Genetic determinants of sensitivity to ethanol in inbred mice

Mice from 15 inbred strains differed in sensitivity to ethanol-induced effects on open-field activity, hypothermia, rotarod ataxia, and anesthesia. Sensitivities to the different behavioral responses were generally uncorrelated. This suggests that the genetic determinants of behavioral sensitivity to one domain of ethanol effects are unrelated to those determining other responses. On the other hand, some variables were genetically related. For example, those strains sensitive to the loss of righting reflex induced by higher doses of ethanol showed reduced activity in the open field at lower doses and were more sensitive to ethanol-induced decreases in rearing. More generally, the pattern of results suggests that genetically influenced sensitivity to ethanol is not a monolithic phenomenon. Rather, it is specific to the particular response variable studied.

Chronic cutaneous ulcers: etiology and epidemiology

The most commonly encountered chronic cutaneous ulcers in the United States are pressure ulcers and leg ulcers; this review is limited to the epidemiology of these ulcers. Chronic leg ulcers are frequently encountered in clinical practice but the extent of the problem is largely unknown. In particular, epidemiologic information within the United States is sadly lacking. Although there are more data available regarding the incidence and prevalence of pressure ulcers in acute and chronic care facilities, national surveys should be considered to obtain more accurate information on their incidence and prevalence. Multicenter studies are necessary to determine the epidemiology and cost of treating pressure ulcers by stage, setting, and other factors. Particular attention should be paid to high-risk groups such as spinal cord injury patients, the elderly, and those who are immobilized or chronically debilitated. Leg ulcers and pressure ulcers probably account for the majority of chronic cutaneous ulcers seen in the United States.

Genetic determinants of sensitivity to ethanol in inbred mice

Mice from 15 inbred strains differed in sensitivity to ethanol-induced effects on open-field activity, hypothermia, rotarod ataxia, and anesthesia. Sensitivities to the different behavioral responses were generally uncorrelated. This suggests that the genetic determinants of behavioral sensitivity to one domain of ethanol effects are unrelated to those determining other responses. On the other hand, some variables were genetically related. For example, those strains sensitive to the loss of righting reflex induced by higher doses of ethanol showed reduced activity in the open field at lower doses and were more sensitive to ethanol-induced decreases in rearing. More generally, the pattern of results suggests that genetically influenced sensitivity to ethanol is not a monolithic phenomenon. Rather, it is specific to the particular response variable studied.

Histologic evaluation of chronic human wounds treated with hydrocolloid and nonhydrocolloid dressings

BACKGROUND

Studies of acute surgical wounds in pigs have shown granulomatous tissue reactions induced by hydrocolloid dressings.

OBJECTIVE

We examined biopsy specimens from chronic wounds in humans treated with hydrocolloid or nonhydrocolloid dressings to determine whether such reactions occurred.

METHODS

A blinded retrospective analysis of 22 chronic ulcer biopsy specimens from 22 patients was performed by two dermatopathologists independently.

RESULTS

No differences were seen between hydrocolloid-treated and non-hydrocolloid-treated wounds. Granulation tissue was seen in all specimens. No cavities, eosinophilic inclusions, polarizable material, or multinucleated giant cells were identified.

CONCLUSION

There are no significant histologic differences between hydrocolloid-treated and non-hydrocolloid-treated wounds in humans.

Wound healing and aging

Age-related differences in wound healing have been clearly documented. Although the elderly can heal most wounds, they have a slower healing process, and all phases of wound healing are affected. The inflammatory response is decreased or delayed, as is the proliferative response. Remodeling occurs, but to a lesser degree, and the collagen formed is qualitatively different. Diseases that affect wound healing are more prevalent in the elderly and have a greater adverse effect on healing than in young adults. Thus, particularly in the elderly, concomitant medical problems should be treated vigorously to allow for maximum healing. Recent trials of novel therapies to enhance wound healing suggest, however, that much can be done to improve the prognosis of elderly patients with risk factors known to adversely affect wound healing.

