferens, although active initially, became less active during this period.     

The sediment column as a record of trophic status: examples from Bosherston Lakes,SW Wales

Bosherston Lakes are a series of interconnected, mesotrophic to hypereutrophic, artificially-created coastal marl lakes in Dyfed, South West Wales. Progressive eutrophication of the lake system has been produced by a high external phosphorus loading which includes phosphorus-rich effluent from a sewage treatment works (STW) in the catchment of the Lakes.Cores were taken from four sites of varying eutrophic status within the Lakes. In the surface sediment layer, organic C, N and P concentrations generally correlate directly with trophic status and reflect distance from the source of P input. At one site, sediment stratigraphy records a clear transition at 20–15 cm depth, marked by a sharp upward increase in porosity, organic C, N, and P, and iron-associated-P; decreases in organic matter C/N, C/P and N/P ratios; a sharp decrease in carbonate, and a change in the subfossil diatom assemblage. Lead-210 dating indicates that this change occurred in the period 1919 to 1938.The diatom stratigraphy and sediment geochemistry suggest that this transition reflects an increase in trophic status at this site, probably as a result of the influx of nutrient-rich water. This took place when the management of the Stackpole estate surrounding the lake system, fell into decline during the period 1919–1938.