Stimulation of wound bursting strength during protein malnutrition

Nutrition is one of the most important factors affecting wound healing. Patients who have significant protein malnutrition and require emergency surgery are frequently encountered. Conventional nutritional preparation for surgery, with intravenous hyperalimentation, requires 10 to 14 days to demonstrate advantageous reversal of catabolism. Growth hormone is known to have an anabolic effect in malnourished animals. The purpose of this investigation was to study the ability of growth hormone, administered from the time of celiotomy, to improve wound strength in protein-malnourished animals and compare its efficacy with preoperative nutritional repletion. Rats were divided into four groups: Group I--normal control rats, group II--malnourished rats, group III--malnourished rats treated with growth hormone for 5 postoperative days, and group IV--malnourished rats refed normal chow for 3 days before operation. Controlled laparotomy wounds were closed with monofilament nylon which was removed at the time wound bursting strength was tested. Bursting strengths at the sixth day postoperative were as follows (means +/- SD): (table; see text) Wound strength of malnourished animals was significantly less than that of controls, (P less than 0.001). Wound bursting strength of groups III and IV was significantly improved over that of malnourished animals (group II), P less than 0.001. The bursting strength of group IV was significantly higher than that of group III. Growth hormone administration following celiotomy is nearly as effective in improving wound healing as preoperative nutritional repletion. These results suggest that growth hormone may be clinically applicable in preventing wound complications in malnourished patients requiring urgent or emergency laparotomy.     

Growth hormone reverses impaired wound healing in protein-malnourished rats treated with corticosteroids.

Corticosteroid (CS) administration amplifies the inhibitory effect of protein malnutrition (PM) on wound healing. Abdominal surgery in protein malnourished patients receiving corticosteroids (eg, advanced malignancy, transplant recipients) may be complicated by wound dehiscence or anastomotic breakdown. Although preoperative parenteral nutrition can reduce the incidence of these complications, this is not possible in patients requiring urgent surgical intervention. In a previous report we demonstrated that postoperative growth hormone (GH) administration could restore normal wound healing in PM rats. This study evaluates the effect of GH on wound healing in PM rats treated with CS. Forty-eight female Sprague-Dawley rats weighing 180 to 210 g were divided into four groups: (1) normally nourished; (2) PM only; (3) PM + CS; and (4) PM + CS + GH. PM rats (groups 2 to 4) received 5.5% protein chow every other day for 8 weeks. Control rats (group 1) received 23.4% protein chow for the same duration. Group 3 and 4 rats received prednisolone (2 mg/kg, intramuscularly) during the last 3 weeks of PM. All animals underwent precise 5-cm midline celiotomies. Postoperatively, rats in all groups were given 23.4% protein chow. Group 3 and 4 rats continued to receive CS postoperatively. Group 4 rats were given GH (0.5 mg/d, intraperitoneally) postoperatively for 5 days. Wound testing was performed on the 6th postoperative day after removal of the sutures. A balloon inserted into the peritoneal cavity through the vagina was gradually inflated. The pressure at which the wound disrupted was recorded as the wound bursting strength.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of tumor necrosis factor-alpha attenuates wound breaking strength in rats.

