Time of copulation during estrus period on estrus duration and LH response in Boer goats.

The objectives of this investigation were to determine the effect of the time of copulation during the estrus period on estrus duration and luteinizing hormone (LH) response in goats. A controlled randomized study with two replicates (first = n = 12; second = n = 24), in which Boer does were divided at each replicate into three groups, was performed. Copulations at the beginning of estrus (two copulas within the first 4 h after estrus; COP-1; n = 12), copulations around the middle of estrus (two copulas around 16 h after estrus; COP-2; n = 12), and noncopulations (only mounts) throughout the estrus period (control group; CON; n = 12) were performed. Estrus duration for CON group was 41.3 ± 8.2 h; for COP-1, it was 34.0 ± 5.3 h, and for COP-2, it was 39.7 ± 6.9 h (P = 0.04). Differences were detected between COP-1 and CON groups (P = 0.01) and between COP-1 and COP-2 groups (P = 0.05) but not between CON and COP-2 groups (P = 0.56). The LH peak time for the CON group was 20.0 ± 8.0 h; for the COP-1 group, it was 13.0 ± 3.6 h, and for the COP-2 group, it was 20.5 ± 5.8 h (P = 0.04). The COP-1 group was different than the COP-2 (P = 0.02) and CON groups (P = 0.03), and no differences were detected between these last two groups (P = 0.87). It was concluded that copulation reduced estrus duration and hastened the LH peak time only when performed during the beginning of estrus.

Crossbreds of Jersey x Holstein compared with pure Holsteins for production, fertility, and body and udder measurements during first lactation.

Jersey x Holstein crossbreds (JxH; n = 76) were compared with pure Holsteins (n = 73) for 305-d milk, fat, and protein production; conception rate; days open; proportion of cows pregnant within fixed intervals postpartum; and body and udder measurements during first lactation. Cows were housed at 2 research locations of the University of Minnesota and calved from September 2003 to May 2005. The JxH were mated to Montbeliarde sires, and Holstein cows were mated to Holstein sires. Best Prediction was used to determine actual production (milk, fat, and protein) for 305-d lactations with adjustment for age at calving, and records less than 305 d were projected to 305 d. The JxH (274 kg) and pure Holsteins (277 kg) were not significantly different for fat production, but JxH had significantly less milk (7,147 vs. 7,705 kg) and protein (223 vs. 238 kg) production than pure Holsteins. The JxH had significantly fewer days open than pure Holsteins (127 vs. 150 d). Also, a significantly greater proportion of JxH were pregnant at 150 and 180 d postpartum than pure Holsteins (75 vs. 59% and 77 vs. 61%, respectively). The JxH had significantly less body weight (60 kg) at calving, but significantly greater body condition (2.80 vs. 2.71). Furthermore, JxH had significantly less udder clearance from the ground to the bottom of the udder than pure Holsteins (47.7 vs. 54.6 cm), and greater distance between front teats (15.8 vs. 14.0 cm) than pure Holsteins during first lactation.

Effect of scrotal insulation on clusterin-positive cells in ram semen and their relationship to semen quality.

Scrotal contents of 2 rams were insulated for 96 hours and the fraction (as a percentage) of clusterin-positive cells (CPCs) and its relationship to semen quality was investigated. Semen collection was started 18 days before insulation and was terminated on day 78 and day 63 after insulation in animals 1 and 2, respectively. Sperm clusterin was localized by immunostaining with anti-bovine clusterin antibody (anti-bCAb) and fluorescein isothiocyanate-conjugated immunoglobulin G. Scrotal insulation led to deterioration of semen quality and increased the percentage of CPCs in both rams. Two types of sperm reactivity were observed: an extensive, intensive staining pattern (ESP); and a localized, less-intensive staining pattern (LSP). The percentage of ESP-CPCs began to increase from day 6 and reached 88.8% and 100% on day 15 after insulation in animals 1 and 2, respectively. The increase in CPCs coincided with the presence of a high percentage of teratoid forms (88.3%) in semen from animal 1, and detached heads (81.4%) in semen from animal 2. After normal semen production was restored on day 60 in animal 1, the percentages of ESP-CPCs and LSP-CPCs returned to preinsulation rates, whereas only the ESP-CPCs returned to normal in animal 2. A negative relationship was observed between ESP-CPCs and total sperm/ejaculate (r = -.62), motility (r = -.78), viability (r = -.68), and filtration rate (r = -.71) in semen from animal 1. Conversely, a positive relationship was seen between ESP-CPCs and total abnormal spermatozoa (r = .82). Similar results were obtained in semen from animal 2. CPCs were nearly completely absent in glass wool-Sephadex (GWS)-filtered semen, suggesting a role for clusterin in the process of trapping abnormal spermatozoa in the GWS filters. We conclude that aberrant spermatogenesis induced by scrotal insulation increases the percentage of CPCs in ram semen. We suggest that the percentage of CPCs in ram semen could be a useful marker in poor-quality ejaculates.

