Specific binding of a potent LHRH agonist in rat testis

High affinity binding sites for the potent LHRH agonist [125I][D-Ser(TBU)6, des-Gly-NH2(10)]LHRH ethylamide are present in dissociated rat testicular interstitial cells, a preparation rich in Leydig cells. The iodinated LHRH agonist binds to a single class of high affinity sites at a KD value of 0.12 nM and the number of binding sites is approx. 2500 per interstitial cell. A close correlation is observed between the potency of representative LHRH agonist to stimulate LH release in anterior pituitary cells in culture and their affinity for the testicular binding sites. The presence of specific LHRH receptors in an enriched population of Leydig cells suggests that these receptors could play a role, not only in the antifertility effects of LHRH agonists, but also in the physiological control of testicular functions.

Temperature-controlled laser photocoagulation of soft tissue: in vivo evaluation using a tissue welding model

BACKGROUND AND OBJECTIVES

Laser surgical procedures involving photocoagulation of soft tissue have relied on subjective visual endpoints. The thermal damage to the denatured tissue in these procedures is highly dependent on the tissue temperatures achieved during laser irradiation. Therefore, a system capable of real time temperature monitoring and closed loop feedback was used to provide temperature controlled photocoagulation (TCPC).

STUDY DESIGN/MATERIALS AND METHODS

The TCPC system consisted of a 1.32 microns Nd:YAG laser, an infrared thermometer, and a microprocessor for data acquisition and feedback control. A porcine skin model was used. Tissue welds were completed to evaluate the photocoagulation effects at different predetermined temperatures. A quantitative measurement of tissue photocoagulation was obtained by tensile strength measurements of the laser repairs. Histology of the irradiated tissue was used to determine the extent of thermal injury associated with different photocoagulation temperatures.

RESULTS

The TCPC system was capable of maintaining a relatively constant temperatures (+/- 4 degrees C) during laser irradiation. The tensile strengths of acute repairs increased with temperature over the range studied (65-95 degrees C). Tensile measurements made after several days of healing showed that higher temperature (95 degrees C) welds had lower strengths than repairs completed at lower (65 degrees C or 75 degrees C) temperatures and were significantly lower at 3 days. Acute histology showed that the amount thermal damage was strongly dependent on the tissue temperature and increased both in tissue depth and lateral to the repair with temperature. The histologic results suggest that the increase in the acute repair tensile strength as the weld temperature increased was due to an increase in the depth of tissue photocoagulation. The increase in the lateral tissue injury measured histologically for higher temperature welds likely resulted in the decreased chronic tensile strengths, as a healing response to excessive thermal damage.

CONCLUSION

Tissue temperatures can be controlled during laser photocoagulation of skin. The degree of acute and chronic tissue damage is highly dependent on the temperature during welding. By controlling the tissue temperature during laser procedures, the surgical outcome can be more reliably predicted and reproduced, as compared to the conventional open loop methods. In addition, the use of a TCPC system should significantly reduce the learning curve for photothermal surgical procedures.

Human albumin solder supplemented with TGF-beta 1 accelerates healing following laser welded wound closure

BACKGROUND AND OBJECTIVE

We examined the possibility that human albumin solder can be used as a vehicle for site specific delivery of growth factors for the purpose of accelerating tissue repair following laser welded wound closure. Certain human recombinant growth factors have been shown to accelerate wound healing in model systems. Pilot in vitro studies have established that several growth factors, including TGF-beta 1, maintain bioactivity following exposure to temperatures achieved during laser tissue welding. Using a temperature controlled laser delivery system (TCL) to precisely maintain welding temperatures, it is now possible to avoid thermal denaturation of exogenous bioactive molecules such as growth factors.

STUDY DESIGN/MATERIALS AND METHODS

HB-EGF, bFGF, and TGF-beta 1 were tested in vitro for maintenance of bioactivity after exposure to 80 degrees C. In vivo experiments using porcine skin determined the efficacy of solders augmented with growth factors. Incisions were repaired using human albumin alone or supplemented with HB-EGF (2 micrograms), bFGF (10 micrograms), or TGF-beta 1 (1 microgram). Wounds were excised at 3, 5, and 7 days post-operatively. Tensile strength, total collagen content, and histology were performed.

