Search PubMed⌕ Search

Biomedical subjects

H D Johnson

Publications and source records attributed to H D Johnson.

At least 37 records · Page 2Linked to original sources
PubMed1987

Physiological, productive, and economic benefits of shade, spray, and fan system versus shade for Holstein cows during summer heat.

During the 1984 summer, effects of spray and fan in freestall areas and feeding areas on milk yield, plasma growth hormone and prolactin, freestall utilization, and economic significance for Holstein cows were studied. Weekly milk and rectal temperatures at morning and afternoon milkings were higher for cows in shade than in shade with spray and fan cooling. Compared with rectal temperature, milk temperature measured in the clawpiece provided a more reliable indicator of heat stress than in the milk meter. Diurnal pattern of rectal temperature from 4-h measurements showed an average of 12 h in which maximal rectal temperatures of cows in shade were greater than 39 degrees C, but cows in the shade plus spray plus fan group had rectal temperatures below 39 degrees C all day. Plasma growth hormone was higher and prolactin lower for cows in shade plus spray and fan than cows in shade only. Cows cooled with spray and fan under shade produced 2 kg/cow per d more than cows in shade alone. Economic analysis showed a net income of 22 cents/cow per day for spray plus fan under shade. Results suggest that milk temperature is a practical technique to assess heat stress in dairy cattle, and the use of spray plus fan is a profitable means to maximize cow comfort and lessen stress-induced decline in milk production.

Animals↗
PubMed1985

Prolactin and its involvement in fluid regulation in the bovine.

Plasma prolactin (PRL) concentrations, osmolality, water consumption, feed intake, urine excretion, and fecal water output were determined in twelve steers of 3 breeds exposed to 5 feed and water regimes. Breed differences were found in water intake and plasma PRL concentrations when feed and water were ad lib., however, during any of the other 4 treatments, responses were similar between breeds. During dehydration and feed restriction, water intake, urine, fecal water, and plasma prolactin decreased; however, during hydration and refeeding such changes were not as clearly related. No consistent relationships between plasma prolactin and osmolality were found. Data suggests that PRL's role in fluid regulation in the bovine is most likely associated with alterations in renal hemodynamics rather than by changes in plasma osmolality.

Animals↗
PubMed1985

Plasma antidiuretic hormone (ADH) concentrations in cattle, during various water and feed regimes.

Twelve steers of three different breeds were exposed to five feed and water regimes in order to characterize changes in plasma antidiuretic hormone (ADH) concentrations. No breed differences were found in plasma ADH concentration. Plasma ADH concentration rose (4.2 to 22.0 pg/ml) during dehydration. By 3 hr hydration, plasma ADH concentrations dropped dramatically (over 50%) to 9.2 pg/ml. No changes in plasma ADH concentrations occurred during feed restriction and refeeding. Hematocrit percentages were also determined and differences are hypothesized to relate to probable differences in environmental adaptability and genetic selection for meat or milk production among the three breeds.

Animals↗
PubMed1985

Spray cooling effects on milk production, milk, and rectal temperatures of cows during a moderate temperate summer season.

During summer 1982, responses of lactating Holstein and Guernsey cows were measured by milk temperature recorded by a Digital Dataloger with thermocouples attached to Boumatic flow meters. Maximum air temperature and temperature-humidity index averaged 30.8 degrees C and 75.6 for July. Breed did not affect milk temperature, but within-breed milk temperature increased with production. In a second study, benefits of spray cooling were evaluated with 24 Holsteins in midlactation assigned randomly to two groups of 12 and maintained under loose-housing conditions. Spray nozzles were installed in the walkways and under the manger shade for the spray treatment group. Maximum temperature and temperature-humidity index during the spray study were 27 degrees C and 73.9. Rectal temperature taken following milking averaged less for treatment than control (38.8 versus 39.1 degrees C). Milk temperature was similar (37.8 versus 38.1 degrees C). Daily milk yield was .70 kg higher than controls. Milk temperature may provide reliable indication of climate stress similar to rectal temperature, and spray cooling improves cow comfort and lessens summer decline of milk production.

Animals↗
PubMed1985

Effect of growth hormone on milk yields and related physiological functions of Holstein cows exposed to heat stress.