Exogenous administration of tumor necrosis factor-alpha has been shown to both enhance and attenuate cutaneous healing in a dose-dependent manner. We examined the effects of tumor necrosis factor inhibition in the healing wound by both systemic and local administration of tumor necrosis factor-binding protein. Male Balb/C mice underwent dorsal skin incision with subcutaneous implantation of 20 mg polyvinyl alcohol sponges (4 per animal). In Experiment I, one group (n = 20) received intraperitoneal injections of tumor necrosis factor-binding protein (3 mg/kg) at the time of wounding, while another group (n = 20) received saline. Four animals from each group were euthanized on days 1, 3, 5, 7, and 14 postwounding. In Experiment II, one group (n = 10) received an intraperitoneal injection of tumor necrosis factor-binding protein (3 mg/kg) at the time of wounding and every third day thereafter. Another group (n = 10) received an intraperitoneal injection of saline at the time of wounding and every third day thereafter. In Experiment III, one group received a single intraperitoneal injection of tumor necrosis factor-binding protein (3 mg/kg) at the time of wounding (n = 7), or on postwounding day 4 (n = 7), or day 7 (n = 7). Another group received saline injections at the time of wounding (n = 7), or on postwounding days 4 or 7 (n = 7, respectively). All animals in Experiments II and III were killed at postwounding day 14. Wound breaking strengths were assessed using a tensiometer. Wound fluid collected from the implanted sponges was assayed for tumor necrosis factor-alpha and tumor necrosis factor-binding protein levels using a biological assay and enzyme-linked immunosorbent assay, respectively. Collagen gene expression in sponge granulomata was assessed by Northern analysis. Collagen deposition in sponges was quantified by measuring hydroxyproline content. Wounds were significantly weaker in the animals that received repeated injections of tumor necrosis factor-binding protein with a mean wound breaking strength of 93.1 g vs. 186.6 g in controls (p < 0.05). Wound breaking strength in groups that received a single injection of tumor necrosis factor-binding protein on either day 0, 4, or 7 postwounding were no different than their respective controls. There was no difference in the mean hydroxyproline content of sponges between any of the tumor necrosis factor-binding protein groups and their respective controls. Northern analysis for collagen I and III expression also revealed no differences. These data indicate that continued systemic administration of tumor necrosis factor-binding protein resulted in significantly weaker wounds with no corresponding differences in wound collagen content, and collagen gene expression. This suggests that tumor necrosis factor-alpha inhibition throughout healing leads to a qualitatively impaired wound without a quantitative alteration in collagen deposition.     

Improvement of growth and food utilization by human recombinant growth hormone in uremia

We compared growth rate, food conversion ratio and morphology of the growth zone in female Sprague-Dawley rats with subtotal nephrectomy or sham operation. Both groups were either given vehicle or 1.4 IU/day recombinant human growth hormone (GH) by s.c. osmotic minipump, or 2.5 IU twice daily intraperitoneally for 14 or 20 days, respectively. Compared to uremic rats infused with vehicle, infusion of GH significantly (P less than 0.01) improved growth; that is, it increased gain of weight (delta 27.0 +/- 7.7 g vs. 11.6 +/- 4.9 g) and length (delta 1.8 +/- 0.3 cm vs. 1.12 +/- 0.44 cm) in ad libitum fed uremic rats. This was accompanied by increased food utilization ratio (0.146 vs. 0.065 g weight gain per g food intake). A similar increment of growth and food utilization ratio was also observed in GH versus solvent infused controls, either pairfed as for the uremic animals or fed ad libitum. Despite administration of GH, growth was not completely restored to normal in uremic animals. Circulating immunoreactive IGF I was not significantly increased by GH infusion in either uremic animals or controls. Histological analyses of the proximal tibia showed increased rate of longitudinal growth, as evaluated by tetracyclin-labeling, and increased volumetric density of primary spongiosa with unchanged width of primary spongiosa trabecules when GH was infused in uremic animals. The data suggest that growth impairment in the uremic rat is partially responsive to GH, and this is not accompanied by an increase of circulating IGF I. Therapeutic trials with recombinant GH in uremic children appear justified.     

Wound tensile strength in the hairless guinea pig following irradiation with pure ultraviolet-A light

Ultraviolet light in the wavelength range of 315-400 nm (UVA) is known to penetrate the epidermis more readily than UVB and to result in significant dermal damage. Fibroblasts within the dermis are responsible for the production of collagen, which is the chief determinant of wound tensile strength during the third week of wound healing. The present study assesses the effects of UV radiation limited to the UVA wavelength on wound tensile strength in the hairless guinea pig. Twenty female hairless guinea pigs were randomly divided into two equal groups (n = 10). Group 1 animals served as controls. Group 2 animals were irradiated with 120 J/cm2 from a pure UVA fluorescent light source every other day for a period of 21.3 weeks (cumulative dose = 8960 J/cm2). Upon completion of the irradiation schedule, a standard 6 cm linear full-thickness surgical wound was created on the dorsum of all animals and allowed to heal for 21 days. The wounds were excised and wound tensile strength was assessed by determining breaking strength and dividing by the breaking-point surface area. Wound tensile strength was significantly lower (p less than 0.0017) in irradiated animals (0.99 +/- 0.12) than in controls (1.54 +/- 0.08). Therefore, UVA at this dose significantly decreased wound tensile strength in this model and raises further concern regarding exposure to this wavelength of ultraviolet radiation.     