Lamprey gonadotropin-releasing hormone-III selectively releases follicle stimulating hormone in the bovine.

Recent studies have shown that lamprey gonadotropin-releasing hormone (l-GnRH) is localized in the mammalian brain, and that l-GnRH-III, can selectively induce FSH secretion in the rat both in vivo and in vitro. Consequently, the purpose of this study was to determine if l-GnRH-III could elicit selective FSH release in cattle and compare this response with that to mammalian luteinizing hormone releasing hormone (m-LHRH). Cattle were chosen as the animal model because previous studies have demonstrated that FSH and LH are secreted by separate gonadotropes in that species. For these studies, crossbred cycling heifers were implanted with jugular cannulae and l-GnRH-III was infused either between Days 9-14 or on Day 20 of the estrous cycle. Blood samples were collected both before and following peptide infusion. Our results demonstrate that during Days 9-14 of the estrous cycle (luteal phase), when progesterone levels averaged between 4 and 5 ng/ml, a dose of 0.25 mg of l-GnRH-III induced the release of FSH (P < 0.05), but not LH. A 0.5 mg dose of l-GnRH-III caused a greater release of FSH (P < 0.01), but still did not induce LH release. Higher doses of the peptide were capable of significantly releasing both gonadotropins. Importantly, during the luteal phase, doses of 0.5 and 2 mg of m-LHRH were ineffective in stimulating FSH, but did elicit marked increases (P < 0.001) in LH. Again, progesterone levels averaged 4-5 pg/ml. In order to assess gonadotropin releasing ability of l-GnRH-III at a different phase of the estrous cycle, some animals were administered the peptide on Day 20, when progesterone levels were below 1.0 pg/ml. At this time, the l-GnRH-III induced the release of LH (P < 0.01), but not FSH. Overall, our results demonstrate that l-GnRH-III can selectively induce FSH in cattle during the luteal phase, whereas m-LHRH was ineffective in that regard. Furthermore, the fact that l-GnRH-III can selectively stimulate FSH when serum progesterone is high, and LH when serum progesterone is low, suggests its actions are under strong control of this steroid. We suggest the FSH releasing capacity of l-GnRH-III in cattle could render this peptide useful for enhancement of reproductive efficiency in this species.

Advanced reproductive techniques in goats.

The use of ultrasonography for pregnancy diagnosis and reproductive tract evaluation in the goat has become more common in the past decade. Pregnancy-specific hormone assays are commercially available for pregnancy determination in goats. Hormonal methods of synchronization of estrus for artificial insemination have been refined, but a number of factors still make pregnancy results variable. Caprine embryo transfer is widely used commercially. More advanced reproductive techniques such as in-vitro production of embryos and cloning have been accomplished in goats; success rates with these techniques will likely rapidly improve.

A note on the effect of continuous ram presence on estrus onset, estrus duration and ovulation time in estrus synchronized ewes.