Retrospective analysis of the results of 151 exploratory laparotomies in horses with gastrointestinal disease

Of 149 horses that underwent 151 exploratory laparotomies for gastrointestinal disorders from September 1987 to May 1991, 107 (72%) were discharged from the hospital: 100 (66%) survived for > 7 months, 94 of which returned to their intended use. Survival rate (64/80) for horses with caecum/large colon obstruction was significantly (P = 0.003) higher than for horses with small intestinal obstruction (33/64). Prolonged surgery was associated with significantly (P < 0.001) lower survival rates than short surgical time. In the large intestine, survival rate (15/29) for strangulated obstructions was significantly (P < 0.001) lower than for simple obstructions (52/58). Generalised septic peritonitis (9 horses) and bowel obstruction associated with adhesions (8 horses) were the most frequent fatal post-operative complications. The rate (6/44) of post-operative adhesions after small intestinal obstruction was significantly (P = 0.006) higher than that (2/68) following large intestinal obstruction. The rate (8/55) of post-operative adhesion formation in horses that required enterotomy/enterectomy was significantly (P = 0.003) higher than that (0/57) in horses that did not require gut wall incisions. Incisional suppuration developed in 42 horses and occurred with a significantly (P = 0.028) higher rate (32/72) after caecum/large colon lesions than after obstruction at other sites, (10/42) but was not associated with known contamination at the time of surgery (P = 0.806).

Biologic skin substitutes

BACKGROUND

The ideal skin substitute should closely approximate the skin in function. The substitute should be readily available, easily sterilized and stored, and relatively inexpensive.

OBJECTIVE

To describe recent developments in the area of biologic skin substitutes.

RESULTS

Considerable advances have been made in keratinocyte and fibroblast culturing when used in conjunction with a biodegradable material as a substrate.

CONCLUSION

There is no skin substitute that perfectly mimics autologous skin. However, recent developments show promise.

A randomized prospective study of a hydroactive dressing vs conventional treatment after shave biopsy excision

BACKGROUND AND DESIGN

Fifty shave biopsy sites were prospectively randomized to treatment with either a hydroactive dressing or conventional therapy (bacitracin plus Band-Aid). Time to complete epithelialization, pain, infection, and convenience of the therapy were assessed.

RESULTS

There was no significant difference between the two dressings with regard to time to heal, wound infection rate, or pain. However, patients preferred the hydroactive dressing because of convenience.

CONCLUSION

Hydroactive dressings did not accelerate healing compared with conventional therapy, but may facilitate wound management because of convenience and time savings in dressing changes.

A randomized single-blind controlled study of cultured epidermal allografts in the treatment of split-thickness skin graft donor sites

BACKGROUND AND DESIGN

In uncontrolled studies, cultured keratinocytes derived from donor tissue (allografts) appear to accelerate healing in a variety of acute and chronic skin wounds ranging from burns to leg ulcers. A randomized clinical trial was undertaken to compare the healing time of split-thickness skin graft donor sites in elderly patients using cultured epidermal allografts vs nonadherent dressings. Fresh-cultured epidermal grafts were used in 10 split-thickness skin graft donor sites in nine patients ranging in age from 63 to 87 years. In each patient, half the donor site was allografted and the other half treated with nonadherent dressings. To provide information about allograft survival, biopsy specimens were taken from allografted areas in three patients 2 months after the grafting procedure, for multilocus DNA analysis.

RESULTS

The mean time to complete healing was 8.4 days in allografted sites compared with 15.3 days in control sites. There was no evidence of survival of cultured allogeneic cells in allografted areas.

CONCLUSION

Cultured allografts can accelerate healing in split-thickness skin graft donor sites in elderly patients compared with nonadherent dressings. Cultured allografts do not survive permanently on the wound bed.

Selective breeding for alcohol withdrawal severity

Mouse lines have been genetically selected to be alcohol Withdrawal Seizure Prone (WSP) or Resistant (WSR). The selection index is the severity of withdrawal handling-induced convulsions seen after removal of mice from chronic exposure to ethanol vapor. Behavioral, pharmacological, and neurochemical results from a replicated bidirectional selection project are reviewed. In reciprocal F1 crosses of the WSP and WSR lines, substantial dominance for resistance to withdrawal was found in both replicated sets of lines. WSP and WSR mice differ principally, and markedly, in traits related to the severity of withdrawal from alcohols and other drugs with depressant properties. This suggests that genes influencing severity of withdrawal from chronic ethanol exposure also pleiotropically influence genetic susceptibility to dependence on other drugs of abuse. However, the results of WSP vs. WSR comparisons for traits related to ethanol sensitivity and tolerance development suggest control in large part by genes different from those influencing withdrawal severity.