Changes in abdominal wounds following treatment with sirolimus and steroids in a rat model

Wound healing complications have been observed in patients receiving sirolimus (SLR). This study examined the degree and duration of delayed healing in various protocols using SLR. Sprague-Dawley rats underwent a standard midline abdominal incision and wound closure. Groups of 6 rats each were randomized to receive different doses of SLR (2 and 5 mg/kg) with or without loading dose (10 mg/kg x3 days), and with or without steroids (20 mg/kg x3 days followed by 5 mg/kg for 2 weeks). Rats were humanely killed on postoperative days 5, 10, or 15. Wound breaking force was measured using the EHMI BIAX-II instrument and tensile strength was calculated. Wounds in control animals had gradual increase in tensile strength during the 15-day observation. In contrast, high and loading doses of SLR caused reduction in wound strength until day 10, but the wounds' tensile strength became equivalent to control by day 15. The addition of steroids prolonged wound recovery with low doses of SLR until day 15 and had very profound effects on healing in high-dose SLR-treated animals (>50% reduction) that continued beyond the 2 weeks of observation. Low doses of SLR in non-steroid-treated animals had a short-term (5-day) impact on wound healing; high dose and loading doses delayed healing for 10 to 15 days. The addition of steroids had a synergistic effect on delayed wound healing, particularly in animals receiving high-dose SLR, which demonstrated prolonged wound weakness. These results may provide practical guidelines for postoperative introduction of SLR in the context of various clinical protocols.     

Effects of recombinant human growth hormone in patients with severe sepsis.

The objective of this study was to evaluate the safety and the effect of recombinant exogenous growth hormone (GH) on nitrogen production in patients with severe sepsis. It was designed as a prospective, randomized, placebo-controlled trial, and performed in the medical intensive care unit of a university hospital. Twenty patients admitted with septic shock and receiving standard parenteral nutrition served as subjects. Treatment consisted of GH 0.1 mg/kg/day or placebo administered as continuous intravenous infusion on the second, third, and fourth days after admission. The study period was eight days. During GH administration, nitrogen production decreased significantly in the GH group and increased in controls (p < 0.01). Nitrogen balance became slightly positive in the GH group during treatment: 1.2 +/- 6.4 versus controls -3.7 +/- 3.8 g/day (day 3) (p < 0.05). Within 24 hours after cessation of treatment, differences between GH and controls disappeared. 3-Methylhistidine excretion as a measure of absolute muscle breakdown declined during the study period, but did not differ between groups. The levels of insulin, insulinlike growth factor 1, glycerol, free fatty acids, and beta-hydroxybutyrate increased during treatment. Despite continuous intravenous administration, GH levels gradually declined during the 3 treatment days, indicating increased metabolic clearance. Side effects other than insulin resistance were not observed. Growth hormone administration reduces nitrogen production and improves nitrogen balance in patients with severe sepsis. These effects are not sustained after cessation of treatment.     

Growth hormone does not attenuate the inhibitory effects of sepsis on wound healing