During fall season, 18 multiparous Corriedale ewes were divided into two equal groups for the continuous (CON) and intermittent (INT) presence of a ram. Estrus was synchronized with fluorgestone acetate intravaginal sponges that were left 14 days, plus an injection of 200&mgr;g of a prostaglandin F-2alpha analog at sponge removal. Estrus was detected three times a day (at 6 a.m., 2 p.m. and 10 p.m.) by using rams with harnessess and markers. Ovulation time was determined by laparoscopy, starting 24h after estrus detection. Estrus onset was (mean+/-S.E.M.) 32.9+/-1.6 and 45.3+/-4.4h for the CON and INT groups, respectively (P<0.01). Estrus duration was 31.1+/-0.9 and 30.2+/-1.2h, for the same groups, respectively (P>0.05). Ovulation time and the interval from sponge removal to ovulation (ISRO) for the CON and INT groups was 29.0+/-1.5, 62.0+/-2.0, 26.7+/-1.3 and 72.0+/-4.2h, respectively. Ovulation time was not different (P>0.05), but ISRO was shown to be different between treatments (P<0.05). It is concluded that the continuous presence of a ram after sponge removal hastens estrus onset and reduces the interval between sponge removal and ovulation, without modifying estrus duration and time between estrus onset and ovulation.

Effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats.

The effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats during breeding season was studied. Nubian does (n=126) were divided into 2 equal groups: service and control. Estrus was synchronized with intravaginal sponges containing either fluorgestone acetate (FGA; 40 mg) or medroxiprogesterone acetate (MAP; 60 mg) for 12 or 14 d, respectively. Two vasectomized teaser bucks were used to detect estrus at 6-h intervals for 5 d after sponge removal (0600, 1200, 1800 and 2400 h). The teasers were fitted with aprons and permitted to mount all does in both groups, but to penetrate only the service does within the first 12 h of estrus. Does in both groups were inseminated twice at 12 and 24 h after estrus was first detected, using 1 straw per insemination containing 200 million of cooled spermatozoa from 1 buck. The semen was placed in mid-cervix. Estrus duration for the service and control does was (mean +/- SD) 29.4 +/- 6.5 and 41.8 +/- 9.6 h, respectively. Fertility for the service does was 73.7% (46/63); for control does it was 58.7% (37/63). Prolificacy was 2.1 (96/46) and 2.0 (74/37) for service and control does, respectively. Estrus duration (P<0.001) and fertility (P<0.05) differed between the service and control group, but prolificacy was similar (P>0.05). It is concluded that sterile service reduces the duration of estrus and increases fertility in artificially inseminated dairy goats.

Imaging pulmonary emboli and deep venous thrombi with 99mTc-bitistatin, a platelet-binding polypeptide from viper venom.

UNLABELLED: An imaging test that could locate both pulmonary emboli (PE) and their source, active deep venous thrombi (DVT), would be valuable in patient management. Bitistatin, an 83-amino-acid polypeptide isolated from Bitis arietans venom, binds avidly to the glycoprotein IIb/IIIa receptor on platelets. The goal of this study was to label bitistatin with 99mTc and assess its potential for imaging thrombi and emboli in vivo. METHODS: Molecular modeling of bitistatin indicated that its primary amines are located on the opposite side of the molecule from the receptor-binding domain. The primary amines were reacted with succinimidyl-4-hydrazino nicotinate hydrochloride to place 2.4 hydrazino nicotinate (Hn) chelating groups per peptide molecule. Hn-bitistatin was labeled by incubation with 99mTc-glucoheptonate to 96 TBq/mmol and then tested for binding to platelets in vitro and for imaging of 24-h-old DVT and PE in a canine model used previously for other thrombus tracers. RESULTS: 99mTc-Hn-bitistatin bound to stimulated platelets with a dissociation constant (Kd) = 32 nmol/L, similar to that of 125I-bitistatin (Kd = 41 nmol/L). In vivo, focal uptake was observed in planar images as early as 30 min (DVT) and 60 min (PE) after injection. Lesion uptake of 99mTc-Hn-bitistatin at 4 h after injection was calculated in terms of percentage injected dose per gram (%ID/g) of tissue and averaged 0.89 %ID/g PE and 0.79 %ID/g DVT. Lesion-to-background ratios averaged 34:1 (PE-to-lung), 18:1 (DVT-to-blood), and 284:1 (DVT-to-muscle). These values were not significantly different from iodinated bitistatin, but uptakes were higher than other tracers tested in the same model. CONCLUSION: 99mTc-Hn-bitistatin retains the functional activity of the iodinated peptide, has higher DVT and PE uptakes than other thrombus tracers in this standardized model, and has target-to-background characteristics suitable for imaging both PE and DVT in a single test.