Responses of milk production and other physiological functions to daily subcutaneous injections of bovine growth hormone (16.6 mg/cow) were studied in six Holstein cows in midlactation under environmental heat stress. Five days were assigned for each treatment of thermoneutral (18.3 degrees C), heat (28.9 degrees C), heat plus growth hormone, and heat. Each period was preceded by at least 3 days of adjustment. Feed and water were available ad libitum. Feed intake, milk production, and rectal temperature were measured twice daily. Blood, energy metabolism, and body weight were measured every 1st, 3rd, and 5th day of each period. Administration of growth hormone under heat stress increased milk production by 3.8 and 12% and fat yield by 9.5 and 12.7% over heat and heat. Feed intake declined by 5.8% with no significant increase of heat production or body weight loss during treatment with bovine growth hormone. Heat increased somatic cell concentration.

Animals↗
PubMed1984

Effect of temperature stress on circulating biogenic amines in bovine.

A sensitive, simple and selective chromatographic method using high performance liquid chromatography was developed to measure circulating levels of histamine (HI), norepinephrine (NE), dopamine (DA) and serotonin (5-HT) as indicators of response to thermal stress in two breeds of cattle. Duplicate exposures for 8 hr to 13 degrees C resulted in significantly elevated plasma NE and DA in longhorns but not in Herefords and suggest a relatively greater sensitivity to the cold (13 degrees C) in the longhorn. Environmental temperatures of 32 and 42 degrees C significantly increased rectal temperatures of both breeds with much higher rectal temperatures in Herefords. The 32 and 42 degrees C effects on circulating NE and DA of Herefords were highly significant but not in the longhorn. However, heat stress significantly elevated HI and 5-HT in the longhorn which may account for their relatively greater heat tolerance based on their lower rectal temperatures.

Animals↗
PubMed1984

Oral benzodiazepine premedication in minor gynaecological surgery.

Clobazam 20 mg, diazepam 10 mg, lorazepam 2 mg and oxazepam 30 mg were compared in a randomized, double-blind, placebo-controlled trial as oral premedication for 150 patients undergoing minor gynaecological surgery. All drugs and placebo significantly decreased anxiety when assessed by the patient on a 10-cm linear analogue rating scale 60 min after premedication. Diazepam 10 mg induced significantly more drowsiness when assessed by a trained observer 60 min after premedication than clobazam 20 mg, oxazepam 30 mg and placebo (P less than 0.01). Lorazepam 2 mg caused significantly more drowsiness 2 h (P less than 0.001) and 4 h (P less than 0.01) after operation, and significantly impaired psychomotor function after operation compared with the other four agents. The data suggest that clobazam 20 mg, diazepam 10 mg, oxazepam 30 mg or placebo offer advantages over lorazepam 2 mg for oral premedication in minor gynaecological surgery where early discharge after operation is preferred.

Adolescent↗
PubMed1983

Environmental heat effects on growth, plasma T3, and postheat compensatory effects on Holstein calves.

Five Holstein heifers, 5 months of age, were housed in the Missouri Climatic Laboratory and subjected to an experiment to measure the effects of heat stress on rates of growth, plasma triiodothyronine (T3) levels, and ability to compensate in rate of gain and thyroid function following the stress period. The experiment consisted of 3 weeks at thermoneutral (TN1), followed by 5 weeks of individually controlled heat stress conditions (32.5 to 34 degrees C) dependent on heat tolerance of individual animals. This was followed by a 4-week thermoneutral, postheat compensatory period (TN2). Average daily gains were significantly depressed during the heat stress period (HS). Following heat stress the average body weights attained the projected or expected levels within a 21- to 28-day period following return of animals to thermoneutral conditions. Ratios of feed intake/body weight (w0.75) were reduced during heat stress treatment indicating the thermal inhibition. Ratios or amount of feed intake per unit of gain were greater during HS treatment indicating less weight gain per unit of daily feed intake. Plasma T3 was reduced during heat treatment similarly to daily weight gain. Following the postheat treatment period (TN2) plasma T3 increased markedly as did daily weight gains to demonstrate strong compensatory responses in both measures. In summary, these results demonstrated parallel and positive changes of plasma T3 with daily weight gain during thermoneutral, heat, and postheat compensatory periods, and an inverse relationship of rectal temperature to weight gain and plasma T3.

Animals↗
PubMed1982

Patient administration of I.V. buprenorphine for postoperative pain relief using the "Cardiff" demand analgesia apparatus.