RESULTS

At 3 days, tensile strength (TS) of TGF-beta 1 wounds were 36% (P < 0.05) and 20% (n.s.) stronger than laser alone and suture closures, respectively. By 5 days the TS of the TGF-beta 1 group increased by 50% (P < 0.05) and 59% (P < 0.02) over laser alone and suture groups, respectively. At 7 days the TGF-beta 1 group was 50% (P < 0.05) and 79% (P < 0.01) stronger than laser solder alone or suture, respectively. The HB-EGF and bFGF groups were equivalent to the laser solder group at all time points. Total collagen TGF-beta 1 Accelerates Healing Following Laser Welding content at 7 days increased in the TGF-beta 1 group by 7% (n.s.) over the suture group and 21% (P < 0.05) in the laser group.

CONCLUSION

Human albumin solder supplemented with TGF-beta 1 increases the early post-operative strength of laser welded wounds. This novel application of laser tissue soldering augmented with a growth factor has the potential to bring about immediate fluid tight seals while providing site specific delivery of biological modifiers. This may lead to an overall improvement in post-operative convalescence, wound infections, and hospital costs.

Effects of endogenous absorption in human albumin solder for acute laser wound closure

BACKGROUND AND OBJECTIVE

Human albumin is currently being used as a biological solder in laser tissue welding. Experiments were performed to characterize the effects of differing albumin concentrations on wound closure when a 1.32 microm Nd:YAG laser is used to repair skin incisions.

MATERIALS AND METHODS

In vivo comparison of acute tensile strength was made in full thickness porcine skin wounds using different solder concentrations. Histology of the repairs was also completed to evaluate the thermal denaturation of the tissue and solder. Transmission measurements were completed for nondenatured and denatured albumin solders. Finally, the real time denaturation pattern of different solder concentrations during laser irradiation was investigated.

RESULTS

A tissue solder consisting of 50% albumin provides the greatest tensile strength for acute in vivo skin closure. The transmission measurements verify that the primary absorber of 1.32-microm laser light was the solder solvent (water). A significant decrease in power transmission occurs when the 25% albumin solder was denatured. The real time denaturation profiles demonstrate that 1.32-microm laser light denatures 25% albumin solder from the outer surface, while in 50% albumin solder, denaturation occurs from within the solder bulk. Wound histology corroborates the pattern of denaturation seen in vitro.

CONCLUSION

The combination of 1.32-microm laser light and 50% human albumin solder can be used to create a deep tissue weld resulting in higher acute repair tensile strength. This permits a deep to superficial closure of wounds, which may result in an optimal method of acute closure for full-thickness wounds.

Effects of mibefradil, a T- and L-type calcium channel blocker, on cardiac remodeling in the UM-X7.1 cardiomyopathic hamster

Abnormalities of T-type calcium channel function reported to occur in the transition phase to heart failure in the hamster cardiomyopathy may contribute to progression of the disease. We tested the hypothesis that chronic exposure to mibefradil, a selective T-type calcium channel blocker, improves the deleterious cardiac remodeling observed in this condition. In the present study, 40 normal (N) and 40 UM-X7.1 cardiomyopathic hamsters (CMH), aged 180 days, were treated daily by gavage for 21 days with mibefradil (30 mg/Kg). Eight to 10 animals from each group were sacrificed at the end of the treatment period while the remainder were followed for an additional 30 days without treatment (washout period). Hearts were harvested, fixed with 10%-buffered paraformaldehyde and then cut in half down the middle. Several slices were dehydrated, embedded in paraffin and stained with Masson Trichrome. Wall thickness and dilatation index of the left ventricle were estimated by planimetry. Myocardial capillary density was also computed. The greater heart weight/body weight ratio seen in untreated CMH (7.7 +/- 0.4 vs 5.5 +/- 0.2 in N, p < 0.05) was improved with mibefradil. The dilatation index averaged 0.504 +/- 0.04 in N was increased in untreated CMH (0.566 +/- 0.03) and ameliorated in mibefradil-treated CMH. The 1-month washout period led to further deterioration of the dilatation index in untreated and mibefradil-treated CMH. Capillary density averaged 10,000 +/- 781 per mm2 in hearts from untreated N hamsters and 8,830 +/- 795 per mm2 in untreated CMH (p = NS). Chronic exposure to mibefradil resulted in a significant reduction of capillary density in both N and CMH hearts. Following the 1-month washout period, the change in myocardial capillary density associated with mibefradil was no longer detectable. In conclusion, chronic exposure to mibefradil, a T- and L-type calcium channel blocker, exerts opposite effects during the transition phase to heart failure in CMH, improving the deleterious left ventricular remodeling in UM-X7.1 hamsters and reducting myocardial capillary density independently of the disease process.