Chronic abdominal sepsis is associated with impaired tissue repair. Treatment of burn patients with growth hormone results in improved healing of skin graft donor sites. The goal of this study was to determine whether administration of growth hormone could attenuate the inhibitory effects of sepsis on cutaneous wound healing. Four groups of male Sprague Dawley rats were studied: control, control + growth hormone, sepsis, and sepsis + growth hormone. Sepsis was caused by implantation of a bacterial focus in the peritoneal cavity. Control animals underwent sham laparotomy, and polyvinyl alcohol sponge implants were placed in subdermal pockets in all animals. Saline or growth hormone (400 microg) was injected subcutaneously every 12 hours. On day 5, the incisional wounds and polyvinyl alcohol sponge implants were harvested. The breaking strength of abdominal incisions was measured. Granulation tissue penetration and quality were determined by scoring polyvinyl alcohol sponge implant histology from 1 to 4 in a blinded fashion. Collagen deposition in polyvinyl alcohol sponge implants was quantitated by hydroxyproline assay. Septic mortality was not altered by growth hormone administration. Septic animals showed a reduction in food consumption for 2 days after surgery (p < 0.05 vs. controls), which was not affected by growth hormone administration. The breaking strength of incisional wounds and hydroxyproline content of polyvinyl alcohol sponge implants was reduced in septic rats (p < 0.001 vs. controls) but administration of growth hormone for 5 days did not improve breaking strength or collagen deposition in either group. We conclude that the administration of growth hormone for 5 days did not improve collagen deposition or breaking strength in cutaneous wounds from control or septic animals. The results suggest that growth hormone treatment is unlikely to improve tissue repair in sepsis-induced catabolic illness.     

Prediction of wound tensile strength: an experimental study.

Wound cell specimens were obtained using a Cellstic device after 24, 48 and 72 h healing time in guinea-pig skin wounds. Cell counts from these were compared with the tensile strength values of the same wounds 7, 14 or 21 days after operation. No single cell type was predictive of wound tensile strength, although absolute numbers of different cells and selected ratios of cell types on the second or third day after operation were more predictive. Absolute and proportional changes from day 1 to day 2 had the greatest predictive power with a mean error of 9.46 per cent (F = 13.6, P less than 0.0001). The same regression model was predictive in animals with lower wound tensile strengths given perioperative hydrocortisone (3 mg/100 g).     

The reversibility of UV-altered wound tensile strength in the hairless guinea pig following a 90-day recovery period.

Investigations in our laboratory showed that exposure to ultraviolet radiation significantly diminishes wound tensile strength in hairless guinea pigs. A recurring question is whether changes in wound tensile strength are reversible. The present project addresses whether wound tensile strength in irradiated and control animals differs following a 90-day healing period after irradiation and wounding. Group 1 animals (n = 10) served as nonirradiated controls. Group 2 animals (n = 10) were irradiated with a UVA/B source receiving a cumulative dose of 8,960 joules/cm2 over a 16-week period. Following completion of the irradiation schedule, a standard 6 cm midline incision was made on the dorsum of each animal and then allowed to heal for 90 days. At this time, wound tensile strength measurements were performed. The mean wound tensile strength value for the control group (4.62 +/- 0.16) was not significantly different compared to the irradiated animals (4.23 +/- 0.24). The alteration in wound tensile strength observed at 21 days in animals irradiated with a UVA/B light source is reversible after a 90-day recovery period.     

EGF increases short-term type I collagen accumulation during wound healing in diabetic rats

Continuous topical application of epidermal growth factor (EGF) to granulation tissue increases the rate of collagen accumulation. It is believed that the clinical use of growth factors, such as EGF, may become common in the treatment of impaired wound healing in the near future. Impairments in the production and degradation of wound collagens have been demonstrated in diabetes mellitus. We studied the effects of a single, local application of EGF on collagen content, collagenase activity, and the ratio of type III and type I collagens within granulation tissue using polytetrafluoroethylene (PTFE) wound cylinders in 48 streptozotocin-induced diabetic rats in order to determine potential benefits of EGF to wound healing in diabetics. Wound collagen content in EGF-treated diabetic animals was significantly higher than in diabetic controls during the first 10 days of wound healing (236% on day 5, P less than .001; 140% on day 10, P less than .01), but decreased to significantly lower levels by day 15 of healing (71% of diabetic controls, P less than .01; 47% of nondiabetic controls, P less than .01). An 18% increase in diabetic wound protease activity was observed following application of EGF (P less than .001). The ratio of type III collagen to total wound collagen within the granulation tissue was significantly reduced (P less than .001) following EGF application. We demonstrate that a single, topical application of EGF promotes early synthesis of type I collagen, thereby deranging the usual type III/total collagen ratio, and is associated with increased wound protease activity.     