In 51 patients undergoing elective abdominal surgery, analgesia was provided for the first 24 h after surgery by bolus injections of buprenorphine 0.1 or 0.2 mg given i.v. on patient demand using a patient-operated syringe driver (the "Cardiff" palliator). Excellent analgesia was reported by 47 patients. Four elderly patients had difficulty in operating the demand apparatus. In two other patients, clinically significant ventilatory depression necessitated abandoning the trial. Although there was a high degree of patient and staff acceptance of the method, the potential for ventilatory depression emphasizes the need for close observation of patients receiving i.v. opioids by this technique.

Adult↗
PubMed1982

Effect of environmental heat and dietary fiber on thyroid physiology of lactating cows.

Six lactating dairy cows were assigned randomly to a diet either of low fiber (30% corn silage) or of high fiber (70% corn silage). Both groups were subjected to 10 days thermoneutral (17.6 degrees C) and 10 days of environmental heat (31.2 degrees C) to determine effects of dietary fiber content and environmental heat on concentrations of thyroxine and triiodothyronine in plasma, milk, urine, and feces. During heat there were significant reductions in concentrations of thyroxine and triiodothyronine in plasma and in excretion of thyroxine and triiodothyronine in milk. Excretion of thyroxine and triiodothyronine increased in urine during heat stress, whereas concentration and excretion of thyroxine and triiodothyronine in feces decreased. Dietary fiber content had little effect upon thyroxine and triiodothyronine concentrations in plasma or excretion in milk, feces, and urine. Excretion of triiodothyronine in milk was negatively correlated with rectal temperature and positively with content in plasma. The reduction in thyroxine and triiodothyronine of plasma and the decline in excretion of thyroxine and triiodothyronine suggested that environmental heat reduced synthesis of both hormones.

Animals↗
PubMed1982

Pathogenesis of tubal pregnancy.

A review was made of 706 ectopic pregnancies treated at Howard University Hospital over a 20-year period. Comparison of two 10-year periods was made with special regard to the association of an inflammatory process in the involved tube. It is not the intention of this study to deny chronic pelvic inflammatory disease as a factor in the etiology of ectopic pregnancy, but it is not considered the main cause.An inflammatory process was associated in 40.1 percent of cases during the first 10 years, and 16.7 percent of cases in the second 10 years. Further study is necessary to elucidate the cause of ectopic pregnancy, probably in the direction of functional disturbances rather than structural defects.

Adolescent↗
PubMed1981

Post concentrations of thyroxine in plasma of dairy cows.

Concentrations of thyroxine in blood plasma were measured by radioimmunoassay in 32 dairy cows postpartum and during estrous cycles. Mean concentrations of thyroxine declined from 1 to 2 days postpartum to 5 or 6 days postpartum. Concentrations of thyroxine remained low at 7 to 10 days postpartum and during the first estrous cycle. During subsequent estrous cycles concentrations of thyroxine were elevated to those 1 or 2 days postpartum.

Animals↗
PubMed1980

Is a microfilter necessary in a single unit blood transfusion.

Pulmonary dysfunction may be caused by microaggregates passing through a standard blood filter (170 mu) during transsfusion. In this study a sheep was repeatedly tranfused with a single unit (about 450 ml) of her own blood to compare the effects of 27 mu and 170 mu pore filters on lung function. Lung function was assessed by comparing cardiac output, pulmonary shunt and alveolar-arterial oxygen tension gradient before, during and after transfusion. There were no significant changes in these parameters. So far as these results can be extrapolated from sheep to man, it is considered that the more expensive 27 mu pore filter is not justified in small volume transfusions.

Animals↗
PubMed1980

Aldosterone and ADH response to heat and dehydration in cattle.

The effect of heat (35 degrees C) and dehydration under heat (30 h) on plasma levels of antidiuretic hormone (ADH) and aldosterone was studied on four nonpregnant dry Holstein cows. Heat exposure caused a rapid significant rise in plasma ADH without significant changes in hematocrit (Hct), small but significant increase in urine output and a significant reduction in total plasma protein. Dehydration under heat caused a sharp increase in ADH levels associated with a significant decrease in urine output and a significant increase in plasma protein, blood Hct, and serum osmolality. A significant reduction in plasma aldosterone level was observed after 24 h of heat exposure. This was associated with a slight rise in urinary sodium excretion and a significant reduction in serum sodium. Both serum and urinary potassium concentrations were significantly lower under heat. Dehydration resulted in a slow rise in aldosterone but did not reach thermoneutral level. This is probably due to the inhibitory effect of higher serum sodium observed during dehydration on plasma aldosterone secretion. The rise in ADH and decrease in aldosterone during heat exposure may explain why cattle are one of the few species that do not concentrate urine during heat exposure.

Aldosterone↗