In vitro platelet binding compared with in vivo thrombus imaging using alpha(IIb)beta3-targeted radioligands.

Radioligands for the alpha(IIb)beta3 integrin on platelets are being studied for their ability to image venous thrombi and pulmonary emboli. One such radioligand, 123I-bitistatin, was previously shown to have higher thrombotic uptake in an animal model than other disintegrins, but the reason for this difference was not clear. The purpose of this study was to evaluate three labeled disintegrins, bitistatin, kistrin and barbourin, to look for in vitro differences in platelet binding which could explain the in vivo behavior. Disintegrins labeled with 121I were compared in vitro for extent of binding to platelets and rates of binding and dissociation. These findings were related to organ distribution and image quality for imaging thrombotic lesions, following administration of 123I-disintegrins in an animal model. Fibrinogen at 8.8 micromol/l was able to displace 125I-barbourin and 125I-kistrin more rapidly from ADP-stimulated platelets, with half-times of 3.5 and 10.7 min, compared with 125I-bitistatin (31.6 min). At equivalent concentrations in whole blood, a higher percentage of bitistatin bound to platelets compared with the other two. In vivo, kistrin and barbourin had significantly lower thrombus:muscle and pulmonary embolus:lung ratios in images compared with bitistatin. There was evidence of more metabolic deiodination of labeled kistrin and barbourin in vivo compared with bitistatin. A surprising finding was that conventional in vitro platelet binding studies did not predict the relative in vivo behavior of labeled disintegrins. The results suggest that labeled bitistatin has improved targeting of thrombi because it is less easily displaced from stimulated platelets, permitting longer lesion retention. It also appears to have a greater association with resting platelets in the blood, which may increase bioavailability and delay metabolic breakdown.

Effect of eCG on the pregnancy rate of ewes transcervically inseminated with frozen-thawed semen outside the breeding season.

An experiment was conducted to determine whether factors affecting pregnancy rate out-of-season are associated more with transcervical artificial insemination (T-AI) procedures or with the reproductive state of the ewe. Twenty Finncross ewes were treated with progesterone sponges, and at sponge removal (0 h) 10 ewes were treated with eCG. Blood samples were collected for LH and progesterone analyses, and follicular development was monitored using ultrasonography. Ewes were inseminated from 48 to 52 h with 200 million motile frozen-thawed spermatozoa. The incidence of estrus, LH surges and ovulation was greater (P < 0.01) and intervals to these responses were shorter (P < 0.01) in the eCG-treated ewes. The number of follicles > 5 mm was higher (P < 0.05) in eCG-treated than control ewes. Progesterone concentrations increased and remained elevated through Day 19 in 7 eCG-treated and in 1 control ewe, and these ewes were pregnant based upon ultrasonographic examination. The results demonstrate that the T-AI technique using frozen-thawed semen produces a relatively high (70%) pregnancy rate out-of-season. The pregnancy rate was found to reflect primarily the reproductive condition of the ewe.

Effect of service on duration of oestrus and ovulation in dairy goats.

In the autumn, Nubian goats (n = 24) were randomly divided into two equal groups after oestrus had been synchronized using fluorogestone acetate intravaginal pessaries (FGA, 30 mg) over a 20 day period. The onset of oestrus was detected at 8 h intervals using either of two vasectomized bucks fitted with an apron during the 5 days following pessary removal. A buck was permitted to mount and serve each doe only twice in 30 min within the first 8 h of oestrus initiation in the SER group. In the CON group, a buck was only permitted to mount. Ovulation was determined by laparoscopy at 8 h intervals starting 24 h after onset of oestrus. Duration of oestrus for SER and CON groups was (mean +/- SD) 26.7 +/- 7.1 and 36.0 +/- 8.0 h, respectively (P < 0.01). The first and last ovulations for SER and CON groups were 34.7 +/- 3.9 and 37.3 +/- 6.2 h, and 35.3 +/- 5.4 and 38.0 +/- 6.0 h from oestrus initiation, respectively (P > 0.05). No differences were found between right and left ovarian activity (P > 0.05). Ovulation rates did not differ (2.17 +/- 0.58 and 2.17 +/- 0.94). Ovulations occurred principally towards the end of oestrus in the CON group and after oestrus had ended in the SER group. Service reduced the duration of oestrus without affecting ovulation times or ovulation rates in Nubian dairy goats.