Quantitative trait loci (QTL) applications to substances of abuse: physical dependence studies with nitrous oxide and ethanol in BXD mice

Recombinant inbred (RI) mouse strains were developed primarily as a tool to detect and provisionally map major gene loci--those with effects large enough to cause a bimodal distribution in the trait of interest. This implied that progress toward gene mapping was possible only for gene loci accounting for at least half of the genetic variance. More recently, QTL (quantitative trait loci) approaches have been advanced that do not require bimodal distributions and are thus applicable to a much wider range of phenotypes. They offer the prospect of meaningful progress toward detecting and mapping minor as well as major gene loci affecting any trait of interest, provided there is a significant degree of genetic determination among the RI strains. This paper presents a review of RI gene mapping efforts concerning phenotypes related to drug abuse and presents new data for studies now in progress for nitrous oxide and acute ethanol withdrawal intensity. These two studies exemplify several strengths and limitations of the RI QTL approach.

Use of genetically distinct mouse populations to explore ethanol reinforcement

Alcohol-induced locomotor stimulation in mice may provide an animal model of human euphoric responses to moderate alcohol (ethanol) doses. If a common mechanism mediates sensitivity to both drug reward (reinforcement) and drug stimulation, rodent models of drug stimulation would provide powerful tools for investigating drug reinforcement. In addition, stimulant sensitivity might provide a simple marker for susceptibility to ethanol reward, and perhaps addiction (e.g., Newlin and Thomson, 1991). This short report describes the use of three genetic mouse models, (1) FAST and SLOW selectively bred lines, (2) BXD Recombinant Inbred Strains, and (3) a panel of inbred strains of diverse genetic origin, to explore mechanisms mediating ethanol stimulation and reinforcement.

Quantitative trait loci associated with brain weight in the BXD/Ty recombinant inbred mouse strains

Adult C57BL/6J (B6) male mice had 37% heavier brains than did DBA/2J (D2) mice, while their body weights did not differ. The BXD recombinant inbred (RI) series of 20 strains, derived from a cross between B6 and D2 inbred strains, was used as the initial screen to determine significant associations between male brain weight and brain:body weight ratio, with allelic variation at 360 known marker gene loci. For brain weight, this yielded five candidate chromosome regions, each reflecting a possible quantitative trait locus (QTL) site affecting brain weight. The second step was to test as many of these five as possible using standard (non-RI) inbred strain data for brain weight previously reported in the literature. For this purpose, only strains possessing the same alleles as the B6 or D2 strains were used. Sufficient data to test two of the five candidate QTL were available. Of these, one was strongly supported as a site affecting brain weight--the D7rp2 region of chromosome 7. For the brain to body weight ratio, four chromosome regions emerged as significantly associated in the BXD series, but none were amenable to testing due to a lack of allelic information for the standard inbred strains. However, two of these regions showed highly significant associations (p less than 0.001, single test) that merit consideration as QTL sites for future testing. These two are the Hba region on chromosome 11 and the D17Tu7 region on chromosome 17. The genetic correlation between brain and body weight was low (r = 0.28), indicating that these two traits are largely genetically independent in the BXD RI series.

Genetic determinants of ethanol reinforcement

In this paper, we present examples of some of the several behaviors which have been taken to indicate the reinforcing efficacy of drugs, including ethanol. Efforts to identify the genetic determinants of these behaviors have employed diverse pharmacogenetic methods. For example, we have used selective breeding to develop mice selected for severe or attenuated ethanol withdrawal and have found that Withdrawal Seizure Prone mice show a greater conditioned preference for ethanol-associated locations than the selected Withdrawal Seizure Resistant line. Similarly, HOT mice, selected for insensitivity to ethanol-induced hypothermia, had greater conditioned place preference after ethanol training than COLD mice, selected for ethanol hypothermic sensitivity. We have also developed selected mouse lines responsive or unresponsive to ethanol-stimulated locomotor activity. These FAST and SLOW lines develop sensitization rather than tolerance to ethanol-induced activity. Using inbred strains of mice, others had shown that strains differed in preference for drinking ethanol solutions. We found that these strains also differed in acceptance of ethanol. Single-gene techniques have been used to show that preference drinking is significantly altered in mutant rodent strains lacking hypothalamic vasopressin, or with nephrogenic diabetes insipidus. In a specific panel of Recombinant Inbred mouse strains, we found that a single gene appeared to control a significant portion of the variance in preference drinking. These examples show that traits putatively related to drug reinforcement show substantial genetic control. Specifically, single-gene methods show promise of identification and mapping of genes related to drug reinforcement.

