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Biomedical subjects

D Falk

Publications and source records attributed to D Falk.

At least 19 recordsLinked to original sources
PubMed2006

Residual feed intake of purebred Angus steers: effects on meat quality and palatability.

Relationships between residual feed intake (RFI) and other performance variables were determined using 54 purebred Angus steers. Individual feed intake and BW gain were recorded during a 70-d post-weaning period to calculate RFI. After the 70-d post-weaning test, steers were fed a finishing ration to a similar fat thickness (FT), transported to a commercial facility, and slaughtered. A subsample of carcasses (n = 32) was selected to examine the relationships among RFI, meat quality, and palatability. Steers were categorized into high (> 0.5 SD above the mean; n = 16), medium (mid; +/- 0.5 SD from the mean; n = 21), and low (< 0.5 SD below the mean; n = 17) RFI groups. No differences were detected in ADG, initial BW, and d 71 BW among the high, mid, and low RFI steers. Steers from the high RFI group had a greater DMI (P = 0.004) and feed conversion ratio (FCR; DMI:ADG; P = 0.002) compared with the low RFI steers. Residual feed intake was positively correlated with DMI (r = 0.54; P = 0.003) and FCR (r = 0.42; P = 0.002), but not with initial BW, d 71 BW, d 71 ultrasound FT, initial ultrasound LM area, d 71 ultrasound LM area, or ADG. The FCR was positively correlated with initial BW (r = 0.46; P = 0.0005), d 71 BW (r = 0.34; P = 0.01), and DMI (r = 0.40; P = 0.003) and was negatively correlated with ADG (r = -0.65; P = 0.001). There were no differences among RFI groups for HCW, LM area, FT, KPH, USDA yield grade, marbling score, or quality grade. Reflectance color b* scores of steaks from high RFI steers were greater (P = 0.02) than those from low RFI steers. There was no difference between high and low RFI groups for LM calpastatin activity. Warner-Bratzler shear force and sensory panel tenderness and flavor scores of steaks were similar across RFI groups. Steaks from high RFI steers had lower (P = 0.04) off-flavor scores than those from low RFI steers. Cook loss percentages were greater (P = 0.005) for steaks from low RFI steers than for those from mid RFI steers. These data support current views that RFI is independent of ADG, but is correlated with DMI and FCR. Importantly, the data also support the hypothesis that there is no relationship between RFI and beef quality in purebred Angus steers.

Animal Feed↗
PubMed2004

DairyBeef: maximizing quality and profits--a consistent food safety message.

To respond to meat safety and quality issues in dairy market cattle, a collaborative project team for 7 western states was established to develop educational resources providing a consistent meat safety and quality message to dairy producers, farm advisors, and veterinarians. The team produced an educational website and CD-ROM course that included videos, narrated slide sets, and on-farm tools. The objectives of this course were: 1) to help producers and their advisors understand market cattle food safety and quality issues, 2) help maintain markets for these cows, and 3) help producers identify ways to improve the quality of dairy cattle going to slaughter. DairyBeef. Maximizing Quality & Profits consists of 6 sections, including 4 core segments. Successful completion of quizzes following each core segment is required for participants to receive a certificate of completion. A formative evaluation of the program revealed the necessity for minor content and technological changes with the web-based course. All evaluators considered the materials relevant to dairy producers. After editing, course availability was enabled in February, 2003. Between February and May, 2003, 21 individuals received certificates of completion.

Animals↗
PubMed2001

The effects of supplementation with 19-nor-4-androstene-3,17-dione and 19-nor-4-androstene-3,17-diol on body composition and athletic performance in previously weight-trained male athletes.

The purpose of this study was to determine the effects of 8 weeks of norsteroid supplementation on body composition and athletic performance in previously weight-trained males. Subjects were weight and percent body fat matched and randomly assigned to receive either 100 mg of 19-nor-4-androstene-3,17-dione (N-dione) and 56 mg of 19-nor-4-androstene-3,17-diol (N-diol; 156 mg total norsteroid per day), or a placebo (a multivitamin). Each subject participated in resistance training 4 days/week for the duration of the study. Body composition was assessed via dual-energy X-ray absorptiometry. Circumference measures were taken of a relaxed and flexed arm (maximum circumference of the arm), waist (level of umbilicus), and thigh (15 cm proximal to the patella). Strength was determined with a one-repetition maximum bench press, while force and power were determined with a dumbbell bench press (60% body weight) on a Stratec Galileo force platform. Profile of mood states scores were evaluated for vigor and fatigue. There were no significant changes in any of the parameters measured. In conclusion, low-dose supplementation with N-dione and N-diol does not appear to alter body composition, exercise performance, or mood states.