Effect of experimental diabetes and growth hormone administration on the strength of colonic anastomoses in rats.

The influence of growth hormone (GH; 2 mg/kg/day) administration on the mechanical breaking strength of colonic anastomoses in diabetic rats has been investigated on the day of operation (suture binding capacity) and after 4 and 7 days of healing. In diabetic rats, the suture binding capacity was decreased by 26% in both ultimate load and relative failure energy. After 4 days of healing, no difference was observed between control and diabetic animals. After 7 days, relative failure energy in the diabetic animals was reduced by 33%. GH administration to diabetic animals did not alter strength during the first week of healing. We found an increased circumference (33%) and defatted dry weight (22%) of the colon in diabetic rats. In conclusion, diabetes impairs the suture-binding capacity of the colon in rats, while there is only little influence on healing in the following week. GH administration could not influence the strength of colonic anastomoses in diabetic animals.     

Effect of nutrition, diet and suture material on long term wound healing.

Although it is known that malnutrition hinders early wound healing, it has not been determined whether this occurs because of formation of a poor scar or a slow rate of normal healing; the ultimate fate of the malnourished wound is unknown. Malnutrition was produced in rats by short gut syndrome. Elemental diet was compared to rat chow and silk was compared with polyglycolic acid suture. Nutritional deficiency was seen in short gut rats for two weeks postoperatively. Thereafter adaptation allowed partial recovery, but relative deficiency persisted. Morbidity and mortality of short gut rats doubled that of controls and all wound complications were limited to this group, occurring within the first two weeks. Malnourished animals surviving for 60 days had wound strength equal to the control rats as determined by gut anastomosis bursting strength, skin wound breaking strength and wound hydroxyproline content. Neither diet nor suture material altered ultimate wound strength. Improved nutrition allowed more animals and wound to survive, but ultimate healing survivors was indistinguishable from that of normal controls. Thus early weakness probably results from slow healing rather than formation of poor scar. Nutrition plays an important role in early strength and survival, but not in ultimate wound healing.     

Metabolic effects of recombinant human growth hormone in patients receiving parenteral nutrition.

Recombinant human methionyl growth hormone (Protropin) (Genetech, Inc., San Francisco, CA) administered to normal volunteers receiving hypocaloric parenteral nutrition minimized weight loss and induced positive nitrogen balance. To evaluate whether growth hormone (GH) can promote anabolism in surgical patients, 11 stable malnourished individuals were studied. In the initial trial, subjects received a constant parenteral infusion of a hypocaloric diet that provided approximately 1100 kcal/24 hr and 1.3 g protein/kg/24 hr for at least 2 weeks. During 1 week, GH 10 mg was given subcutaneously daily, whereas the other week served as the control. Daily balance studies demonstrated that administration of GH resulted in significant retention of nitrogen (+3.4 g/24 h) and phosphorus (+218 mg/24 h), despite provision of only 60% of caloric requirements. With GH, serum blood urea nitrogen (BUN) and potassium fell, whereas glucose and insulin tended to rise, and levels of insulin-like growth factor 1 increased three to fourfold. Weight gain occurred with GH and was associated with positive mineral and water balance. Six patients received GH (10 mg subcutaneously daily) for 13-25 consecutive days after an initial control week. Significant nitrogen and phosphorus retention occurred over the entire period of GH administration, and no significant side effects were observed. In these depleted patients, GH caused significant and sustained nitrogen retention over a wide range of nutritional support. GH appears to enhance the efficacy of parenteral nutrition in stable individuals requiring repletion of body protein.     