Acute sensitivity of FAST and SLOW mice to the effects of abused drugs on locomotor activity

The universal nature of the stimulant or euphoric effect of addictive drugs suggests that it may be an important predictor of a drug's addiction potential. Furthermore, assessment of stimulant sensitivity could be useful for predicting the liability of individuals to drug abuse. The stimulant actions of abused drugs from different pharmacological classes may share a common biological mechanism. We investigated this notion by assessing the drug responses relative to base-line locomotor activity of mice selectively bred for increased (FAST) and reduced (SLOW) sensitivity to ethanol-induced stimulation. FAST mice were more sensitive than SLOW mice to the stimulant effects of methanol (1.5-3.0 g/kg), t-butanol (0.2-0.6 g/kg), n-propanol (0.15-1.2 g/kg), pentobarbital (10-40 mg/kg) and phenobarbital (15-120 mg/kg). FAST and SLOW mice were similarly stimulated by d-amphetamine (1.25-10 mg/kg) and caffeine (2.5-20 mg/kg). The activity of FAST and SLOW mice was equally depressed by nicotine (0.5-2.0 mg/kg) and morphine (4-75 mg/kg). Finally, FAST mice were unaffected, whereas SLOW mice were depressed by diazepam (1-8 mg/kg). Selection for relative sensitivity to stimulation by ethanol has generalized to other alcohols and to barbiturates, but not to several other abused drugs, including amphetamine. The data presented here support a hypothesized common mechanism of stimulant action for alcohols and barbiturates, and suggest that differences in sensitivity to drug stimulant effects can be seen in the absence of dopamine system differences.

Clinical applications of cultured epithelium

Techniques that allowed the successful serial subcultivation of human keratinocytes into sheets of epithelium suitable for grafting have made possible a variety of clinical applications for cultured epithelium. Following the first description of this technique in 1981 to treat third-degree burns, cultured keratinocytes derived from a small biopsy of the patient's normal skin (autografts) have been used in centres throughout the world to provide permanent wound coverage for extensive burns. Over the years, applications have expanded to include the treatment of leg ulcers and blistering skin disorders. A further development in this field has been the use of cultured epithelium derived not from the patients own skin, but from an allogeneic donor (cultured allograft). Cultured allografts have also been widely used in the treatment of burns, leg ulcers, the donor sites for split-thickness grafts, and other dermatological disorders. These allografts seem to act as a potent stimulus to wound healing, but do not survive permanently on the wound bed. Their postulated mechanism of action is through release of multiple cytokines that stimulate epithelialization from the wound periphery as well as from adnexal elements within the wound bed. Allograft application is a simple outpatient procedure which involves no discomfort for the patient. No skin biopsy is necessary and cryo-preservation of grafts for future use is possible.

Locomotor responses to benzodiazepines, barbiturates and ethanol in diazepam-sensitive (DS) and -resistant (DR) mice

Diazepam-sensitive (DS) and -resistant (DR) mice were selectively bred for increased and reduced sensitivity to the ataxic effects of diazepam (40 mg/kg). Other response differences between DS and DR mice may reflect pleiotropic effects of the genes fixed during their selection. These mice were tested for their sensitivity to the locomotor stimulant effects of several doses of diazepam, flunitrazepam, pentobarbital, phenobarbital, and ethanol. DR mice were more sensitive than DS mice to the locomotor stimulant effects of all drugs except phenobarbital. These results largely support the hypothesis that a common biological mechanism mediates sensitivity to the stimulant effects of sedative-hypnotic drugs. Receptor mediation of the benzodiazepine effects was examined by administering the benzodiazepine receptor antagonist, RO15-1788. Locomotor depression produced by diazepam and flunitrazepam in DS mice was blocked by RO15-1788. However, while the locomotor stimulation produced by diazepam in DR mice was antagonized, the stimulant effect of flunitrazepam was not. This suggests that binding of flunitrazepam to the GABAA-benzodiazepine receptor is not necessary for production of locomotor stimulation.

An overview of moist wound dressings: the under cover story

The variety of wound dressings available is growing as more is learned about wound healing. The major types of moist dressings are discussed with descriptions of their uses, advantages, and disadvantages.

Leg ulcers

The treatment of leg ulcers is a common and sometimes difficult problem. They can be costly to treat and are associated with loss of working capacity and sometimes significant morbidity. In the western world, leg ulcers are most frequently caused by venous insufficiency, arterial insufficiency, neuropathy (usually diabetic), or a combination of these factors. The pathogenesis, clinical features, and management of these types of leg ulcers are emphasized in this review.

Nonhealing leg ulcers: a manifestation of basal cell carcinoma

Seven patients with basal cell carcinomas presenting as nonhealing ulcers are reported. The importance of considering malignancy and taking biopsy specimens of leg ulcers that fail to respond to treatment is emphasized.