Comparison of iodine-123-disintegrins for imaging thrombi and emboli in a canine model.

UNLABELLED: Disintegrins are peptides found in viper venoms which bind to platelets through the glycoprotein IIb-IIIa receptor. The purpose of this work was to evaluate the ability of disintegrins to image thrombi and emboli in vivo. METHODS: Eight disintegrins (bitistatin, albolabrin, echistatin, eristostatin, kistrin, mambin, halysin and barbourin) were purified from snake venom. After radiolabeling with 123I, disintegrins were tested for their ability to image 24-hr-old experimental deep vein thrombi (DVT) and pulmonary emboli in a canine model. Labeled fibrinogen and platelets were used as controls. Gamma camera imaging was performed during the first 4 hr, after which tissue samples were collected for counting. RESULTS: Of the disintegrins tested, 123I-bitistatin had higher uptake in DVT (0.21 +/- .06% ID/g) than any other disintegrin (0.009-0.036%/g, p < 0.05). Bitistatin had higher DVT-to-blood ratios (9.8 +/- 2.5) than all other disintegrins, 125I-fibrinogen or 99mTc-HMPAO-platelets (p < 0.05). Images of DVT obtained with 123I-bitistatin were focally positive within 1 hr and improved by 4 hr. In pulmonary emboli, the absolute uptake of 123I-bitistatin (0.64 +/- 0.17% ID/g) was higher than all other compounds (p < 0.05), although barbourin had moderate uptake (0.23 +/- 0.11% ID/g) and may also be useful for imaging pulmonary embolism (PE). The uptake of bitistatin in PE was superior to both 125I-fibrinogen (0.18 +/- 0.02% ID/g) (p < 0.05) and 99mTc-HMPAO-platelets (0.14 +/- 0.02% ID/g, p < 0.05). Iodine-123-bitistatin had embolus-to-blood ratios averaging 27 +/- 7, which was higher than platelets, fibrinogen, echistatin, mambin or halysin (p < 0.05). Iodine-123-bitistatin background in lungs, liver and heart were low, which permitted visualization of all pulmonary emboli by 2-4 hr after injection. CONCLUSION: Labeled bitistatin should be investigated further as an agent which may permit rapid imaging of both thrombi and emboli.

Effect of service and vaginal-cervical anesthesia on estrus duration in dairy goats.

The object of this experiment was to study the effect of sterile service and vaginal and cervix anesthesia on estrus duration in dairy goats. During the fall season 21 Nubian goats (9 nulliparous and 12 multiparous) were randomly assigned to 1 of 3 treatment groups (n = 7 animals per group). The following groups were formed: service (SER), vaginal and cervix anesthesia (VCA) and control (CON). Estrus was synchronized using fluorgestone acetate intravaginal pessaries (FGA, 30 mg) over a 14-d period. Estrus was detected using a vasectomized buck at 6-h intervals over 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the SER group the male was permitted to service each female. In the VCA group the vagina and cervix of the does were anesthesied, after which the male was permitted to service the females. Both treatments were done once within the first 12-h initiation of estrus. Does were permitted to be mounted only in the control group (CON). Estrus duration for SER, VCA and CON groups was (mean +/- SD) 24.0 +/- 10.9, 42.0 +/- 15.9 and 40.3 +/- 10.8 h, respectively. The SER group was significantly different from the VCA and CON groups (P < 0.01); however, the VCA group was not different from the CON group (P > 0.05). It is concluded that service shortens the duration of estrus due to the mechanical effect of the penis against the vagina and cervix, and not to the accessory gland fluid.

Effects of different stimuli of service on estrus duration in dairy goats.