Adult↗
PubMed2000

Endocranial capacity in Sts 71 (Australopithecus africanus) by three-dimensional computed tomography.

In a recent report on early hominid endocranial capacity, it was predicted that future studies would show that: (1) "several key early hominid endocranial estimates may be inflated"; (2) "current views on the tempo and mode of early hominid brain evolution may need reevaluation"; and (3) endocranial capacity in one of these, Sts 71, was "probably closer to 370 cm(3), very near the mean value for female chimpanzees, and not the currently accepted 428 cm(3)" (Conroy et al., Science, 1998; 280: 1730-1731; Falk, Science 1998; 20:1714). Subsequent studies tend to support the first two predictions, but not the third (Culotta, Science, 1999; 284: 1109; Falk, Am. J. Phys. Anthropol. Suppl., 1999; 28: 126; Falk et al., J. Hum. Evol. [in press]). Here we detail the reasons for thinking the currently accepted endocranial value for Sts 71 is probably correct by providing the first quantitative details of endocranial reconstruction in Sts 71 using three-dimensional computed tomography. Relative brain expansion in the hominid lineage started some half-million years before the earliest appearance of the genus Homo, possibly coincident with enhanced tool-making skills and carnivory.

Animals↗
PubMed2000

Early hominid brain evolution: a new look at old endocasts.

Early hominid brain morphology is reassessed from endocasts of Australopithecus africanus and three species of Paranthropus, and new endocast reconstructions and cranial capacities are reported for four key specimens from the Paranthropus clade. The brain morphology of Australopithecus africanus appears more human like than that of Paranthropus in terms of overall frontal and temporal lobe shape. These new data do not support the proposal that increased encephalization is a shared feature between Paranthropus and early Homo. Our findings are consistent with the hypothesis that Australopithecus africanus could have been ancestral to Homo, and have implications for assessing the tempo and mode of early hominid neurological and cognitive evolution.

Animals↗
PubMed1999

A quantitative and qualitative reanalysis of the endocast from the juvenile Paranthropus specimen l338y-6 from Omo, Ethiopia.

Based on an analysis of its endocast, Holloway (1981 Am J Phys Anthropol 53:109-118) attributed the juvenile Omo L338y-6 specimen to Australopithecus africanus (i.e., gracile australopithecines) rather than to Paranthropus (Australopithecus) boisei (robust australopithecines) favored by other workers (Rak and Howell [1978] Am J Phys Anthropol 48:345-366). Holloway's attribution was based on the specimen's (1) low cranial capacity, (2) gracile-like meningeal vessels, (3) gracile-like cerebellar hemispheres, and (4) absence of an enlarged occipital/marginal (O/M) sinus system. Recent work, however, has shown that criteria 1 and 2 are not useful for sorting gracile from robust australopithecines (Culotta [1999] Science 284:1109-1111; Falk [1993] Am J Phys Anthropol 92:81-98). In this paper, we test criterion 3 by quantifying the endocranial cerebellar and occipital morphology reproduced on the Omo L338y-6 endocast, and comparing it to seven endocasts from South and East African early hominids. Our preliminary results show that metric analysis of this specimen cannot be used to sort it preferentially with either robust or gracile australopithecines. Finally, we demonstrate that, contrary to previous reports, the Omo L338y-6 endocast reproduces an enlarged left occipital sinus (criterion 4). This observation is consistent with the original attribution of the Omo specimen to robust australopithecines (Rak and Howell [1978] Am J Phys Anthropol 48:345-366). Furthermore, if Omo L338y-6 was a robust australopithecine, this discovery extends the occurrence of an enlarged O/M sinus system to one of the earliest known paranthropines. Am J Phys Anthropol 110:399-406, 1999.

Animals↗
PubMed1998

Characterization of staphylococcal bovine mastitis isolates using the polymerase chain reaction.

A polymerase chain reaction (PCR) assay was adapted to detect toxin genes of staphylococcal isolates from cases of bovine mastitis. Samples were obtained from three geographical areas: Korea and Idaho and Washington in the northwest United States. Samples from Korea and Washington were randomly chosen. Idaho samples were from a prospective study of mastitis etiology. Forty-one milk samples from 25 commercial farms in south-central Idaho were collected from cows with symptoms of mastitis. Although Staphylococcus aureus constituted 37.5% of mastitis isolates, these isolates lacked genes for staphylococcal enterotoxins (SEs), toxic shock syndrome toxin, and exfoliative toxins. In contrast, 4 of 13 isolates from Washington and 6 of 20 isolates from South Korea expressed SEs. These results suggest that PCR may be an effective means of screening bovine isolates for toxins. They also emphasize the potential for significant geographic differences in mastitis etiology.

Animals↗
PubMed1997

A comparative study of stereolithographically modelled skulls of Petralona and Broken Hill: implications for future studies of middle Pleistocene hominid evolution.