Effects of Hibiscus rosa sinensis L (Malvaceae) on wound healing activity: a preclinical study in a Sprague Dawley rat

Hibiscus rosa sinensis (H rosa sinensis), a plant product, has been used for the treatment of a variety of diseases as well as to promote wound healing. The wound-healing activity of the ethanol extract of H rosa sinensis flower was determined in rats, using excision, incision, and dead space wound models and is presented in this report. The animals were randomly divided into 2 groups of 6 each in all the models. Test group animals in each model were treated with the ethanol extract of H rosa sinensis orally by mixing in drinking water (120 mg kg(-1) day(-1)), and the control group animals were maintained with plain drinking water. Healing was assessed by the rate of wound contraction, period of epithelialization, tensile strength (skin breaking strength), granulation tissue weight, and hydroxyproline content. The antimicrobial activity of the flower extract against selected microorganisms that infect the wounds was also assessed. Animals treated with the extract exhibited an 86% reduction in the wound area compared with controls, who exhibited a 75% reduction. The extract-treated animals were found to epithelize their wounds significantly faster than controls (P < .002) and have shown significantly higher skin-breaking strength than controls (P < .002). The dry and wet weight of granulation tissue and hydroxyproline content were also increased significantly when compared with controls. The reported observations suggest H rosa sinensis aids wound healing in the rat model.     

Acceleration of tensile strength of incisions treated with EGF and TGF-beta.

The ability of surgeons to accelerate wound healing through pharmacologic intervention is limited. The effects of locally applied, biosynthetic human epidermal growth factor (EGF) and transforming growth factor-beta (TGF-beta) on tensile strength of experimental incisions were investigated. A single dose of EGF in saline failed to increase tensile strength over controls. Thus, EGF was incorporated into multilamellar liposomes, which prolonged the exposure of incisions to EGF (p less than 0.001). A single dose of EGF in multilamellar liposomes produced a 200% increase in wound tensile strength over controls between 7 and 14 days (p less than 0.05). Light and electron microscopy of the wounds revealed increased collagen formation and fibroblast proliferation. A single dose of TGB-beta in a collagen vehicle stimulated a 51% increase in wound tensile strength at 9 days (p less than 0.01). We conclude that addition of EGF and TGF-beta in appropriate vehicles stimulates early transient increases in wound tensile strength in normal rats.     

Supplemental L-arginine enhances wound healing in diabetic rats

L-arginine has been shown to enhance wound strength and collagen deposition in rodents and humans. Diabetes mellitus, which impairs wound healing, is accompanied by a reduction in nitric oxide at the wound site. The amino acid L-arginine is the only substrate for nitric oxide synthesis. We sought to determine whether supplemental L-arginine can restore the impaired wound healing of diabetic rats. Fifty-six male Lewis rats were used in this study, of which twenty-nine rats were rendered diabetic 7 days prior to surgery with intraperitoneal streptozotocin. Twenty-seven untreated rats served as controls. Animals underwent a dorsal skin incision with implantation of polyvinyl-alcohol sponges. Sixteen diabetic and 14 normal rats received 1 g/kg/day of L-arginine by injection, while the remainder received saline injections only. Animals were euthanized 10 days postwounding, and their wounds were analyzed for breaking strength. The wound sponges were assayed for total hydroxyproline and nitrite/nitrate content. Plasma and wound fluid concentrations of L-arginine, ornithine, and citrulline were determined. Wound sponge RNA was extracted and subjected to Northern blot analysis for procollagen I and III. Diabetic wounds had greatly decreased breaking strengths compared with controls. L-arginine significantly enhanced wound breaking strengths in both control (+23%) and diabetic animals (+44%), and also increased wound hydroxyproline levels in both diabetic (+40%) and control animals (+24%) as compared to their saline-treated counterparts. mRNA for procollagen I and III were elevated by L-arginine treatment in both diabetic rats and controls. Treatment with L-arginine significantly increased wound fluid nitrite/nitrate levels in diabetic animals. The data show that the impaired healing of diabetic wounds can be partially corrected by L-arginine supplementation, and that this effect is accompanied by enhanced wound nitric oxide synthesis.     