The object of this experiment was to study the effects of different stimuli of service on estrus duration in dairy goats. Twenty Nubian goats were assigned randomly to 4 groups of 5 animals each: service (SER), mechanical stimulation of vagina (MES), accessory gland fluid insemination (AGF), and control (CON), Estrus was synchronized by using medroxyprogesterone acetate intravaginal pessaries (60 mg) over a 12-d period. Estrus was detected using 1 aproned vasectomized buck at 6-hour intervals during 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the SER group the male was permitted to service each female. In the MES group, stimulation was accomplished using a penis-like device maintained in the vagina 15 sec with light pressure on the fornix. In the AGF group, 1.0 ml of accessory gland fluid was deposited into the external cervical os. The CON group was only permitted to be mounted. All treatments were performed only once within the first 12 h of estrus. Estrus duration for the SER, MES, AGF and CON groups was (mean +/- SD) 22.8 +/- 5.0, 27.6 +/- 6.8, 37.2 +/- 2.7 and 42.0 +/- 9.5 h, respectively. The SER group was different from the AGF and CON groups (P<0.01), but not from the MES group (P>0.05). The MES group was different from the AGF (P<0.05) and CON groups (P<0.01). The AGF and CON groups did not differ from each other (P>0.05). It is concluded that service shortened estrus duration due to the mechanical effect of stimulation of the penis-like device against the vaginal fornix.

Effect of service number on estrus duration in dairy goats.

The object of this research was to study the effect of sterile service number on estrus duration in dairy goats. Twenty-four Nubian goats (20 nulliparous and 4 multiparous) were randomly assigned to 1 of 4 treatment groups (n = 6 animals per group). The following Groups were formed: no service (GS-0); 1 service (GS-1); 2 services (GS-2); 3 services (GS-3). Estrus was synchronized by using fluorogestone acetate intravaginal pessaries (40 mg) over a 12-d period plus 400 IU im pregnant mare serum gonadotropin (PMSG) at pessary removal. Estrus was detected by using a vasectomized buck at 6-h intervals over 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the GS-0 group the teaser was outfitted with an apron and was permitted to mount. In the GS-1, GS-2 and GS-3 groups, the teaser was permitted to mount and service 1, 2 and 3 times, respectively, within the first 12 h after initiation of estrus. The duration of estrus for the 4 groups (GS-0, GS-1, GS-2 and GS-3) was (mean +/- SD) 41.0 +/- 5.9, 24.0 +/- 5.4, 22.0 +/- 4.9 and 22.0 +/- 7.2 h, respectively. These results show differences between the serviced groups and the nonserviced group (P<0.01), but they fail to show differences among the serviced groups (P>0.05). It is concluded that sterile service shortens estrus duration and that service number (1, 2 or 3) does not affect estrus duration.

Effect of service on estrus duration in dairy goats.

The objective of this research was to determine the effect of sterile service on estrus duration in multiparous and nulliparous dairy goats. Twenty Nubian goats (10 multiparous and 10 nulliparous) were randomly assigned to of 4 treatment groups (n = 5 animals per group). Group MNS, multiparous without service; Group MS, multiparous with service; Group NNS, nulliparous without service and Group NS, nulliparous with service. Estrus was synchronized by utilization of fluorogestone acetate intravaginal pessaries (40 mg.) over a 12-day period plus 250 IU, i.m. of pregnant mare serum gonadotropin (PMSG) at pessary removal. Estrus was detected with the aid of a vasectomized buck for 5 days after pessary removal for 6-hour intervals (0600, 1200, 1800 and 2400 hours). In the groups that were not serviced the teaser was equipped with an apron and was only allowed to mount. In the serviced groups, the teaser was permitted to mount and service each female on 2 occasions during the first 12 hours of estrus. Estrus initiation for Groups NNS, NS, MNS and MS were (mean +/- SD) 61.5 +/- 29.5, 61.2 +/- 35.4, 63.0 +/- 22.2 and 69.6 +/- 32.5 hours, respectively (P>0.05). Estrus duration for the same groups were (mean +/- SD) 42.0 +/- 12.0, 30.0 +/- 6.0, 42.0 +/- 7.3 and 28.8 +/- 10.7 hours, respectively. These results show that estrus duration was shortened by serving (P<0.01), and that there were no differences between multiparous and nulliparous goats with or without serving (P>0.05). It is concluded that estrus duration in goats is shortened by serving and that no differences in duration exist between multiparous and nulliparous.

