Preservation of connexin 43 and transzonal projections in isolated bovine pre-antral follicles before and following vitrification

PURPOSE

Gap junctions and transzonal projections play a crucial role in intercellular communication between different follicular components and are necessary for follicle development. We aimed to demonstrate gap junction protein connexin 43 (Cx43) and transzonal projections (TZPs) in viable, category 1, isolated bovine pre-antral follicles (PAFs) during short-term culture and after vitrification and warming.

METHODS

This study involved four experimental groups: fresh control, 2-day culture, 4-day culture, and vitrified secondary PAFs. Isolated PAFs were vitrified using a simple and efficient cryopreservation method by means of mini cell strainers.

RESULTS

Cx43 and TZPs were detected in pre-antral follicles of all stages, as well as in every experimental group. The group fresh follicles showed a higher percentage of follicles that were positive for Cx43 (91.7%) than the follicles that were vitrified (77.4%). All follicles that were cultured for 2 days were Cx43-positive (100%). Follicles cultured for 4 days (65.8%) (P = 0.002) showed the lowest percentage of follicles that were Cx43-positive. The percentages of the presence or (partial) absence of the TZP network were shown to be very heterogeneous between follicles in different treatment groups.

CONCLUSIONS

These results suggest the maintenance of communication between the oocyte and the somatic companion cells after vitrification and warming. The varying percentages of the expression of the TZP network within groups suggests that it will be of interest to investigate whether this is truly due to variability in TZP integrity and follicle quality or due to methodological limitations.

Effects of vitrification on the viability of alginate encapsulated isolated bovine pre-antral follicles

PURPOSE

Individual follicle cryopreservation techniques, without hydrogel support, are labor-intensive and a substantial proportion of isolated follicles are lost during handling and after warming. Therefore, the viability and morphology of isolated bovine (as a model for human) pre-antral follicles after vitrification and warming, when encapsulated in alginate beads, were investigated.

METHODS

Bovine pre-antral follicles were mechanically isolated and divided into four different groups: (1) culture in 2% alginate beads (3D system) and vitrification in beads using mesh cups (3DVIT), (2) culture in 2% alginate beads (3DCUL), (3) culture in 96-well plates (2D system) and vitrification using High Security Vitrification straws® (2DVIT), (4) culture in a 2D system (2DCUL). The same vitrification and warming protocols were used for embedded (3DVIT) and non-embedded follicles (2DVIT).

RESULTS

No differences were observed in follicle viability between group 2DCUL and 3DCUL. Group 3DVIT showed the lowest viability (45.9%) according to calcein and neutral red staining among all groups. Group 2DVIT displayed the highest viability (87.5%) and largest percentage of follicles with a well-preserved morphology.

CONCLUSIONS

Our results show that, using a vitification protocol optimized for non-embedded follicles, 2D culture is more effective in vitrifying isolated follicles. However, embedding in alginate allow to handle follicles more efficiently, i.e., without excessive manipulation and thus less labor-intensive in combination with a reduced loss of follicles during the procedure. Based on the increased work efficiency, but lower viability and higher proportion of follicles showing impaired morphology, we consider it advantageous to optimize the protocol for the vitrification of embedded follicles to increase survival and maintain morphology after vitrification.

[Acid-base equilibrium in the blood in cattle in relation to the incidence of DFD (dark, firm, dry) meat]

We studied changes in the parameters of the acid-base balance of the blood in cattle before animal transport to the slaughterhouses, after transport, after stunning and before bleeding. At the same time we studied the occurrence of DFD meat by measuring the pH value of the muscle and by determining the meat color. We found out that the disorder of acid-base balance was less manifest, with respect to the large capacity of the buffer systems of the blood, than the changes caused by glycogenolysis in the muscle.

[Seasonal changes in the concentration of total blood proteins in cows during various phase intervals]

In four one-year stages (A, B, C, D) in the summer (L) and winter (Z) feeding seasons, the total protein (CB) of blood plasma was determined in 3207 cows included in three groups: I - the first stage of lactation, II - the second stage of lactation, and III - the 8th to 9.5th month of pregnancy. 1948 cows were examined when given the winter feed rations and 1259 cows on the summer rations. At the same time, the supply of required digestible crude protein (SNL) and energy (starch units) was calculated for the feed rations of different groups of cows. High-pregnant cows (III) had the lower total protein in all the four years and feeding seasons, as compared with the groups of lactating cows. The difference was significant in nine out of ten cases in relation to group I and in eight cases in relation to group II. This is a regular phenomenon, independent of the summer or winter feed ration type and of the seasonal climatic effects of each year. The trend of decreasing crude protein levels with the length of lactation is less conclusive (significant in four out of ten cases); nevertheless, it is still apparent, since none of the three reverse cases was significant. The differences in total protein concentration between cows of different groups are absolute and their causes must be endogenous: they cannot be attributed to differences in the supply of required nutrients. A rise of total protein content was recorded in both feeding seasons at stages C and D in all groups of cows. The higher occurrence of hyperproteinaemia is ascribed to increased proteosynthesis at better utilization of the supplied crude protein. Relative (concentration) hyperproteinaemia was excluded. The effect of the summer or winter type of feed rations on total protein concentration was insignificant when considered for the whole four-year period; at individual stages significantly higher total protein values in the summer feeding season than in the winter feeding season were recorded three times and the reverse case was recorded only once.

[Ketonuria in dairy cows]

In 3337 dairy cows, urine was examined for ketone bodies by help of Bililabstix during the first and second phase of lactation and in the eighth to the ninth and a half month of pregnancy; at the same time needed supply of energetic nutrients in 175 summer and 308 winter feed rations was calculated. Intensity and frequency of ketonuria in lactating cows fed winter rations is significantly higher than in those fed green feeds; it decreases significantly with a phase of lactation and with milk production. On the contrary, cows in late pregnancy have higher intensity and frequency of ketonuria (32.9%) when fed green feeds than when fed winter rations (30.7%). In winter feed rations energy input was significantly lower, percentage of deficient feed rations at a relatively broader caloric-protein ratio was higher than in summer season. The highest deficits of energy and digestible nitrogen compounds were observed in cows in the first phase of lactation. Discussion concerns the causes and mechanisms of different ketonuria in groups of dairy cows in relation to deficit of energetic nutrients, caloric-protein ratio, to the level of glycaemia, non-esterified fatty acids in plasma, triglycerides of plasma and to the state of liver function.

[Effect of potassium-hydrogen interaction in the excretory mechanism of the kidneys on the acid-base and other biochemical values of the blood and urine in calves]

The effect of the competitive relationship between potassium and hydrogen in the excretory mechanism of the kidneys on metabolism was studied in calves. The intraruminal exposure of calves to 5.6 meq potassium chloride (KCl) per kg per day has, in itself, only a slight acidotic effect ascribable to a slight reduction of the excretion of acid by the kidney. The same dose of ammonium chloride (NH4Cl) has a strong acidotic effect combined with a negative influence on weight gain. Both basic types of exposure increase the concentration of inorganic phosphorus and reduce the concentration of chlorine in the blood serum. The addition of 2.8 meq of potassium chloride per kg per day to the basic dose of ammonium chloride increases metabolic acidosis, worsens the health condition (being, at times, hazardeous to life) and leads to weight losses. The same amount of ammonium chloride added to the basic dose of ammonium chloride has a relatively small acidotic action on the blood, evoking only a slight and temporary potassium retention in the serum. The negative action on the weight gains and clinical symptoms are generally weaker than in the other group. The results indicate that the acidotic environment creates in ruminants a very dangerous situation if the organism is excessively exposed to the effect of potassium at the same time.