Homologous growth hormone accelerates healing of segmental bone defects

The effect of homologous recombinant porcine growth hormone (r-pGH) on secondary fracture healing was investigated in a diaphyseal defect of the tibia in Yucatan micropigs. A 1 cm defect of the tibia was created surgically and stabilized with an AO 3.5 mm DCP plate. The treatment group (12 animals) received 100 microg of r-pGH per kilogram of body weight subcutaneously once per day, whereas the control pigs (12 animals) received 1 mL of sodium chloride as placebo. For evaluation of the GH-axis, serum levels of insulin-like growth factor-I (IGF-I) were sampled every fourth day. The animals were killed 6 weeks after surgery. Quantitative computed tomography (qCT) was performed to determine bone mineral density (BMD) and bone mineral content (BMC) of the defect zone. The torsional stiffness and the torsional failure load were measured by destructive torsional testing of the defect and contralateral tibiae. qCT measurements revealed a significant increase in the BMC of the defect zone in the treatment group compared with controls (GH BMC = 2833 +/- 679 mg, placebo BMC = 2215 +/- 636 mg; p < 0.05), whereas the BMD values were similar in both groups (GH BMD = 668 +/- 60 mg/mm(2), placebo BMD = 629 +/- 52 mg/mm(2), p = 0.12). Torsional failure load was 70% higher and torsional stiffness 83% higher in the treatment group than in the control group (p < 0.05). The mean serum level of IGF-I in the treatment group increased to 382% of the preoperative basal level and decreased to 69% in the control group, and this difference was highly significant (p < 0.001). Our data indicate that daily administration of recombinant GH leads to an increase of serum IGF-I levels and stimulates secondary fracture healing, resulting in increased mechanical strength and stiffness of the callus.     

Growth hormone is not able to counteract osteopenia of rat cortical bone induced by Glucocorticoid with protracted effect

Osteopenia and inhibited longitudinal growth in childhood are serious side effects during glucocorticoid therapy. The effects of glucocorticoids on bone have been confirmed in animal experiments. Long-term glucocorticoid administration to rats results in reduced body weights, reduced bone growth (length and cross-sectional area), and bone strength. Glucocorticoid treatment also resulted in a reduced bending stress, indicating reduced bone quality. Growth hormone, on the other hand, increased body weights, bone dimensions, and bone strength. The aim of the present study was to evaluate if growth hormone administration would have an anabolic effect on rat bone when given to animals also receiving a high dosage of glucocorticoid. Five groups of female rats, 3.5 months old, were treated as follows: (1) saline control; (2) glucocorticoid (prednisolone: Delcortol 5 mg/kg/day); (3) growth hormone (recombinant human growth hormone 5 mg/kg/day); (4) glucocorticoid and growth hormone; and (5) food restriction, consisting of restricted access to food to reduce their weight gain to match that of the glucocorticoid injected rats. After 80 days of hormone administration the animals were sacrificed. The right femur was removed and tested biomechanically in a three-point bending procedure. The left femur was used for determination of bone dimensions. Biomechanical parameters (ultimate load and ultimate stiffness) were then normalized to diaphyseal cross-sectional diameters of the femur, giving the values of ultimate bending stress and Young's modulus. Results: administration of both hormones simultaneously could not reverse the decrease in body weights, bone length, and diameters, or the decreased bone strength induced by glucocorticoid administration. In conclusion, growth hormone cannot prevent cortical osteopenia in female rats induced by a high dose of glucocorticoid with protracted effect.     

The effect of methionine on colonic wound healing in malnourished rats.

Recent studies have suggested that the healing of colonic anastomoses is impaired in malnourished subjects. It has been claimed that the healing of skin and abdominal wounds in experimental animals is improved by the administration of the essential amino acid methionine, and in the present study the effects of methionine on colonic wound healing were studied in malnourished rats. Test animals were fed a protein-free diet for 7 weeks before surgery. Methionine-treated animals received the amino acid by subcutaneous injection during the seventh week of protein deprivation and throughout the postoperative period. Anastomoses were made in the left colon, and colonic wound healing was assessed by measurements of the bursting wall tension and collagen content of anastomoses. The results were compared with those of control animals fed a normal rat diet. Protein deprivation for 7 weeks resulted in a 34% reduction in body weight, and a significant reduction in the tensile strength and collagen content of colonic anastomoses was observed. Methionine supplements had no apparent effect on these parameters of wound healing. The concept of single amino acid supplementation in cachetic patients undergoing surgery is an attractive one, but it has yet to be established that methionine supplements alone can alter the course of wound healing in such cases.