Computer generated three-dimensional stereolithographic models of middle Pleistocene skulls from Petralona and Broken Hill are described and compared. The anterior cranial fossae of these models are also compared with that of another middle Pleistocene skull, Arago 21. Stereolithographic modelling reproduces not only the outer surfaces of skulls, but also features within the substance of the bones, and details of the internal braincase. The skulls of Petralona and, to a somewhat lesser degree, Broken Hill are extremely pneumatized. Previously undescribed features associated with pneumatization are detailed, along with their possible functional significance, polarity, and potential for understanding hominid cranial variation. Petralona and Broken Hill also exhibit a dramatic suite of cerebral features that is probably related to extensive pneumatization of the skull, namely frontal lobes that are tilted and located behind rather than over the orbits, laterally flared temporal lobes, marked occipital projection, and basal location of the cerebellum. Comparison of the anterior cranial fossae of Petralona, Broken Hill, and Arago 21 suggests that external resemblance of skulls may not always correlate with endocranial similarity. We believe that stereolithographic reconstructions have the potential for helping to resolve difficult questions about the origins of Neanderthal and anatomically modern people.

Animals↗
PubMed1994

Relationship of squamosal suture to asterion on external skull surfaces versus endocasts of pongids: implications for Hadar early hominid AL 162-28.

The relationship between the squamosal suture and asterion was quantified in 15 hemispheres of eight chimpanzee endocasts that were aligned in the conventional lateral view (i.e., with frontal pole [FP]-occipital pole [OP] horizontal). Using a three-dimensional digitizer, x, y, and z coordinates were collected for the highest and lowest points of the squamosal suture, and the most rostral point of the suture approximate to the coronal suture. Our results were compared to a similar study of the squamosal suture on the external surfaces of chimpanzee skulls that were oriented in the Frankfurt horizontal (Holloway and Shapiro, 1992). The relationship between the squamosal suture and asterion differs markedly between the outsides of skulls and endocasts. Whereas the squamosal suture is very rarely below asterion on the external skull, we found that most of the squamosal suture is located inferior to asterion on endocasts. We also found that the squamosal suture courses approximately 2.0 mm lower on the right side than the left. (An asymmetry of the same magnitude was reported for the external skull but, curiously, in the opposite direction.) It may be that a lowered right squamosal endosuture on chimpanzee endocasts is associated with earlier closure on that side. The discrepancy in results for the external skull versus endocast is partially attributable to orienting chimpanzee skulls in the Frankfurt horizontal, which usually results in the endocasts being tilted so that FP is above OP, i.e., FP-OP is not parallel with the Frankfurt horizontal. Falk's (1985) orientation of the early hominid endocast from Hadar (AL 162-28) is consistent with data determined from endocasts of chimpanzees.

Animals↗
PubMed1993

Meningeal arterial patterns in great apes: implications for hominid vascular evolution.

Arterial meningeal patterns were observed for 100 hemispheres from great ape endocasts (Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus). Eight patterns emerged based on the relative contributions to the walls and dura mater of the middle part of the braincase of meningeal arteries that stem from two sources. These arteries enter the braincase through either the orbit (delivering blood from the internal carotid artery) or through the base of the middle cranial fossa (via the middle meningeal artery whose blood comes from the external carotid artery). The three genera of apes manifest different frequencies of the eight patterns, with orangutans highly dependent on orbital meningeal arteries at one extreme, and chimpanzees showing the greatest reliance on the middle meningeal artery at the other. As was the case in an earlier study of rhesus monkeys, there is a trend across the two genera of African apes for increased mean cranial capacity to be associated with increased reliance on the internal carotid artery for supplying the middle portion of the braincase. However, unlike the case for macaques, this trend does not reach statistical significance in African apes. Because it is rare for humans to manifest significant arterial contributions from the orbit to the middle cranial fossa, the comparative data on monkeys, apes, and humans suggest that, during the course of vascular evolution in Homo, the middle meningeal artery eventually took over supply of the entire middle cranial fossa. This hypothesis should be tested in the hominid fossil record. Earlier work on meningeal arterial patterns in apes has traditionally relied on Adachi's system that was determined from humans and focuses on the origin of the middle branch of the middle meningeal artery. As a result, the extensive orbital contributions to the middle portion of the braincase that characterize apes were not recognized and the eight patterns described in this paper were often erroneously assigned to the three patterns that adequately describe only humans. Adachi's system should therefore be abandoned for nonhuman primates and early hominids. A correct understanding of meningeal arterial evolution cannot be achieved until the orbital contributions to the meningeal arteries are recognized and incorporated into an evolutionary study that spans from apes to fossil hominids to living people.

Animals↗