Maintaining long-term vessel patency in microvascular surgery using tissue-type plasminogen activator.

The primary cause of free flap failure remains vascular thrombosis at the microanastomosis site. Four-hour local infusion of tissue plasminogen activator (t-PA) has been proved to effectively lyse thromboses in microvascular studies of animals; however, rethrombosis occurs once the infusion of t-PA has been terminated. The present study was designed to examine the efficacy of 48 hours of a continuous local t-PA infusion in maintaining long-term venous patency. Our previously described modified arterial inversion graft reanastomosed into the venous system was used in rabbits to form venous thrombi. Three mg of t-PA was infused over 48 hours in eleven rabbits. Seven of eleven grafts were patent at 48 hours and four remained patent at 1 week. In comparing the patency rates in this study with the overall patency rate using the modified arterial inversion graft model (1/22), there are statistically significant differences at both 48 hours (p less than 0.001) and 7 days (p less than 0.05). We conclude that lengthening the infusion time of t-PA may increase the long-term patency rate in this animal model.

Thrombolysis in microvascular surgery using tissue-type plasminogen activator.

Thrombosis at the microanastomotic site is the primary cause of free flap failure. Tissue-type plasminogen activator, a potent thrombolytic agent, effectively lyses vessel thromboses. This study examined the efficacy of tissue-type plasminogen activator in a microvascular model using a modified vascular inversion graft in rabbits. Seventeen rabbits underwent this procedure with formation of thromboses in all but one inversion graft. Ten rabbits were locally infused with 1 mg of tissue-type plasminogen activator over a period of 4 hours; 6 control rabbits received normal saline infusions. Blood flow across the graft was reestablished in all 10 rabbits receiving tissue-type plasminogen activator and in none of those with normal saline infusions. Systemic fibrinolysis was not significantly altered. We conclude that local infusion of tissue-type plasminogen activator is effective in lysing thromboses that may occur at the venous microvascular anastomotic site without significant activation of systemic fibrinolysis.

Changes in cartilage proteoglycans associated with calcification.

The purposes of these experiments were to study the biosynthetic and postbiosynthetic relationships between proteoglycans in noncalcified growth cartilage and calcified cartilage in metaphysis from the costochondral junctions of immature rabbits. Based on in vivo experiments in which 35 S-sodium sulfate was injected into rabbits, it is shown that proteoglycans from the hypertrophic region becomes part of the calcified cartilage matrix which is to be incorporated into the metaphysis. The proteoglycan aggregates in the growth apparatus undergo partial disaggregation and degradation. There is approximately a 25% decrease in aggregation from regions of the rib distal to the metaphyseal-growth plate junction (69%) to the region proximal to it (50%). In contrast, in their final state in calcified cartilage, the proteoglycans are more completely disaggregated and the proteoglycans subunits are smaller, as adjudged from gel chromatography. Control experiments indicate that although some artifactual disaggregation is produced by the extraction process, it is not of the same magnitude as that seen in the actual isolation experiments nor are the subunits reduced in size.

[Spontaneous dissection of the coronary arteries]. / Disección espontánea de las arterias coronarias.

We describe a 31 years old female who suffered an spontaneous dissection of the left main coronary trunk. She presented with an acute hemorrhagic myocardial infarction complicated with bifascicular block and fatal left ventricular failure. Pathological features demonstrated severe proximal left coronary artery intimal dissection and extensive hemorrhagic infarction of the left ventricle, as well as absence of atherosclerotic aortic or coronary artery disease. The severity of the clinical picture and relentless deterioration of the patient precluded the utilization of coronary arteriography to assess an emergency surgical procedure. Early and vigorous management including emergency coronary angiography, balloon counterpulsation and surgical treatment are stressed and should be carefully weighted in similar cases.