Attachment of epiphyseal cartilage cells and 17/28 rat osteosarcoma osteoblasts using mussel adhesive protein

These experiments show that mussel adhesive protein (MAP) enhances the attachment of osteoblasts and epiphyseal cartilage cells to plastic culture dishes and Vitallium. When MAP was applied to culture plate surfaces, there were two- to fivefold increases in the numbers of cells attaching compared to control surfaces (no MAP). Results were confirmed using two different cell attachment assay techniques. Osteoblast replication and culture on MAP is possible, suggesting that MAP is not toxic to cells. MAP also holds applied cells to surfaces as initially attached.

Modulation of rat pituitary gonadotrophin secretion by porcine granulosa cell 'inhibin', LH releasing hormone and sex steroids in rat anterior pituitary cells in culture

The incubation of female rat adenohypophysial cells in primary culture with porcine granulosa cell culture medium (GCM) led to the complete inhibition of responses of LH and FSH to LH releasing hormone (LHRH) as well as to the inhibition of spontaneous release of FSH. These effects of GCM suggest the specificity of the 'inhibin'-like activity of this material. Granulosa cell culture medium completely reversed the stimulatory effect of oestradiol-17 beta on the responses of LH and FSH to LHRH, as well as reversing the stimulatory effect of progesterone, oestradiol or a combination of both steroids on the spontaneous release of FSH, while not affecting the spontaneous release of LH. The antioestrogenic effects of progesterone observed on the response of LH to 0.3 nM-LHRH were amplified in the presence of GCM while the stimulatory effects of progesterone, oestradiol or both on the response of FSH to 0.3 nM-LHRH were completely reversed by the medium. Moreover, the presence of GCM led to an additive inhibitory effect with dihydrotestosterone on the response of LH to LHRH while it completely reversed the stimulatory effect of the androgen on spontaneous and LHRH-induced FSH release. The present data show that the presence of porcine granulosa cell 'inhibin' activity can exert marked interactions with sex steroids in the control of gonadotrophin secretion. This 'inhibin' activity reversed all the stimulatory effects and potentiated all the inhibitory effects of sex steroids on gonadotrophin secretion. Although the physiological role of 'inhibin' remains to be defined well, the importance of this activity is clearly demonstrated in anterior pituitary cells in culture.

Modulation of cyclic AMP formation and progesterone secretion by human chorionic gonadotropin, epinephrine, buserelin and prostaglandins in normal or human chorionic gonadotropin desensitized rat immature luteal cells in monolayer culture

It is now well recognized that hCG-induced luteolysis is associated with hCG-induced desensitization, but the physiological significance of luteal cell GnRH, PGs and beta-receptors is still undefined. Therefore, we intend in this study to observe the effects of prostaglandin F2 alpha and prostaglandin E2 and the interactions between epinephrine, a potent LHRH agonist [(D-Ser-(TBu)6, des-Gly-NH10(2) LHRH ethylamide: Buserelin] and hCG in normal and in vitro hCG-desensitized rat immature luteal cells in monolayer culture, on basal, hCG or cholera toxin stimulated intracellular and extracellular cAMP and progesterone secretion. The present report shows that incubation of immature rat luteal cells in monolayer culture with Buserelin, led to 25-50% inhibition of the epinephrine-as well as PGE2-induced cAMP and progesterone responses. The LHRH agonist can also reverse the stimulatory effects of cholera toxin in the presence of hCG and led with PGF2 alpha, to additive inhibitory effects on extracellular cAMP accumulation induced by cholera toxin. Both Buserelin and PGF2 alpha can reverse the hCG-induced cAMP and progesterone release but no effect could be observed when the incubation was carried out with either substance in the absence of hCG. Prostaglandin E2, in acute conditions of incubation, seems to share agonist properties with hCG when both were incubated with luteal cells. Buserelin reversed the stimulatory effects of PGE2, hCG, epinephrine and cholera toxin on cAMP and progesterone responses to these substances. These results suggest that Buserelin and PGF2 alpha have luteolytic-like effects and that there may be a complementary action for the two substances. Preincubation of rat luteal cells in monolayer culture with 1 nM hCG for a 24 h period led to the inhibition of cAMP and progesterone responses after a subsequent exposure to hCG and epinephrine. Luteal cells were no longer responsive to hCG while the presence of epinephrine in hCG-desensitized cells led to a 40% stimulation of cAMP and progesterone production. These observations suggest that occurred a partial alteration of the N component activity of the adenylyl cyclase system.

Modulation of cyclic AMP formation and progesterone secretion by human chorionic gonadotropin, epinephrine, buserelin and prostaglandins in normal or human chorionic gonadotropin desensitized rat immature luteal cells in monolayer culture

It is now well recognized that hCG-induced luteolysis is associated with hCG-induced desensitization, but the physiological significance of luteal cell GnRH, PGS and beta-receptors is still undefined. Therefore, we intend in this study to observe the effects of prostaglandin F2 alpha and prostaglandin E2 and the interactions between epinephrine, a potent LHRH agonist [(D-Ser-(TBu)6, des-Gly-NH2(10)) LHRH ethylamide: Buserelin] and hCG in normal and in vitro hCG-desensitized rat immature luteal cells in monolayer culture, on basal, hCG or cholera toxin stimulated intracellular and extracellular cyclic AMP and progesterone secretion. The present report shows that incubation of immature rat luteal cells in monolayer culture with Buserelin, led to 25-50% inhibition of the epinephrine--as well as PGE2--induced cyclic AMP and progesterone responses. The LHRH agonist can also reverse the stimulatory effects of cholera toxin in the presence of hCG and led with PGF2 alpha, to additive inhibitory effects on extracellular cyclic AMP accumulation induced by cholera toxin. Both Buserelin and PGF2 alpha can reverse the hCG-induced cyclic AMP and progesterone release but no effect could be observed when the incubation was carried out with either substance in the absence of hCG. Prostaglandin E2, in acute conditions of incubation, seems to share agonist properties with hCG when both were incubated with luteal cells. Buserelin reversed the stimulatory effects of PGE2, hCG, epinephrine, and cholera toxin on cyclic AMP and progesterone responses to these substances. These results suggest that Buserelin and PGF2 alpha have luteolytic-like effects and that there may be a complementary action for the two substances. Preincubation of rat luteal cells in monolayer culture with 1 nM hCG for a 24 h period led to the inhibition of cyclic AMP and progesterone responses after a subsequent exposure to hCG and epinephrine. Luteal cells were no longer responsive to hCG while the presence of epinephrine in hCG-desensitized cells led to a 40% stimulation of cAMP and progesterone production. These observations suggest that there occurred a partial alteration of the N component activity of the adenylyl cyclase system.

Modulation of gonadotropin secretion by Sertoli cell inhibin, LHRH, and sex steroids

Sertoli cell culture media (SCM) from 10-, 20-, 30-, 35-, and 40-day-old male Wistar rats were assayed to determine the inhibin activity in anterior pituitary cells in culture. In agreement with previous data, SCM did not affect the luteinizing hormone (LH) spontaneous release at all ages studied, whereas it inhibited specifically follicle-stimulating hormone (FSH) spontaneous release by 40% for the 40-day-old rats. Younger animals (10-, 20-, and 30-day-old) showed a 60% inhibition of the FSH basal release. The inhibin activity was also different at all stages studied, the IC50 being markedly displaced to the right as the age increased, leading to a fivefold difference between 10- and 30- to 40-day-old rats. The same pattern was observed when the LH and FSH responses to 0.3 nM LH-releasing hormone (LHRH) were studied. SCM from 35-day-old rats did not alter total LH, whereas total FSH was markedly reduced, thus suggesting a reduced FSH synthesis in the presence of inhibin. SCM exerts an additive inhibitory effect with dihydrotestosterone on the LH response to LHRH, whereas it reverses the stimulatory effect of the androgen on spontaneous and LHRH-induced FSH release. Moreover, SCM reversed the stimulatory effect of 17 beta-estradiol on both spontaneous and LHRH-induced LH and FSH release, whereas the stimulatory effect of progesterone on FSH release was 50-80% inhibited. The present data show that inhibin activity of Sertoli cell origin can exert marked interactions with sex steroids in the control of gonadotropin secretion. These data also demonstrate that the inhibin component is an important factor in sexual maturation of the rat and that high FSH levels of 10-day-old rats could suggest a modulation by a nonandrogenic factor of gonadotropin secretion in developing rats.